Screening Of Synergist Formula And Its Control Effect On Cucumbe Downy Mildew

Cucumber downy mildew is one of the main leaf diseases in cucumber growing area worldwide.It occurs in every cucumber producing area in China.It has the characteristics of rapid occurrence and rapid epidemic.The occurrence of the disease of cucumber,yellow leaves,fruit small and early fruit or not uprooting death,seriously affecting the yield and quality of cucumber.In order to solve the downy mildew,it is the main approach to find a new fungicide or a new compound preparation with excellent structure innovation and excellent efficacy.Azoxystrobin and Dimethomorph in 1:1,2:1,2:3,3:1 and 3:2 mixed proportion of cucumber downy mildew showed synergistic effect,the EC₅₀ values were 0.34,0.30,0.35,0.26 and 0.33mg/L,the CO toxicity coefficient were 136.02,122.39,156.51,128.02 and121.26,of which two with the ratio of 2:3 synergism better.The field trial showed that 50%azoxystrobin Dimethomorph?20:30?WP in two years of experiment,and compared with control medicament showed significant control effect on cucumber downy mildew,the last drug defence effect reached 72.81⁹0.25%.Azoxystrobin and Dimethomorph mixture can significantly improve the control effect on cucumber downy mildew,50%azoxystrobin Dimethomorph wettable powder?20/30?recommended dose of 225³00 g/hm²,were evenly spray to control cucumber downy mildew in early onset.