Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/25/2012
Publication Date: 6/12/2012
Citation: Unruh, T.R., Pfannenstiel, R.S., Peters, C., Brunner, J., Jones, V.P. 2012. Parasitism of leafrollers in Washington fruit orchards is enhanced by perimater plantings of rose and strawberry. Biological Control. 62:162-172. dx.doi.org/10.1016/j.biocontrol.2012.04.007. Interpretive Summary: Leafroller insects damage both leaves and the fruits in apples, pears, cherries, and peaches in Washington State. Insecticides used to control leafrollers in spring are only moderately effective and can disrupt biological control of other pests, but are used by growers because biological control of leafrollers is poor. Researchers from the USDA ARS laboratory in Wapato WA and Washington State University in Wenatchee, Washington tested plantings of a native rose that acts to export a beneficial parasite of leafrollers as a way to increase biological control of pest leafrollers in orchards. The rose plantings led to significantly increased parasitism of pest leafrollers in orchards by the beneficial wasp over a period of 5 years. Overall, the results of the study suggest this habitat modification is easy for growers to implement and may increase biological control of leafroller complex while reducing overall pesticide use in orchards. Thirty-five such rose habitats have been planted by cooperating orchards throughout Washington State.
Technical Abstract: Pandemis pyrusana and Choristoneura rosaceana are the dominant leafroller pests in apple, pear and cherry orchards in Washington State. Parasitism rates of these pests are usually too low to avert the use of insecticides for control, despite the presence of a diverse parasitoid complex. In a previous study, parasitism rates of leafrollers were observed to be higher in orchards adjacent to thickets of Rosa woodsii. Here we show that plantings of R. woodsii and strawberry (Fragaria x ananassa) on the perimeter of orchards can significantly increase parasitism rates of leafrollers in the adjacent orchards. In late summer of 2000, R. woodsii and strawberries were planted near the perimeter of four apple orchards. These plantings were infested with the strawberry leafroller, Ancylis comptana, which develops and overwinters as mature larvae on R. woodsii throughout Central Washington. In fall, these larvae were parasitized by Colpoclypeus florus, a parasitoid of European leafrollers that was introduced into North America in 1968. In spring 2001, moderate rates of parasitism by C. florus were observed on P. pyrusana larvae placed along transects into apple orchards up to 200 m from the experimental plantings. In summer, parasitism by C. florus increased and was observed up to 500 m from the plantings. This pattern of parasitism continued through 2005, at one site. In contrast, little or no parasitism by C. florus at these sites was observed in 1999 and 2000, before creating the rose plantings. Using a protein marking technique, self-marked C. florus originating from a marked rose planting were captured up to 100 m away in an adjacent orchard. We conclude that rose and strawberry plantings showed value as potentially sustainable landscape modification to improve biological control of leafrollers in Washington fruit orchards.