Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size

Abstract

Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.

Diversity and Global Distribution of Viruses of the Western Honey Bee, Apis mellifera

“…However, large pollination events bring bees and colonies from all over the country and with unknown pathogen loads into close contact: a perfect storm for epidemic disease transmission. One study showed that BQCV and SBV are significantly more prevalent in migratory bees [110], and this was confirmed for colonies being transported for almond pollination [111]. However, in the latter study, BQCV levels were similar between the migratory and the stationary colonies one month after they returned to their home apiaries.…”

Longitudinal monitoring of honey bee colonies reveals dynamic nature of virus abundance and indicates a negative impact of Lake Sinai virus 2 on colony health

“…Specifically, the rate of change in DWV abundance decreased from 0-100 days of the study and then increased from 150-250 days of the study (Fig 8). The time period between 0 and 100 days (i.e., November 2015 and March 2016) of the study encompasses the transport of colonies from Montana to California for almond pollination, which is noteworthy since reports on pathogen abundance before and after transportation events have indicated that pathogen load may increase [92,104]. In addition, prior to this transportation event, all colonies in this study were treated with miticides to reduce Varroa destructor mite infestation levels.…”

“…The Canadian National Honey Bee Health Survey data includes virus analysis of over 2,500 apiary-level samples (i.e., samples from 10 colonies per apiary) collected between July–September 2017, and indicates a high incidence of BQCV, DWV, LSV2, and SBV [ 90 ]. There have been relatively few longitudinal monitoring studies performed at the colony or superorganism level [ 53 , 89 , 91 , 92 ]. Previous studies indicate that virus prevalence and abundance varies with sample date (or season) and that peak abundance typically coincides with increased brood rearing and foraging activities during the summer months in temperate climates [ 53 , 54 , 85 ] (reviewed in [ 44 , 55 ]).…”

The Great Bee Migration: Supply Analysis of Honey Bee Colony Shipments into California for Almond Pollination Services

“…Without adequate forage, beekeepers must supply colonies with sucrose syrup and artificial pollen (Alger et al, 2018). To reduce the amount of food supplements that must be purchased, many commercial beekeeping operations move colonies from one blooming crop to another (Bond, Plattner, and Hunt, 2014).…”