CURATIVE AND PROTECTIVE ACTIVITIES OF STROBILURIN FUNGICIDES AND THEIR MIXTURES ON POWDERY MILDEW DISEASE IN CUCURBIT CROPS

Abstract

Squash is a significant crop of cucurbits family. The powdery mildew Podosphaera xanthii (syn. Sphaerotheca fuliginea) causes serious damage on leaves, stems and fruits of plant this reduce the amount of yield every year. Strobilurin group is common fungicides used to control powdery mildew disease. Many studies have indicated for powdery mildew resistance of the strobilurin fungicides group, which indicated the importance of mixing the strobilurin with other chemical compounds such as triazols to face the fungus resistance for the effect of strobilurin fungicides group. This study focusses on effectiveness of azoxystrobin as one of important strobilurin active ingredients, three application, ten days interval, alone and in mixture with difenoconazole and tebuconazole. Besides knowing the induction of resistance for plants by using Mono-potassium Phosphate (KH2PO4) and dipotassium phosphate (K2HPO4) as foliar fertilization treatments against powdery mildew on squash and extent the benefits that will accrue to the yield. In addition to evaluate the protective and curative applications effect for these treatments. The results showed that, all of fungicides were applied provided controlling of powdery mildew on squash and achieved increases in yield compared to untreated. Azoxystrobin alone and in mixture were most effective against powdery mildew on squash compared to difenoconazole, tebuconazole, in both protective and curative applications. However, the protective method was better in activity compared to the curative method. The mixture of azoxystrobin with difenoconazole was superior effectiveness and recorded the highest yield compared to all tested treatments followed by the mixture of azoxystrobin with tebuconazole and both treatments were slightly better or comparable in activity to azoxystrobin alone. In addition, the foliar application by KH2PO4 and K2HPO4 showed inferior effect to the induction of resistance for plants to powdery mildew infection under the field conditions.