Herbicide Screening For Controling Malignant Broad-leaved Weeds In Wheat Fields And Snsitivity Mchanism To Dfferent Herbicides In Veronica Didyma Tenore

Wheat is an important food crop in China,and the occurrence of farmland weeds seriously affects the yield and quality of wheat,while malignant weeds have the characteristics of wide distribution,fast propagation speed,strong resistance to conventional herbicides,and large occurrence area,they cause serious harm to wheat.In this paper,taking malignant broad-leaved weeds in wheat fields,such as Veronica didyma Tenore,Malachium aquaticum L.,Lithospermum arvense L.,Galium aparine L.,Brassica juncea L.,Geranium carolinianum L.,as research objects,The control effect of seven herbicides such ascypyrafluone on malignant broad-leaved weeds was studied using the method of combining the pot method in the greenhouse and the field efficacy test.On this basis,the research focused on the feasibility of mixing the new herbicides cypyrafluone with fluroxypyr,and the biochemical mechanism of the difference in the sensitivity of Veronica didyma Tenore to the herbicides,As a result,to provide theoretical basis formalignant broad-leaved weeds control in wheat fields.The main findings of this paper are as follows:1.Systematic determination of susceptibility of malignant broad-leaved weeds in wheat fields such as Veronica didyma Tenore to seven herbicides by greenhouse pot method.The results showed that at the lower recommended dose limit in the field,the corresponding weeds for herbicides with a control effect of more than 90%were:cypyrafluone is used for Veronica didyma Tenore and Brassica juncea L.,bipyrazone is used for Malachium aquaticum L.,Lithospermum arvense L.,fluroxypyr is used for Malachium aquaticum L.,Lithospermum arvense L.,Galium aparine L.,Brassica juncea L.,Geranium carolinianum L.,MCPA-sodium is used for Veronica didyma Tenore,Malachium aquaticum L.,Lithospermum arvense L.,Brassica juncea L.,Geranium carolinianum L.,pyroxsulam is used for Veronica didyma Tenore,carfentrazone-ethyl is used for Veronica didyma Tenore,Malachium aquaticum L.,Lithospermum arvense L.and bromoxynil octanoate is used for Malachium aquaticum L.and Brassica juncea L..It can be seen from the above that the control of hormonal herbicides fluroxypyr and HPPD（p-hydroxyphenylpyruvate dioxidase）inhibitors in the control of malignant broad-leaved weeds in wheat fields is somewhat complementary which is consided mixing the two.2.On the basis of the above research,this paper studies the indoor combined action of a new herbicide,cypyrafluone,and fluroxypyr.The results showed that the combined action type of cypyrafluone and fluroxypyr acid in a 1:1 ratio was synergistic or additive.The results of determination of the selectivity coefficients of the two mixed use showed that after mixing cypyrafluone and fluroxypyr acid in a 1:1 ratio,the five tested wheat varieties Shannong 16,Shannong 22,and Taikemai 33,Hongdi 95,Taishan 24,and three test weeds Veronica didyma Tenore,Malachium aquaticum L.,and Galium aparine L.have higher selectivity coefficients;After the combination of cypyrafluone and fluroxypyr acid at a ratio of 1:2,the four tested wheat varieties Shannong 16,Shannong 22,Hongdi 95,Taishan 24 and three test weeds Veronica didyma,Malachium aquaticum L.,and Galium aparine L.have higher selectivity coefficients,but for Taikemai 33 and Malachium aquaticum L.,and Galium aparine L.have higer selectivity coefficients,Taikemai 33 and Veronica didyma have lower selectivity coefficients.3.Taking Veronica didyma Tenoreas the research object,the synergistic effect of the P450s inhibitor malathion on different herbicides was determined.The results showed that after the malathion pretreatment,the GR₅₀ values of Veronica didyma Tenore pairs of seven herbicides all showed different levels of decline,the decrease is 1.76 to 3.21 times of the herbicide alone,indicating that P450s-mediated metabolism may be responsible for the difference in the sensitivity of Veronica didyma Tenoreone of the reasons.4.After pretreatment with the GSTs inhibitor NBD-Cl,the effect of Veronica didyma Tenoreon on the sensitivity of different herbicides was explored.The results showed that after the NBD-Cl pretreatment,the GR₅₀ values of seven herbicides in Veronica didyma Tenore all showed different levels of decline,the decrease is 1.66 to 6.20 times of the herbicide alone;CDNB was used as a substrate to determine the change of GSTs activity of Veronica didyma Tenore on different herbicides.The results show,the GSTs activity of the control group showed a small fluctuation within the measurement time,but the activity of GSTs showed the highest value on the first day after the treatment with pyroxsulam,and it showed a continuous downward trend,and the peak value was significantly higher than that of the control group;The activity of GSTs after treatment with six other agents except for pyroxsulam all showed a small fluctuation.The peak reached around the 5th day,and the peak value of the 5th agent treatment group was significantly higher than that of the control group.Comprehensive analysis shows that GSTs-mediated the metabolic effect of herbicides,and it is another reason for the difference in the sensitivity of Veronica didyma Tenore to different herbicides.5.Field efficacy test results show:cypyrafluone,carfentrazone-ethyl have higer control effects in the field of Veronica didyma Tenore and Descurainia sophia L..The field control effect of pyroxsulam on Veronica didyma Tenore was higher than that on Descurainia sophia L..And the field control effect of bipyrazone and bromoxynil octanoate on Descurainia sophia L.was higher than that on Veronica didyma Tenore.The field control effect of cypyrafluone and fluroxypyr is lower than that of cypyrafluone and higher than that of fluroxypyr.