Extreme Temperatures During Shipping Can Affect Honey Bee Queens’ Reproductive Abilities
Many beekeepers order honey bee queens from breeders, who ship them to the beekeepers by mail. According to an article in the journal PLOS One, high temperatures during shipping and elevated pathogen levels may be contributing to honey bee queens failing faster today than they did in the past.
“Either stress individually or in combination could be part of the reason beekeepers have reported having to replace queens about every six months in recent years when queens have generally lasted one to two years,” said entomologist Jeff Pettis, a USDA-ARS entomologist and one of the co-authors.
Queens only mate in the first few weeks of their lives, and they use the stored semen to fertilize eggs for the rest of their lives. Queen failure occurs when the queen dies or when the queen does not produce enough viable eggs to maintain the adult worker population in the colony. Replacing queens cost about $15 each, a significant cost per colony for beekeepers.
Commercial beekeepers usually order their replacement queens already mated, and the queens are shipped to apiaries from March through October. Pettis and his colleagues wondered whether temperature extremes during shipping could damage the sperm a queen has stored in her body, so they conducted a lab experiment and found that inseminated queens exposed to temperatures of 104 °F (40 °C) for 1-2 hours or to 41 °F (5 °C) for 1-4 hours had sperm viability drop to 20 percent from about 90 percent.
In real-world testing, queens were shipped from California, Georgia and Hawaii to their lab in Maryland by either U.S. Postal Service Priority Mail or United Parcel Service Next Day Delivery in July and September, and the packages contained thermometers that recorded the temperature every 10 minutes. The researchers found that as many as 20 percent of the shipments experienced temperature spikes that approached extremes of 105.8 °F and 46.4 °F for more than two hours at a time. Those exposed to extreme high or low temperatures during shipping had sperm viability reduced by 50 percent.
“The good news is with fairly simple improvements in packaging and shipping conditions, we could have a significant impact on improving queens and, in turn, improving colony survival,” Pettis said.
The researchers also assessed queens that were sent to them by beekeepers, and almost all of them had a high incidence of deformed wing virus; Nosema ceranae was the next most commonly found pathogen.
Beekeepers were asked to rate the performance of each colony from which a queen came as either in good or poor health, and a clear link was found between colonies rated as better performing and queens with higher sperm viability. Poorer performing colonies strongly correlated to queens with lower sperm viability.
“We saw wide variation in both pathogen levels and sperm viability in the queens that were sent in to us, and sometimes between queens from the same apiary in July and September, so there is still more research to do. But getting queens back to lasting two years may well be one of the links in getting our beekeeping industry back to a sustainable level,” Pettis said.
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