On California’s central coast, everybody’s gone Syrphid

Adult aphidophagous Syrphidae often visit flowers, and mouthpart morphology differs between species that mainly feed on nectar and those that also take pollen. Adult hover flies require honeydew or nectar and pollen to ensure reproduction, whereas larvae usually require aphids to complete development. However, in the absence of aphids, larvae of some species can subsist and complete development on sole diets of plant materials such as pollen, e.g., Melanostoma and Allograpta obliqua and Toxomerus (Mesograpta sp.).

Organic lettuce growers in Monterey and Santa Cruz counties of California commonly use nectar- and pollen-bearing insectary plants in efforts to enhance biological control. The evidence is not yet conclusive, but suggestive that the schemes do work. The primary insectary plant has been sweet alyssum (Lobularia maritima), an annual forb in the Brassicaceae. Other options include woody perennial native plants and harvestable culinary herbs and cut flowers. Several research programs are addressing these issues, including projects by Rebecca Chaplin Kramer, Kent Daane, Erik Nelson, Tara Pisani-Gareau, and Hugh Smith.