Mortality in Tephritid Fruit Fry Puparia and Adults Caused by Metarhizium Anisopliae, Paecilomyces Fumosoroseus and Beauveria Bassiana

Abstract

Tephritid fruit flies are recognized as the most economically important group of phytophagous Diptera, and cause large losses to fruits and vegetables throughout the world. In the small developing island state, Mauritius, the key major pest of fruits and vegetables are Bactrocera zonata (Saunders) and B. cucurbitae (Coquillett), respectively. At present, growers have recourse to chemical pesticides which are hazardous to both the environment and human health. The objective of the study was to evaluate entomopathogenic fungi isolated from the soils of Mauritius as biocontrol agents of fruit flies. The pathogenicity of six isolates of M. anisopliae, three isolates of B. bassiana and one isolate of P. fumosoroseus were determined for late third-instar larvae, puparia and emerging adults of B. zonata and B. cucurbitae. A standard concentration of 1 x 10⁸ conidia/ml (5 ml) was used to inoculate 50 g lots of sand. Twenty mature third-instar larvae of either B. zonata or B. cucurbitae that were ready to pupate within the next 24 h were then introduced into each Petri dish for pupation. The overall result showed a significant reduction in adult emergence for both fruit fly species. For B. zonata, the percentage adult emergence varied from 60 to 93% in fungal treated sand; while, 1 to 30% of the puparia showed visible signs of mycosis. As regards B. cucurbitae, adult emergence ranged from 52 to 92% in fungal-treated sand and the highest percentage of mycosed puparia recorded with an isolate of M. anisopliae was 48%. Given the fact that there was significant reduction in adult emergence and a corresponding large mortality on puparia, the most virulent isolates could be potential candidates for soil application against fruit flies.

Keywords: Bactrocera cucurbitae, Bactrocera zonata, fruit flies, pupae,
biocontrol