When Pol-line colonies and standard colonies were treated against Varroa mites in both fall and December, Pol-line bees had a winter survival rate of 72 per cent while standard bees had a survival rate of 56 per cent
Pol-line honey bees, a type of Varroa mite resistant honey bee developed by the Agricultural Research Service (ARS), are more than twice as likely to survive through the winter than standard honey bees, according to a study published in Scientific Reports.
Although ARS developed Pol-line bees in 2014, the study was the first time that they were tested head-to-head alongside standard honey bee stock in commercial apiaries providing pollination services and producing honey. Colonies’ ability to survive winter without being treated to control Varroa mites was followed in four states: Mississippi, California, and North and South Dakota.
In this study, Pol-line colonies that were given no treatment to control Varroa mites in the fall had a survival rate of 62.5 per cent compared to standard bees colonies in commercial apiaries also given no fall Varroa treatment, which had a winter survival rate of 3 per cent.
When Pol-line colonies and standard colonies were treated against Varroa mites in both fall and December, Pol-line bees had a winter survival rate of 72 per cent while standard bees had a survival rate of 56 per cent. So, Pol-line bees still had a better winter survival rate regardless of receiving double Varroa mite treatment.
This research was the culmination of breeding efforts to develop honey bee colonies with naturally low Varroa populations that began at the Baton Rouge lab in the late 1990s.
Winter colony survival is crucial for beekeepers because in February each year, about 2.5 million honey bee colonies are needed in California to pollinate almond crops. Larger, healthier colonies bring beekeepers premium pollination contracts at about $220 a colony.
Varroa mites can cause massive colony losses; they are the single largest problem facing beekeepers since they spread to the US from South East Asia in 1987. While miticides used to control Varroa exist, resistance is developing to some of them.
In addition, overall winter survival, the scientists examined the levels of viruses in Pol-line and standard bee colonies that are commonly transmitted by varroa mites.
The Pol-line colonies showed significantly lower levels of three major viruses: Deformed wing virus A, Deformed wing virus B and Chronic bee paralysis virus, all of which can cause significant problems for colonies.
