The Impacts of Habitat Management on Beneficial Insects in Lowbush Blueberry Agroecosystems

Abstract

Insect pollinators and natural enemies deliver vital pollination and pest control services in agricultural ecosystems (‘agroecosystems’), yet reported population declines threaten the production of many global food crops. The efficacy of various habitat management techniques to promote pollinator and natural enemy communities in agroecosystems were tested, using lowbush blueberry (Vaccinium angustifolium Aiton) as the model crop. Artificial trap nests were evaluated as nesting substrates for cavity-nesting bees (Hymenoptera: Megachilidae). Megachilidae nesting occupancy was highest in milk carton trap nests, while nesting occupancy in wooden trap nests and overturned clay lids was low. Emergence after overwintering was low for all trap nests, and parasitism from wasps (Hymenoptera) and flies (Diptera) was observed. Buckwheat plantings along blueberry field margins were compared to unenhanced ‘control’ blueberry field margins for impact on wild bee and natural enemy abundance and diversity after blueberry bloom. Higher bee abundance in buckwheat transects was only detected during mid-August. Bee fauna during blueberry bloom was documented to determine if the same bees visiting buckwheat were also involved in blueberry pollination. All bee genera recorded during blueberry bloom were also collected in buckwheat transects. Bee diversity was found to be significantly greater during late blueberry bloom than early or mid-bloom. Bee abundance was also higher during late blueberry bloom, although not significantly so. Aerial netting and pan trapping provided complementary collections of bees. Natural enemy abundance was generally higher in buckwheat transects than in control transects for many groups evaluated, although not significantly so. Six forage crops were seeded to monitor their attractiveness to bees. Sweet clover, red clover, alsike clover, and birdsfoot trefoil were visited most frequently by bees. Red clover, birdsfoot trefoil, and sweet clover bloomed for the longest period. Based on these findings, red clover, sweet clover, alsike clover, and to a lesser degree, birdsfoot trefoil, are attractive forages to use for habitat management for pollinators. My findings demonstrate that lowbush blueberry agroecosystems host a diverse and abundant beneficial insect fauna when alternative nesting substrates and flowering resources are present, and floral enhancements may be beneficial at certain times during the season.