113274331 co dai va bien phap phong tru weed and control weed

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B GIO DC & O TO

TRNG I HC TY NGUYN

BI GING

C DI &

BIN PHP KIM SOT

Bin soan: Th.S. Th Kiu An

Daklak, nm 2010

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MC LC

CHNG 1. KHI NIM V VAI TR CA C DI ............................................................ 1 1.1. KHI NIM C DI ............................................................................................. 1 1.2. TC HI CA C DI ........................................................................................ 2

1.2.1. Lm gim nng sut cy trng, gia tng chi ph sn xut ................................ 3 1.2.2. C di tit ra cc cht ha hc c ch s sinh trng, pht trin ca cc loi thc vt khc (allelopathy) ......................................................................................... 3 1.2.3. C di l k ch ca su bnh v chut ............................................................ 3 1.2.4. nh hng n cht lng nng sn ............................................................... 4 1.2.5. Gim hiu qu ca qu trnh thu hoch ........................................................... 4 1.2.6. nh hng n sc khe gia sc ..................................................................... 4 1.2.7. nh hng n sc khe con ngi ................................................................ 5 1.2.8. Gy nhim v cn tr ngun nc ................................................................ 5 1.2.9. nh hng n cng nghip v cc cng trnh cng cng .............................. 5 1.2.10. Gy thit hi cho rng v cc sn phm lm bng g ................................... 6

1.3. LI CH CA C DI .......................................................................................... 6 CHNG 2. PHN LOI V NH DANH C DI ............................................................... 8

2.1. CC HNH THC PHN LOI C DI ............................................................ 8 2.1.1. Phn loi theo kh nng thch ng vi hm lng nc trong t .................. 8

22..11..11..11.. C a cn: ................................................................................................. 8 22..11..11..22.. C chu hn: .............................................................................................. 8 22..11..11..33.. C chu nc: ............................................................................................ 8 22..11..11..44.. C a nc: .............................................................................................. 8

2.1.2. Phn loi theo thi gian sinh trng v theo ma v xut hin ....................... 9 22..11..22..11.. C nht nin (annual): rau dn, lu lu, rau mui ....................................... 9 22..11..22..22.. C nh nin (biennial) ............................................................................... 9 22..11..22..33.. C a nin (perennial) .............................................................................. 9

2.1.3. Phn loi theo phng thc sng ................................................................... 10 22..11..33..11.. C di k sinh .......................................................................................... 10 22..11..33..22.. C di khng k sinh: .............................................................................. 11

2.1.4. Theo s l mm .............................................................................................. 11 22..11..44..11.. C 1 l mm: gm cc loi c thuc h ha tho, ci lc ...................... 11 22..11..44..22.. C 2 l mm: rau dn, rau dic, c hi .............................................. 11

2.1.5. Phn loi da theo c im thn cnh .......................................................... 12 22..11..55..11.. Cy thn tho: ......................................................................................... 12 22..11..55..22.. Cy thn g: ............................................................................................ 12 22..11..55..33.. Cy bi: ................................................................................................... 12 22..11..55..44.. Cy bi leo: ............................................................................................. 12 22..11..55..55.. Cy leo: ................................................................................................... 12

2.1.6. Phn loi theo mi trng sng ..................................................................... 12 2.1.7. Theo h thng phn loi thc vt ................................................................... 13

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2.2. CC PHNG PHP PHN LOI C DI .................................................... 13 2.2.1. Phng php hnh thi so snh ...................................................................... 13 2.2.2. Phng php gii phu: ................................................................................. 14 2.2.3. Phng php bo t phn hoa: ....................................................................... 14 2.2.4. Phng php t bo hc: ................................................................................ 14 2.2.5. Phng php lai ghp: ................................................................................... 14 2.2.6. Phng php sinh thi:................................................................................... 14 2.2.7. Phng php ha sinh hc: ............................................................................ 14 2.2.8. Cc phng php khc ................................................................................... 14

CHNG 3. C IM CA C DI ................................................................................... 16 3.1. C IM CA C DI ................................................................................... 16

3.1.1. C di c nhiu hnh thc sinh sn ................................................................ 16 3.1.2. Kh nng nhn ging cao ............................................................................... 16 3.1.3. Ht chn khng u, d rng v c nhiu hnh thc lan truyn ..................... 17 3.1.4. Ht c di c thi gian ng ngh (min trng) ............................................... 18

33..11..44..11.. Min trng di truyn (ng, ngh t nhin) .............................................. 18 33..11..44..22.. Min trng cm ng (ng ngh bt buc) ............................................... 18

3.1.5. Ht c di c kh nng gi sc ny mm trong khong thi gian di ........... 18 33..11..55..11.. Kh nng gi sc ny mm trong t ..................................................... 19 33..11..55..22.. Kh nng gi sc ny mm trong nc ngp ......................................... 19 33..11..55..33.. Kh nng gi sc ny mm trong phn chung ..................................... 19

3.1.6. Ht c di ny mm khng u ...................................................................... 20 3.1.7. C di c tnh bin ng ln .......................................................................... 20

33..11..77..11.. S thay i thi gian sinh trng, thi k pht dc ................................ 21 33..11..77..22.. S thay i v sinh trng v hnh thi .................................................. 21 33..11..77..33.. S bin i v sinh l ............................................................................... 21

3.1.8. Kh nng chng chu cao ............................................................................... 21 33..11..88..11.. Kh nng chu lnh ................................................................................. 21 33..11..88..22.. Kh nng chu nng ................................................................................ 22 33..11..88..33.. Kh nng chu hn .................................................................................. 22 33..11..88..44.. Kh nng chu ngp ................................................................................ 22

3.2. c im cnh tranh ca c di ............................. Error! Bookmark not defined. 3.2.1. Thi im c mc mm ................................................................................. 23 3.2.2. Hnh thc sinh trng .................................................................................... 26 3.2.3. Mt c ....................................................................................................... 26

CHNG 4. PHNG PHP QUN L C DI ................................................................ 27 4.1. PHNG NGA C DI ..................................................................................... 27

4.1.1. Kim dch thc vt ......................................................................................... 27 4.1.2. S dng ht ging sch, khng ln c di ..................................................... 27

44..11..22..11.. Sn xut ht ging khng ln c di ....................................................... 27 44..11..22..22.. Loi b ht c khi ht ging cy trng ................................................. 27

4.1.3. Ngn nga c di xm nhp vo ng rung thng qua phn bn ................ 28 4.1.4. Ngn nga c di xm nhp thng qua nng c, my mc v gia sc .......... 29

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4.1.5. Gi sch c khu vc quanh rung .............................................................. 29 4.1.6. Thng xuyn gim st ng rung .............................................................. 29

4.2. KIM SOT C DI THNG QUA CC K THUT TRNG TRT ......... 29 4.2.1. Xc lp qun th cy trng v cng lc cy con mnh .......................... 29 4.2.2. S dng ging c kh nng hn ch c di .................................................... 30 4.2.3. Chn thi v & mt gieo trng thch hp ................................................. 30 4.2.4. Lun canh, xen canh, tng v ......................................................................... 30

44..22..44..11.. Lun canh cy trng (Crop rotation) ..................................................... 30 44..22..44..22.. Xen canh (intercropping) ........................................................................ 30 44..22..44..33.. Tng v .................................................................................................... 31

4.2.5. Bn phn ........................................................................................................ 31 4.3. KIM SOT C DI BNG BIN PHP VT L ......................................... 31

4.3.1. Lm c ............................................................................................................ 31 4.3.2. Lm t (tillage) ............................................................................................. 32 4.3.3. Ngm nc rung .......................................................................................... 32 4.3.4. Dng la ......................................................................................................... 32 4.3.5. Che ph mt t (mulching) .......................................................................... 33

44..33..55..11.. Che ph t bng cc vt liu t nhin: ................................................. 33 44..33..55..22.. Che ph t bng cc vt liu nhn to ................................................. 34

4.4. QUN L C DI BNG BIN PHP SINH HC ........................................ 34 4.4.1. Cn trng dit c ............................................................................................ 34 4.4.2. Chn th gia cm ............................................................................................ 35 4.4.3. Nm ................................................................................................................ 35 4.4.4. Thuc dit c sinh hc (bioherbicides) .......................................................... 35 4.4.5. Trng cy cnh tranh (Competitive crops) .................................................... 36 4.4.6. S dng thm thc vt (Smother crops) ........................................................ 36 4.4.7. Tiu chun thnh cng ca mt tc nhn sinh hc ........................................ 37 4.4.8. S tng tc gia bin php sinh hc v cc bin php khc: ...................... 37

4.5. KIM SOT C DI BNG BIN PHP HA HC ..................................... 37 4.5.1. Vai tr ca thuc tr c.................................................................................. 37

44..55..11..11.. u im: ................................................................................................. 37 44..55..11..22.. Nhc im: ............................................................................................ 38

4.5.2. C ch tc ng ca thuc i vi c ............................................................ 38 4.5.3. Tnh chn lc ca thuc tr c ...................................................................... 38 4.5.4. Phn nhm thuc tr c ................................................................................. 39

44..55..44..11.. Phn loi da vo ph tc dng ca thuc ............................................ 39 44..55..44..22.. Phn loi da vo thi im p dng ..................................................... 39 44..55..44..33.. Phn loi theo kiu tc ng ca thuc .................................................. 39 44..55..44..44.. Da vo c ch tc ng ca thuc n c di ...................................... 40 44..55..44..55.. Da trn thnh phn ha hc ................................................................. 40

4.5.5. Cc yu t nh hng n hiu lc thuc tr c ........................................... 42 44..55..55..11.. Giai on sinh trng v loi c di ...................................................... 42 44..55..55..22.. Cc yu t kh hu ................................................................................... 43

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44..55..55..33.. Yu t t ai .......................................................................................... 43 44..55..55..44.. Yu t ha hc (cng thc ha hc ca thuc) ....................................... 43

4.5.6. Tiu chun chn lc thuc tr c: .................................................................. 44 4.5.7. Bin php nng cao hiu lc thuc tr c ...................................................... 44 4.5.8. Nhng iu cn lu khi s dng thuc tr c ............................................. 44

CHNG 5. C DI TRONG RUNG LA & BIN PHP KIM SAT .......................... 45 5.1. nh hng ca c di n sinh trng, pht trin v nng sut la .............. Error! Bookmark not defined. 5.2. Thnh phn v c im mt s loi c di chnh trong rung la ............... Error! Bookmark not defined.

5.2.1. Thnh phn c di trong rung la ................................................................ 47 5.2.2. c im mt s loi c di chnh trong rung la ....................................... 48

55..22..22..11.. La c (weedy rice, la ln, la ln, la ma, la c, la ry ) ......... 48 55..22..22..22.. C lng vc nc (c go, c m) .......................................................... 51 55..22..22..33.. C lng vc cn ...................................................................................... 51 55..22..22..44.. C ui phng (mnh ha Trung Quc, c lng cng) .......................... 52 55..22..22..55.. C san i (c san nc) ........................................................................ 52 55..22..22..66.. C cho (c lc m, c t ty) .................................................................. 52

5.3. Bin php kim sot c di trong rung la .......... Error! Bookmark not defined. 5.3.1. Bin php canh tc ......................................................................................... 53

55..33..11..11.. Chn ht ging la sch c .................................................................... 53 55..33..11..22.. Gieo cy vi mt thch hp ................................................................ 53 55..33..11..33.. Chm sc rung la ................................................................................ 53 55..33..11..44.. Lun canh ................................................................................................ 53

5.3.2. Bin php c gii, vt l ................................................................................ 54 55..33..22..11.. Lm t k ............................................................................................... 54 55..33..22..22.. Lm c bng tay ...................................................................................... 54 55..33..22..33.. Dng dng c lm c .............................................................................. 55

5.3.3. Bin php sinh hc ......................................................................................... 55 5.3.4. Bin php ha hc .......................................................................................... 55

55..33..44..11.. Chn loi thuc ....................................................................................... 55 55..33..44..22.. Thi gian s dng thuc ......................................................................... 55 55..33..44..33.. Liu lng v nng thuc .................................................................. 55

CHNG 6. C DI TRN RUNG CY TRNG CN & BIN PHP KIM SOT ..... 57 6.1. c im ca mt s c di ph bin trn rung cy trng cn . Error! Bookmark not defined.

6.1.1. C g (c ch, c ng, c Bermuda...) ............................................................ 57 6.1.2. C mn tru .................................................................................................... 57 6.1.3. C tranh .......................................................................................................... 58 6.1.4. C gu (c gu, Hng ph, Tam lng) ........................................................ 59 6.1.5. C hi (b xt, cy ct ln, c ct heo) ......................................................... 60 6.1.6. C lo (yn bch, c hi, c Vit Minh, cy cng sn, lp bp, cy ba bp, bp bp, cy phn xanh, c Nht) ........................................................................... 60

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6.1.7. Trinh n (mc c) .......................................................................................... 60 6.2. Kim sot c di ..................................................... Error! Bookmark not defined.

