Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2005
Publication Date: 3/24/2006
Citation: Lacey, L.A., Arthurs, S.P., Unruh, T.R., Headrick, H.L., Fritts, R. 2006. Entomopathogenic nematodes for control of codling moth (Lepidoptera: Tortricidae) in apple and pear orchards: Effect of nematode species and seasonal temperatures, adjuvants, application equipment and post-application irrigation. Biological Control. 37:214-223. Interpretive Summary: Codling moth is a major pest of apple, pear and walnut in many parts of the world and the principal pest of apple in the Pacific Northwest of the United States. Significant reduction of overwintering codling moth larvae would provide substantial protection to apples and pears early in the following growing season. Overwintering codlin moth larvae utilize cryptic habitats in which to spin their cocoons. With adequate moisture and temperature, entomopathogenic nematodes can be effective control agents of insects in cryptic habitats. Researchers at the USDA-ARS, Yakima Agricultural Research Laboratory are conducting studies to develop and evaluate insect-specific nematodes for control of cocooned larvae in apple and pear orchards. It was found that infective stages of two species of nematodes were highly effective at controlling cocooned larvae in orchards when temperature was 15°C or higher and moisture was maintained in the orchard for several hours. Formulation of the nematodes to improve penetration of larval habitats and to retard drying of the nematodes improved their activity. These findings indicate that insect-specific nematodes could provide a non-chemical means of control of codling moth when all or most of the population is in the overwintering (cocooned) phase.
Technical Abstract: Field trials of the insect-specific nematodes, Steinernema carpocapsae and S. feltiae were conducted in apple and pear orchards under a variety of conditions to determine the effects of nematode species and seasonal temperature, formulation, post-application irrigation and method of application on efficacy. Applications of one million infective juveniles (IJs) of S. carpocapsae or S. feltiae per apple tree with a backpack sprayer plus wetting agent and supplemental wetting in late summer and early fall with mean temperatures of 16.6°C and 10.3°C during the initial 24 h following treatment resulted in larval mortalities caused by S. carpocapsae of 94.4 and 58.2, respectively and 95.1% and 90.1%, respectively, due to S. feltiae. Similar tests with S. feltiae in the same location in mid-October (mean temp. 7.3°C) using cocooned sentinel larvae in logs and cardboard strips were conducted with and without: post-application wetting, wetting agent and a humectant. The highest mortality (80%) was observed in cardboard substrates receiving post-application wetting, and either wetting agent or humectant. Apple trees that were treated in late summer (mean temp. 20.1°C) with two million IJs of S. feltiae per tree using an airblast sprayer or with a hand-held lance applicator plus supplemental wetting resulted in 83 and 92% mortality in sentinel CM larvae, respectively. CM mortality under two types of irrigation, conventional over head springlers and micro-sprinklers, in a older commercial pear orchard that was treated with one billion IJs/acre of S. carpocapsae using an airblast sprayer resulted in nearly 100 % mortality in sentinel larvae.