Toxicity Determination And Field Efficacy Of Eight Fungicides Against Alternaria Solani

Nowadays,potatoes have been listed as the world’s major food crops,because they are rich in protein,starch,vitamins and other trace elements needed by the human body and have important food value and economic value.Potato Early Blight is a globally common disease on potatoes,which can seriously affect the quality and yield of potatoes when it breaks out.In this study,through the indoor mycelial growth rate method and two-year field efficacy test,eight kinds of test agents were screened out to control Potato Early Bligh,which provided scientific basis for the prevention and control of Potato Early Bligh.The results of mycelial growth rate in laboratory showed that eight kinds of test chemicals could inhibit the mycelial growth of Alternaria solani to varying degrees.The bacteriostasis effect of 42.4%pyraclostrobin-fluxapyroxad SC was the most remarkable.Its virulence regression equation was Y=0.9296X+4.7603,the correlation coefficient was0.9953,and the EC₅₀0 value was 1.81μg·mL^-1;the antibacterial effect of 75%trifloxystrobin-tebuconazole SC was second,and it’s EC₅₀0 value was 2.84μg·mL^-1;The inhibition effect of 33.5%oxine copper SC on Alternaria solani was the least obvious,and its EC₅₀0 value was 47.55 ug·mL^-1;The EC₅₀0 values of 44%difenoconazole-chrolothalonil SC,50%boscalid WG,500 g/L fluazinam SC,80%dithane z-78 WP and 250 g/L azoxys-trobin SC were 13.42μg·mL^-1,3.99μg·mL^-1,7.82μg·mL^-1,33.61μg·mL^-11 and3.74ug·mL^-11 respectively.The results of field efficacy test in Yan’an and Ankang for two years showed that compared with other test agents and control agents,42.4%pyraclostrobin-fluxapyroxad SC had significant control effect in prevention and treatment of Potato Early Blight in Yan’an test site and Ankang test site.Its control effect was obviously higher than that of other medicines,and the control effect of both sites was above 77%,with the highest control effect of 85%.250 g/L azoxys-trobin SC and 75%trifloxystrobin-tebuconazole SC had better control effect on Potato Early Blight.The control effect of the two places reached over 71%and the highest control effect could reach 81%.The control effect of 33.5%oxine copper SC on Potato Early Blight was poor.The control effects in Yan’an test site and Ankang test site were 52%-62%and 54%-62%respectively.Several other test chemicals had a certain effect in the prevention and control of Potato Early Blight.Taking into consideration the cost factor,we think 42.4%pyraclostrobin-fluxapyroxad SC,250 g/L azoxys-trobin SC,75%trifloxystrobin-tebuconazole SC and 50%boscalid WG could be used in potatos as the specific agents for the control of Potato Early Blight.When used,the dosage of each agent is 42.4%pyraclostrobin-fluxapyroxad SC 10 mL/mu-20mL/mu,250 g/L azoxys-trobin SC 40 mL/mu-50 mL/mu,75%trifloxystrobin-tebuconazole SC 10 g/mu-15 g/mu and 50%boscalid WG 20 g/mu-30 g/mu,respectively,and each agent should be applied continuously for 2 times at intervals of about 7 days or so.It should also be noted that different types of medicines should be used alternately in order to prevent disease resistance due to long-term use of the same medicament.