Effect of Metarhizium anisopliae on the fertility and fecundity of two species of fruit flies and horizontal transmission of mycotic infection.

P Sookar,S Bhagwant,M N Allymamod

doi:10.1673/031.014.100

Abstract

In Mauritius, the peach fruit fly, Bactrocera zonata Saunders (Diptera: Tephritidae), and the melon fly, Bactrocera cucurbitae (Coquillett), are the major pest of fruits and vegetables, respectively. Fruit growers make use of broad-spectrum insecticides to protect their crops from fruit fly attack. This method of fruit fly control is hazardous to the environment and is a threat to beneficial insects. The entomopathogenic fungus, Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae), which was isolated from the soils of Mauritius, was used to investigate whether fungus-treated adult fruit flies could transfer conidia to non-treated flies during mating, and whether fungal infection could have an effect on mating behavior, fecundity, and fertility of the two female fruit fly species. When treated male flies were maintained together with non-treated female flies, they were able to transmit infection to untreated females, resulting in high mortalities. Similarly, fungus-infected female flies mixed with untreated males also transmitted infections to males, also resulting in high mortalities. Infection by M. anisopliae also resulted in the reduction of the number of eggs produced by females of B. cucurbitae. The results suggest that M. anisopliae may have potential for use in integrated control programs of B. zonata and B. cucurbitae using the sterile insect technique in Mauritius.

Highlights

The fruit flies Bactrocera zonata (Saunders) (Diptera: Tephritidae) and B. cucurbitae (Coquillett) are major pests limiting the production of fruits and cucurbits, respectively, in Mauritius (Sookar et al 2006)
Male and female donors of B. zonata and B. cucurbitae exposed directly to conidia of M. anisopliae became infected and all died of fungal infection within six to seven days post-exposure
Male and female donors of B. cucurbitae exposed directly to conidia of M. anisopliae became infected and all died of fungal infection within six to seven days post-exposure

Summary

Introduction

The fruit flies Bactrocera zonata (Saunders) (Diptera: Tephritidae) and B. cucurbitae (Coquillett) are major pests limiting the production of fruits and cucurbits, respectively, in Mauritius (Sookar et al 2006). A complex set of interacting processes, both environmental and biotic, is necessary for or inhibitory to development of epizootics caused by entomopathogenic fungi These include sensitivity to solar radiation (Inglis et al 1993; Alves et al 1998); microbial antagonistics; host behavior, physiological condition, and age; pathogen vigour and age (Moore et al 1995); presence of pesticides (Inglis et al 2001); and appropriate temperature, humidity, and antagonists in the soil or on the host cuticle (Moore and Prior 1993). Autodissemination is regarded as an appropriate strategy to increase the persistence of entomopathogenic fungi in the environment This strategy uses target pests as carriers to selectively disseminate entomopathogens among their populations (Maniania 1998, 2002; Meadow et al 2000; Rath 2000)

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