6.2.1. Tr c cho cy trng cn hng nm ............................................................... 61 66..22..11..11.. Tr c bng cc bin php lm t ........................................................ 61 66..22..11..22.. Bin php xi xo chm sc cy trng ................................................... 62 66..22..11..33.. Bin php lun canh ............................................................................... 63 66..22..11..44.. Che ph t ............................................................................................. 63 66..22..11..55.. Bin php ha hc .................................................................................. 63 66..22..11..66.. Tr c cho bp ........................................................................................ 64 66..22..11..77.. Tr c cho u tng: ............................................................................ 65 66..22..11..88.. Tr c cho ma (Sacharum spp.) ............................................................. 65 66..22..11..99.. Tr c cho bng vi ................................................................................ 66

6.2.2. Tr c cho cy trng cn a nin ................................................................... 67 66..22..22..11.. Trng xen ................................................................................................ 67 66..22..22..22.. Bin php c gii, vt l ......................................................................... 68 66..22..22..33.. Bin php ha hc .................................................................................. 68 66..22..22..44.. Kim sot c trong vn c ph ............................................................. 68 66..22..22..55.. Kim sot c trong vn iu ................................................................. 69


CHNG 1. KHI NIM V VAI TR CA C DI

1.1. KHI NIM C DI

c th qun l tt c di, trc ht chng ta cn phi hiu th no l c di. Hin c rt nhiu nh ngha khc nhau v c di ty thuc vo tng trng hp c th ni c di xut hin v i tng cy trng lin quan. Booth et al. (2003) tng hp mt s nh ngha thng dng v c di nh sau: c di l nhng thc vt gy phin tai cho con ngi (Harper 1960) hay nhng thc vt mc ni con ngi khng mong mun (Salisbury 1961) hoc l nhng thc vt ngoi lai xm ln (Babour & ctv 1999).

Ngay t nm 1731, Jethro Tull nh ngha v c di nh sau: C di l nhng thc vt mc ni m con ngi khng cn n, ngha l n bao gm c khi nim cy mc hoang v cy mc ln.

- Cy mc hoang: l nhng thc vt mc t nhin nhng khng xut hin trn ng rung hay trn c quan thc vt c ch m thng mc trn nhng bi t hoang nh s, vt, da di

- Cy mc ln: l nhng thc vt mc ngoi mun ca con ngi, thng l ht ca cy trng v trc mc ln vo rung cy trng v sau trn ng rung, chng hn nh u mc ln trong rung bp hay rau mung mc ln trong rung la.

Khi nim v mc khng mong mun nh hng n nhn nh ca con ngi v c di v cc c tnh ca n. Bng 1.1. lit k mt s c tnh ca c di c lin quan n con ngi trong nh ngha th no l c di.

Crawley (1997) tha nhn nhng kh khn trong vic nh ngha c di v ngh rng thc vt ch c coi l c di khi mc ph bin ca chng phi vt qua mt ngng nht nh v chng phi l mi bn tm, lo lng ca nhiu ngi. nh ngha ny t chng ta trc mt tnh hung kh khn mi l xc nh ngng ti thiu m ti thc vt b coi l c di. nh ngha ny cng tha nhn rng c di ch l c di trong nhng trng hp nht nh v rng vic xp mt thc vt no vo nhm c di l ty thuc vo nhn nh ca con ngi.

nh ngha c di thng c dng ph bin hin nay nh sau: C di l nhng loi thc vt bn a hay ngoi lai sinh trng, pht trin ngoi mun ca con ngi. S hin din ca chng gy kh chu v cn tr cc hot ng ca con ngi hoc nh hng bt li n li ch ca h.

Nh vy, c di c nh ngha ty theo nhn nh ca con ngi ch khng ty thuc vo h thng phn loi bi gia c di v cy trng c th chuyn ha cho nhau trong nhng iu kin sng nht nh.

- C di nu c chn lc v bi dc tt th s tr thnh cy trng hu ch cho con ngi. V d: trc y rau dn, rau m tng c coi l c di nhng nay do nhu cu s dng chng lm rau xanh, con ngi trng chng trn din rng.


- Nu cy trng khng cn ph hp vi con ngi v b thi loi th s tr thnh c di. V d: mt s loi ci lc li bin thnh c ci lc.

- C khng t loi thc vt, ni ny, lc ny l c di nhng ni khc, lc khc li l cy trng. V d: c g, c ch nu c trng lm thc n cho gia sc v lm thm c th chng c coi l cy trng; nhng nu chng mc ln trong rung la, ng, u v cnh tranh cc iu kin sng vi cy trng th chng c xem l c di.

Chnh v vy, ty tng trng hp, tng iu kin c th, cn phn bit gia c di v cy trng nhm xc nh chnh xc i tng cn phi phng tr v la chn phng n phng tr thch hp.

Tuy nhin, hu ht cc loi c di nguy him u c cc c tnh sinh vt hc c trng gip chng c th sinh trng pht trin tt trong nhiu h sinh thi khc nhau. Baker (1974) lit k 12 c im c trng ca c di, l: (i) c th ny mm trong nhiu iu kin mi trng khc nhau; (ii) ny mm khng lin tc, ht c tui th cao; (iii) pht trin nhanh qua giai on sinh trng sinh thc ra hoa kt ht; (iv) ra hoa kt ht lin tc min l iu kin sng cho php; (v) t tng hp nhng khng t giao hay tip hp v tnh; (vi) th phn cho nh gi hoc cc tc nhn khng chuyn khc; (vii) kh nng sinh sn cao trong iu kin mi trng thch hp; (viii) c kh nng kt ht trong nhiu iu kin mi trng khc nhau, kh nng chng chu vi iu kin bt li ca mi trng tt; (ix) c cc b phn ph thch hp vi vic pht tn ht i xa, (x) nu l c a nin, kh nng sinh sn v tnh v ti sinh t cc mnh ca cc b phn sinh sn v tnh cao; (xi) nu l c a nin, d b t ri thnh nhiu mnh nh do khng th ko ht cc b phn sinh sn v tnh di mt t ln mt cch d dng; (xii) c kh nng canh tranh vi cc loi khc bng nhiu cch (mc vng, tn l rng, pht trin ln t cc loi khc v tit ra cc cht c ch sinh trng).

Tiu chun quan trng xc nh mt loi thc vt no c phi l c di hay khng l ti mt vi ni vo thi im no loi thc vt c cn tr cc hot ng ca con ngi v gy tn hi n li ch ca h hay khng.

1.2. TC HI CA C DI

C di xut hin mi ni, mi lc v l mi quan tm ca tt c mi ngi. C di khng ch gy cn tr hot ng sn xut nng nghip v lm gia tng chi ph sn xut m cn nh hng n sc khe ca cng ng v gy kh khn cho vic bo tr cc cng trnh xy dng, nh ca, cnh quan

Theo ti liu ca FAO, thit hi do c di gy ra hng nm trn th gii c th nui sng 100 triu ngi mi nm. Kt qu nghin cu ca t chc mi trng "Land Care of New Zealand" cho thy c di gy ra thit hi 95 t la M mi nm do lm gim sn lng lng thc thc phm trn tan cu trong khi bnh cy, cn trng v cc ng vt c xng sng (khng k con ngi) gy tn tht 85,46 v 2,4 t la M. Vi thi gi hin nay, 95 t la c th mua c 380 triu tn la m, hn phn na sn lng la m tan th gii d kin t c trong nm 2009. Trong s 95 t th c khong 70 t thit hi gy ra cc nc ngho.


Nhng s thit hi v kinh t c th ln hn na nu tnh n kha cnh l hn phn na thi gian m nng dn lao ng trn ng rung l dnh cho cng vic nh c.

1.2.1. Lm gim nng sut cy trng, gia tng chi ph sn xut

C di tranh chp cc iu kin sinh sng ca cy trng (nh sng, nc, dinh dng v cardon dioxide) dn n lm gim nng sut cy trng. Tuy nhin, ty theo nhng iu kin khc nhau m c di lm cho nng sut cy trng gim nhiu hay t.

S hin din ca c di trn ng rung cn lm tng chi ph sn xut, bao gm: thuc tr c, chi ph phun v ri thuc tr c, chun b t, trng trt v chm sc, dng c tr c v thi gian lm c

Bng 1.1. Thit hi do c di gy ra cho mt s loi cy trng ti n Cy trng Nng sut l c

dit c (t/ha) Nng sut l

khng dit c (t/ha) T l gim nng

sut (%)

u phng 132,4 87,6 33,8

Bp 34,4 20,7 39,8

La 37,5 21,9 41,6

u nnh 29,1 20,2 30,5

Ma 948,0 623,2 34,2

La m 23,7 19,9 16,0

1.2.2. C di tit ra cc cht ha hc c ch s sinh trng, pht trin ca cc loi thc vt khc (allelopathy)

Mt vi loi c di c kh nng hn ch s cnh tranh ca cc loi khc bng cch tit ra cc ha cht c hi c ch s sinh trng, pht trin bnh thng ca cc loi thc vt khc gi l hin tngallelopathy (s cm nhim qua li). s sinh trng, pht trin ca cy trng gim mnh trong nhng trng hp ny.

V d: c tranh, loi c ph bin trn t thot nc km, cn tr kh nng ti sinh ca rng (Anjum et al. 2005), lm c ch s pht trin ca u Stylo Stylosanthus guyanensis (cy thc n gia sc), k ui chn Setaria italica, c ba l Medicago polymorpha v thng Pinus roxburghii (Anjum et al. 2005). Ngi ta cng thy rng chit xut r ca c lng vc v c gu Cyperus rotundus nh hng tiu cc lm gim kh nng ny mm ca ht v kh nng tng trng ca chi mm v r bp (Hamayun et al. 2005). Hay nh r ca loi c Broomrape c th tiu dit u v rau xanh, khng ch lm tht thu v thu hoch , m cn lm cho t mt kh nng canh tc trong nhiu nm.

1.2.3. C di l k ch ca su bnh v chut

C di l ni tr n ca su bnh hi v l ni tr n ca chut. Cc loi c di cng h, b vi cy trng l k ch rt tt ca su bnh hi trn nhng cy trng tng ng.


C lng vc Echinochloa crus-galli l k ch ph ca nm Colletotrichum graminicola gy bnh thn th, Cercospora fujimaculans gy bnh m l, Exserohilum monoceras gy ri l, Rhizoctonia solani gy bnh ho cy con v Ustilago crus-galli gy bnh than en, ry nu hi la Nilaparvata lugens.

C g (c ch) Cynodon dactylon l k ch ca nm Puccinia graminis gy bnh g st, Helminthosporium sp. gy bnh m l, Bipolaris, Gaeumannomyces, Leptosphaeria sp., Marasmius sp., Sporisorium, Sorosporium sp., Ustilago sp., Xanthomonas cynodontis, virus gy bnh vng ln la mch, bnh virus sc l la v bp, cc loi tuyn trng, c bit l tuyn trng nt sng Meloidogyne spp., su t Spodoptera spp., su ko mng Herpetogramma licarsisalis

K ch ph ca b xt en (Scotinophora sp.) l c mm Ischaemum rugosum, c bc Leersia hexandra v c ui chn Setaria aurea

Ci di l k ch ph ca di c r ci bp.

1.2.4. nh hng n cht lng nng sn

- C mt s loi c di nu gia sc n phi s lm gim cht lng sa v tht (Parthenium, ti di lm gim cht lng tht v sa v c th lm cho sn phm khng tiu th c).

- Nui cu ly lng th trn ng rung c cy k u nga, ht c dnh vo lng cu lm gim cht lng lng cu thng phm.

- Ht ca cy ci du hoang (Brassica spp.) ln trong ht la m, bt m xay ra c mi ci du hoang, ngi tiu dng khng chp nhn.

- Ht c Parthenium ln vo ht ging c lm thc n gia sc lm gim cht lng ht ging v b cm trao i bun bn nhng vng cha b nhim loi c ny.

- Ht c lng vc ln trong thc go lm gim gi tr thng phm ca thc go.

- Ht v on gy ca thn c c m cao ln trong ht cy trng sau thu hoch, tip tc h hp lm cho ht nng sn nng ln v c th b thi.

- nhng rung cy trng c ln c di, hm lng dinh dng ca sn phm b gim st.

1.2.5. Gim hiu qu ca qu trnh thu hoch

- Thi gian thu hoch b chm li i c cht kh

- Lm chm tc ca qu trnh thu hoch, c bit thu hoch bng c gii

- Gy tn tht nng sn trong khi thu hoch

- Mt c di cao cn lm tng chi ph bo h lao ng trong khi thu hoch.

1.2.6. nh hng n sc khe gia sc

- Mt s loi c cha hm lng rt cao cc cht nh alkaloid, tanins, glucosides, oxalates, nitrates gy c cho gia sc khi tiu ha chng.


V d: + Hm lng amino acid, mimosine c trong cy mai dng Mimosa pigra gy c cho khng ch gia sc m cn cho c cy trng.

