Biocontrol potential of Bacillus thuringiensis var. aizawai and Metarhizium anisopliae SPW isolate against insect pests of pechay and lettuce grown under protected and open field cultivation

Abstract

Insect pests are one of the constraints in lettuce and pechay production. Although synthetic chemical insecticides are widely used, organic growers are interested in using alternative options which have no toxic residues. This study aimed to evaluate the biocontrol potential of Bacillus thuringiensis var. aizawai (Bta) and Metarhizium anisopliae (Ma) SPW isolate against insect pests of pechay and lettuce grown under protected and open field cultivation. Weekly spraying of each treatment was done using the recommended rates (RR) of application: Ma at 3L spore suspension per 13L water (1×108 spore concentration); Bta at 20g per 16L water; cypermethrin 5EC at 30mL per 16L water. Insect infestation was monitored weekly based on insect count and damage ratings. Yields were recorded at harvest. Results showed that application of either Bta, Ma or cypermethrin significantly reduced populations and damage of Spodoptera litura Fabr. and Plutella xylostella L. Pechay plants applied with Bta and Ma showed higher yields than cypermethrin in both types of cultivation. These findings suggested that Bta and Ma SPW isolate were effective against S. litura and P. xylostella and can be used as an alternative non-chemical option for their management.