Varroa mite alert from the Honey Bee Lab
September 22, 2015
From: Oregon State University | College of Agricultural Science
Honey Bee Lab News
Hope all of you had a relatively successful bee year with strong hives and significant honey production, and have prepared your hives for successful overwintering. I just wanted to take this opportunity to alert / caution you about possibility of high mite populations in the colonies this year due to an unusually long bee season. As you all are aware we had a long bee season this year (at least in the Willamette Valley) as a result of warm weather that prevailed for almost more than 7 months. Longer brood cycle (abundance of larvae) usually results in higher mite populations, as the mites get a greater opportunity to breed and increase their populations relative to bees. Most of you might agree that this year was a year with longest brood cycle seen in the recent past (I have been in Oregon only for the past 6.5 years, so can’t go beyond that number). It has been reported that mite populations could increase exponentially (up to about 50 fold increase) in years when the brood is present in colonies almost round the year (Martin 1998).
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Following is a question relevant to Varroa mite biology that an Oregon beekeeper asked me few months ago.
Question: How many days is the female Varroa mite outside of the capped brood before it re-enters another cell for reproduction? Do the young female mites that emerge along with the new bees also take the same amount of time to re-enter another larval cell for reproduction?
Answer: The time a female Varroa takes to re-enter (re-infest) a new cell depends on the availability of older larva (ready to be capped) to enter, and also on the number of bees in the hive at that point of time. One study showed that on average female mites take about 4 to 6 days to re-infest new larval cells. In a lab study, female mites that were artificially reintroduced into new cells with appropriate aged larvae (ready to be capped) immediately after emergence from a cell were able to reproduce successfully without any problems. Young female mites that emerge along with the foundress mite (parent mite) need time to achieve full maturity and hence may take a little more time to enter a cell for reproduction than the parent mite. Research pertaining to these new young mites is scarce, hence providing an average time for infestation is difficult.
Regards,
Ramesh Sagili
Oregon State University
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