+ Cc loi c thuc h kinh gii Chenopodium, dn Amaranthus bnh thng th khng c nhng trong iu kin mi trng bt li, cc loi c ny tch ly mt lng ln cht nitrate (c th ln ti 1000 ppm). Trong qu trnh tiu ha trong c th ng vt, nitrate bin thnh nitrite gy c cho gia sc.

- Gai nhn, l sc ca mt s loi c di cn gy tn thng cho gia sc (to di, c tranh, dn gai, trinh n, mai dng ). Gai nhn ca cy mai dng lm tn thng c quanh h Tr An.

1.2.7. nh hng n sc khe con ngi

- C gy nh hng trc tip n sc khe con ngi nh gy thng tch v d ng. Cc loi c phn hng Ambrosia spp. gy bnh st c kh do c cha protenin gy d ng Amb a1. Mt s loi c gy ng c cho con ngi v c th gy cht nu n phi: da di Datura stramonium, lu lu c Solanum americanum. Mt s loi c c gai nhn (to di, dn gai, trinh n, mai dng ), mc (c may ), l sc (cc loi c h ha tho) d gy thng tch cho con ngi khi tip xc.

- C cn l ni tr n, cung cp thc n v ni sinh sn ca cc vector truyn bnh, cc loi gm nhm, rn, rt, V d: bnh ng do rui Tse-Tse chu Phi gy ra, chng sng v sinh sn mnh cc bi c. Bnh st rt, st xut huyt v mt s bnh khc do mui truyn. Bo Pistia lanceolata cung cp ch tt cho mui. Lc bnh Eichhornia spp. cung cp oxy qua r toiu kin tt cho lng qung ny n v sinh trng.

1.2.8. Gy nhim v cn tr ngun nc

- C lm gim cht lng nc, cn tr dng chy v giao thng ng thy, gy kh khn cho sn xut thy sn. V d: Cc cm bo ci Pistia stratoidescn tr s trao i kh trong mt phn gii nc-khng kh, iu ny lm gim lng xy trong nc v git cht nhiu loi c, chng cng ngn cn s chiu sng v git cht nhiu loi thc vt sng ngm di nc, cng nh lm thay i cng ng thc vt sng ni trn mt nc bng cch chn p chng.

- C di lm mt nc trong h mt cch nhanh chng. V d: lc bnh thot nc qua l rt ln. Tng lng nc bc thot trn mt h c lc bnh bng 130 250% so vi mt h sch c.

- C cnh tranh ngun dinh dng ca cc vi sinh vt trong nc (l ngun thc n ca thy sn), tit ra cc kh v cc cht hu c phn hy, gy bt li cho s sinh trng ca cc loi thy sn. Vic thu hoch thy sn s gp kh khn v tht thot ln trn din tch mt nc c nhiu c.

- Cn tr tm nhn trn b mt ao h.

- Cht hu c phn hy t c to mi kh chu gy nhim khng kh.

1.2.9. nh hng n cng nghip v cc cng trnh cng cng

- D gy chy cho cc khu cng nghip trong ma kh


- Gy hao mn, h hng cho my mc khi hot ng tip xc vi c.

- Mc leo ln tng, hng ro, che chn tm nhn ca con ngi, che khut cc ng ng dn, cc van, ng lm nh hng n dy in, dy in thoi

1.2.10. Gy thit hi cho rng v cc sn phm lm bng g

C di cnh tranh nc v dinh dng vi cy rng lm cho cy rng sinh trng cn ci.

Cc loi cy bi v c di khng c gi tr kinh t ln t cc loi cy rng c gi tr kinh t khc.

Lm gim gi tr gii tr ca cc khu rng

D gy chy rng trong ma kh.

1.3. LI CH CA C DI

Nhng tc ng tch cc ca c di i vi sn xut v con ngi t c quan tm, nghin cu hn so vi nhng tc ng tiu cc ca chng. Nhng tc ng tch cc ny rt kh nh lng v chng din ra trong mt khong thi gian di. C di cng c mt s li ch nht nh sau:

Lm tng thm cht hu c v mn cho t. Trong qu trnh sinh sng, c di tch ly vo tng t cy cc cht dinh dng nh N, P, K, (thng c nhng tng t su v trong nc ma). Trn t mi khai ph, lng bn ny c ngha rt ln.

Trong mt s trng hp, c di gip cy trng pht trin tt. Chng hn nh ti mt s vng t kh hn n 3 loi c Arnebia hispidissima, c nt o Borreria articularis v Celosia argentea gip cy k sinh trng pht trin tt nhng li hn ch s sinh trng v pht trin ca cy m (vng).

Gi cho t khi b xi mn, lm cho t v dinh dng khi b tri i; gi cho cc cng trnh thy li, giao thng nh iu khi b h hng

L ngun thc n cho cc loi gia sc nh tru, b, nga, cu v cc loi gia cm nh ngng, vt, g ty, v c.

Cc loi c nh ci, c gng, c dy, c tranh cn c dng lm cht t, lm nguyn liu lp nh.

Nhiu loi c cn c dng lm dc liu v cc mc ch khc. V d: bo ci cha chng st pht ban, ph thng, nht v tr mui (phi kh v t nhng ni c nhiu mui); rau sam (Portulaca oleracea) dng lm thuc st trng tr nhng chng l lot ngoi da, lm tiu nht c v lm li tiu trong chng tiu but, tiu rt, tr ho, lao phi, gii c rn hoc cn trng cn; cy trinh n (Mimosa pudica)c tc dng c ch thnh kinh, chn kinh, gim au.

Trng lm cnh: ng sc, xng rng, mo g, l bn, n ngy, dm bt


Nh vy, c di nh hng hai mt n nng nghip v i sng ca con ngi, va c hi va c li do ty tng trng hp c th m phng tr trit chng hay li dng chng lm nhng vic c ch khc.


CHNG 2. PHN LOI V NH DANH C DI

2.1. CC HNH THC PHN LOI C DI

C khong 250.000 loi thc vt n hoa trn th gii (Radosevich et al. 2007), trong c khong 250 loi gy thit hi c bit nghim trng cho trng trt (Holm et al. 1977). Nu mi mt loi c di i hi mt bin php kim sot c bit th con ngi khng th no kim sot chng mt cch kinh t. May thay, nhiu loi c phn ng tng t i vi mt bin php dit c do c s tng ng v chu k sng, sinh l v hnh thi. iu ny gip chng ta khi qut ha hiu qu ca cc bin php phng tr tng nhm c di thay v trn tng loi c lp. D nhin, khi xp nhm th s c mt s ngoi l v trng lp.

C di c th c phn loi theo nhiu cch khc nhau tin vic lp k hoch v nh gi kt qu kim sot c di. Sau y l mt vi cch phn loi c di ph bin trn th gii.

2.1.1. Phn loi theo kh nng thch ng vi hm lng nc trong t

22..11..11..11.. C a cn:

Nhm ny gm cc loi c sng trn t trng cy trng cn, trn t i dc v nhng ni c m t di 100% m tng i. V d: c gu (Cyperus rotundus), c rau mui (Chenopodium oleracea), rau sam (Poturlaca oleracea)

22..11..11..22.. C chu hn:

Thuc nhm ny l nhng loi c thch m nhng c kh nng chu hn c trong mt thi gian thi gian tng i di (1 ma kh 6 thng). V d: c tranh (Imperata cylindrica), c may (Chrysopogon aciculatus), c su rm (Setaria viridis), c ui chn (Setaria spp.)

22..11..11..33.. C chu nc:

Nhng loi c ny thng sinh trng ni t cn nhng khi m tng ln qu m bo ha chng vn c th sinh trng pht trin bnh thng c. V d: mt s loi c h ci nh lc m

22..11..11..44.. C a nc:

Nhng loi c thuc nhm ny pht trin mnh t bo ha hoc c mc nc trn mt t

C sng ni trn mt nc: bo ong, bo tm

C c thn l khng vt ra khi mt nc: cc loi rong nh rong l h, rong ui ch ...

C c r cm su vo t v thn l vt ln khi mt nc: c lng vc, da nc, c ci lc v c h trch t


2.1.2. Phn loi theo thi gian sinh trng v theo ma v xut hin

22..11..22..11.. C nht nin (annual): rau dn, lu lu, rau mui

Loi c ny kt thc chu k sng trong vng 1 nm nhng thng thng trong vng 1 ma. Ch c ht l qua c ma ng. Loi ny c chia lm 2 nhm:

a. C ma ng:

Ny mm vo u ma ng, ra hoa kt ht v cht vo cui ma xun

L loi c c tnh chu hn v chu lnh

b. C ma h:

Ny mm vo ma xun v kt thc ton b chu k pht trin vo u ma ng

Xut hin vo ma nng, m, ma nhiu

Ty Nguyn, c di chu nh hng rt nhiu bi 2 ma ma v nng. Hu ht cc cy hng nin u ny mm vo u ma ma v cho ht vo ma nng.

Vic phng tr c nht nin tng i d thc hin v t tn km. Tt nht l tm cch phng tr chng trc thi k m hoa kt ht. Nh vy, ht c s b o thi trc khi chng c hnh thnh hay thnh thc.

Nhiu loi ht c b chn vi lu nm trong t m vn gi c sc ny mm. Khi gp iu kin thun li chng c th ny mm thnh cy con. Do vy, vic tr c cn phi c tin hnh lin tc nhiu nm th mi c hiu qu trit .

22..11..22..22.. C nh nin (biennial)

C kt thc chu k sng trong vng 2 nm: sinh trng dinh dng trong nm u v sinh trng sinh thc trong nm sau. Tuy nhin, iu ny cn ty thuc vo mi trng sng, c khi chng kt thc chu k sng trong vng 1 nm nhng cng c khi ko di ti 3 nm.

S lng loi c di thuc nhm ny t hn nhiu so vi c thuc nhm nht nin v a nin. Thuc nhm ny gm cc loi: c ba l ngt sweet-clover Melilotus albus (h u), Echinospermum (h Vi voi Boraginaceae), nodding thistle Carduus nutans (h Cc Compositae).

C nh nin phi c kim sot ngay trong nm u, trc khi chng c c hi tch ly dinh dng trong r.

22..11..22..33.. C a nin (perennial)

C a nin thng c thi gian sng trn 2 nm vi nhiu hnh thc sinh sn. C a nin thng ra hoa u tin vo nm th 2 sau th ra hoa hng nm.

C a nin rt kh phng tr v chng sinh sn va bng ht va bbfd cc c quan sinh sn v tnh. Vic nhn bit cc hnh thc sinh sn ca c a nin l rt quan trng nhm la chn bin php thch hp kim sot s pht trin v ti sinh ca c.

Cc loi c a nin


a. C a nin thn tho n gin: Cc loi c thuc nhm ny sinh sn ch yu bng ht. Sinh sn v tnh ch xut hin khi r v thn b ct ra bng c hc, mi phn b ct ra sau s ra r v tr thnh cy mi. V d: rng nha (Taraxacum officinale), m (Plantago major)

b. C a nin thn c/r c (tuberous stem/ tuberous root): Nhng loi c ny c thn ngm hoc r phnh to thnh c, trn c c nhng mm ng li ln. C c th ra r v nhng di thn/r ngm mi, ti nhng thn/r ngm ny li c th c nhng c phnh to ra thnh c. v d: c gu Cyperus rotundus, c gu n Cyperus esculentus, thc dc, cy mao lng (Ranuculus spp.)

c. C a nin thn b (runner or stolon): Cc loi c thuc nhm ny lan truyn khp mt t bng thn b v bng ht. Thn rt ngn vi nhng l vy mng. Thn pht trin theo chiu ngang bn trn mt t. Mi u thn s cho ra mt cy con, cy ny s mc r v bm vo t. T cy con ny s ny ra mt thn b, b c mt on thn ny li cho ra mt cy con mi. Lng ca thn b c th cht i hoc b ct t m chi mi c hnh thnh vn sng c lp. Thn b khng cha thc n d tr m ch chuyn thc n t cy m sang cy con cho n khi cy con pht trin y . V d: rau m (Centella asiatica), me t (Oxalis repens).

d. C a nin thn r (rhizome): thn pht trin theo chiu ngang bn di mt t. Thn ngm c nhng mm ng v r t thn. T nhng mm ng ny c th mc thnh nhng thn ngm mi hoc thn ng mang l trn mt t. thn ngm c b l mc t bo v mm ng. Cc loi c ny c h thng r rt pht trin. V d: Cirsum arvense, rau dip di Sonchus arvensis, c tranh Imperata cylindrica, c gng Panicum repens, c g Cynodon dactylon (L.) Pers., c dy (Hemarthria compressa),

e. C a nin thn hnh (bulb): nhm ny chim t l rt t. C ca chng l bin thi ca thn, c cu to ging c hnh, hnh cu, bn trong cha ng phi mm ca mt cy y gm r, thn, l v hoa. cc k vy mng nc ca thn hnh hnh thnh nn nhng hnh con. V d: lily, tulip,

f. C a nin thn gi hnh (corm): c do thn phnh to to thnh, c v c bao bc bi lp l kh bn ngoi c dng hnh vy. Trn c gi hnh c cc t v lng. V d: layn, ngh ty, lan Nam Phi,

Trn t canh tc nhiu, c nht nin v c ngn ngy thng xut hin v pht trin mnh trong khi c a nin th ngy cng t i.

