Date of Award

8-2005

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Stephen A, Woods

Second Committee Member

Frank Drummond

Third Committee Member

Constance Stubbs

Abstract

Conservation of natural enemies can be an effective form of pest management. If beneficial Hymenoptera, native to the area, can be protected and encouraged to multiply, the benefits of natural insect pest control might be realized. Hymenoptera as "natural enemies" as well as "pollinators" have been studied intensively in many agroecosystems worldwide. However, lowbush blueberry is not an ecosystem where ecology of Hymenoptera has been well studied. This thesis discusses two studies conducted in lowbush blueberry fields in Washington County, Maine in 1997 and 1998. In the first study, I investigated "towers" as a method for deploying insect traps along both a horizontal and vertical gradient. The objective was to define the spatial distribution of native bees and wasps, and interpret where these insects tend to be most abundant in and around lowbush blueberry fields. A single tower was erected near the center, along the edge, and within the surrounding forest of each blueberry field. Flight intercept traps were suspended from towers at 1, 7 and 14 m above the ground. Bees exhibited differences in both vertical and horizontal distribution. More than 85% of all bees captured were from traps 1 m above the ground, and a majority was captured at the edge of blueberry fields. Most wasps captured in this study were tiny parasitica less than 3 mm in length. Unlike bees, no height effect was detected with wasps. However, using towers allowed me to see temporal changes in the vertical distribution of wasps from June to July. Wasps showed no difference in their overall horizontal distribution. However, categorizing them by size and antenna length (i.e. 4 categories) revealed an interaction between wasp category and tower position. Relatively large wasps were more abundant in the surrounding forests, while small wasps showed no association with any trap position. In the second study, I investigated various field variables that might explain the abundance of wasps captured across 33 blueberry fields. A single malaise traps was placed at the field interior, along the field edge and within the surrounding forest of each field. Thirteen morphospecies were identified from wasp samples. In addition, flowering weeds were sampled at various intervals across all fields. The overall wasp population and most morphospecies were positively associated with a common flowering weed, sheep laurel {Kalmia angustifolia). Multiple groups of morphospecies appeared to be responding to the same flowering plants and were treated as foraging guilds. In addition, multiple morphospecies were found distributed within blueberry fields in a similar spatial pattern and were treated as communities. No two morphospecies identified in the same foraging guild were also found in the same community. This suggests wasps could belong to stable communities and maintained by different species utilizing different floral resources. Based on the results of these studies, blueberry growers should consider integrating efforts to conserve populations of native Hymenoptera into their management practices. In doing this, growers may also want to research methods of pesticide use that will minimize lethal effects on these beneficial bees and wasps.

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