Effect of target spot disease on sesame cultivation
1990
Supaluck Janetanomma
Pathogen produced a target like symptom on the susceptible host (Var. Roi Ed-1) with several consecutive concentric rings. The typical target spot occurred when disease occurred in severe and lesion was loosen from diseased leaves. Pathogen when infected on seedlings decreased growth rate drastically and brought the seedling to die. Continuation of infection in the endemic condition caused reduction in yield production. Pathogenicity of C. cassiicola on various host, weeds that grew in the adjacent sesame field was impossible. The most resistant varieties, Nakornsawan, produced yield normally with lesion size of 1.67 cm in diameter. In moderate resistant varieties, viz, Pitsanulok, Roi Ed-1 and Mahasarakarm varieties, also produced normal yeild but the lesion size is 1.67-2.1 cm in diameter. The Petchaboon varieties were the susceptible varieties with the biggest size of lesion (2.1-2.3 cm in diameter) but the yield reduction was not significant. Evaluation on the efficacy of chemical control both in Laboratory and in the field indicated thdt the ED 50 of these fungicides (benomyl, procymidion, carbendazim, pyracarbolid, chlorothalonil, Delsene Mx, mancozeb and captan) were 25, 30, 50, 80, 100, 125, 300 and 500 ppm respectively. Field evaluation on the efficacy of these fungicides spraying when the host plants were inoculated with C. cassiicola spore suspension (av. 50,000 spore/ml) at the age of 1 month old, with twice times of spraying took placed thereafter within 2 days and the results revealed the same effectiveness as occurred in the laboratory
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