2.1.3. Phn loi theo phng thc sng

22..11..33..11.. C di k sinh

a. C k sinh hon ton: nhng loi c sng nh hon ton vo mui khong v cht hu c do cy ch cung cp nh dy t hng (Cucusta)

b. C bn k sinh: l nhng loi c c th t tc mt phn cht hu c, nhng loi c ny c l xanh nh cy tm gi


22..11..33..22.. C di khng k sinh:

Phn ln c di thuc nhm ny, chng c cc c quan dinh dng t tng hp cht hu c cn thit cho qu trnh sng.

2.1.4. Theo s l mm

22..11..44..11.. C 1 l mm: gm cc loi c thuc h ha tho, ci lc

a. C ha tho (grasses)

t c, lng rng, thn trn hoc dp

Thn khng c s phn ha ra min v v min tr

C h r chm do r chnh khng pht trin.

L thng khng phn bit cung, nhiu khi c gc pht trin thnh b. L thng c li b v i khi tai l. L n mc i ni tip l kia t t. L di v hp, gn l song song. L sc, c nhiu lng.

nh sinh trng c bc kn trong b l.

Phi c 1 l mm

Hoa thng mu 3, i khi mu 2, rt t khi mu 4, khnmg c mu 5

b. C ci lc (sedges/rushes)

Thn thng hnh tam gic v c rut.

Khng phn bit b l v phin l. L khng c tai l hoc li b. L nh trn thn theo 3 hng t 3 pha quanh thn. Phn gc ca cc l hnh thnh mt ng bao quanh thn. L di v hp, gn l song song. L mm v mng.

nh sinh trng c bc kn trong b l.

C mt s loi c di mt l mm nhng c nhng c im khc trn: c trch t hay m nc (Alisma plantago-aquatica L. var orientalis).

22..11..44..22.. C 2 l mm: rau dn, rau dic, c hi

L thng, rng, nm ngang, mm v t lng.

L thng c cung, gn l hnh mng li.

C h r tr do r chnh pht trin, vi cc r bn.

nh sinh trng l ra ngoi.

Phi c 2 l mm

Hoa mu 5, i khi mu 4

Thn c s phn ha ra min v v min tr

C 1 l mm khng 2,4-D (thuc chuyn v bit tnh), trong khi c 2 l mm th b nhim.


2.1.5. Phn loi da theo c im thn cnh

Ty thuc vo s pht trin m g trn thn v nhnh, c c th c chia thnh cc nhm: c thn tho, thn g, thn bi, thn bi leo v thn leo.

22..11..55..11.. Cy thn tho:

Cc loi c thuc nhm ny c thn nm trn mt t, thn cy khng ha g, cht li vo thi k to qu. Vd: m , c mn tru.

22..11..55..22.. Cy thn g:

Cc loi thuc nhm ny sng nhiu nm, c thn sinh trng th cp ha g, thn chnh pht trin mnh, trn thn chnh phn cnh v chi mang vm l. Thn chnh ca cy g to, nh, cao, thp, c cnh nhnh nhiu hay t ty thuc vo tng loi. Vd: bch dng Populus alba, n trinh t Ligustrum lucidum

22..11..55..33.. Cy bi:

Thuc nhm ny gm cc loi thn g nhiu nm, thn chnh khng c hoc km pht trin, cnh nhnh bt u t gc ca thn chnh. Chiu cao ca cy bi thng khng vt qu 7m. Vd: ng sc (trm i) Lantana camara, mai dng (trinh n thn g, trinh n mc) Mimosa pigra

22..11..55..44.. Cy bi leo:

Nhm ny gm nhng cy bi c cnh ha g da vo nhng cy khc leo ln.VD dy bng giy Bougainvillea spectabillis.

22..11..55..55.. Cy leo:

Nhm ny gm cc loi c tua cun mm, khng mc thng ng c phi da vo cc cy khc hoc vt khc lm gi th (nh cc c quan c bit nh tua cun, dy mc, r ph, nhnh hoc l). Vd: bm bm

Vic phn bit c thn tho v thn bi, thn g l rt cn thit trong cng tc qun l c di v bin php kim sot cc nhm c ny hon ton khc nhau.

2.1.6. Phn loi theo mi trng sng

Da vo ni chng xut hin, c c chia thnh 9 nhm ln:

a. C trn t canh tc

b. C trn t b ha

c. C trong ng c

d. C trn t khng trng trt (t cng nghip)

e. C thy sinh

f. C trn t rng v cy ly g

g. C trn thm c v vn


h. C trong n in

i. C trong vn cy n tri v vn nho.

Mt s loi c trng lp trong cc nhm trn. Tuy vy, vic phn nhm theo mi trng sng ca c rt quan trng v trong mi mi trng sng khc nhau, bin php tr c c th khc nhau mc d tiu dit cng mt loi c.

2.1.7. Theo h thng phn loi thc vt

Phng php phn loi ny thng c dng trong cng tc nghin cu. Nn tng c bn phn loi thc vt l h thng phn loi, nh danh v nhm thc vt da vo cc c tnh chung ca chng. Theo h thng phn loi thc vt, c di c chia thnh b, h, chi, loi. n v phn loi c s l loi (species). Loi l tp hp ca nhiu c th cng xut pht t mt t tin chung, tri qua qu trnh u tranh sinh tn v chn lc t nhin m cch ly vi cc sinh vt khc, cc c th ny c th giao phi t nhin vi nhau sinh ra cc th h con ci c kh nng sinh sn. Nhng loi c tnh cht ging nhau, c t tin chung tp hp li thnh mt n v ln hn gi l chi (genus), nhiu chi ging nhau hp thnh h (family), nhiu h ging nhau hp thnh b (order).

l nhng bc phn loi chnh, i khi ngi ta cn dng cc bc trung gian nh: di loi c th, dng, gia chi v loi c lot hay dy, gia h v chi c tng, hay cc bc ph c ghi bng cch thm cc tip u ng sub- (phn hay di) ch cc bc trung gian thp hn, hoc super- (lin hay trn) ch cc bc cao hn; v d: lin b, lin h, phn lp, phn h

Phn ln c di thuc ngnh thc vt c hoa Anthophyta (hi kn, n hoa), tuy nhin, cng c vi ngoi l (dng x: khng ht; thc vt hnh nn; nhng thc vt c ht nhng khng c hoa cng c th c coi l c di.

2.2. CC PHNG PHP PHN LOI C DI

Cc phng php phn loi u da trn nguyn tc sau: nhng thc vt c chung ngun gc, c nhng tnh cht ging nhau. Thc vt cng gn nhau th tnh cht ging nhau cng nhiu. S ging nhau c th v c im hnh thi, gii phu, sinh l sinh ho, phi sinh hc,... do c rt nhiu phng php nghin cu khc nhau trong phn loi c di k c vic s dng cc k thut n gin n cc phng tin thit b ti tn, gm cc phng php sau:

2.2.1. Phng php hnh thi so snh

y l phng php phn loi da vo c im hnh thi, c bit l hnh thi c quan sinh sn (v loi c quan ny t bin i hn so vi c quan sinh dng khi iu kin mi trng thay i) phn loi v nh danh c di. Nhng thc vt cng gn nhau cng c nhng c im chung v hnh thi. y l phng php c in nhng hin nay vn c dng ph bin v l ch yu. Hin nay, ngoi nhng c im hnh thi bn ngoi ngi ta cn dng c nhng c im hnh thi gii phu hay vi hnh thi (micromorphologie), tc l hnh thi cu trc bn trong c th, ca m, ca t bo, k c cu trc siu hin vi, phn loi. Xu hng ny ngy cng c ch .


2.2.2. Phng php gii phu:

Phng php ny tuy cha chim u th nhng l phng php chnh xc v khch quan, cho php xc lp mi quan h thn cn khng nhng cho cc bc phn loi cao nh lp, b, h m cn cho c cc bc phn loi c bn nh chi v loi. Dng phng php gii phu cc nh phn loi hc c th nghin cu quan h chng loi ca nhiu nhm thc vt. V d: cy Hai l mm phn bit vi cy Mt l mm bi cu to v s sp xp ca m dn truyn trong thn.

Phng php ny b sung thm cho phng php hnh thi so snh.

2.2.3. Phng php bo t phn hoa:

Nghin cu bo t, ht phn, c bit l hnh thi v ht phn s cung cp nhiu dn liu, nht l cc dn liu c thc vt, cho vic xy dng h thng chng loi pht sinh.

2.2.4. Phng php t bo hc:

Nghin cu s lng, hnh thi v cu trc ca nhim sc th.

2.2.5. Phng php lai ghp:

xc nh mi quan h thn cn ca cc loi gn, v chng ta bit rng s lai to ch xy ra nhng loi c quan h h hng mi lai to c v con ci sinh ra mi c th pht trin bnh thng.

2.2.6. Phng php sinh thi:

Phng php ny c ngha trong nghin cu s bin d ca loi do nh hng ca iu kin sng, c nhng loi sng ven bin, c nhng loi sng trn ni cao

2.2.7. Phng php ha sinh hc:

Cc nh thc vt nhn thy rng cc loi cy c quan h gn nhau thng c cc qu trnh sinh ho ging nhau dn n tch t mt s hp cht ho hc ging nhau. V d: cc loi thuc h C ph thng cha caffein, cc loi thuc l cha nicotin, cy thuc h Hoa mi thng cha tinh du, nhiu cy thuc h Thu du cha cht cao su

Phng php ny c ngha thc tin rt ln, n cho ta hng tm nhng hp cht cn thit trong cc loi gn gi nhau.

2.2.8. Cc phng php khc

Phng php min dch s dng cc phn ng ca cy ch i vi s xm nhp ca nm hay vi khun k sinh. T s ging nhau ca cc phn ng ca cc cy i vi nm k sinh m cc nh phn loi c c nhng dn liu c gi tr v mi quan h ca cc loi .

Phng php a l thc vt hc xc nh quan h h hng da trn vic nghin cu khu phn b ca thc vt.

Phng php pht trin c th da trn c s ca quy lut pht trin c th xt on quan h ngun gc ca thc vt.

Phng php h tr nh xc sut thng k, phng php phn tch tng quan.


Vic nghin cu phn loi khng th ch da vo mt phng php no m phi dng kt hp nhiu phng php khc nhau gii quyt, nh vy nhng kt lun mi tha ng v gn vi chn l. Cc phng php nu trn cung cp nhiu thng tin, c im quan trng cho cc nh phn loi hc khi tin hnh xc nh mt taxon nht nh trong th gii sinh vt.


CHNG 3. C IM CA C DI

3.1. C IM CA C DI

Mc d c di c nh ngha ty theo nhn nh ca con ngi ch khng ty thuc vo h thng phn loi, chng c mt s c im ni bt c th phn bit vi cy trng v thch ng vi nhiu iu kin khc nghit ca mi trng sng tn ti

3.1.1. C di c nhiu hnh thc sinh sn

C di c th ra hoa kt ht quanh nm, lun hin din trn ng rung gy tr ngi cho cc hot ng sn xut ca con ngi. S a dng v hnh thc sinh sn ca c di chnh l mt trong nhng nguyn nhn gip chng c th thch ng vi cc iu kin t nhin lun c mt trn ng rung.

C a nin sinh sn v tnh c th hnh thnh cy mi t cc t thn, nch l, thn ngm, thn c, thn r v chi r, thm ch, c loi c c th pht trin thnh 1 cy mi t 1 mu l (cy l bng).

Nhiu loi c va sinh sn hu tnh va v tnh lm cho kh nng lan truyn cng mnh v mi khi iu kin t nhin thay i th c t nht mt hnh thc sinh sn lan truyn v sau. Do vy, mun phng tr c di trit th cn phi ngn chn mi hnh thc sinh sn ca chng.

Vd: C c (Cyperus rotundus) v c tranh (Imperata cylindrica), 2 loi c mc rt ph bin trn t canh tc v cnh tranh gay gt vi cc loi cy trng, c th sinh sn va bng ht va bng thn ngm.

C g (Cynodon dactylon), c a nin h ha tho, mc khp cc vng, c th sinh sn bng ht, thn b v thn ngm.

3.1.2. Kh nng nhn ging cao

Kh nng ny th hin qua s ht sinh sn hu tnh v s mm ng sinh sn v tnh

Stevens (1932) m s ht 101 loi c nht nin th thy chng c trung bnh 20.832 ht/cy, 19 loi c nh nin c trung bnh 26.600 ht/cy, 61 loi c a nin c trung bnh 16.629 ht/cy.

S lng ht/cy ca c di nhiu, m bo cho chng c h s nhn ging cao, c li cho duy tr ni ging; ng thi cng cho chng ta thy tr lng ht c di trn mt n v din tch s rt ln, e da vic sn xut nng nghip.

