Effects of the insect growth regulator, novaluron on immature alfalfa leafcutting bees, Megachile rotundata
1Department of Entomology, Iowa State University, Ames, Iowa 50011-3140
2USDA-ARS Bee Biology and Systematics Laboratory, Utah State University, Logan, Utah 84322
3University of Idaho, Parma Research and Extension Center, Parma, Idaho 83660
Abstract
Alfalfa leafcutting bees, Megachile rotundata F. (Hymenoptera: Megachilidae), are the most common pollinators of alfalfa in the Pacific Northwest. Reports from users of M. rotundata in Idaho, Utah and Colorado have indicated exceptionally poor bee return from fields treated with novaluron to control Lygus spp. Our goal was to evaluate novaluron toxicity to immature M. rotundata using two different possible mechanisms of exposure. One goal was to assess immature mortality via treating nectar-pollen provisions and adults with novaluron. Immature M. rotundata mortality in all novaluron provision dosing treatments was significantly higher than the water or blank controls, providing evidence that novaluron is toxic to progeny in nest cells. The mean cumulative frequency showed that more eggs and 1st-2nd instars died compared to older instars. Female M. rotundata nested similarly in field cages during the field cage experiment; however, there was greater immature mortality in cages where females were fed sugar-water + novaluron compared to sugar-water only. Although females provided adequate provisions, there was a low percentage of egg hatch and larval development when females ingested novaluron before mating and nesting. Novaluron was also present in egg provision of bees collecting resources from novaluron-sprayed plants. At least 84% of progeny died when the females were allowed to mate and nest 24 hours after a novaluron application. Novaluron could be contributing to poor bee return in alfalfa grown for seed. Timely insecticide applications to suppress Lygus spp. is an important consideration to improve ongoing bee health.
Keywords: pollinator, alfalfa seed, Rimon, egg mortality
Correspondence:
aewh@iastate.edu,
bTheresa.Pitts-Singer@ars.usda.gov,
cjbarbour@uidaho.edu
Editor: TX Liu was editor of this paper
Received: 2 April 2010 | Accepted: 7 September 2010 | Published: 8 April 2011
Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.
ISSN: 1536-2442 | Volume 11, Number 43
Hodgson EW, Pitts-Singer TL, Barbour JD. 2011. Effects of the insect growth regulator, novaluron on immature alfalfa leafcutting bees, Megachile rotundata. Journal of Insect Science 11:43 available online: insectscience.org/11.43
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