Combined effect of entomopathogenic nematode, Heterorhabditis indica with entomopathogenic fungi, Metarhizium pinghaense and M. robertsii against the obscure mealybug, Pseudococcus viburni

Abstract

In this study, we evaluated the combined application of entomopathogenic nematodes (EPN), Heterorhabditis indica, with entomopathogenic fungi (EPF), Metarhizium pinghaense or M. robertsii, against Pseudococcus viburni (Signoret), in laboratory trials. Three EPF-EPN combinations were used, where P. viburni was either exposed to the EPF and EPN isolates simultaneously or sequentially, at different time intervals. The combined application of H. indica with each of the two EPF isolates resulted in higher mortality of P. viburni, under laboratory conditions, relative to when applied individually. With sequential application, the H. indica and M. robertsii combination was shown to be more effective, resulting in 85 ± 3.1% and 88.8 ± 3.9% mortality after four and three days, respectively. Heterorhabditis indica combined with M. pinghaense was more effective for simultaneous application of the entomopathogens, resulting in 95 ± 6.5% mortality after five days. Insect mortality was mostly due to EPN infection. The single application of H. indica against P. viburni resulted in 76.3 ± 2.9% after 48 h, while M. pinghaense and M. robertsii resulted in 73.8 ± 7.9% and 82.5 ± 3.3% respectively, after a week. Interactions between H. indica and the two EPF isolates were shown to have an additive effect, when used simultaneously and sequentially. The results from the study indicate that the combined application of EPF and EPN could potentially be used as an alternative strategy for management of P. viburni in fruit production areas.