Testing Novel Repellents to Protect the European Honeybee, Apis mellifera, From Insecticides
Author:Sophia de Alba
- Daniel F. Woods, Ph.D., President, Inscent, Inc.
- Jo Wu, Ph.D., Professor of Biology, Fullerton College
The European honeybee, Apis mellifera, pollenates many crucial crops and is essential to US agriculture, but it is threatened by Colony Collapse Disorder (CCD), which is currently causing severe beehive losses. CCD has been linked to the use of insecticides in agriculture and to reduce honeybees exposure to these insecticides, we are developing novel repellents for honeybees. Foraging honeybees mark visited flowers with 2-heptanone to repel conspecifics from spending time on nectar-depleted flowers, but 2-heptanone is not useful as a commercial repellent because it dissipates quickly. We have isolated an Odorant Binding Protein (OBP) in the bee olfactory pathway that binds to 2-heptanone and used this to select a number of novel compounds from a small molecule library that bind the same OBP and may elicit a similar repellent response. To test the behavioral effects of novel compounds in vivo, a "Free Flight" box assay has been developed that measures bee feeding behavior. Approximately 30 bees are allowed to feed from several honey dishes within the box for 15 minutes. The dishes are weighed before and after all tests to determine which dishes the bees preferred. The dishes are removed for 30 min and then fresh dishes are offered, either with the candidate repellent near the two most visited dishes or without it (control). If the favored dishes contain the repellent compound and the bees do not feed from these, it is likely that this compound acts as a repellent. Conversely, if the bees continue to feed in favored dishes containing compound, the compound is not considered a successful repellent. The weight consumed is calculated to determine whether bees are less likely to return to the dish when the compound is present. Twenty potential repellent compounds have been tested of which 6 demonstrated significant repellence (Student's t-test, p <0.05).