As Washington state apple growers have adopted integrated pest management and switched to softer chemistries, pest populations have reacted.
Secondary pests, such as woolly apple aphids that used to be controlled by broad-spectrum insecticides, are becoming more of a problem, according to a news release.
Woolly apple aphids can damage plants as they feed on the sugary phloem, or plant sap. They also can feed on roots, reducing the plant's ability to take up soil nutrients.
To help control this up-and-coming pest, Washington State University entomologist Betsy Beers is exploring how growers could entice more beneficial insects into their orchards.
Of particular interest to Beers and her team, who are based in Wenatchee, are syrphids—also known as flower flies or hoverflies.
Adult syrphids feed primarily on flower nectar.
But the larvae thrive on a diet of aphids, including woolly apple aphids.
Beers and her colleagues are exploring how planting specific low-growing flowering plants in orchard middles might increase syrphid populations.
Growers typically have grasses or native vegetation in orchard middles.
Results of a small-scale experiment show alyssum, a low-growing plant also used for ornamental borders, holds promise.
The researchers' next step is to conduct experiments in commercial orchards.