| At present,the chemical control method is still the quickest and most effective method to control the Echinochloa crusgalli(L.)Beauv.and Leptochloa chinensis(L.)Nees.in the rice field,and the bispyribac-sodium and cyhalofop-butyl are two of the most commonly used herbicides that have advantages of high activity and low cost to control their.However,bispyribac-sodium is less safe for rice,use of cyhalofop-butyl for long-term,single and high-dose applications has led to problems such as decreased efficacy.In order to increase the efficacy of herbicides,ensure the safety of crops and reduce the spread of resistant weeds,the application of adjuvants has important theoretical and practical significance.GY-Tmax is a vegetable oil pesticide synergist that independently developed by Beijing Guangyuan yinong chemical limited liability company.Studies have shown that GY-Tmax has a good synergistic effect on herbicides such as nicosulfuron and atrazine in corn fields,but its synergistic effects on bispyribac-sodium and cyhalofop-butyl have been rarely reported.On the basis of previous studies,this study used E.crusgalli and L.chinensis as the target weeds,explored the synergistic effect of bispyribac-sodium and cyhalofop-butyl on the control of E.crusgalli and L.chinensis,as well as the safety of rice by using adjuvant GY-Tmax,and studied of its synergistic preliminary mechanism,aims to provide a theoretical basis for effective control of E.crusgalli and L.chinensis in rice fields.The results of the study are as follows:1.The synergetic effect of adjuvant GY-Tmax for bispyribac-sodium to controlling E.crusgalli and L.chinensis,as well as safety of rice:After treatment for 30 days,the ED90 value of the fresh weight of E.crusgalli was 3.6511 g a.i./667 m2.Added adjuvant GY-Tmax in bispyribac-sodium can significantly increase the herbicidal activity of the E.crusgalli,the ED90 value of the bispyribac-sodium on the fresh weight of the E.crusgalli was reduced to 0.9329 g a.i./667 m2.Bispyribac-sodium had poor efficacy against L.chinensis and the control effects have no change after added adjuvant GY-Tmax.Bispyribac-sodium was safe to three kinds of rice,and the selectivity index of three kinds of rice and E.crusgalli was between 1.14-1.31,after added GY-Tmax,it had no phytotoxicity to rice,but due to the ED90 value for E.crusgalli was dereased significally,the selective index of E.crusgalli between rice and E.crusgalli is increased to more than 4.Based on the synergistic mechamism of GY-Tmax,it was found that the surface tension of the bispyribac-sodium solution was decreased from 36.824-42.347 mN/m to 31 mN/m when the adjuvant GY-Tmax was added,the contact angle was also significantly reduced.,and the wetting performence of the liquid was significantly improved.In addition,GY-Tmax can also increase the retention of bispyribac-sodium solution on the surface of E.crusgalli leaves and the drying time is shortened.2.The synergetic effect of adjuvant GY-Tmax for cyhalofop-butyl to controlling E.crusgalli and L.chinensis,as well as safety of rice:after treatment for 30 days,the ED90 value of cyhalofop-butyl hebricide was 10.9035 g a.i./667 m2 for the fresh weight of E.crusgalli.After added adjuvant GY-Tmax 90 ml/667 m2,the ED90 value of cyhalofop-butyl decreased to 5.2311 g a.i./667 m2.The ED90 value of fresh weight of L.chinensis was reduced from 6.8400 g ai/667 m2 to 2.8736 g ai/667m2 after add adjuvant GY-Tmax.Cyhalofop-butyl is safe to three kinds of rice,and after added GY-Tmax,cyhalofop-butyl has no harm to them,but its selectivity index to E.crusgalli and L.chinensis is obviously improved.After the addtion of GY-Tmax to the solution of cyhalofop-butyl,the retention is increased on the surface of E.crusgalli and L.chinensis leaves,the contact angle gradually decreased with time,and the drying time was shortened.However,the surface tension value of the cyhalofop-butyl solution was relatively low.After added adjuvant GY-Tmax,the surface tension of the cyhalofop-butyl solution did not decrease significantly.In summary,this study revealed the synergistic effect of GY-Tmax,a vegetable oil adjuvant,on the control of bispyribac-sodium and cyhalofop-butyl,and further explained GY-Tmax’s mode of action from the perspective of improving the wetting properties This can provide insights for the use of additives GY-Tmax for the application of other pesticide formulations,and it can also provide theoretical support for the reduction of the use of bispyribac-sodium and cyhalofop-butyl to prevent and control weed hazards in the field. |
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