Pollination Services Provided by Bees in Pumpkin Fields Supplemented with Either Apis mellifera or Bombus impatiens or Not Supplemented

Jessica D Petersen,Jeff Ollerton,Brian A Nault,Stephen Reiners

doi:10.1371/journal.pone.0069819

Jessica D Petersen, Jeff Ollerton + Show 2 more

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https://doi.org/10.1371/journal.pone.0069819

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Abstract

Pollinators provide an important service in many crops. Managed honey bees (Apis mellifera L.) are used to supplement pollination services provided by wild bees with the assumption that they will enhance pollination, fruit set and crop yield beyond the levels provided by the wild bees. Recent declines in managed honey bee populations have stimulated interest in finding alternative managed pollinators to service crops. In the eastern U.S., managed hives of the native common eastern bumble bee (Bombus impatiens Cresson) may be an excellent choice. To examine this issue, a comprehensive 2-yr study was conducted to compare fruit yield and bee visits to flowers in pumpkin (Cucurbita pepo L.) fields that were either supplemented with A. mellifera hives, B. impatiens hives or were not supplemented. We compared pumpkin yield, A. mellifera flower visitation frequency and B. impatiens flower visitation frequency between treatments. Results indicated that supplementing pumpkin fields with either A. mellifera or B. impatiens hives did not increase their visitation to pumpkin flowers or fruit yield compared with those that were not supplemented. Next, the relationship between frequency of pumpkin flower visitation by the most prominent bee species (Peponapis pruinosa (Say), B. impatiens and A. mellifera) and fruit yield was determined across all pumpkin fields sampled. Fruit yield increased as the frequency of flower visits by A. mellifera and B. impatiens increased in 2011 and 2012, respectively. These results suggest that supplementation with managed bees may not improve pumpkin production and that A. mellifera and B. impatiens are important pollinators of pumpkin in our system.

Highlights

Bee pollination is an essential ecosystem service for the successful production of many crops [1] and the demand for pollination services is increasing [2,3,4,5,6]
Our expectation that pumpkin yield would be positively correlated with the frequency of B. impatiens visits to pumpkin flowers was confirmed, but only in 2012, which was the warmest of the two years and the year that B. impatiens visits to pumpkin flowers was greatest
A. mellifera was confirmed as an important pollinator of pumpkin, but only in 2011, as fruit yield significantly increased as its visitation frequency to flowers increased

Summary

Introduction

Bee pollination is an essential ecosystem service for the successful production of many crops [1] and the demand for pollination services is increasing [2,3,4,5,6]. The risk of insufficient crop pollination may be increasing as populations of both managed and wild pollinators in North America decline [7]. In areas where bees have declined, crops may not be pollinated sufficiently, leading to yield reduction and potential economic hardships for farmers [8] and a reduced supply of nutritious food [9]. Pumpkin production in North America is concentrated in the Midwest and Northeast regions of the U.S [11] and cultivars may be grown for consumption (i.e., fruit is processed) or for fall decoration (i.e., jack-o-lanterns). The effect of supplementation on pumpkin fruit yield has not been empirically examined

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