Sensitivity of Verticillium dahliae to prochloraz and prochloraz-manganese complex and control of Verticillium wilt of cotton in the field

Twenty-eight isolates of Verticillium dahliae from the cotton growing areas of Cukurova and Amik plains of Turkey were evaluated in vitro for their sensitivities to prochloraz and prochloraz-manganese complex. The fungicide sensitivity was determined by measuring mycelial growth on agar medium amended with prochloraz and prochloraz-manganese complex at dosages up to 100 mug ml(-1). The mean ED50 values for both locations ranged from 0.2590 to 0.3574 mug ml(-1) for prochloraz and 0.5239-0.8409 mug ml(-1) for prochloraz-manganese complex. The resistance factors for both fungicides were greater for the Cukurova than the Amik isolates. In field trials, the higher concentration of prochloraz (506 g a.i. ha(-1)) gave a slight reduction in disease severity. However, the higher concentration (1250g a.i. ha(-1)) of prochloraz-manganese complex resulted in a significant effect (P = 0.05) on disease control. (C) 2002 Elsevier Science Ltd. All rights reserved.