Making a feast out of a fly: The asparagus miner (Ophiomyia simplex; Diptera: Agromyzidae) and the composition, longevity and flower preference of its parasitoid community

The asparagus miner is a specialist pest in most major asparagus producing regions of the United States. Both adults and immatures are more abundant along field edges than inside commercial asparagus fields, thus planting flowering resources in field perimeters could be used to increase the longevity and fecundity of its parasitoids. The addition of flowers may also have negative impacts since adult miners also use flowers as resources; therefore, it is important to identify flowers that aid the parasitoids, but not the pest. Our study had three objectives: 1) evaluate the species composition and abundance of the asparagus miner’s pupal parasitoids, 2) determine the impact of different diets on the longevity of the miner and its parasitoids, and 3) investigate the benefit of different flowers as food for parasitoids. We collected miner pupae from commercial asparagus fields and reared them in environmental chambers to investigate the species identity of parasitoids. The longevity of different parasitoid species and miner adults was recorded after feeding them one of five diets (no food, sugar, honey, asparagus, or water), or exposing them to one of four flowering plant species (horsemint, Riddell’s goldenrod, buckwheat or fava bean). Our results indicate that the parasitoids belong to at least three families, and that pteromalids are the most abundant in commercial fields. Additionally, feeding the parasitoids with honey or sugar solution more than doubled their lifespan, while it increased miner longevity 8-fold. Overall, our results show that the parasitoid community is diverse, and we discuss implications for management.