EFFECT OF CERTAIN AGROCHEMICALS ON THE EFFICACY OF FUNGICIDES AGAINST DAMPING-OFF OF COTTON

This study was carried out to investigate the interaction between the cotton seed dresser fungicides monceren, monceren-combi, moncer­en-euparen, fixates-7 and vitavax-300, the fertilizer superphosphate and herbicides cotoran, goal and stomp in a soil infested with Rhizoctonia so- tani Kuhn under suitable conditions for infection in the greenhouse. All fungicides significantly reduced the infection. Monceren-euparen was the most effective compound, while monceren alone was the least effective. The efficacy of monceren in mixtures (monceren-combi and monceren­euparen) was better than monceren alone. Superphosphate had no sig­nificant effect on the efficacy of the fungicides. Herbicides alone or in combination with superphosphate had no effect on cotton damping-off. The interaction between fungicides and herbicides improved monceren efficacy when goal was applied, while stomp decreased the effect of monceren-euparen. In the presence of superphosphate, the interaction between fun­gicides and herbicides indicated that the effect of monceren was re­duced with cotoran, while a little improvement in efficacy occurred with goal and stomp. Monceren-oombi lost its effect gradually with goal, but improved with cotoran through four weeks, then a slight reduction in ef­ficacy was observed. No marked change was noticed In the efficacy of monceren-euparen when the tested herbicides were applied, except In case of stomp which reduced fungicides effect after 3 weeks. Rizolex-T and its combination with the herbicides started with nearly equal effica­cies, but in the case of goal, the efficacy was reduced between the 2nd and the 3rd week. Application of stomp reduced the efficacy of vitavax­300 at the beginning of the experiment. In spite of vitavax-300 and its combinations with cotoran and goal started with approximately equal ef­ficacies, vitavax-300 alone and with cotoran lost their effects gradually to become similar to vitavax + stomp. Generally, In the presence of su­perphosphate, the most effective treatments were monceren-euparen + goal, monceren-oombi + cotoran, monceren-euparen alone, monceren + goal and monceren + stomp, respectively. Without superphosphate, there is no change in efficacies of fungicides except the reduction of ef­ficacy in case of monceren + stomp and monceren-combi + cotoran.