By KEVIN WALKER
Michigan Correspondent

COVENTRY, England — “The pattern of spread of varroa mites looks almost exactly like that of the rapid expansion of tracheal mites, with about a two-year delay. (Although) there are probably some locations, even some counties that are still free, the movement will surely continue until every apiary and colony in Michigan is infested.”

This was written by Roger Hoopingarner in B-Plus, a Michigan State University Department of Entomology newsletter, in the summer of 1992. In the 16 years since, the varroa mite has remained the number-one killer of honeybees in the United States.

It’s also a major problem in England and elsewhere. Varroa made it to England in 1992 and to the United States in 1987.

Effective chemical treatments for varroa have been developed, but the pest has developed resistance to some of these treatments over time. Recent research at the University of Warwick seeks a way around this problem, through the use of biological pest control. Microbiologist and entomologist David Chandler says it’s a way of “working with nature rather than against it.”

Recently, Chandler discussed his research with a university interviewer and made it available as a podcast online.

“If we go outside and sample leaves or soil, we’ll find lots of microorganisms that naturally kill invertebrates, and we can actually use them to our advantage for biological pest control,” he said.
He stated that it’s not unusual for bees to be used for delivery of beneficial microorganisms to plants. He said his system works sort of in reverse, since with his scheme bees are meant to bring beneficial microorganisms into the bee colony, via the front of the hive, rather than to some other target.

Since the bees bring the material into the hive on their feet, this particular method of delivery is known as a fungal footbath. He said that paper could be used to deliver the treatment as well, since bees love to chew through paper. Powder sprays or granules could also be used to deliver the treatment to the bees.

He described his research as a kind of screening process to identify exactly which microorganisms would be effective in killing the pest. Chandler, along with other researchers, examined 50 different types of fungi that afflict other insects to see if they would kill varroa. They discovered four types that could be effective.

“We’ve identified strains of fungi that kill the mites on bees, but which don’t kill bees and which don’t have an adverse effect on other non-target organisms,” he said.

He said the fungal spores grow inside the mites and, much as in the sci-fi movie Alien, burst out of the creatures later on.

Chandler thinks his research is important not only because it will help commercial and hobbyist beekeepers as well as farmers who need pollination services, but because it also furthers the principle that it’s best to fight agricultural pests in environmentally sustainable ways. (He added that he is not opposed to the use of chemical pesticides.)

Chandler and his research colleagues – Gill Prince, Brenda Ball, Judith Pell and Caroline Birchall – are hoping to find more funding to further study the four fungi types and identify the best delivery mechanisms.

Michigan, which produces 4.8 million pounds of honey annually, is ranked among the top 10 states for honey production. It also has an estimated 65,000 commercial honeybee colonies. Chandler believes his method of treating varroa will be effective everywhere, since the environment inside the hive is much the same no matter where it is located.

More on Chandler’s research is online at www2.warwick.ac.uk by typing in “honeybee research” at the search engine.