Hoverflies provide pollination and biological pest control in greenhouse-grown horticultural crops

Abstract

Beneficial insects provide pollination and biological control in natural and man-made settings. Those ecosystem services (ES) are especially important for high-value fruits and vegetables, including those grown under greenhouse conditions. The hoverfly <i>Eupeodes corollae</i> (Diptera: Syrphidae) delivers both ES, given that its larvae prey upon aphid pests and its adults pollinate crops. In this study, we investigated this dual role of <i>E. corollae</i> in three insect-pollinated and aphid-affected horticultural crops i.e., tomato, melon and strawberry within greenhouses in Hebei province (China). Augmentative releases of <i>E. corollae</i> increased fruit set and fruit weight of all three crops, and affected population dynamics of the cotton aphid <i>Aphis gossypii</i> (Hemiptera: Aphididae). On melon and strawberry, <i>E. corollae</i> suppressed <i>A. gossypii</i> populations by 54-99% and 50-70% respectively. In tomato, weekly releases of 240 <i>E. corollae</i> individuals/100 m²led to 95% fruit set. Meanwhile, releases of 160 hoverfly individuals per 100 m²led to 100% fruit set in melon. Also, at hoverfly/aphid release rates of 1:500 in spring and 1:150 in autumn, aphid populations were reduced by more than 95% on melon. Lastly, on strawberry, optimum levels of pollination and aphid biological control were attained at <i>E. corollae</i> release rates of 640 individuals/100 m². Overall, our work shows how augmentative releases of laboratory-reared hoverflies <i>E. corollae</i> can enhance yields of multiple horticultural crops while securing effective, non-chemical control of resident aphid pests.