If you have bagworms in your landscape, those moth larvae that spin large, bag-like eyesores in tree branches, you’ve probably been told there’s not much you can do but cut them out of the tree and destroy them. That’s not always easy to do, depending on the height of the tree.
Now there is hope of deterring the bagworm pest altogether. New studies at the University of Illinois at Urbana-Champaign show promise that planting members of the Aster family near and/or around the susceptible tree will attract a natural predator of bagworm, ichneumonid wasps.
Before you get alarmed at the thought of attracting wasps, these are not the type to be interested in stinging you. In fact, most don’t even have stingers. These tiny members of the wasp family parasitize other insects by laying their eggs inside their prey.
The report below, courtesy of Brooklyn Botanic Garden’s “Plants and Garden News”, suggests planting Shasta daisies, New England asters, and Gazania. Any of these would look better in your garden than bagworms.
Plant Daisies to Fight Bagworms
The bagworm (Thyridopteryx ephemeraeformis) is a common pest of many coniferous and deciduous trees in the eastern U.S. This moth’s larvae spin unsightly baglike shelters in tree canopies and can cause serious damage through defoliation. Typical control methods include mechanical removal of the bagworm shelters (when feasible) and the application of pesticides. However, the bagworm has a number of natural enemies —in particular, parasitoid insects, such as ichneumonid wasps—and research at the University of Illinois at Urbana-Champaign has shown that bagworm control by these insects can be enhanced by planting certain flowering plants near trees and shrubs that are susceptible to bagworm infestations.
The flowering plants used in the UIUC research were all members of the Asteraceae, or aster family, which includes many species with daisylike blossoms known to attract parasitoids. Among them were a shasta daisy cultivar (Leucanthemum × superbum ‘Alaska’), a cultivar of the Newfoundland aster (Aster novi-belgii ‘Professor Anton Kippenburg’), and the treasure flower (Gazania rigens), a South African native.
The bagworm host plant was an arborvitae cultivar (Thuja occidentalis ‘Woodwardii’). In one trial, surrounding host plants with flowers led to a 70 percent increase in the parasitism of bagworms. In another trial, attacks on bagworms by parasitoid insects increased by a factor of three when host plants were surrounded by a high density of daisy flowers. Many plants in the Asteraceae are native to North America.
Source: J.A. Ellis et al., “Conservation Biological Control in Urban Landscapes: Manipulating Parasitoids of Bagworm (Lepidoptera: Psychidae) with Flowering Forbs,” Biological Control 34(1), July 2005, 99–107 (Elsevier Science, 6277 Sea Harbor Dr., Orlando, FL 32887).
Reprinted courtesy of Brooklyn Botanic Garden