Responses of Peach Blossom Blight and Brown Rot Fungus Monilinia fructicola to Benzimidazole and Diethofencarb in Korea

다국어 초록 (Multilingual Abstract)

The population shifts of Monilinia fructicola isolates which were resistant to the fungicide benzimidazoles were investigated in four regions of Korea from 1998 to 2000. The isolation frequency of benzimidazole-resistant isolates ranged from 18.8% to 29.6% in Chongdo and from $22.0\%$ to $26.8\%$ in Gyeongsan during the same period. However, the frequency of benzimidazoleresistant isolates was less than $4.0\%$ in Chochiwon and Youngduk during the same period. Benzimidazoleresistant isolates showed cross-resistance among benzimidazoles. On the other hand, none of the isolates showed cross-resistance to diethofencarb and carbendazim. Regardless of the year, the benzimidazole-resistant isolates of $EC_{50}$ higher than 500 $\mug%$ a.i./ml were isolated more frequently in mid and late season than in early season. In an orchard of Gyeongsan that had not been exposed to any fungicides for several years, the population of benzimidazole-resistant isolate had persisted without much fluctuation for three years. These results suggest that benzimidazole resistance of M. fructicola is becoming a problem in controlling brown rot and blossom blight of peach in regions like Chongdo and Gyeongsan.