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United States Department of Agriculture

Agricultural Research Service

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Research Project: ASSESSING AND MITIGATING PROBLEMS CAUSED BY VARROA MITES AND SMALL HIVE BEETLES ON HONEY BEES IN HAWAII

Location: Honey Bee Breeding, Genetics, and Physiology Research

2011 Annual Report


1a.Objectives (from AD-416)
1. Determine the level of the expression of the trait ‘Varroa specific hygiene’ (VSH) needed to obtain useful resistance to Varroa destructor mites in commercial queen production operations in Hawaii. Mite parasitism is expected to be high in these operations because of the production of large numbers of drones in many colonies, and the extended brood rearing season in the tropics. The test results may indicate a reduced need for treatment in colonies having greater levels of VSH. 2. Determine if small hive beetle (SHB) larvae can successfully pupate in lava rock. It is possible that the rough texture or the presence of holes in lava rock will serve as pupation sites for SHB. The growth of plants in the apiaries also serves as an indication of the presence of soil which may increase pupation success of SHB. 3. Determine reproductive success of SHB on different Hawaiian fruits. Many of these fruit trees grow in the wild and fruits are left on the ground.


1b.Approach (from AD-416)
1. Each of three participating queen breeders will establish an apiary in a Varroa-infested area with colonies of several levels of VSH (0, 50 and 75%). The colonies will be started as splits with no sealed brood. Varroa densities on adult bees will be measured and colonies assigned to equalize mite densities among levels of VSH within each breeder’s splits. Colonies will be managed initially without Varroa treatments. Cooperator will sample colonies every two months to monitor density of Varroa, and treat individual colonies that reach a predetermined density of mites on adult bees. Participating queen breeders will rate the beekeeping characteristics of the colonies. 2. In a laboratory bioassay, mature larvae of SHB will be reared in cylinders containing one of three treatments: lava rock alone, soil alone and a combination of lava rock and soil. In the field, pupation success will be determined in at least 5 apiaries. 3. Reproductive success of SHB will be assessed in the laboratory using different fruits commonly grown in Hawaii. In the field, fresh and rotting fruits from trees in and near test apiaries also will be examined for different stages of SHB.


3.Progress Report

Three participating queen breeders established colonies with various levels of Varroa specific hygiene (VSH) in late FY 10. University of Hawaii (UH) personnel sampled the colonies bimonthly to measure the density of varroa mites and colony sizes. After eight months, data from one queen breeder showed that the addition of VSH genetics suppressed population growth of varroa mites even under the tropical conditions of Hawaii. However, colonies with high levels of VSH had less brood. The data also showed that all non-VSH colonies either died or replaced their queens. In contrast, 70-90% of the VSH colonies were alive with original queens.

Useful data were not obtained from two queen breeders because colonies mistakenly were treated with miticides or initially were too unhealthy to develop properly. However, the research contributed to the decision by two of the three queen breeders to continue incorporating VSH into their breeding programs.

A bioassay determined the pupation success of small hive beetle (SHB) in a’a (porous) lava rocks. Three substrate types were compared: soil alone, a’a lava rock alone, and soil and a'a lava rock combination. For each treatment type, mature SHB larvae were reared to adulthood in containers that held the substrates. SHB successfully emerged from soil (95%) and soil and lava rock (94%). Water accumulation in the lava rock treatment caused larval mortality. Another trial will be conducted.

The potential role of alternative food sources for SHB in HI was evaluated by comparing SHB responses to avocado, banana, cantaloupe, grapefruit, papaya, pineapple, poha berry, and tangelo. The choice test revealed that adult SHB were attracted to all fruits except avocado. When one pair of SHB was held with fruits, egg-laying was observed in banana (33 eggs), papaya (8), pineapple (7), poha berry (58) and tangelo (45). A trial using multiple pairs showed a higher egg-laying capacity of SHB; another trial using multiple pairs will be conducted. The results to date suggest that the abundance of fruits in HI may allow SHB to survive in the absence of honey bee colonies.


Last Modified: 10/1/2014
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