Study On Chemical Control Techniques Of Weeds In Wheat Fields With Fenoxaprop-P-Ethyl-Resistance Beckmannia Syzigachne As The Dominant Species

Beckmannia syzigachne is an annual or overage grass weedy weed,and rice/wheat or rice/canola rotation is the most serious in the middle and lower reaches of the Yangtze River.Fenoxaprop-P-ethyl is an ACCase enzyme inhibitor herbicide.It is widely used in wheat field to control grass weeds due to its high activity and wide herbicidal spectrum.However,its target is single.Long-term single use is generally increasing year by year,and the occurrence and development of Beckmannia syzigachne resistance is severe.So far,Beckmannia syzigachne cross-resistance problems is also common in other ACCase enzyme inhibitor herbicides,such as oxazolin and clodinafop.Therefore,ACCase enzyme inhibitor herbicides have not been effective to control with field fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.In order to screen out suitable herbicides that can be used in wheat field to control with fenoxaprop-P-ethyl-resistant Beckmannia syzigachne,this study used indoor whole-plant bioassay to determine the toxicity of non-ACCase enzyme inhibitors herbicides that control with annual weeds to sensitive and fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.The results show that:in the soil treatment herbicides,chlorotoluron,isoproturon,pretilachlor,acetochlor,oxyfluorfen,pendimethalin,imazamox and flufenacet have high toxicity to sensi-tive and fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.In stem and leaf treatment herbicides,chloromeron,isoproturon,mesosulfuron-methyl,pyroxsulam and amicarbazone have high or relatively high toxicity to sensitive and fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.The results of wheat safety studies indicate that pretilachlor,acetochlor,oxyfluorfen,pendimethalin,imazamox and amicarbazone is unsafe to wheat,and obvious phytotoxicity occurs after drug observation.Therefore,these herbicides cannot be used for wheat field to control with fenoxaprop-P-ethyl-resistant Beckmannia syzigachne.Because of the amount of chlorotoluron and isoproturon is relatively large,and the toxicity of mesosulfuron-methyl and pyroxsulam is relatively general in the stem and leaf treatment herbicides.In order to reduce the amount of herbicide and improve the toxicity,screening out the synergistic effect of stem and leaf treatment herbicides,and identifying the best synergistic dose,the best synergistic combination with herbicides and the synergistic mechanism are particularly important.In this study,two kinds of adjuvants were screened by indoor whole-plant bioassay:non-ionic surfactant Jijian and silicone auxiliaries Silwt806.At the same time,the synergistic mechanism was preliminarily clarified by measuring the physical indicators such as surface tension,contact angle,expanded diameter and maximum retention of the herbicide’s liquid.The results showed that the optimal synergistic doses of Jinjian and Silwt806 were 0.05%(v/v)and 0.1%(v/v).0.05%(v/v)Jijian combination with chlorotoluron 800 g a.i./hm2,isoproturon 800 g a.i./hm2,mesosulfuron-methyl 16 g a.i./hm2 or pyroxsulam 32 g a,i./hm2 have the best synergistic effect.0.1%(v/v)Silwet806 combina-tion with chlorotoluron 800 g a.i,/hm2,isoproturon 600 g q.i./hm2,mesosulfuron-methy1 16 g a.i./hm2 or pyroxsulam 32 g a.i./hm2 have the best synergistic effect.The research on the mechanism of synergistic effect on herbicides shows that the Jijian can significantly reduce the surface tension and contact angle,and significantly increase the expanded diameter and the maximum retention of the herbicide’s liquid.Therefore,Jijian can exert its synergistic effect by changing the physical properties of the herbicide’s liquid.In order to delay the production of herbicide resistance,expand the herbicide’s spectrum,reduce the herbicide use times in the field,and improve the control effect of herbicides,this study through the two highly toxicity herbicides flufenacet and pretilachlor mixture with diflufenican and metribuzin to screening formula and ratio.Among them,the binary combinations and the ternary combinations of herbicide adopt Gowing and Colby methods respectively.The results showed that the combinations have highly toxicity to fenoxaprop-P-ethyl-resistant Beckmannia syzigachne and Capsella bursa-pastor is.After that,by simulating the field efficacy test method,the difference between the different combination’s spectrums was studied.The results showed that flufenacet mixture with diflufenican(1:1.5)at the dose of 200-240 g a.i./hm2,flufenacet mixture with diflufenican(1:2)at the dose of 240-300 g a.i./hm2,flufenacet and pretilachlor mixture with diflufenican(1:2.5:3)at the dose of 260-325 g a.i./hm2 and flufenacet mixture with metribuzin(1:2)at the dose of 200-240 g a.i./hm2 have highly toxicity to fenoxaprop-P-ethyl and mesosulfuron-methyl-resistant Beckmannia syzigach-ne andAlopecurus aequalis,fenoxaprop-P-ethyl-resistance Alopecurus japonicas and Lolium perenne,sensitive Malachium aquaticum and Veronica persica.Pretilachlor mixture with diflufenican(1:1.2)at the dose.of 220-260 g a.i./hm2 and flufenacet mixture with diflufe-nican(1:1.5)early stem and leaf treatmentat at the dose of 300-360 g a.i./hm2 have highly toxicity to fenoxaprop-P-ethyl and mesosulfuron-methyl-resistant Beckmannia syzigachne and Alopecurus aequalis,sensitive Malachium aquaticum and Veronica persica.The wheat safety study of all combinations show that except the flufenacet mixture with metribuzin(1:2),several other combinations were safe for wheat.