A fungal-based pesticide does not harm pollination service provided by the African stingless bee Meliponula ferruginea on cucumber (Cucumis sativus)

Abstract

Stingless bees (Apidae: Meliponini) provide pollination services to crops and produce high–quality honey. The application of agrochemicals during the management of crop pests is an increasing threat to pollinators and the ecosystem services they provide. Biopesticides are considered as better alternatives; however, there is limited evidence of their impact on stingless bees. We evaluated the effect of the most widely used African fungal biopesticide (Metarhizium anisopliae ICIPE 69) on mortality, foraging behavior and pollination success of the African stingless bee Meliponula ferruginea under semi-field conditions. Colonies of M. ferruginea were introduced into four 24 m2 greenhouse compartments containing blooming cucumber (Cucumis sativus) plants. Cucumber plants were sprayed with a suspension of the biopesticide alongside a sterile 0.05% Triton–100–X (control). The experiment was repeated three times during different cucumber growing seasons. Biopesticide application did not significantly affect M. ferruginea mortality, flight activity, flower visitation, pollen foraging, C. sativus fruit set or C. sativus yield. Forager bees acquired a high number of conidia (7,600 ± 54 conidia /bee) immediately after biopesticide application; however, a significant decline was observed in the subsequent days. Conidial persistence and viability on plant surfaces declined significantly with days. There was no correlation between conidial acquisition and pollen load by forager bees (657 ± 29 pollen/bee). This study demonstrates that M. anisopliae ICIPE 69 did not negatively impact M. ferruginea mortality, pollination behaviour and success, and can therefore be safely used in stingless bee–dependent crop systems.