Inevstigation on the susceptibility of apple black spot Venturia inaqualis to some fungicide and alternative controlmethods in apple orchards of Çanakkale region

In Çanakkale province, Apple Black Spot (Venturia inaequalis) disease causes epidemics and producers makes intense chemical control applications against the disease. In this study 20 isolates from 4 different locations of Çanakkale was tested to determine their susceptibility against hexaconazole from sterol biosynthesis inhibitors, trifloxystrobin from Strobulirins and Captan from Trichloromethylthiocarboxamides in vitro. Also biological effects of hexaconazole and trifloxystrobin alone and mixed with alternative materials potassium sorbate and eugenol was investigated in vivo.V. inaequalis isolates were tested with LD50 values as 7 isolates with 0,01-0,03 µg/ml, 12 isoltes with 0,03-0,1 µg/ml, 1 isolate with 0,1-0,3 µg/ml doses for captan, 6 isolates with 0,01-0,03 µg/ml, 13 isolates with 0,03-0,1 µg/ml and 1 isolate with 0,1-0,3 µg/ml doses for hexaconazole, 12 isolates with 0,01-0,03 µg/ml and 8 isolates with 0,03-0,1 µg/ml doses for trifloxystrobin. These isolates were tested with MIC values as 5 isolates with 0,3-1 µg/ml, 9 isolates with 1-3 µg/ml and 6 isolates with 3-10 µg/ml doses for captan, 5 isolates with 1-3 µg/ml and 15 isolates with 3-10 µg/ml doses for hexaconazole and 8 isolates with 0,3-1 µg/ml, 10 isolates with 1-3 µg/ml and 2 isolates with 3-10 µg/ml doses for trifloxystrobin. In vitro studies showed that susceptibility of V. inaequalis against hexaconazole, captan and trifloxystrobin has decreased.In the biological efficiency test with Hexaconazole and trifloxystrobin, expected performance wasn?t acquired from fungicides because of the high disease pressure (92,01% in control), also mixture of alternative materials and fungicides didn?t show the expected synergistic effect. The efficiency of the fungicides was found as 52,1% for hexaconazole, 69,7% for trifloxystrobin, 46,7% for hexaconazole+eugenol, 48,9% for hexaconazole+potassium sorbate, 69,9% for trifloxystrobin+potassium sorbate, 67,0% for trifloxystrobin+eugenol against apple black spot.Results of the research showed that susceptibility of V. inaequalis against fungicides is decreasing in Çanakkale region and new control strategies must be developed against the disease by monitoring fungicide resistance.