ARS | Publication request: Impact of Metarhizium brunneum (Hypocreales: Clavicipitaceae) on pre-imaginal Rhagoletis indifferens (Diptera: Tephritidae) within and on the surface of orchard soil

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 16, 2011
Publication Date: December 12, 2011
Repository URL: http://handle.nal.usda.gov/10113/54942
Citation: Cossentine, J., Jaronski, S., Thistlewood, H., Yee, W.L. 2011. Impact of Metarhizium brunneum (Hypocreales: Clavicipitaceae) on pre-imaginal Rhagoletis indifferens (Diptera: Tephritidae) within and on the surface of orchard soil. Biocontrol Science and Technology. 21(2): 1501-1505.

Interpretive Summary: Cherry fruit fly is a serious pest of Northwest U.S. and western Canadian sweet and sour cherries. The larvae feed in the fruit before they drop to the orchard floor and burrow into the soil to pupate for ca. 11 months. This larval drop offers an opportunity to intercept the larvae with a fungus to allow suppression of the pest, as alternative to chemical insecticides, and particularly in organic orchards. The objective of the present study was to evaluate if a commercial fungus can infect and cause mortality of larval cherry fruit fly within non-sterile orchard soil. We also tested whether a lethal Metarhizium infection would result from larvae passing through spores on the surface of the soil. Larvae in treated soil, and prepupae entering treated orchard soil suffered significant mortality from the fungus. The information generated in this study point towards the practical possibility that a commercial mycoinsecticide can be used to control the insect by applying the fungus to the vegetation ground cover beneath the trees.

Technical Abstract: When last instar laboratory-reared Rhagoletis indifferens (Cherry Fruit Fly) were allowed to pupate within non-sterile orchard soil containing incorporated Metarhizium brunneum isolate F52 conidia, a dose-related proportion died from developmental abnormalities and mycosis. Similarly, when prepupal larvae entered soil that was superficially treated with 4.5 x 106 M. brunneum conidia per cm2, over 80 % of the pupae died of developmental abnormalities. Metarhizium was isolated from some of the aseptically dissected pupae removed from the treated soils. The susceptibility of laboratory reared R. indifferens to damage by M. brunneum when entering soil indicates that orchard floor management of this pest may be possible.