Study On The Resistance Of Echinochloa Oryzicola Vasing. To Butachlor In Rice Fields Of Heilongjiang Province

Heilongjiang province is the main rice producing area in China,and it’s rice production ranks second in our country.In recent years,the hazard index and harm area of Echinochloa oryzicola Vasing.in Heilongjiang province have risen rapidly.Echinochloa oryzicola Vasing.has become a malignant weed in rice fields after barnyardgrass,which does serious harm to rice yield.Butachlor has been used for more than 30 years in Heilongjiang province,and it’s effect is getting worse.Echinochloa oryzicola Vasing.in some areas has been resistant to butachlor.In this paper,the resistant level to butachlor and the cross-resistance to cell-division inhibitors have been detected by using Echinochloa oryzicola Vasing.biotypes from 53 plots in 14 areas of Heilongjiang province.The method of breaking dormancy of Echinochloa oryzicola Vasing.has been determined.The differences between resistant and sensitive biotypes in biological characteristics have also been compared.The damage level of rice caused by resistant and sensitive biotypes at different densities was cleared.The biological activities of resistant Echinochloa oryzicola Vasing.to non-cell division inhibitors were determined.We have also evaluated the effect of the mixture of cyhalofop-butyl and penoxsulam to Echinochloa oryzicola Vasing and clarified the optimum proportion of mixture.The main results are as follows:1.The resistant level to butachlor and the cross-resistance to cell-division inhibitors of Echinochloa oryzicola Vasing.（1）Echinochloa oryzicola Vasing.in Heilongjiang province has developed different resistant level to butachlor.The resistant level of Echinochloa oryzicola Vasing.to butachlor detected by Agar method showed that there are four biotypes such as Qingan03 and Dongjingchengzhen02 have developed a medium level of resistance,accounting for 7.55% of the tested biotypes.Four biotypes such as Xinglongzhen04 have developed a low level of resistance,accounting for 7.55% of the tested biotypes.Five biotypes such as Qingan01 are at the stage of decreased sensitivity,accounting for 9.43% of the tested biotypes.Other 40 biotypes such as Acheng02 are sensitive,accounting for 75.47% of the tested biotypes.The resistant level of Echinochloa oryzicola Vasing.to butachlor detected by Filter method showed that there are three biotypes such as Qingan03 and Dongjingchengzhen02 have developed a medium level of resistance,accounting for 5.67% of the tested biotypes.Five biotypes such as Wuchang01 have developed a low level of resistance,accounting for 9.43% of the tested biotypes.Six biotypes such as Qingan01 are at the stage of decreased sensitivity,accounting for 11.32% of the tested biotypes.Other 39 biotypes such as Acheng02 are sensitive,accounting for 73.58% of the tested biotypes.Using the whole plant method to confirm the resistant level of suspected biotypes determined by Agar method and Filter method.The resistant level is same by the three methods.This result indicates that Qingan03（R1）and Dongjingchengzhen02（R2）biotypes developed a medium level of resistance to butachlor and Acheng02（S）biotype is sensitive to butachlor.（2）R1 and R2 have developed cross-resistance to some cell division inhibitors.R1 developed cross-resistance to butachlor and pretilachlor.R2 developed cross-resistance to butachlor,pretilachlor and anilofos.2.The biological characteristics of Echinochloa oryzicola Vasing.（1）Soaking in chemical reagents（H₂SO₄,NaOH,KNO₃ and GA3）,manual processing and hot water treatment can break the dormancy of Echinochloa oryzicola Vasing.Among them,80℃ treatment is the most simple and practicable method of breaking dormancy.Soaking in H₂SO₄ for 40-50 min or in 2000mg/L GA3 for 48 h can break the dormancy of Echinochloa oryzicola Vasing.primely and promote the germination rate over 83%.Soaking in 0.0625% NaOH and 1% KNO₃ for 24 h or in 80℃ water or manual processing could break the dormancy of Echinochloa oryzicola Vasing.effectively,which could promote the germination rate of about 64.67% to 72.67%.（2）Resistant biotype and sensitive biotype of Echinochloa oryzicola Vasing.are different in biology.The emergence patterns of resistant and sensitive biotypes are essentially similar.The three biotypes are all emerging on the fourth day after sowing.The 6th day after sowing is the highest peak,at this time the number of germination of resistant biotype is more than that of sensitive biotype.The germination rate of resistant biotype is higher than that of susceptible biotype,and the difference is significant at 1% level.The germination rates of R2,R1 and S biotypes are 97.33%,95.33% and 76% respectively.The plant height,upper ground weight,tillers per plant,grains per panicle and thousand seed weight of sensitive biotype are higher than those of resistance biotypes after 75 days of sowing,and the differences are significant at 5% level.This indicates that the suitability of resistant biotype is lower than that of sensitive.（3）The competition on rice caused by sensitive biotype is higher than that of resistant biotype.With the increase of Echinochloa oryzicola Vasing.density,the plant height,tiller,effective panicle number,grains per panicle,thousand seed weight and rice yield are decreased.When the density of Echinochloa oryzicola Vasing.is same,the inhibition rate of plant height,tiller,effective panicle number,grains per panicle,thousand seed weight and rice yield caused by sensitive biotype are significantly higher than that of other two biotypes,indicating that sensitive biotype has stronger competitive ability to rice than resistant biotype.When the density of sensitive and resistant Echinochloa oryzicola Vasing.is 5 plants/m2,the inhibition rates of rice yield are more than 5%,which are significantly different from that of no grass control.When the density of Echinochloa oryzicola Vasing.is 40 plants/m²,the inhibition rates of rice yield are more than 50%.When the density of Echinochloa oryzicola Vasing.is 50 plants/m²,the rice can be reduced by more than 60%.Although the competition effect on rice of sensitive biotype is higher than that of resistant biotype,the effect of resistant biotype on rice yield is not much worse.The resistant biotype still has great harm.So the resistant biotype needs to pay enough attention.3.Screening of herbicides against resistant Echinochloa oryzicola Vasing.（1）Alternate using of non-cell division inhibitors such as penoxsulam can be used to control the resistant Echinochloa oryzicola Vasing.For the S biotype,the effect of quinclorac is poor and can not be used for rotation;the other eight kinds of herbicides which have good effect are bispyribac-sodium,thiobencarb,penoxsulam,pyribenzoxim,cyhalofop-butyl,oxadiazon,oxadiargyl and metamifop respectively,these eight herbicides can be used alternately in different types of herbicides.For the R1 biotype,the herbicides which have good effect are thiobencarb,oxadiargyl,metamifop,cyhalofop-butyl,quinclorac,penoxsulam and oxadiazon respectively.These seven herbicides can be used alternately in different types of herbicides.The effect of pyribenzoxim and bispyribac-sodium are not good and don’t recommend for rotation.For the R2 biotype,the herbicides which have good effect are thiobencarb,penoxsulam,quinclorac,oxadiargyl,cyhalofop-butyl and bispyribac-sodium respectively.These seven herbicides can be used alternately in different types of herbicides.The effect of oxadiazon,pyribenzoxim and metamifop are not good and don’t recommend for rotation.（2）Cyhalofop-butyl mixed with penoxsulam can be used to control resistant biology.Using the equivalent line method to evaluate the mixing effect,the optimum proportion of mixture is 4.5: 1.