Varroa mites (also known as varroa destructor mites and honeybee mites) are the most serious pest to honey bee populations and can cause deformed bees and can seriously destroy hive populations. Since these mites can be transferred from hive to hive it is likely that most hives have some level of the varroa mite. While complete eradication is unlikely, you can diminish populations and damage from varroa mites.
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Varroa mite females are 1.1 to 1.5 millimeters long, reddish brown in color with oval, flattened bodies. They are easily seen by the naked eye (about the size of the head of a pin). The male varroa mites are much smaller and rarely studied. They have piercing, sucking mouthparts and feed on the blood of adult, pupal and larval bees.
Adult females enter unsealed honeybee larval cell and lay about 5 eggs. The eggs hatch and the mite larvae and nymphs feed on the developing bee and emerge when the bee emerges. They can live from 2-3 months in the summer and 6-8 months in the winter. The mites use adult and pupal bees as intermediate food sources and transportation.
The natural hosts of varroa mites are the Asian honeybee, and the mites seldom reach a destructive level in this host. However, these mites are now common across the United States and are causing destruction in many honeybee populations. Heavy infestations can cause bees to be deformed, with misshapen legs, wings, and shortened bodies, and sometimes death.
Integrating several varroa mite control methods and treatments is the best way to keep varroa mites from destroying your bee populations. Removal and destruction of infested bee broods has been shown to reduce mite populations, but this method is labor intensive and can cause the hive stress. Testing bees to check the number of mites is also and important step.
Some pesticide products formulated for varroa mites are available and have shown some success. Resistant bee lines can reduce mite populations, and some organic oils (like neem, thymol, and canola) can be used with other methods. There are traps and screens you can put into the hives, but check bee keeping catalogues and books for the latest in varroa treatment methods, as research is ongoing.
Information via DoMyOwnPestControl.com experts, Clemson University Cooperative Extension, and Purdue University Extension.