The Actual Note of Resistant Strains of the Tea Anthracnose Fungus Gloeosporium theae-sinensis against Benzimidazole Fungicides in Japan

Abstract

To investigate occurrence of resistant strains of the tea anthracnose fungus Gloeosporium theaesinensis against benzimidazole fungicides (Topsin M, Benlate), tea laeves affected by the disease were collected from 17 major tea producing prefectures in Japan. An isolate from each diseased leaf was examined on PDA media containing thiophanate-metyl (Topsin M) in concentration of 0, 1 and 100 ppm. The minimum inhibitory concentration (MIC) of several isolates was also examined.
In 83 tea fields out of 145 tested the resistant strains were detected, although most of them were intermediate-resistant (1 ppm<inhibition<100 ppm). The highly resistant ones (100<inhibition) were obtained from only 5 fields. Resistant strain ratio of isolates from each prefecture ranged within 3.1-43.9% and the average was 16.2%.