Research On The Fungicides Screening And Chemical Control Of Potato Early And Late Blights

Potato early blight and late blight are two mainly aeroborne, epidemic diseases,which could cause enormous losses in the most potato main production areas inChina. At present, the chemical control is the most effective and simple method forthe diseases because of lacking resistant varieties. On the basis of fungicidesscreening in vitro, the chemical fungicides were further screened and chemicalcontrol programs were examined in order to obtain high control effect of fungicidesand chemical program on early and late blights and on controlling potato early andlate blights in the field. In addition, we also tested the sensitivity to three fungicidesof30isolates of Phytophthora infestans collected from Inner Mongolia in2013. Themain results of the study are as follows:1. Of screening seven kinds of fungicides, the control effect of threefungicides i.e. Azoxystrobin, Propiconazole· Azoxystrobin and Azoxystr-obin·Chlorothalonil were the best and their control percentages were98.9%,98.4%and97.6%, respectively. Yield increases on three fungicides were also obvious, theiryield increases were separately357.3kg/667m2,282.7kg/667m2and298.7kg/667m2and their increase percentages were separately were13.56%,10.73%and11.34%.2. Of three sets of chemical control programs, one set of program wasscreened to control potato early blight. This program needs sparing fungicides fivetimes in one growing season. The first time of spraying was at the beginning ofdiseases (June23), the interval of spraying was10-20d, and their spraying orderwas Mancozeb75%WG, Famoxadone68.75%WG, Azoxystrobin25%SC,Iprodione50%WP and Trifloxystrobin·tebuconazole75%WG. The last controleffect percentage was93.6%in this program. The mean yield/667m2of potato usingthis program was3085.4kg, the increase yield/667m2was346.8kg, and theincreasing percentage of commodity potato was11.67%, compared with CK. Theincrease economic income was￥268.9/667m2.3. Appropriate nitrogen amount in the soil had some control effect on potato early blight, however, chemical fungicides still be needed to control this disease.4. Of screening five kinds of fungicides, the control effect ofDimethomorph·Initium and Cyazofamid were the best and their control percentageswere94.5%and94.1%, respectively. Yield increases on three fungicides were alsoobvious, their yield increases were separately407.1kg/667m2and479.8kg/667m2and their increase percentages were separately were17.41%and20.42%.5. Of three sets of chemical control programs, one set of program wasscreened to control potato late blight. This program need sparing fungicides fivetimes in one growing season according to potato late blight forecasting, when thecenter disease plant was found in the field., and their spraying order was Mancozeb80%WP, Famoxadone·Cymoxanil52.50%WG, Fluopicolide·propamocabhydrochloride68.75%SC, Mandipropamid23.40%SC and Yl-ethyl·metiram60%WG.. The last control effect percentage was90.9%in this program.The increaseyield/667m2was687.6kg, and the increasing percentage of commodity potato was37.33%.The increase economic income was￥872.8/667m2.6. The average EC50value of50%Dimethomorph was(0.1022±0.0053)μg/mL and the EC50value of68.75%Fludioxonil·Propamocarb was(2.8573±0.1041)μg/mL to the tested30strains of late blight, all of strains wereresistance to Metalaxyl.