Three biocontrol agents i.e., Bacillus subtilis, Pseudomonas fluorescens, Trichoderma harzianum, were evaluated for their efficacy in controlling powdery mildew on squash plants. In greenhouse experiment, the highest inhibition of disease severity percentage was achieved by P. fluorescens, B. subtilis and T. harzianum, and application of Amistar 250 SC on squash plants resulted significant reduction of disease severity. The bacterial bioagents, i.e. P. fluorescens, and B. subtilis exhibited the highest reduction in disease severity. On the other hand, T. harzianum gave the lowest reduction in the disease severity. All resistance inducers (i.e., potassium  nitrate (KNO₃), potassium phosphate monobasic (KH₂PO₄), potassium phosphate dibasic (K₂HPO₄ and salicylic acid) treatments resulted in significant reduction in disease severity under greenhouse conditions. Under field conditions, similar reduction in disease severity of powdery mildew was observed in treated plants.       All treatments significantly increased squash yield per plant. More than 75% increase     in yield was observed in treated plants with (KNO₃ at 100 mM).