Protective and Curative Activity of Azoxystrobin and its Mixtures against Powdery Mildew on Squash.

Squash is one of the important crops of the cucurbits family and powdery mildew causes less yield every year, Strobilurin group are common fungicides used to control powdery mildew disease. In addition, Strobilurin is more safe for humans and the environment because it is derived from a natural fungicidal source (the production of the active ingredients are achieved by wood-rotting of Strobilurus tenacellus). Strobilurin contains a group of active ingredients that control various diseases such as powdery and downy mildew on cucumber, grapes, and watermelon, early blight and late blight on tomatoes and potatoes, scab on apple and others. This study focuses on the effectiveness of protective and curative applications of Azoxystrobin as one of the active ingredients of Strobilurin group alone and mixtures against powdery mildew on squash. The induction of resistance of plants against powdery mildew by using KH2PO4 and K2HPO4, protective and curative applications. The tested compounds against powdery mildew on squash at protective method were Azoxystrobin mixture with Difenoconazole 83.3%, Azoxystrobin mixture with Tebuconazole 76.6% , Azoxystrobin alone 70.7% , Difenoconazole 62.3% , Tebuconazole 55.9%, K2HPO4 16.7% and KH2PO4 10.8%. The curative effectiveness of the tested products against powdery mildew on squash was as follows Azoxystrobin mixture with Difenoconazole 69.3% > Azoxystrobin mixture with Tebuconazole 61.2% > Azoxystrobin alone 57.6% > Difenoconazole 44.2% > Tebuconazole 42.7% > K2HPO4 12.1% > KH2PO4 7.4%. Accordingly, Azoxystrobin alone and its mixtures were most effective against powdery mildew on squash compared to Difenoconazole, Tebuconazole, K2HPO4 and KH2PO4 alone in both protective and curative applications. However the protective method was more effective compared to the curative method and the mixture of Azoxystrobin with Difenoconazole was more effective compared to all tested treatments followed by the mixture of Azoxystrobin with Tebuconazole and both treatments were slightly better or comparable to Azoxystrobin alone. In addition, the foliar application by KH2PO4 and K2hPO4 was inferior in activity to resistant powdery mildew infection under the field conditions.