S lng mm ng trn mt on thn hoc trn mt n v trng lng c di sinh sn v tnh cng nhiu hn so vi 1 on thn cy trng c cng chiu di hoc trng lng, do kh nng nhn ging ca c di cng rt cao.

Vd: s mm ng trn 1 m chiu di thn c l: 25-40 (c dy), 50-100 (c g), 100-120 (c tranh) trong khi 1 m dy khai lang ch c t 20-30 mm ng.


Bng 3.1 . Kh nng sinh sn ca mt s loi c ph bin Tn Vit Nam Tn khoa hc SL ht/cy

C gu n Cyperus esculentus 2.400 C lng vc Echinochloa crus-galli 7.000 C ui co Setaria faberi 10.000 C c rt (c phn hng) Ambrosia artemisiifolia 16.000 Mn tru Eleusine indica 41.200 Rau dn Amanthus viridis 50.000 C bng ln; C bng hi Eragrostis cilianensis 82.000 Rau dn r Amaranthus retroflexus 117.000 Th l c Solanum nigrum 178.000 Rau sam Portulaca spp. 193.000 C ma k sinh Striga asiatica 500.000

3.1.3. Ht chn khng u, d rng v c nhiu hnh thc lan truyn

Sau khi chn xong, ht c li d ri khi cy m v rng xung t. Hin tng ny km theo hin tng chn khng u lm cho c di ko di thi gian phng thch ht dn n hin tng c mc mm khng tp trung, gy kh khn v tn km cho cng tc phng tr.

C di c th pht tn bng nhiu con ng: (i) ht ging, thc n gia sc, rm r v c kh; (ii) gi; (iii) nc; (iv) ng vt; (v) my mc, nng c Do chng c th lan truyn t rung ny sang rung khc, t ni ny sang ni khc bt chp con ngi tm mi cch ngn cn s pht trin ca chng. Ngi ta pht hin c s xm nhp ca c di t Chu u sang Chu M v ngc li, t lc a u, sang Chu M, i Ty Dng v Thi Bnh Dng. Do vy, phi tm cho c ngun gc ca c di xut pht t u th mi c th xut bin php phng tr c hiu qu.

Cc c im gip c di c kh nng pht tn rng ri:

Ht nh v nh

Qu v ht c nhiu b phn ph nh ru, lng, mc, cnh gip chng d dng pht tn bng nhiu con ng.

C di c hnh thi bn ngoi ging vi cy trng

C di cn l ngun thc n cho gia sc.


3.1.4. Ht c di c thi gian ng ngh (min trng)

Ht c di li c th gi sc ny mm trong thi gian tng i di, to nn mt ngun ht c lin tc trong t gy kh khn v tn km cho cng tc phng tr c di. iu ny l do chng c thi gian ng ngh (min trng) nht nh. C 2 kiu min trng:

33..11..44..11.. Min trng di truyn (ng, ngh t nhin)

Sau khi tch ri khi cy m, ht cn mt thi gian ng ngh nht nh th mi c th ny mm. y l thi gian cn cho s bin i, hnh thnh phi mm, phi nh mt cch y . Ht c min trng loi ny l do c im di truyn, hon ton khng ph thuc vo nhng yu t bn ngoi. Thi gian ng ngh ca ht l thi gian ti thiu cn thit cho s ny mm sp ti.

S ng ngh t nhin ca ht do nhiu nguyn nhn:

Ht chn sinh l cha y

Trong ht cha cc cht km hm, hm lng nhng cht ny gim n mc khng gy c ch th cn phi c mt thi gian nht nh.

V ht qu dy do kh thm nc v kh.

33..11..44..22.. Min trng cm ng (ng ngh bt buc)

Khi bn thn ht khng c c tnh ng ngh t nhin hoc ht thi gian ng ngh t nhin nhng vn cha th ny mm th hin tng ny gi l min trng cm ng (induced dormancy)

S ng ngh bt buc ca ht do nhiu nguyn nhn gy ra:

Nhng cht c ch xm nhp t bn ngoi vo bn trong lp v ht nhng cha n mc gy cht.

Ht c b chn vi di su

V ht qu dy

Khi nghin cu v mi quan h gia s trng thnh ca ht ging v s ng ngh, ny mm ca ht, ngi ta thy rng:

Ht ging cha trng thnh th cn c thi gian ng ngh trong khi ht ging trng thnh th khng.

i vi nhiu loi c, mc chn ca ht khng nh hng n s ng, ngh v ny mm ca ht.

3.1.5. Ht c di c kh nng gi sc ny mm trong khong thi gian di

Ht c di c kh nng gi sc ny mm lu hay ni cch khc chng c th ko di thi gian ng, thi gian sng chm trong cc iu kin mi trng khc nhau lu hn cy trng.


33..11..55..11.. Kh nng gi sc ny mm trong t

Kh nng gi sc ny mm ca ht c khi b chn vi trong t rt khc nhau, c loi ch gi c sc ny mm trong 8 thng nhng cng c loi sau khi b chn vi trong t 80 nm, t l ny mm vn cn gi mc 70% (Verbascum blattaria) (Ross & Lembi 1999).

Bng 3.2. Kh nng gi sc ny mm ca mt vi loi c trong t (Ross & Lembi 1999) Tn Vit Nam Tn Latinh Kh nng gi sc ny

mm (nm) C sa thng Asclepias syriaca 3 La min ngt Sorghum bicolor 10 C bng Agropyron repens 1 - 6 K u nga Xanthium strumarium 16 K ng Cirsium arvense 21 Rau dn r Amaranthus retroflexus 40 C voi Pennisetum Alopecuriodes 20 Hoa phi nh Verbascum blattaria 100

33..11..55..22.. Kh nng gi sc ny mm trong nc ngp

Kh nng gi sc ny mm ca ht c cng khc nhau ty thuc tng loi. Vd: ht ngh (Polygonum convolvulus) v lu lu (Solanum sp.) c th gi sc ny mm c 8 thng; ht rau gin (Amaranthus paniculatus) v lu lu c (Solanum nigrum) c 20 thng; ht lng vc cn (Echinochloa cruss-galli) v rau mui (Chenopodium album) gi sc ny mm c 44 thng.

Mc d ht c c th gi sc ny mm trong nc kh lu nhng khi ngm vo nc th thi gian gi sc ny mm u gim so vi ngoi khng kh v trong t. Do vy, ti ngp l mt trong nhng bin php lm hn ch s ny mm v ph hy ht c.

33..11..55..33.. Kh nng gi sc ny mm trong phn chung

Ht c di sau khi qua d dy ng vt vn c th ny mm c. Tuy nhin, ty c im tiu ha ca tng loi ng vt m t l ny mm ca ht c c s khc nhau. T l ht c ny mm c sau khi qua h tiu ha ca b l 23,0 %, ca nga l 12,9 % ca cu l 10,7 % (Kott 1947).

Ht c ln trong phn mc c hay khng l ty thuc vo nhit , m cc cht ha hc v vi sinh vt trong ng phn .

V ma h, ht c trong ng phn u thng mt sc ny mm.

Nu 2 thng lin nht 30-50oC th cc ht c s cht; 30oC th ch c 1 phn ht c b cht; 10oC th tt c ht c u c th ny mm.

Thi gian cng lu th ht c di cng t i.


Kh nng gi sc ny mm ca ht trong mt thi gian di cng vi kh nng sinh sn cao ca loi m bo rng mt khi c di c thit lp ti mt ni no , n s t tip tc ti hnh thnh. iu ny gii thch cho vic ti sao mmt loi mc d c kim sot tt trong vi nm li bng dng tr thnh loi c chnh trn ng rung thay i cc bin php kim sot hay hoc h thng canh tc hoc l khi c di c a ln lp t mt

3.1.6. Ht c di ny mm khng u

Vic kim sot c di s rt n gin nu tt c ht v chi mm ca cng mt loi c ny mm cng lc. Vic p dng cc bin php kim sot ngn khng cho c di ra hoa kt ht s gip loi b hn loi c ra khi ng rung. Th nhng, cng tch ri khi cy m v ri xung t mt thi gian nhng c ht mc trc, c ht mc sau. Hin tng ny gi l hin tng ny mm khng u.

Nguyn nhn ca hin tng ht ny mm khng u:

Ht chn khng u

V ht dy, mng khc nhau do kh nng thm nc v kh phc v cho qu trnh ny mm khc nhau.

Do cy c nhiu loi ht khc nhau. Chng hn nh cy rau mui (Chenopodium album) c 3 loi ht: ht to v nu mc ngay trong nm u tin; ht nh, en v xanh mc vo nm th hai; ht rt b, trn v en mc trong nm th ba.

Do iu kin ngoi cnh khc nhau: ht oc phi nng lu th s rn chc v do , kh thm nc v kh; ht b chn vi vo lp t su th s ny mm chm hn ht trn b mt t.

Do thi gian ng, ngh khng u

Hin tng ny mm khng u cng thng thy cc loi c c hnh thc sinh sn v tnh. Vic chia ct c di ra lm nhiu mnh lm cho mm ng c hm lng cht kch thch mc kch thch v ny mm ng lot hn so vi nguyn 1 on thn di hoc nguyn c.

C di mc khng u, mc lai rai vo nhiu thi gian khc nhau lm cho trn ng rung lc no cng c s hin din ca chng gy tn km v kh khn cho vic xc nh thi k tr c c hiu qu. V vy, cn nghin cu nhng nguyn nhn lm cho c mc khng u v nhng iu kin cn thit cho s ny mm ca c c bin php tc ng tch cc kch thch cho c mc ng u v nhiu, lm tng hiu qu phng tr c di.

3.1.7. C di c tnh bin ng ln

Tnh bin ng ca c di l phn ng ca c di vi mi trng xung quanh c th sinh trng, pht trin v tn ti.


33..11..77..11.. S thay i thi gian sinh trng, thi k pht dc

Cc loi c hng nin thng c thi gian sinh trng t vi thng tr nn th s ra hoa kt ht nhng nu iu kin ngoi cnh khng thun li th thi gian sinh trng ca chng c th rt ngn ch cn 20-30 ngy.

Trong iu kin nh sng, m v dinh dng, trong khi cc loi c di hng nin sinh trng mnh, kt ht nhiu; cc loi c a nin sinh trng thn l mnh v gim vic kt ht.

Trong iu kin mi trng qu kh v nng, c di c th ra hoa, kt ht nhiu ln trong mt nm nh c lng vc cn, c Ranphanus raphaniotrum.

33..11..77..22.. S thay i v sinh trng v hnh thi

Trn rung la m gieo dy, c su rm Setaria glama ch c mt thn nh v mt bng nhng cng gieo la m tha, c sinh trng cng mnh, thn c th cao ti 7 cm v cho 200 bng/cy v kt 10.000 ht.

Trong trng hp s cnh tranh t (mt tha), cc nhnh c nm xe ngang xung quang gc thnh hnh trn c ng knh ln ti 1 m, bnh thng cc nhnh chm li mc thng ng hoc hi nghing nh c mn tru (Eleusine indica) v c lng vc cn Echinochloa cruss-galli. S thay i ny lm cho c di sinh trng mnh hn v cho nhiu bng v ht hn.

33..11..77..33.. S bin i v sinh l

Biu th bin i sinh l c di m ngi ta thy c l s thay i yu cu v nc. C lng vc nc c th sinh trng trn t m v ngp nc, c g nc pht trin trn t ngp nc v t kh. t ngp nc cao, thn l ca chng mc ln theo mc nc ch khng b c ch do ngp su v thiu xi. t cn, chng vn c th sinh trng v pht trin tt.

Khi iu kin ngoi cnh thay i, sinh l v hnh thi ca c di cng thay i. Trong iu kin kh hn, phn ln c di bin i hnh thi nhm hn ch qu trnh bc thot hi nc nh: c b r n su hn, trn thn l xut hin lp sp dy v cht hn, trn l xut hin nhng lng cng, l hp i.

Hiu c tnh bin ng ca c di rt c ch trong cng tc phng tr. Thng qua k thut canh tc, chng ta c th to iu kin ngoi cnh bt li cho c di duy tr chng mc sinh trng ti thp, khng gy hi cho cy trng.

3.1.8. Kh nng chng chu cao

C di c kh nng chng chu vi cc iu kin ngoi cnh bt thun tt hn cy trng. y l kt qu ca qu trnh thch nghi v chn lc t nhin lu i.

