Combining entomopathogenic fungi and parasitoids to control the green peach aphid Myzus persicae

The green peach aphid, Myzus persicae, is a major insect pest worldwide. The parasitoid Aphidius colemani and more recently, the entomopathogenic fungus Lecanicillium muscarium strain KV01 (Mycotal®), have been considered as potential biological control against M. persicae. However, no studies have been carried out on the interaction between L. muscarium and A. colemani against M. persicae. This study, therefore, was conducted to determine the most effective timing of application of this fungal strain in combination with either naturally occurring or introduced parasitoids to control Myzus persicae in the laboratory and controlled field environments. In the laboratory, mummification, emergence of parasitoid adults from mummified aphids and female sex ratio of the emerging adults, were not affected when the fungus was applied 6 or 7 days after the parasitoids were added, compared with treatment with A. colemani only. Although a 40% reduction in the female sex ratio of emerging parasitoid adults was recorded when fungi applied 3 days after the parasitoids were added, fungal application had no significant effect on longevity and fecundity of the female A. colemani F1 generation that emerged from fungus-treated aphids. In the semi-field experiment, the mean number of aphids per leaf was significantly lower in the treatment involving A. colemani in combination with L. muscarium than those with A. colemani alone. However, aphid reduction in the treatments involving naturally occurring parasitoids alone and those in combination with L. muscarium was not significantly different. This study suggests that it is possible to combine L. muscarium with A. colemani to increase the level of aphid control. A more detailed knowledge of the effects of naturally occurring parasitoids on pest control and their interaction with other biological control agents will help to develop environmentally sound crop management strategies with reduced insecticide applications.