Dr. Mike Simone-Finstrom met with Person County Beekeepers to share his latest research.The beekeeping industry has reported that winter colony losses of about 15 percent annually are sustainable, though beekeepers expect that percentage to rise slightly if the winter is particularly harsh. However, since 2006 annual colony losses have been around 30 percent due to parasites, viruses, poor nutrition, agrochemicals, management, and queen health/genetics. He encouraged us to keep our focus on the bee and promoting bee health. His efforts focus on understanding how bees defend themselves and using that understanding as part of an Integrated Pest Management strategy.
He is especially interested in the interplay between individual immunity and the immunity of the colony, the superorganism. He is curious about how changes in the defense strategies of a dense population of close relatives might impact the genes devoted to individual immune defense strategies. Individual strategies include physical characteristics …like the “skin” and physiological … like the production of antimicrobial peptides that attack bacteria (like our white blood cells). Social strategies include traits like grooming behavior and the use of propolis. In one test, he found that a propolis-enriched environment reduced hive bacteria which in turn reduced the immune function in individual bees.
His continuing research explores ways that colonies invest in multiple defenses ….both social and individual immunity. He built on prior research in which four characteristics were shown to be effective against some maladies: Multiple mating of queens…queens may mate with 4 to 40 drones, but the average is 12. Grooming both alo-grooming (nest-mates) and self-grooming which knocks down Varroa. Hygienic behavior in which workers sense sick larva and remove them from the hive before their contagious Use of resin/propolis.
His goal for PCBA members? Be awed by the strength and resilience of the bees. To help beekeepers who breed queens for these characteristics, Michael wanted to show whether there were positive or negative associations among these defense strategies. A prior study showed that multiple matings of queen, resulting in higher genetic diversity in the colony, both (a) reduced the prevalence and intensity of infections AND (b) increased the overwintering survival rate. In his test, he weighted queens with a “top hat” amounting to about 15 percent of their body weight to increase the effort required on the mating flight and therefore (hopefully) reducing the number of matings. This resulted in two groups of hives: one with low genetic diversity (queen mated with 4-7 males) and one group with high genetic diversity (queens mated with 14-30 males). Queens were only permitted ONE mating flight.
The result? A significantly higher level of chalkbrood infection in the hives with LOW diversity. To test the impact on resin foraging (the number of bees returning to the hive with resin on hind legs), he counted resin-foragers before and after “the challenge”-infection with chalkbrood. To test the impact on hygienic behavior, a heritable trait, he freeze-killed brood, then checked in 24 hours to see how many larvae had been removed. In his colonies, the range was from 100 percent to 0 percent removal. (A beekeeper could cut out a section of comb, freeze it, and re-insert it in the “hole” to determine whether his queen carried the trait for significant hygienic behavior.) To test the impact on grooming behavior, instead of tediously collecting mites on sticky board and counting how many had been bee-bitten, he coated bees with flour and measured flour-removal in pixils as the bee bodies were digitally-scanned.
The result? He found that the colonies with higher genetic diversity did do more grooming, but he found no relationship with the other defense strategies. To measure individual immunity, he grafted 1st instar larvae, put them on an artificial diet and gave AFB to half of the test group, then analyzed immune response. He found no relationship between the individual response and social resin-gathering or grooming behaviors. In the colonies with higher genetic diversity, he found decreased variance in the individual immune response. He was intrigued that the colony response was driven by larval response because the olfactory function is the basis for hygienic behavior so… how did the larvae sense the maladies?
What’s a beekeeper to do? Use resistant, local stocks. Select for hygienic behavior in your own bees, encourage bees to enrich the hive with propolis by roughing up the interior walls, and continuously monitor colony health.