33..11..88..11.. Kh nng chu lnh

Mt s loi c di c kh nng sng v duy tr ni ging ngay c khi nhit xung n mc -40oC hoc thp hn. Quan st cc loi ny, ngi t thy chng c mt s c im sau:


Ra hoa, kt ht trc ma rt khc nghit. Khi gp rt, c di dng ht, c v dy bo v phi mm khi b rt

Sng tim sinh khi iu kin nhit xung thp

33..11..88..22.. Kh nng chu nng

C di c mt s c im sau gip chng chng chu trong iu kin thi tit nng nc:

H s thot hi nc ln, thn l cha nhiu nc gip gim thn nhit khi nhit tng cao

Thn l c nm lp t su gip chng khng b hi v nng (c tranh Imperata cylindrica c thn ngm nm lp t su nn vic t la khng lm cho cc b phn ny b cht).

iu kin nhit trn 70oC trong 2-3 ngy, ht ca mt s loi c khng b mt sc ny mm, tri li, qua giai on ny nu gp iu kin thun li chng li ny mm nhanh hn.

33..11..88..33.. Kh nng chu hn

C di c kh nng chu hn tt do chng c mt s c im sau:

B r pht trin mnh, su v rng

L c cu to lm gim s thot hi nc: din tch l hp, l c lng, lp biu b dy, c sp mt l

Hm lng nc trong thn l nh, cy khng cn nhiu nc lc hn tuy nhin, cc qu trnh trao i cht vn khng b suy gim.

C kh nng to ht trong iu kin bt li ca mi trng. V d: trong iu kin thun li c rau mui Chenopodium album c th mc cao t 30 30 cm trc khi ra hoa kt ht nhng trong iu kin hn nng, cy ch mc cao khong 3 cm v to mt t ht trc khi cht.

33..11..88..44.. Kh nng chu ngp

Khi hm lng nc trong t tng ln nhiu, vt qu mc yu cu bnh thng ca c, chng thay i hnh thi, sinh l c th tip tc duy tr s sng. V d nh c lng vc nc v c g nc sinh trng trn t m nhng trong mi trng t ngp nc cao, thn l ca chng mc ln theo mc nc ch khng b c ch do ngp su v thiu xi. Ht v mm ng c di cng c th gi sc ny mm khi b ngm nc trong mt thi gian di.

3.2. C IM CNH TRANH CA C DI

Mi thc vt c mu xanh u cn nh sng, nc v dinh dng khong sinh trng pht trin. Do , khi c s hin din ca c di trong ng rung, s cnh tranh gia cy trng v c di xy ra mnh m, c bit l khi ngun cung cp mt trong cc dng cht ny b hn ch. Chng hn nh khi m t thp, triu chng qun l bp do thiu nc cc rung b


nhim c xut hin sm hn nhiu so vi cc rung bp sch c. Tng t, triu chng cy trng thiu dinh dng s th hin r rng hn trong cc rung b nhim c.

Kh nng cnh tranh nh sng, nc v dinh dng ca c di ph thuc vo nhiu yu t nh: thi im mc mm, hnh thc sinh trng v mt c trong rung.

3.2.1. Thi im c mc mm

Thi im ny mm ca c c ngha rt quan trng trong vic cnh tranh. Thc vt no xut hin trc s tn dng c ngun nc, nh sng v dinh dng trc sinh trng pht trin v do vy c c li th cnh tranh hn so vi cc thc vt mc sau . Hn na, s sinh trng ca nhng thc vt mc trc (s pht trin ca tn l hp th nh sng v ca h thng r ht nc v dinh dng cc tng t su) cn nh hng tiu cc n s sinh trng ca cc thc vt pht trin sau. Thc t, cy trng pht trin trc khi c di ny mm s c kh nng cho nng sut c th chp nhn c; ngc li, nu qun th c di c thit lp trc cy trng (trong trng hp khng lm t trc khi canh tc hoc cy trng c canh tc trn t ni cc loi c a nin thn ngm pht trin mnh m), nng sut cy trng s b nh hng ng k. Qun th c di c hnh thnh trc cy trng lm gim s sinh trng, pht trin khng nhng ca cy trng m cn ca c cc loi c di ny mm sau .

Bng 3.3. Giai on ng rung cn gi sch c sau khi gieo trng khng b nh hng n nng sut cy trng (Ross & Lembi 1999)

Cy trng Giai on cn gi sch c (tun sau gieo trng)

C di

Bp 4 ui co

u tng 4 5 Cc loi c nht nin

u c-ve 2 Rau sam

Hng dng 4-6 Cc loi c nht nin

Bng vi 6 8 Cc loi c nht nin

u phng 6 Dn ui chn, c ch trng

Hnh ty 12 Dn r , c ha bn

C ci 10 - 12 Cc loi c nht nin

S cnh tranh gia c di v cy trng din ra gay gt nht trong giai on khi cy trng cn nh. Chnh v vy, nng sut cy trng thng b gim mnh nu c di khng c qun l tt ngay t u v. Trong giai on u ca s pht trin, cy trng rt d b tn thng do tc ng tiu cc ca c di (cnh tranh nc, nh sng v dinh dng). Thc t, nu cy trng c kh khng canh tranh tt (tc tng trng nhanh, tn l rng) v rung c gi sch c trong giai on vi tun u sau khi gieo trng th cc loi c ny mm v pht trin ngay sau s nh hng t hoc khng nh hng n nng sut cy trng trong v . Chng hn nh nu cy c phn hng ny mm v pht trin cng lc vi cy u trng vi mt 1,5 cy/m hng u trng th nng sut u s gim 19- 20% nhng nu c ny mm khi u vo giai on 2


l kp th nng sut ch gim 4 9%. Cc cy trng khng c kh nng cnh tranh cao (c ci, hnh ty) th khong thi gian cn gi cho rung sch c phi ko di hn th mi khng nh hng n nng sut cy trng (10 12 tun).

Giai on cc trng ca s cnh tranh l mt khong thi gian ngn trong chu k sng ca cy trng m lc vic dit c t c hiu qu kinh t ti a. Nng sut cy trng khi c dit c trong giai on ny t tng ng vi nng sut cy trng khi c lm sch c sut v. Nhn chung, nu c di v cy trng ny mm cng lc, nng sut cy trng t b nh hng nht nu c di ch tn ti trong ng rung trong khong thi gian vi tun u sau khi ny mm. Khong thi gian vi tun tip theo (nu rung khng c dit c) l khong thi gian cy trng b nh hng nng n nht bi s cnh tranh ca c di. Khong thi gian ny oc gi l giai on cc trng trong cnh tranh (critical period). Sau giai on ny, s cnh tranh ca c di khng hoc t nh hng n nng sut cy trng. Giai on cc trng khng bt u ngay lc cy trng mc mm m ty thuc vo vng t c th v tng loi cy trng c th. Bit c giai on cc trng trong cnh tranh c ngha rt quan trng trong vic xc nh thi im cn p dng cc bin php tr c cho cy trng nng sut cy trng t b nh hng nht.

Giai on cc trng trong canh tranh c xc nh cho tng cy trng v nhm c di c th da trn 2 lot th nghim c bn:

Th nghim th nht: khng dit c. Trong cc th nghim ny, ngi ta cho php c di ny mm v pht trin trong rung cy trng trong nhng khong thi gian khc nhau trpng sut qu trnh sinh trng v pht trin ca cy trng. V d, ngi ta cho c mc trong rung cy trng trong khong thi gian t sau khi gieo trng n khi gieo trng c 1 tun; vo cui tun th nht, rung c tr c bng cch nh bng tay hoc thuc tr c. mt th nghim khc, ngi ta cho c mc trong rung cy trng trong khong thi gian t sau khi gieo trng n cui tun th 2 th p dng cc bin php tr c; cc th nghim khc, c ch c php mc trong 3 tun u, 4 tun u, 5 tun u, trc khi b tiu dit. Nng sut thu c trong cc th nghim loi ny cho php chng ta xc nh c khong thi gian m cy trng c th sinh trng pht trin cng vi c di m khng b nh hng v mt nng sut. y l thi im bt u ca giai on cc trng trong cnh tranh (Biu 1.2 (Ross & Lembi 1999) khi s cnh tranh t c di bt u pht huy tc ng v vic p dng cc bin php tr c l cn thit hn ch nhng tn tht v mt nng sut.

Th nghim th 2: dit c. Trong cc th nghim ny, rung c gi sch c trong nhng khong thi gian nht nh trong sut qu trnh sinh trng, pht trin ca cy trng. V d, rung c gi sch c trong vng 1 tun u, 2 tun u, 3 tun u, 4 tun u, 5 tun u, , trc khi cho c mc t do. Nng sut cy trng thu c t cc th nghim trong th nghim th hai ny gip chng ta xc nh c khong thi gian rung cy trng cn c gi sch c hn ch s tn tht v mt nng sut. y l thi im kt thc giai on cc trng trong cnh tranh.

Thi im l tng cho vic p dng cc bin php dit tr c di l thi im bt u giai on cc trng trong cnh tranh v tc dng ca cc bin php tr c phi di ngn


khng cho la c mi ny mm trc khi giai on cc trng kt thc th nng sut cy trng mi khng b nh hng.

Biu 3.1. Giai on cc trng trong cnh tranh

Giai on cc trng trong cnh tranh thay i ty theo tng loi cy trng v kh nng cnh tranh ca chng vi c di, mc nhim c, v c im ca ng rung. thng thng, giai on cc trng i vi cc cy trng ngn ngy nm trong khong thi gian t 1/4 n 1/3 thi gian sinh trng t khi gieo ging ca loi cy trng .

Trong mt s trng hp, giai on cc trng ca cnh tranh bt u ngay trc khi cy trng mc mm. l trng hp trn ng rung trng cc loi cy trng t c kh nng cnh tranh, trn ng rung b nhim c di nng hoc trn rung p dng bin php khng lm t nhng c di hin din v thit lp qun th trc khi cy trng c gieo cy. V d, nng sut bng vi (cy trng c kh nng cnh tranh va) gim 11.2%/tun nu c di khng c qun l kp thi ngay t u v. s cnh tranh ca c di sau tun th 9,5 tr v sau ch lm gim nng sut bng vi 0,2%/tun. Chnh v vy, vic tiu tr c di ngay t khi cy bng vi mi nh l vic lm ht sc cn thit nhm lm gim thit hi v mt nng sut. Nng sut khoai ty (kh nng cnh tranh tng i kh) bt u gim nu c quackgrass khng c kim sot bt u t ngy th 15 v ngy th 3 k t khi khoai ty mc mm trong ng rung c quackgrass mc vi mt thp v trung bnh. Trong trng hp mt c trong rung cao, giai on cc trng cnh tranh bt u ngay trc khi khoai ty nh mm. Trn rung p dng bin php khng lm t, c di phi c kim sat trc khi cy trng ny mm nhm lm gim kh nng canh tranh ca c di v hn ch tn tht v mt nng sut.

Trong mt s trng hp, c di pht trin mun cng c th gy gim nng sut cy trng. cy trng c gieo trng trong iu kin thi tit lnh c th khng phi chu s cnh tranh ca c di trong giai on u v cho n khi iu kin thi tit m dn lm cho c di


ny mm v pht trin hng lot mt cch nhanh chng. Hnh ty, mt loi cy trng pht trin chm v khng to c che ph t tt, l loi cy trng c kh nng cnh tranh km i vi cc loi c ny mm mun.

Cc loi c di ny mm mun tuy t nh hng n nng sut ca nhiu loi cy trng nhng li nh hng n cht lng ca cy trng, gy cn tr vic thu hoch nng sn v to ra ngun ht v chi mm ly lan cho cc v sau. Chnh v vy. vic a ra cc quyt nh qun l c di khng ch n thun da vo vic liu s c mt ca c di c gy nh hng n nng sut cy trng hay khng.

3.2.2. Hnh thc sinh trng

Hnh thc sinh trng (s pht trin h thng r, chiu cao cy, din tch l, phn cnh) v tc pht trin ca c di chu s chi phi ca gen v cc nhn t mi trng. Nu iu kin mi trng thun li (c bit giai on nh mm) cho php c di pht trin nhanh chng t chiu cao v xe tn ti a, chng s c nhiu li th cnh tranh hn cc loi c tc pht trin chm, thp cy v tn l hp. Mt vi loi c khng ch pht trin tn l rng m cn chu bng (k u nga Xanthium strumarium) do vy chng vn c th pht trin v to tn ngang ngay di tn cy trng. Kh nng sinh trng nhanh v chu bng ca cy c phn hng l nguyn nhn gy thit hi nng sut u tng mt cch nghim trng nu rung b nhim loi c ny.

Cc loi c kh nng sinh trng chm nhng xe tn nhanh (c thm Mollugo verticillata, rau sam Portulaca oleracea) l nhng loi c kh nng cnh tranh tt trong rung cc cy trng c kh nng sinh trng chm v t to bng (x lch, hnh, c rt ) nhng cnh tranh km vi cc loi cy trng cao cy v che ph t ln (bp, u nnh ). Cc loi c kh nng sinh trng chm nhng c tua cun (bm bm, m lng, t hng ) vn c th pht trin khi cy trng giao tn bng cch mc b ln thn cy trng.

