Effect of Collection Month, Visible Light, and Air Movement on the Attraction of Male Agriotes obscurus L. (Coleoptera: Elateridae) Click Beetles to Female Sex Pheromone

Elaterid female sex pheromone, while currently used for monitoring the adult life stage (click beetle), has only recently been explored as a potential management tool. Consequently, there is little understanding of how abiotic and biotic conditions influence the response of click beetles to the pheromone. We examined whether the response of male Agriotes obscurus L. (Coleoptera: Elateridae) beetles to a cellulose-based formulation of female sex pheromone (‘pheromone granules’) is influenced by air movement, presence of visible light, and month of beetle collection. In addition, we investigated the distance from which beetles were attracted to the pheromone granules. Click beetle response was determined by measuring movement parameters in free-walking arena experiments. The response to pheromone was not affected by the presence or absence of visible light. We found that beetles collected earlier in the season had increased activity and interaction with pheromone under moving air conditions, compared to beetles collected later. When controlling for storage time, we confirmed that individuals collected in May were less active than beetles collected in March and April. In the field, beetles were recaptured from up to 14 m away from a pheromone granule source, with over 50% being recovered within 4.4 h from a distance of 7 m or less. Understanding how abiotic and biotic factors affect pest response to pheromone can lead to more effective and novel uses of pheromone-based management strategies

Removal of Varroa jacobsoni infested brood in honey bee colonies with differing pollen stores

The effects of high or low pollen storage on Apis mellifera L. brood removal behavior and Varroa jacobsoni reproduction were examined. High pollen storage colonies removed 49% of the infested larvae compared to 33% removal by the low pollen storage colonies. No difference was found in the proportion of fertile mites between those reared in high or low pollen storage colonies, although mite fertility appeared to decrease from mid to late summer in British Columbia, Canada. These findings indicate that the presence of pollen stores increases the rate of cell removal, and warrants further investigation into colony management as a potential means of V. jacobsoni infestation control.Élimination du couvain infesté par Varroa jacobsoni dans des colonies d'abeilles en fonction des réserves de pollen. L'influence d'un stockage plus ou moins élevé de pollen sur le comportement d'élimination du couvain et la reproduction de V. jacobsoni a été étudié. On a pris des colonies qui élevaient du couvain et égalisé leur surface de couvain, leur population d'abeilles adultes et leurs réserves en miel. On a fourni un supplément de pollen au groupe de colonies “ à pollen élevé " et placé une trappe à pollen sur celles du groupe “ à pollen faible ". Un acarien V. jacobsoni a été introduit dans chacune des cellules fraîchement operculées des colonies des deux groupes (cellules tests) et des cellules ouvertes et refermées sans ajout d'acarien ont servi de cellules témoins. Dix jours plus tard, les cadres de couvain ont été retirés des colonies et la présence ou l'absence des cellules manipulées a été notée. La reproduction de l'acarien a été considérée comme positive si des deutonymphes mâles et femelles étaient présentes lors de l'émergence des abeilles. Les colonies à pollen élevé comme les colonies à pollen faible ont éliminé une plus forte proportion de cellules et de larves infestées que de cellules témoins. Chaque groupe a éliminé respectivement 42,7 et 30,5 % de cellules. Les colonies du groupe à pollen élevé ont éliminé 49 % de larves infestées contre 33 % pour les colonies du groupe à pollen faible. On n'a pas trouvé de différence dans la proportion d'acariens fertiles entre les acariens élevés dans les colonies à pollen élevé et ceux élevés dans les colonies à pollen faible, bien que la fertilité des acariens ait semblé décroître du milieu vers la fin de l'été en Colombie britannique, Canada. Les ouvrières semblent être capables de détecter la présence de V. jacobsoni dans une cellule operculée, puisqu'une plus grande proportion de couvain infesté est éliminé. Parce que, dans les colonies à pollen élevé, la demande en récolte de pollen est plus faible, les ouvrières peuvent être disponibles en plus grand nombre pour inspecter les cellules et éliminer le couvain ; ceci peut expliquer le plus grand pourcentage d'élimination chez les colonies à pollen élevé. Puisque la reproduction de l'acarien n'augmente pas avec les réserves en pollen, la gestion du pollen par les colonies devrait être étudiée comme outil potentiel pour gérer les populations d'acariens

Inheritance of Resistance to Bacillus thuringiensis subsp. kurstaki in Trichoplusia ni

The genetic inheritance of resistance to a commercial formulation of Bacillus thuringiensis subsp. kurstaki was examined in a Trichoplusia ni colony initiated from a resistant population present in a commercial vegetable greenhouse in British Columbia, Canada. Progeny of F(1) reciprocal crosses and backcrosses between F(1) larvae and resistant (P(R)) and susceptible (P(S)) populations were assayed at different B. thuringiensis subsp. kurstaki concentrations. The responses of progeny of reciprocal F(1) crosses were identical, indicating that the resistant trait was autosomal. The 50% lethal concentration for the F(1) larvae was slightly higher than that for P(S), suggesting that resistance is partially recessive. The responses of both backcross progeny (F(1) × P(R), F(1) × P(S)) did not correspond to predictions from a single-locus model. The inclusion of a nonhomozygous resistant parental line in the monogenic model significantly increased the correspondence between the expected and observed results for the F(1) × P(R) backcross but decreased the correspondence with the F(1) × P(S) backcross results. This finding suggests that resistance to B. thuringiensis subsp. kurstaki in this T. ni population is due to more than one gene

Mechanism of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Greenhouse Population of the Cabbage Looper, Trichoplusia ni

The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus thuringiensis in agricultural situations. The trait of resistance to B. thuringiensis toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. thuringiensis Cry toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. thuringiensis toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait, which is consistent with the recessive inheritance of Cry1Ab/Cry1Ac resistance in this greenhouse-derived T. ni population. Therefore, it is concluded that the mechanism for the greenhouse-evolved Cry1Ac resistance in T. ni is an alteration affecting the binding of Cry1Ab and Cry1Ac to the Cry1Ab/Cry1Ac binding site in the midgut