The effect of pymetrozine (Plenum WG-50®) on proboscis extension conditioning in honey bees (Apis mellifera: Hybrid var. Buckfast)

Experiments are designed to examine the effects of pymetrozine (Plenum WG-50 (R)), a recent systemic pesticide of the pyridine-azomethin family, on Pavlovian conditioning of harnessed foragers. In one set of experiments bees learned a task in which they associated a conditioned stimulus with feeding. A second set of experiments required the bees to learn a discrimination task. Within each experiment, bees received 5 mu l of sucrose only, the recommended field dose of Plenum (R) (5 mu L of 3 g L-1, 16 g L-1 of pymetrozine measured), or 100 times the field dose of Plenum (R) WG 50 thirty minutes prior to training (5 mu L of 30 g L-1, 14 g L-1 of pymetrozine measured). The Plenum (R) WG 50 was diluted with 88 M sucrose to facilitate the drinking of the pesticide. In addition to varying the concentration, we also investigated the effect of Plenum (R) WG 50 on bees confined to an observation hive and a hive located outside. The results indicated that prior exposure to Plenum (R) WG 50 affected Pavlovian conditioning only when bees were exposed to 100 times the recommended dosage. (C) 2011 Elsevier Inc. All rights reserved.