Evaluation of biocontrol agents for management of Stemphylium blight of onion

Abstract

Onion is an important commercial crop grown all over the world. It is attacked by many diseases which cause yield losses and result in lowering the quality and export potential of the produce. Stemphylium blight caused by Stemphylium vesicarium (Wallr.) Simmons is one such disease, which has become an economic threat since past few years, especially in Northern and Eastern India. In the present study, field evaluation as well as in vitro tests were conducted for evaluating some biocontrol agents for the management of Stemphylium blight, as well as to record their effects on yield and quality parameters of onion. The results of the in vitro study revealed that Trichoderma harzianum strain PBAT-21 gave h ighest mycelial inhibition (60%), followed by Pseudomonas fluorescens strain PBAP-27 (57.45%). From the results of the field experiments, all the treatments were found to be significantly better over check in reducing the disease severity. T. harzianum was found to be most effective, giving almost 50% disease control over check after spray at 45 days after transplanting, followed by P. fluorescens. The yield and proportion of A-grade bulbs were also higher in the T. harzianum treatment. Thus, it was concluded that T. harzianum PBAT 21 was most effective among the tested bioagents in managing the Stemphylium blight of onion.