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Funded Project

Funding Program: Regional IPM Grants (S-RIPM)

Project Title: IPM Economic Threshold for a Two-Pest Complex in Honey Bees

Project Director (PD): Keith S. Delaplane [1]

Lead State: GA Lead Organization: University of Georgia

Research Funding: $104,855

Start Date: Jun-01-2004 End Date: May-30-2006

Site/Commodity: honey bees

Summary: This proposal, IPM Economic Threshold for a Two-Pest Complex in Honey Bees, requests funding for a Research Project under the Improved Pest Monitoring Techniques and Decision Tools emphasis area. The American beekeeping industry has become highly chemical-dependent. Applications of the synthetic acaricides fluvalinate (ApistanTm) and coumaphos (CheckMiteTm) are routinely used to control the exotic blood­feeding mite Varroa destructor, and coumaphos and permethrin (GardStarTm) are used to control the small hive beetle (Aethina tumida), a recently-introduced hive scavenger. The combined effect of these two pests is acute in the Southeast - a region responsible for 13% of the nation's honey production and about half of the nation's queen and package bee output. In this proposal we argue that an effective IPM strategy against this two-pest complex cannot get off the ground before a research-based economic threshold is developed. Thus, in this proposal we offer a protocol for developing an economic threshold for varroa and small hive beetles replicated across three states, GA, SC, and NC. The PDs are well-published in the biology and control of both pests, and two of them (KSD and WMH) were the first to develop a research based economic threshold for V. destructor. Each brings to the project strong professional resources and documented support of clientele beekeeper groups. We estimate that the benefits accruing to the Southeastern states from IPM practices growing from this economic threshold should over a five-season period translate to: 1,023,400 fewer chemical applications for varroa control 190,890 fewer chemical applications for SHB control 719 kg reduction in the active ingredient fluvalinate 1651 kg reduction in the active ingredient coumaphos 179 kg reduction in the active ingredient permethrin $4,488,047 savings in chemical applications Objectives: The objective of the project is to develop an IPM economic threshold for a two-pest complex in honey bee colonies comprised of parasitic Varroa mites and hive-scavenging small hive beetles. Specifically, we aim to: 1. Determine a range of varroa mite and small hive beetle densities in honey bee colonies that are non-damaging, non-damaging but warranting treatment, and damaging, then 2. Determine a sampling protocol that reliably estimates colony populations of varroa and small hive beetles and corresponds them to levels determined in objective 1.

Final Report:

Results PROGRESS: 2004/06 TO 2006/05 In 2005 the project was completed, on schedule, with no fatal deviations in the design or execution. To recap, we tested the effects on honey bee colonies of five levels of small hive beetles (0, 150, 300, 600 or 1200 per hive) and three levels of Varroa mite (treatment delayed until Aug, until Oct, or treated continuously). The design permitted an examination of interactions between these two pests, but none was detected. Based on end-of-year sampling, bee populations were significantly reduced in colonies in which small hive beetle numbers were maintained at or above 600 beetles. The percentage of bee brood capped was significantly lower (51%) in colonies with 1200 beetles than colonies with zero beetles added. In our study, Varroa mites were the more serious of our two test disorders. As remedial mite treatments are delayed from August to October, there is a predictable increase in mite populations. Conversely, those colonies treated continuously have the lowest mite populations, but this is a non-sustainable practice used in our study to provide an experimental check. Based on end-of-year (December) sampling, colony weight (kg) followed the pattern (August, continuous) > October. The patterns were the same for colony bee populations. Negatively, the patterns were October > (August, continuous) for colony mite populations, mites per 100 bees, percentage brood capped, and percentage bees infested with tracheal mites, Acarapis woodi. August-treated colonies performed as well as continuously-treated colonies. Hence, we can assume that mite populations sustained by these colonies up to time of treatment (1979 plus/minus 349 mites, mean plus/minus SE, range 0-7401) constitute a treatment threshold. By October, colony mite populations were actually smaller (1754 plus/minus 420 mites) but the range wider (0-11,903) and mites per 100 bees higher (20.4 plus/minus 6.1 versus 19.4 plus/minus 4.0), suggesting that declining mite populations reflect collapsing colonies. Although the present study detected no interaction between levels of Varroa mite or small hive beetles, the value of 1979 mites is lower than our previous Varroa threshold (3172-4261 mites) published before small hive beetles arrived in North America. This suggests that the addition of a second pest reduces host resistance to the first. IMPACT: 2004/06 TO 2006/05 This study sets the necessary theoretic groundwork for a subsequent decision-based IPM program targeting Varroa mites and small hive beetles, demonstrably the most serious pests affecting beekeeping in the Southeast. PUBLICATIONS (not previously reported): 2004/06 TO 2006/05 No publications reported this period

Outcomes N/A

Impacts From report submitted by the PI to USDA CRIS report system This study sets the necessary theoretic groundwork for a subsequent decision-based IPM program targeting Varroa mites and small hive beetles, demonstrably the most serious pests affecting beekeeping in the Southeast.

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