Attractiveness of common insectary and harvestable floral resources to beneficial insects

Resources for natural enemies are often lacking in agricultural fields. The provisioning of floral resources in crop fields can ameliorate this problem by providing nectar and pollen to natural enemies. To select an appropriate floral resource, plants must be screened for their flowering times and attractiveness to natural enemies and pests. We tested the attractiveness of nine species of annual flowering plants to hoverflies, which are important predators of aphids in California lettuce fields. We also sampled arthropods in the foliage of tested plants, to assess the abundances of other natural enemy and pest species that were present. Tested plants included three commonly-used insectary plants and six flowering plant species that showed potential as either harvestable herbs or cut flowers. Harvestable insectary plants may provide additional economic incentive for growers to set aside land for floral resources. The commonly-used insectary plant sweet alyssum consistently attracted the most hoverflies and the least bees, while potentially harvestable plants attracted few hoverflies. Competition with bees may have reduced hoverfly visits to several of the tested plant species. Sweet alyssum also stayed in bloom the longest, and contained the highest numbers of predatory hemipterans. Results suggest that plants should be screened for their attractiveness to not only the target biological control agent, but also to other potential competitors for floral resources. While this initial study focused on a limited selection of harvestable annual plants, a wide variety of other marketable plant species, particularly perennials, remain to be tested for their attractiveness to hoverflies or other beneficial arthropods.

Nectar and pollen are critical for the survival and reproductive success of many natural enemy species, but are often lacking in agricultural monocultures. To enhance the effectiveness of natural enemies in agroecosystems, candidate insectary plants must be screened for traits that are appropriate for the targeted natural enemies. In this study, we screened three commonly-used insectary plants and six potentially harvestable flowering plants for their attractiveness to predatory hoverflies and other beneficial insects and pests. The common insectary plant sweet alyssum flowered the longest and consistently attracted the most predatory hoverflies and the least honey bees.Figure optionsDownload as PowerPoint slideResearch highlights
► The common insectary plant sweet alyssum attracted the most hoverflies.
► Potentially harvestable plants attracted mainly honey bees.
► Sweet alyssum stayed in bloom the longest of all tested plants.
► Sweet alyssum also contained the highest numbers of predatory hemipterans.