Variability in small hive beetle, Aethina tumida, reproduction in laboratory and field trials

Authors: Meikle, William; HOLST, NIELS - Aarhus University; Cook, Steven; Patt, Joseph - Joe

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2015
Publication Date: 5/4/2015
Citation: Meikle, W.G., Holst, N., Cook, S.C., Patt, J.M. 2015. Variability in small hive beetle, Aethina tumida, reproduction in laboratory and field trials. Journal of Economic Entomology. doi: 10.1093/jee/tov101.

Interpretive Summary: Small Hive Beetles were accidentally introduced into North America over 15 years ago and they have become serious pests of honey bees in some parts of the United States. In this study we conducted laboratory and field experiments to explore how beetle reproduction with and without bees present. The laboratory experiment simply monitored the number and weight of beetle larvae produced when adult beetles were exposed to 10 or 20 grams of food. We found that, even in a situation in which temperature, relative humidity, and beetle movement is highly controlled, larval production was inconsistent and hard to predict. We also conducted three different field experiments: one in which beetles were introduced into hives via infested frames; one in which the ability of the bee colonies to clean themselves was weakened by removing all sealed brood (the young bees do most of the cleaning) before introducing adult beetles; and one in which adult beetle groups were repeatedly put in the hives. No larvae were found in any of the field experiments, suggesting there may be other ecological factors that are controlling beetle populations in the field. Taken together, the laboratory and field experiments indicate that forecasting beetle population growth in the field may be difficult.

Technical Abstract: Two kinds of experiments were conducted with groups of Aethina tumida adults: Laboratory experiments exposing adult beetles in closed boxes to two different levels of food availability and kept at two temperatures (28ºC and 32ºC); and 3 field experiments in honey bee colonies, the typical environment for A. tumida. The laboratory experiments were intended to simulate simplified bee hives with small amounts of food (10g or 20g of a honey and pollen mixture) in containers that allowed larvae, but not adults, to escape. Although adult age (emerged within two weeks) and sex (1:1 sex ratio) were controlled, daily larval counts and daily larval total masses were highly variable within each food and temperature treatment. In some cases a single cohort of larvae emerged from the containers, in other cases two or more cohorts. Larval number was not significantly affected by food mass for larvae kept at 32ºC, but it was at 28ºC. Larval mass, however, was affected by temperature at the higher food mass treatment but not the lower. The field trials were intended to observe A. tumida population growth in hives that were stressed by removal of bee brood or by multiple introductions of A. tumida adults. However, no A. tumida larvae were observed to emerge from any of the hives in any of the trials, and none were observed within during inspection. The lack of an impact on the bees in the field trials may have implications in forecasting the severity of A. tumida as a honey bee pest in similar locations or environments.