| Early blight, caused by Alternaria solani, is an impotant potato disease and can result in major yield loss and damage of tuber quality. Effective control of this disease is becoming an increasingly important factor for stable potato production in China. The main goals of the current research include:(1) to examine the toxicities of five different types of fungicides to Alternaria solani;(2) to investigate the effect of nine different fungicides on early blight control;(3) to study the suppressive impact of application of foliar fertilization on early blight;(4) to develop a early blight prediction system.1. The toxicities of eleven fungicides to Alternaria solani were determined based on the growth rate of pathogen in the lab. The results showed that30%Hexaconazole,25%Trifloxystrobin-Tebuconazole,50%Cyprodinil and250g/L Prochloraz, the inhibition activity (EC50) below0.2μg/mL, which are better than80%Mancozeb and10%Difenoconazole.2. Using conventional spray fungicide method to determination of seven fungicides for controlling Potato Early Blight in the fields. The results showed that after4applications,7fungicides had different functions in the prevention and cure, also in production. Among in Hohhot xiaotai field, Azoxystrobin-Difenoconazole had the highest controlling efficacy which was95.74%, Cyprodinil had the highest potato yield which was882.52kg/Mu, improve potato rate was79.45%, the improve commodity potato rate was79.45%; In Kalaqinqi Sanxingzhuang field, Cyprodinil had the highest controlling efficacy which was76.59%, the second was Azoxystrobin-Difenoconazole, which was75.98%. According to cost accounting:Cyprodinil (45yuan/Mu)and Azoxystrobin-Difenoconazole(47yuan/Mu) were cheaper10yuan/Mu than the conventional fungicides-Mancozeb(59yuan/Mu) and Difenoconazole(55yuan/Mu). From what has been discussed above: Azoxystrobin-Difenoconazole and Cyprodinil have a better prospect and great promotional value.3. Application of foliar fertilizers has been indicated to have a positive impact on reducing the damage from early blight. We selected urea as a foliar fertilizer to test the potential role on early blight control. We applied different numbers of sprays at different potato growing stages. Applications of2%urea at30days after emergence, and multiple applications with7-day intervals, effectively reduced the early blight severity and yield loss. In Hohhot xiaotai field, the application of three times foliar fertilizers and the application of one or two times foliar fertilizers had significant difference, the controlling efficacy was58.90%, the yield was765.99kg/Mu, the improve commodity potato rate was46.00%; In Kalaqinqi Sanxingzhuang field, the application of two times foliar fertilizers and the application of three or four times foliar fertilizers had not significant difference, the controlling efficacy was26.91%, the yield was1168.92kg/Mu, the improve commodity potato rate was38.97%. Potato yield and AUDPC showed a negative correlation with a correlation index>0.8. From what has been discussed above:the application of two times foliar fertilizers, the comprehesive of price ratio was the highest.4. The results of showed the prediction explore that P-days, Early blight occurred in seven checking stations in2012(from sowing to appear disease spot, the accumulated value of daily highest and lowest temperature), Xiaotai of Hohhot is300, Sanxingzhuang of KaLaQinQi is300, Tongbu of linxi388, zhalantun of Hulun buir is322, Yakeshi of Hulun buir is338, woyuan of Xilinhhot is464, Zhangjiakou of Hebei is347.I advice start spraying protect when P-Days minus20, and when emerge disease spot to spray treatment fungicides, then spraying interval of7-15Days. Due to need large amounts of data to support prediction model, the critical value needs to be further validation. |
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