Jacques Mignon

Honey bee colony losses in Belgium during the 2008–9 winter

(2010). Honey bee colony losses in Belgium during the 2008–9 winter. Journal of Apicultural Research: Vol. 49, No. 4, pp. 337-339.

The impact of sperm precedence in malathion resistance transmission in populations of the red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Malathion resistance in the red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is actually a worldwide problem, and studies on resistance transmission are needed to improve insecticide resistance management. Females of Tribolium castaneum commonly mate with several males, and the last batch of male sperm preferentially fertilizes subsequent eggs. This phenomenon, a particular form of sexual selection, helps to increase resistance transmission in populations of stored product insects. We confirmed the last male sperm precedence and, in the absence of further matings, examined the evolution of mixed susceptible and malathion-resistant progeny during a 3-month period. The proportion of resistant phenotypes in female progeny was 99.6 and 3%, respectively, after the first mating with a resistant male and the second mating with a susceptible one. When females thus mated twice were isolated from males, the proportion of the resistant phenotype increased to 34.1% after 30 days. From 72 days onwards, this proportion ranged from 14.2 to 29.7%.

Effect of ice-nucleating bacteria (Pseudomonas syringae Van Hall) on insect susceptibility to sub-zero temperatures

Abstract Many stored product insect pests are termed “freeze-intolerant” because they cannot survive ice formation in their extracellular body fluid. In grain silos, the progressive decrease in temperature permits the acclimation of insects and enhances their cold tolerance. The objective of this study was to examine the influence of the concentration of the ice-nucleating-active bacterium Pseudomonas syringae (10, 100 and 1000 ppm), temperature and duration of sub-zero exposure on the cold tolerance of the granary weevil Sitophilus granarius (L.) and the saw-toothed grain beetle Oryzaephilus surinamensis (L.). After an application of 1000 ppm of powdered P. syringae to grain, the mortality of S. granarius and O. surinamensis was increased after 24-h exposure to −4 °C. Higher mortality was observed after exposure to colder temperatures and a dose-response relationship was evident. At near-zero (−4 to 0 °C) negative temperatures, no dose response was observed, and the mortality in treated grain was the same as that in untreated grain.

Influence of thermal acclimation on the survival of Sitophilus granarius (L) and Oryzaephilus surinamensis (L) at low temperatures

Low temperatures have been used for many years to control populations of stored-product insects. The aim of aeration was primarily to cool down the grain and then to prevent its deterioration by reducing the number of insects. In Belgium, the mild winters enable insects to survive to the next season. In autumn, the progressive lowering of temperature has an acclimation effect on stored-product insects. The present study was undertaken to determine the survival at low temperatures of non cold-acclimated and laboratory- and field-cold-acclimated insects. We have chosen to work with the granary weevil Sitophilus granarius (L.) and the saw-toothed grain beetle Oryzaephilus surinamensis (L.). They are the most frequent stored-grain pests in Belgium. To compare the cold-hardiness of different laboratory cold-acclimated insects, S. granarius and O. surinamensis were placed at nine different cold-acclimation temperature regimes. Insects were kept at 5°C for 2, 4 and 6 weeks or at -5°C for 4, 7 and 14 days. To assess the field-cold-acclimation in autumn and in winter, insects were monthly taken from a bin and transferred to 5°C for 6 weeks. S. granarius adults were more cold-hardy than O. surinamensis, but O. surinamensis adults compensated their cold-sensibility by a great ability to acclimate. S. granarius is able to survive the winter in Belgium because of its cold-hardiness while O. surinamensis survives because of its ability to acclimate to low temperatures.