Row crop environments provide an all-you-can-eat buffet and pesticide exposure to foraging honey bees

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Date
2021-06-03
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Virginia Tech
Abstract

The western honey bee, Apis mellifera, provide invaluable economic and ecological services while simultaneously facing stressors that may compromise their health. For example, agricultural landscapes, such as a row crop system, are necessary for our food production, but they may cause poor nutrition in bees from a lack of available nectar and pollen. Row crops are largely wind or self-pollinated, and while previous studies have focused on the impact of bees to row crops, fewer studies have examined the reciprocal relationship of the row crops on honey bees. Here we investigated the foraging dynamics of honey bees in a row crop environment. We decoded, mapped, and analyzed 3460 waggle dances, which communicate the location of where bees collected food, for two full foraging seasons (April – October, 2018-2019), and concurrently collected pollen from returning foragers. We found that bees foraged mostly locally (< 2 km) throughout the season. The shortest communicated median distances (0.48 and 0.32 km), indicating abundant food availability, occurred in July in both years, which was when our row crops were in full bloom. We determined, by plotting and analyzing the communicated locations, that most mid-summer foraging was in row crops, with at least 40% of honey bee recruitment dances indicating either cotton or soybean fields. Bees also largely foraged for nectar when visiting row crop fields, only returning to the hive with Glycine spp. pollen, and foraging on nearby trees and weeds for pollen. Foragers were exposed to thirty-five different pesticides throughout the foraging season, based on pesticide residues in collected pollen. Overall, row crop fields are contributing a surprising majority of mid-summer forage to honey bee hives and suggests that similar agricultural landscapes may also provide abundant, mid-summer forage opportunities for honey bees, however, at the risk of pesticide exposure.

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Keywords
waggle dance, Apis mellifera, foraging ecology, row crops
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