3.2.3. Mt c

Mt c cng cao th tc ng ca chng n cy trng cng nghim trng

Bng 3.2. nh hng ca mt k u nga n nng sut bng vi v t ngt (Ross & Lembi 1999)

Bng vi t ngt

Mt c (cy/m hng)

Nng sut bng vi Mt c (cy/m hng)

Nng sut t ngt

Kg/ha % gim Kg/ha % gim

0

1.0

1.5

3.0

2810

1084

586

255

-

61

77

90

0

0.3

0.6

0.9

4808

3448

3175

2358

-

28

34

51


CHNG 4. PHNG PHP QUN L C DI

4.1. PHNG NGA C DI

Ngn nga s ly lan v xm nhim ban u ca c di l mt bin php u tin, quan trng v t tn km nht trong vic qun l c di. Phng nga bao gm cc bin php loi b kh nng xm nhp v thit lp qun th c mi mt vng. Bin php ny s em li hiu qu cao trong vic qun l c di nu c p dng ng lot trn din rng vi s hp tc cht ch ca cc nng h trong vng. Cng tc phng nga s ly lan v xm nhim ca c di c th c thc hin bng nhiu cch:

4.1.1. Kim dch thc vt

Kim dch thc vt l bin php s dng cng c php lut kim tra hng ha lu thng gia cc vng, min, quc gia nhm cch ly v ngn nga s ly lan ca cc loi c c hi. Cc loi C ma k sinh S.a (Striga angustifolia), C ma k sinh S.l (Striga asiatica), T hng Nam (Cuscuta australis), T hng Trung Quc (Cuscuta chinensis) l cc loi c tuy ch mi xut hin mt vi ni trn lnh th ca nc ta nhng kh nguy him, do vy vic kim tra hng ha lu thng nhm pht hin v cch ly cc l hng c ln cc loi c ny l mt vic lm ht sc cn thit nhm lm hn ch s ly lan ca chng sang cc vng khc.

4.1.2. S dng ht ging sch, khng ln c di

S ly lan ca c di do gieo trng cc ging cy trng ln c di l rt ph bin v quan trng. Ngn nga c di lan truyn bng con ng ht ging thng qua 2 cch:

44..11..22..11.. Sn xut ht ging khng ln c di

Cn p dng mi bin php duy tr tnh trng hon ton sch c cho rung nhn ging. Tp qun gi li mt phn nng sn trong v lm ging cho v sau cn phi hy b hon ton.

44..11..22..22.. Loi b ht c khi ht ging cy trng

Cng vic tch b ht c ra khi ging cy trng cn phi c tin hnh trc khi tn tr ht v trc khi gieo trng. Cc ht c sau khi c tch ra cn phi em i thiu thy bng xng hoc du, khng c ht c tip xc t trong mi trng hp.

Mt s phng php loi b ht c khi ging cy trng:

a. Sng:

y l bin php thng dng nht nhm loi b cc loi ht c c kch thc khc nhiu so vi cy trng. nhiu loi sng vi nhiu kch thc l khc nhau c s dng. trong my gt p lin hip, ht c c t ng tch ra khi nng sn v c ng trong mt bao ring.

b. Tch bng dung dch mui

Ht ca nhiu loi c c t trng khc nhau do vy c th dng dung dch nc mui nng 5 10% tch chng khi ht ging cy trng. ht cy trng nng nm di y cn ht


c di nh nn ni bn trn mt dung dch v c vt b. Sau khi x l bng nc mui, ht ging cn phi c ra k.

c. Gi my

Lung khng kh vi tc c nh c thi qua dng chy ca ht. Ht nh s c thi bay xa hn ht nng. Cc ht ny s c tch ra cc khay khc nhau.

d. Da c l

Nu ht c v ht cy trng khc nhau nhiu v hnh dng, ta c th to ra cc da c l vi hnh dng khc nhau hng tng loi ht c c th

e. Trc ln ngc chiu

Cc ht c nhm khc nhau s c tch ring ra bng cch s dng 2 trc ln ngc chiu c bc n nhm. Khi quay, cc ht nhm s c li theo trc ln cn c ht c b mt lng th khng.

f. Tch ht bng in

Mt lp ht ging mng c cho di chuyn qua mt vng c in th cao. S khc nhau v in tch b mt ht ging gip tch cc loi ht khc nhau.

g. Tch ht bng t trng:

Trn hn hp ht c v ging cy trng vi mt t bt st. bt st s c dnh chy yu vo b mt nhm ca ht c m khng dicnhs vo b mt lng ca cy trng. hnc hp ny c cho qua mt t trng, ht c b ht i v c dnh bt st.

4.1.3. Ngn nga c di xm nhp vo ng rung thng qua phn bn

Phn hu c l loi phn c nhiu mm mng c di do tp qun ca ngi dn l n nhiu xc b thc vt k c ht c vo hm phn nhm t c lng phn chung cng nhiu cng tt. Mun hn ch c mm mng ca c di khi bn phn hu c cn p dng cc bin php sau:

Khng dng cc loi c sinh sn v tnh lm cht n chung hoc trn thm vo cc phn khc nu cc bin php tip theo khng tiu dit sc sng ca chng.

Khng s dng cc loi c sinh sn hu tnh ra hoa, kt ht lm nguyn liu ch bn phn bn.

Cc loi thc n gia sc nu c ln ht c di th phi nu chn.

phn k trong vng 4 5 thng nhit 50 60oC tiu dit ht c ln trong ng phn .

S dng cc ha cht nh aerocyan amide (70% hydrated lime + 20.6% N2), methan, ammonium thiocyanate tiu dit ht c trong ng phn . Hot tnh ca cc cht ny s bin mt trong vng 6 8 tun.


4.1.4. Ngn nga c di xm nhp thng qua nng c, my mc v gia sc

Ngn khng cho gia sc di chuyn t vng rung nhiu c sang vng rung sch c.

Hn ch s di chuyn ca my mc v cng c sn xut trong thi gian ht c c kh nng ly lan.

Thit lp cc con ng nh dc theo ng di chuyn ca my mc, cng c sn xut (i vi quy m sn xut ln).

Ra dng c v phng tin trc khi di chuyn chng ra khi khu vc nhim c.

Khng a my mc, nng c vo hot ng trn ng rung ca mnh nu chng cha c v sinh sch mm mng c di.

4.1.5. Gi sch c khu vc quanh rung

Cc mnh t khng trng trt quanh rung l vng t thun li cho c di to ht v pht tn. Do vy, cn phi lm sch cc b rung, cc vng t trng quanh rung bng mi bin php. Vic dit sch c cc vng t ny l iu khng th v c th dn n hin tng xi mn, l b. Cch tt nht l thng xuyn pht quang b bi hoc s dng thuc tr c Glyphosan 480 DD (thuc tr c ni hp, hu ny mm, khng chn lc) x l cc khu vc ny.

4.1.6. Thng xuyn gim st ng rung

Cn theo di ng rung thng xuyn pht hin sm v x l kp thi cc loi c l mi xut hin trn ng rung. Khi pht hin cc loi c l cn o gc ln v dit trit , trnh ly lan.

4.2. KIM SOT C DI THNG QUA CC K THUT TRNG TRT

4.2.1. Xc lp qun th cy trng v cng lc cy con mnh

Qun th cy trng mc ng u sau khi gieo trng v cy con sinh trng pht trin khe, mau che kn mt t s khng c khong khng cho c pht trin. to c qun th cy trng ng u, cn tin hnh cc bin php sau:

Chn loi cy trng & ging ph hp

Gieo trng cc ging c t l ny mm cao

X l t & ht ging trc khi gieo (ph v min trng, kch thch ht ny mm)

S dng lng ht ging ti ho

Thi gian v phng php gieo trng ph hp

Dm cng sm cng tt nu cy b khuyt

Trnh gieo ht qu su khng cn thit lm chm s ny mm v cy con yu.


4.2.2. S dng ging c kh nng hn ch c di

Nhng ging cy trng cao cy, sinh trng nhanh v mnh giai on u, gc l tri rng, h thng r khe, kh nng nhnh cao c kh nng cnh tranh dinh dng v nh sng tt hn do c th hn ch qu trnh ny mm, sinh trng v pht trin ca c di tt hn nhng ging thp cy, gc l ng, nhnh km. Nhng ging mi hin nay c gc l ng cho php nhiu nh sng lt xung di tn l do c di c c hi ny mm v cnh tranh dinh dng vi cy trng tt hn. Nhng ging ngn ngy kh nng cnh tranh dinh dng km hn hn nhng ging di ngy. Hn na cc ging mi thng i hi thm canh cao ko theo vic s dng nhiu phn bn do vn c di cng nghim trng hn

4.2.3. Chn thi v & mt gieo trng thch hp

Trong mi vng sinh thi, cc loi c mc theo ma thng mc nhiu trong mt khong thi gian nht nh. Thi gian ny cng thng l thi gian ph hp gieo cc loi cy trng. C th trnh t c d di u tin bng cch gieo hi sm hn hoc mun hn thi v bnh thng.

Gieo trng vi mt hp l c ngha quan trng trong vic hn ch c di v tng nng sut v mt s xc nh vng tn v din tch che ph ca cy trng, do , quyt nh kh nng cnh tranh dinh dng v nh sng vi c di. Mt tha, khong cch rng s to iu kin cho nh sng lt xung nhiu hn do c di ny mm v sinh trng tt hn. Mt khc, mt hp l cng gip cy trng sinh trng tt v cho nng sut cao hn. Tuy nhin, mt gieo trng ti ho cn ty thuc vo nhiu yu t nh ging, ph ca t, ma v

4.2.4. Lun canh, xen canh, tng v

44..22..44..11.. Lun canh cy trng (Crop rotation)

Vic trng c canh mt loi cy trng lin tc trong nhiu nm trn cng mt din tch c th s dn ti vic tch ly ngun ht v chi mm c di trong t, to iu kin cho chng bo tn sc sng. Chnh v vy, lun canh cy trng l mt vic lm ht sc cn thit, lm thay i t ngt mi trng sng ca c di khin chng kh thch nghi v s b cht.

Bin php lun canh hu hiu nht l lun canh cy trng cn vi cy trng nc.

Lun canh gia cy ngn ngy vi cy di ngy cng c tc dng hn ch c di.

Khi p dng lun canh phng tr c di, cn lun canh vi nhng cy trng khc hn c di v c tnh thc vt cng nh c tnh sinh l.

44..22..44..22.. Xen canh (intercropping)

Vic trng xen cy ph gia cc hng cy chnh lm tng din tch l cy trng che ph t, lm cho c di thiu nh sng v cc iu kin khc ny mm vi s lng ln v b ln t khng gy hi cho cy trng. Cy trng xen phi l nhng cy mau che ph mt t hoc cao cy th mi em li hiu qu phng tr cao.


44..22..44..33.. Tng v

Canh tc nhiu v trong nm, lm t nhiu ln, thi gian mt t c cy trng che ph tng th c hi cho c di ny mm v pht trin gim. Nhng i khi tng v cng c th khng lm gim c c di, l trng hp tng v ch lm gim c di ngy, sinh sn v tnh cn c di sinh sn hu tnh, ngn ngy li pht trin mnh. Do vy, tng v phi i i vi vic canh tc nhng loi cy trng sinh trng nhanh, mau che kn mt t hoc tng v i i vi xen canh. Tng v c xen canh hoc tng v bng nhng cy phn xanh mc nhanh lm cho c di b ln t v tng thm lng phn xanh bi dng t.

4.2.5. Bn phn

C di v cy trng u s dng phn bn lm ngun dinh dng, do vic bn phn, c bit l phn m c nh hng ln n qun th c di. Ch phn bn hp l c th hn ch c di cng nh kh nng cnh tranh ca chng. Ch phn bn hp l khi gieo trng cc ging mi l khu ht sc quan trng v nhng ging ny yu cu phn bn nhiu hn cc ging c truyn. C di c kh nng cnh tranh dinh dng tt hn cy trng, do , trong trng hp rung nhiu c, vic s dng nhiu m khng nhng khng n b c thit hi v mt nng sut do c sinh ra m cn kch thch c sinh trng, lm tng kh nng cnh tranh dinh dng ca c vi cy trng. Nh vy, vic bn phn cho cy trng ch nn tin hnh trong iu kin qun l tt c di, ngc li s b phn tc dng. Bn nhiu m to iu kin cho c ha tho pht trin nhng t nh hng n c l rng v ci lc. Trong iu kin c di khng c qun l tt th khng nn bn phn hoc bn t khi c di gim kh nng s dng m (sau khi c ra hoa).

Bn vi lm thay i pH t, lm gim c di thch hp vi t chua: ci lc, rong ru rung ngp nc. bn vi khi c cha mc s lm gim t l ny mm ca c. Bn vi khi c mc lm c b h hi nhng khng hoc t gy hi cho cy trng. Nn bn sm lc c cn t, bn ri u, trnh ri vo cy trng.

Xianamit canxi cung cp m v canxi cho cy trng. Sn phm phn gii ca n (canxi xianamit axit & xianamit) c kh nng lm cho nguyn sinh cht t bo b kt ta, lm cho l thc vt b chy. Xianamit canxi dng tr c 2 l mm mi mc trn rung u, thuc l, khoai ty (phun trc khi gieo trng 10 14 ngy vi lng 1.5 2 t/ha).

