Integrating Natural Products – Genetic Resources for Control of Varroa Jacobsoni, a Parasitic Mite of the Honey Bee
The current project focuses on integrating mite-resistant stocks of honey bees with other treatment modalities, including natural products and other non-chemical methods. During year one, we established a population of about 200 colonies of honey bees, half from mite-resistant stock, the other half from unselected stock. We also evaluated a new formulation of formic acid, tested the use of drone combs as mite traps, and tested something called a screened bottom board that has been receiving considerable publicity lately as a non-chemical control method.
- To evaluate honey bee stocks that are partially resistant to the parasitic honey bee mite, Varroa jacobsoni;
To optimize formic acid for control of Varroa mites
To evaluate drone brood as a trap crop for control of Varroa mites.
Mite resistant bees: We produced about 100 virgins from the SMR stock developed by Dr. John Harbo, USDA-ARS, and an equal number from unselected commercial control stocks. Virgins were naturally mated in a common apiary and then distributed to colonies. After re-queening colonies of bees, it takes nine or ten weeks for the old bees to be completely replaced by the offspring of the new queen. Consequently, we did not collect data on the colonies this summer. Instead, we treated them all with pesticide to ensure that they entered the winter in a healthy condition. This will allow us to evaluate their true wintering potential, without any confounding from variation in mite levels. This coming season, we will estimate the worker bee populations, honey production, tendency to swarm, temper, and mite levels for all colonies.
Formic Acid: Previous work at CU has demonstrated that the efficacious dose of formic acid as a fall treatment is considerably greater than that available in the current approved formulation. The manufacturer of this product has adopted our recommendation for increased dose. Formic acid also eats through the current packing system. We tested a new packing system with the increased dose of formic acid in two apiaries, each with 20 colonies. Half of the colonies in each yard received the new product; the other half received no treatment and served as controls. The mites from this project are still being counted. We plan to repeat this experiment next fall, incorporating into our next protocol whatever relevant information we learn about the product this year.
Drone brood trap crop: Mites are found in drone brood five to ten times as often as in worker brood. We evaluated drone comb traps as a practical way to slow the rate of growth of the mite population. We used the strength of the worker population as an indicator of the effectiveness of the treatment. We also evaluated screen bottom boards to determine if they had any effect on mite levels. The theory is simple: Mites tend to fall off of bees. If these can be removed from the population (the screen bottom lets them fall through and out of the colony where they cannot regain a host), the mite population should grow more slowly. The screen bottom board was evaluated in four apiaries, each with 16 colonies of bees. Half of the colonies in each apiary received the screen bottom board; the other half received the regular bottom board. In the fall, we measured worker population and the mite to adult bee ratio.
Impacts and Contributions/Outcomes
Mite resistant bees: It is too early to say how this project will turn out. Data will be collected this coming spring, summer, and fall and will be analyzed during the winter of 2002-2003.
Formic Acid: The data are still being analyzed.
Drone brood trap crop: Results were very encouraging. Colonies receiving the drone comb treatment had worker bee populations about 2.5 times as great as those not receiving the drone comb treatment (P < 0.05). The screen bottom board did not control mite populations when evaluated as a stand-alone treatment.
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