Caracterização de isolados de Corynespora cassiicola e avaliação da sensibilidade in vitro a fungicidas

Once there is no chemichal product registered to control Corynespora cassiicola on tomato and cucumber in Brazil, the control has been made by the use of fungicides registered for early blight of tomato and target spot of soybean. This an illegal and inappropriate procedure that may lead to a decrease of sensitivity and resistant of some product.. Because these factors, this work aimed to test the in vitro mycelial sensitivity of C. cassiicola isolates from different host and different geographic regions of Brazil to different fungicides. In a preliminary test, using some C. cassiicola isolates, it was obtained the efective dose able to decrease micelial growth of C. cassiicola in 50% (ED50). As a result the fungicides cloratalonil and carbendazim showed great ED50 values to most isolates tested, with average upper 50 mg.L -1 . For the tebuconazole fungicide the values of ED50 varied from 0,50 to 18,79 mg.L -1 . The ED50 of fungicides pyrimethanil, fludioxonil and cyprodini, was lower when compared the former fungicides. These fungicide ED50 were 1 mg.L -1 to fludioxonil fungicide, 3 mg.L -1 to cyprodinil, mg.L -1 to boscalid and Fluopyram, 10 mg.L -1 to tebuconazole, azoxystrobin and pyrimethanil and 50 mg.L -1 to chlorothalonil and carbendazim. In the mycelial growth inhibition test (ICM) there was a greate variation among fungicides and the 55 C. cassiicola isolates tested. The fludioxonil fungicide at a concentration of 1 mg.L -1 showed higher ICM when compared to fungicides tested, with average of 85.69%. Chlorothalonil fungicide showed the lowest ICM values with average of 31.56%. As to the isolates tested, the EH-1710 showed higher ICM of 74.14% and the isolate EH-2125 showed the lowest value of ICM between the isolates tested, with average of 34.57%. The results show a great expectation of good effects of fludioxonil fungicide on target spot control. Key-words: target spot, fungicides, chemical control.