Effect of Bark Application With Beauveria bassiana and Permethrin Insecticide on the Walnut Twig Beetle (Coleoptera: Curculionidae) in Black Walnut Bolts.

Formulations of entomopathogenic (insect-killing) fungi represent alternatives to synthetic insecticides in the management of forest and shade tree insects. We evaluated bark spray applications of the entomopathogen Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) strain GHA (BotaniGardES), permethrin insecticide (Astro), and water (control) on colonization of black walnut (Juglans nigra L.) (Fagales: Juglandaceae) bolts by the walnut twig beetle (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae), vector of the fungus that causes thousand cankers disease. Treated bolts were baited with a P. juglandis aggregation pheromone lure and deployed in infested walnut trees. Bark application of permethrin prevented P. juglandis colonization of the phloem. Although treatment of bolts with the B. bassiana suspension did not reduce P. juglandis colonization or short-term emergence relative to the control treatment, it increased the B. bassiana infection rate from 25 to 62% of emerged adults. Results suggest that commercial applications of B. bassiana strain GHA may help augment natural levels of infection by this entomopathogen in the eastern United States, and support continued exploration of entomopathogens for biological control of the walnut twig beetle.

Chronic exposure of imidacloprid and clothianidin reduce queen survival, foraging, and nectar storing in colonies of Bombus impatiens.

In an 11-week greenhouse study, caged queenright colonies of Bombus impatiens Cresson, were fed treatments of 0 (0 ppb actual residue I, imidacloprid; C, clothianidin), 10 (14 I, 9 C), 20 (16 I, 17C), 50 (71 I, 39 C) and 100 (127 I, 76 C) ppb imidacloprid or clothianidin in sugar syrup (50%). These treatments overlapped the residue levels found in pollen and nectar of many crops and landscape plants, which have higher residue levels than seed-treated crops (less than 10 ppb, corn, canola and sunflower). At 6 weeks, queen mortality was significantly higher in 50 ppb and 100 ppb and by 11 weeks in 20 ppb-100 ppb neonicotinyl-treated colonies. The largest impact for both neonicotinyls starting at 20 (16 I, 17 C) ppb was the statistically significant reduction in queen survival (37% I, 56% C) ppb, worker movement, colony consumption, and colony weight compared to 0 ppb treatments. Bees at feeders flew back to the nest box so it appears that only a few workers were collecting syrup in the flight box and returning the syrup to the nest. The majority of the workers sat immobilized for weeks on the floor of the flight box without moving to fed at sugar syrup feeders. Neonicotinyl residues were lower in wax pots in the nest than in the sugar syrup that was provided. At 10 (14) ppb I and 50 (39) ppb C, fewer males were produced by the workers, but queens continued to invest in queen production which was similar among treatments. Feeding on imidacloprid and clothianidin can cause changes in behavior (reduced worker movement, consumption, wax pot production, and nectar storage) that result in detrimental effects on colonies (queen survival and colony weight). Wild bumblebees depending on foraging workers can be negatively impacted by chronic neonicotinyl exposure at 20 ppb.