4.3. KIM SOT C DI BNG BIN PHP VT L

4.3.1. Lm c

Bin php s dng cc cng c th s nh cuc, xng, dao, no, lim oc ng dn cc cp khc nhau trong vic kim sat c di. Sau , cc cng c ny c ci tin thnh nhng my n gin chy bng ng c nh hay y bng tay. Mc d tt kim c cng lao ng hn so vi cc cng c lm c bng tay thng thng nhng do cc cng c ny ch c th tin hnh c trn din din tch gieo trng thng hng hoc bng my nn phm vi ng dng ca chng b hn ch.

Tuy hn ch v mt nhn lc nhng bin php lm c bng tay cho hiu qu tr c cao v trit nht, hn ch gy tn thng n cy trng ng thi kt hp vi xi xo, ph vng


trong qu trnh nh c to iu kin cho cy trng sinh trng tt, do nng sut cy trng cao hn so vi cc bin php khc.

Hai vn quan trng ca vic lm c bng tay l s ln lm c v khong thi gian gia 2 ln lm c. S ln lm c ph thuc vo tc pht trin ca cy trng v c di v khong thi gian khng hong cnh tranh gia c di v cy trng. Khong thi gian gia 2 ln lm c ph thuc vo tc pht trin v ln chim ca c di i vi cy trng, thng l 15 20 ngy v nn chn ngy nng ro tng hiu qu tr c.

i vi cc loi c a nin c thn ngm nm su trong t, lm c bng tay s khng tiu dit oc chng v s mc li sau rt nhanh.

Bin php lm c bng tay cn c nhc im l ch c kh nng p dng trn ng rung ni cy trng c gieo trng thng hng, ngc li, bin php ny d gy tn thng cho cy trng, c bit l giai on cui.

4.3.2. Lm t (tillage)

Cc hot ng lm t nh cy, ba, trc, san phng mt rung u trc tip hoc gin tip tiu dit c di c bit l c a nin.

Thng qua cc hot ng cy t, ht c cng nh cc c quan sinh sn b vi xung tng t su lm cho chng b cht hoc mt sc ny mm

u im ca lm t l: (i) tiu dit nhanh v trit c di; (ii) dit c an ton (iii) tng cng s sinh trng ca cy trng; (iv)c th dit ton b cc loi c di. tuy nhin, khng phi lc no cng c th tin hnh lm t kim sat c di c, chng hn nh khi cy trng qu ln, gieo trng khng thn hng li, c bm cun vo cy trng, t qu m

4.3.3. Ngm nc rung

Cho nc ngp rung l mt bin php thng c s dng kim sat c trong rung la v c a nin b. iu chnh ch ti tiu hp l vn c th hn ch c s sinh trng v pht trin ca cc loi c a m trong rung la.

C quan sinh sn ca cc loi c a nin thn b cng c th b tiu dit khi ngm nc rung. Bin php ny ch c th thnh cng nu tng cy cht gi nc. Vi nhng rung c nhiu c a nin, vic gi rung ngp trong 15 25 cm nc lin tc trong vng 3 8 tun trong ma h s hn ch c mt s loi c di. Phng php ny ch c th thc hin c nhng ni c nc.

Phng php ny khng th p dng c vi tt c cc loi c di sinh sn v tnh v mm ng ca nhiu loi c di sng tim sinh v vn c th sng st sau khi b ngm ngp trong nc.

4.3.4. Dng la

Vic dng la phng tr c di c p dng khi trn ng rung khng c cy trng, lc khai hoang hoc lm t trc khi gieo trng.


Khi t la, nhit cao s lm ngng t hay phn gii nguyn sinh cht, lm h hi cc enzime. Nhit ti a m cc t bo thc vt c th chu ng c l l 45 55oC. Li dng tnh cht trn, ngi ta dng la tiu dit c di. La c th lm cht cc b phn trn mt t v mt phn cc c quan sinh sn v tnh v ht c di trong t. Phng php ny p dng trong ma kh sau khi thu hoch nng sn dit c v su bnh c trong tn d cy trng.

Phng php ny lun phi c km theo phng php cy ba th mi c kt qu cao, nu khng c di sau s tip tc mc tr li, c bit l c a nin c thn r ngm nh c tranh, c c, c ng s tr thnh b ch.

u im ca phng php:

- n gin, d lm v t tn km

- Tiu dit c cy c v cc ht c trn cy

- C th dit c nhanh chng trn mt din tch ln

- Tiu dit c mm mng su bnh gy hi cho cy trng

Nhc im:

- t chy ht cht hu c

- Khng tiu dit c hon ton c di, c bit l thn ngm v ht c trong t. Dit tr c nhiu c di ngn ngy nhng lm tng c di a nin c thn ngm di t

nng cao hiu qu ca t la trong vic kim sot c di, cn lu :

- t c vo ma kh, sau thu hoch hoc trc lc gieo trng

- Kt hp vi cy ba tiu dit thn ngm c di

- Trnh gy chy ly lan, c bit cn phng chy rng.

4.3.5. Che ph mt t (mulching)

Che ph mt t bng cc vt liu khc nhau c tc dng kim sot c di thng qua vic ngn cn khng cho nh sng lt xung mt t (i) ht v mm ng ca c di khng ny mm c; (ii) mm c mc khng nh sng ln ln v vt ra khi lp che ph. Vt liu che ph mt t c th l cc vt liu t nhin (rm r, c kh, bt giy, mt ca ) hay nhn to (giy hay mng ph polyethen, plastic mu en). Mun hiu qu th lp che ph phi dy ngn nh sng v hn ch quang hp.

44..33..55..11.. Che ph t bng cc vt liu t nhin:

Thm che phi dy t nht l10 cm.

u im:

- C th p dng cho bt k loi cy trng, loi t no

- Lp ph c ngun gc thc vt cn lm gia tng hot ng ca cc sinh vt trong t ng thi gi nhit t n nh, tng tc phn gii cht hu c, lm cho t xp, thong, cy sinh trng nhanh, pht dc sm t 10 15 ngy.


- nhng vng t nhim mn, phn, thm che c tc dng gim bc hi nc ng thi ngn mn v phn bc ln mt.

- Mt s vt liu sau khi che ph b hoai mc li tr thnh phn bn, tng hm lng dinh dng v xp cho t.

Nhc im:

- Khng khng ch c cc loi c da nin ngay c khi ph dy t 60 120 cm

- Cht che ph c ngun gc thc vt l cha mm mng cn trng, bnh hi v cn tr hot ng ca my mc

44..33..55..22.. Che ph t bng cc vt liu nhn to

Cc vt liu che ph nhn to nh giy plastic c thm du v khng thm du, tm nha do vi cc dy khc nhau ang ngy cng c s dng rng ri hn ch s pht trin ca c di. y l cc vt che ph dit c hon ho v an ton i vi cy trng.

Cht che ph tng hp hin ang c sn xut hng lot dng cun, c kch thc b ngang khc nhau ph hp vi nhiu loi cy trng. Tuy nhin, chi ph s dng tm nha cn cao nn ngi ta ch s dng cho cc loi cy c gi tr kinh t cao nh rau qu, cy cnh, trong sn xut cy ging, ht ging

4.4. QUN L C DI BNG BIN PHP SINH HC

Trn khp th gii, ngi ta ngy cng quan tm hn n cc bin php sinh hc (s dng sinh vt hay cc sn phm ca chng nhm ngn chn hoc gim bt thit hi do c di gy ra) kim sot c di, c bit l c mc di nc v cc phng php khc tn nhiu cng sc v t tin.

4.4.1. Cn trng dit c

Cn trng dit c l tc nhn sinh hc c s dng rng ri kim sot nhiu loi c nguy him trn th gii. Thnh cng u tin ca tc nhn sinh hc trong vic dit tr c di oc bit n vo nm 1902 trn cy trm i (ng sc Lantana camara) ti o Hawaii. Cc th nghim ch ra mt s loi cn trng rt hiu qu trong vic kim sot loi c ny, bao gm: (i) u trng ca Crocidosema lantana (bm su cun l) (c vo trong cung hoa, nm trn ca cm hoa v n hoa qu); (ii) u trng ca rui n ht Agromyza lantana n qu v lm cho qu kh hn ch chim mang ht i pht tn ni khc; (iii) u trng ca bm Thecla echion v Thecla bazochi ph hy hoa ngn khng cho cy kt ht, gim kh nng sinh sn. Nhng cn trng ny qu hiu qu trong vic kim sot Lantana camara n ni c di khng th xm ln mt ln na, ngay c khi t b b trng. Lantana camara cng c kim sot bi cn trng n , c v Fiji.

Thnh cng ni bt cng thu c trong vic kim sot cc loi xng rng Opuntia spp. ti c khi nhn th bm su c thn Cactoblastis cactorum (c ngun gc ti Argentina) v rp sp Dactylopius opuntiae (ngun gc Hoa K). u trng ca Cactoblastis cactorum o hm bn trong thn cy v ph hy ton b cc b phn trn mt t. Chng cng thm nhp v


gy hi cc b phn di mt t to iu kin d dng cho nm v vi khun tn cng tiu dit xng rng. Dy t hng Cuscuta spp., mt loi c di k sinh, cng c kim sat mt cch c hiu qu nh cc loi cn trng nh rui Melanagromyza cuscutae (k sinh chuyn tnh trn cc loi xng rng), mt Smicronyx cuscutae v Acro-clita spp.

S thnh cng ca cc tc nhn sinh hc trong vic kim sat c saphony Clidemia hirta li l mt trng hp th v khc. Mt ca loi c ny c kim sat thng qua vic kt hp tn cng ca b tr Liothrips urichi v s cnh tranh ca cc loi thc vt khc. B tr khng trc tip tiu dit c saphony m ch lm suy yu s sinh trng ca c to iu kin cho c loi thc vt khc trong vic cnh tranh vi c saphony.

C lo (yn bch Eupatorium adenophorum), mt loi c l rng ph bin ng Bc v Nam n cng c kim sot mt cch thnh cng nh mt loi mui Mexico to mn cy (gall fly) Procecidochares utilis c nhp khu t New Zealand nm 1963.

nc ta, Vin BVTV tin hnh nhn th thnh cng 2 tc nhn sinh hc l su c thn Carmenta mimosa tr cy mai dng Mimosa pigra v b cnh cng Neochetina bruchi tr cy lc bnh Eichornia crassipes.

4.4.2. Chn th gia cm

C di trong vn cy a nin c th c kim sot bng phng php th nui gia cm.

Vic s dng 1000 1.500 con vt/ha trong h thng canh tc la vt cho hiu qu phng tr c di cao hn so vi cng thc x l thuc dit c 2 ln/v.

4.4.3. Nm

Ngi ta phn lp c nhiu loi nm k sinh trn c. Cy keo du c th b tiu dit khi chch dung dch bo t nm Cephalosporious sp., nm Rhizoctonia sp. gy chy l trn lc bnh cng c nghin cu kim sot loi c di ny.

Hin nay, ti cc nc ng Nam , ngi ta nghin cu, phn lp v nh gi c tim nng tr c ca nhiu chng nm trn cc i tng c di khc nhau trong nm Exoserohilum monoseras c coi l c trin vng nht. dng thng phm du hay bt kh vi nng bo t trn 2,5.107 nm ny c th tr c trn 90% 3 loi c lng vc trong khi la non chi b cht khi nng bo t l 5.107. Nm Alternaria sp. Cng c coi l c trin vng tr c t Monochoria invisa.

4.4.4. Thuc dit c sinh hc (bioherbicides)

Thuc dit c sinh hc thng l vi sinh vt gy bnh c trong t nhin c phn lp, nui cy v nhn ln vi s lng ln p dng cho cc loi c m con ngi nh kim sat. Hin c 4 loi thuc dit c sinh hc c ang k tn thng mi v s dng rng ri l: DeVine (Phytophthora palmivora) tr c Morrenia odarata trn vn cam, COLLEGO (Colletotrichum gloesporioides) kim sat c Aeschynomena virginica trn la v u nnh, BIOMAL (Colletotrichum gloeosporioides var. malva) kim sot lai Malva pusilla (round-


leaved mallow) Canada v Hoa K v Dr.Biosedge (Puccinia canalicuta) kim sot c nng ngt Cyperus esculentus L.

4.4.5. Trng cy cnh tranh (Competitive crops)

C nhiu loi cy trng ny mm nhanh, tn l pht trin rng, hiu sut quang hp cao c th cnh tranh hiu qu vi c di, chng hn nh cy u b (cowpea), c linh lng (Medicago sativa L.), c ba l Ai Cp (Trifolium alexandrinum L.)

C nhng loi c cnh tranh mnh, mc rt nhanh v t nguy him cho con ngi hn cc loi c khc c trng v to iu kin ln t cc loi c nguy him hn. V d: c nng (Eleocharis acicilaris) thn thp, mc nhanh, c k

113274331 co dai va bien phap phong tru weed and control weed

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