Biosafety of Nanoemulsion of Hexanal to Honey Bees and Natural Enemies

Abstract

One of the main drawbacks of mango is its post harvest losses. Hexanal, a volatile plant component inhibits Phospholipase D (PLD), the key enzyme involved in the initiation of plasma membrane deterioration to induce the ripening of fruits. Nanoemulsion of hexanal would be more effective than the conventional form of treatment owing to its smaller droplet size. Studies were conducted to develop nanoemulsion of hexanal and its biosafety to pollinators and natural enemies in mango ecosystem. Combination of hexanal, Tween 20, ethanol at 1:10:10, was found to have good emulsion. The average droplet size was 9.9 nm with the zeta potential of -20.0 mV. This combination was used for the biosafety studies on honey bees Apis cerana indica F., egg parasitoid Trichogramma chilonis Ishii and predator Chrysoperla carnea Stephens. Nanoemulsion of hexanal on honey bees and exposure of bees to hexanal treated mango varieties had no adverse effect on honey bees (0% mortality). Nanoemulsion at recommended field dose (0.04%) showed 96.53% parasitization and 96.61 per cent adult emergence of the egg parasitoid and recorded 85.05 per cent emergence in the predator. When the grubs were fed with hexanal sprayed Corcyra eggs as well as by direct spraying of hexanal nanoemulsion on the grubs, there was 100 per cent pupation and adult emergence.