Effect of Leafy Spurge (Euphorbia esula) Genotype on Feeding Damage and Reproduction of Aphthona spp.: Implications for Biological Weed Control

Abstract

Abstract North American leafy spurge (Euphorbia esula L.) is genetically diverse and composed of multiple genotypes introduced from several areas of Europe and Asia. Five species of leafy spurge flea beetle (Aphthona spp.) have been introduced as biological control agents for leafy spurge, but were collected in a relatively small region of Europe. Greenhouse and field experiments were conducted to determine if observed variation in feeding preference and reproduction of Aphthona spp. on North American leafy spurge may be due in part to leafy spurge genotype. Leafy spurge genotypes were collected from Austria; Manitoba in Canada; and the states of Montana, Nebraska, North Dakota, South Dakota, and Wyoming in the United States. Leafy spurge genotype affected feeding but not egg laying by Aphthona spp. adults. Aphthona czwalinae/lacertosa fed slightly less in a free-choice test on a genotype from Manitoba (7%) compared to genotypes from Nebraska and North Dakota (14%). Aphthona flava tended to feed less on the Nebraska genotype than any other genotype evaluated. Reproduction of Aphthona spp. was greatly affected by leafy spurge genotype. For instance, A. czwalinae/lacertosa produced 72 adults per plant from a Nebraska genotype compared to 11 to 32 adults per plant from all other genotypes evaluated. Thus, some observed variation in establishment and reproduction of Aphthona spp. can be attributed to leafy spurge genotype.