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Title: Laboratory virulence and orchard efficacy of entomopathogenic nematodes against the lesser peachtree borer (Lepidoptera: Sesiidae)

Author
item Cottrell, Ted
item Shapiro Ilan, David
item HORTON, DAN - University Of Georgia
item MIZELL, R - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2010
Publication Date: 2/3/2011
Citation: Cottrell, T.E., Shapiro Ilan, D.I., Horton, D.L., Mizell, R.F. 2011. Laboratory virulence and orchard efficacy of entomopathogenic nematodes against the lesser peachtree borer (Lepidoptera: Sesiidae). Journal of Economic Entomology. 104:47-53.

Interpretive Summary: The lesser peachtree borer, Synanthedon pictipes (Grote & Robinson) (Lepidoptera: Sesiidae) is indigenous to eastern North America where it is a pest of commercially grown peach, cherry and plum. It is a serious pest, especially to southeastern peach orchards where insecticide regulatory changes affected usage on peach and facilitated pest populations. Here we tested species and strains of insect-killing nematodes against the larval stage of the lesser peachtree borer and consistently found that strains of the nematodes Steinernema carpocapsae provided better control than other Steinernema or Heterorhabditis nematode species. We showed that larger larvae are more susceptible to the nematodes than the smaller larvae. Additionally, we demonstrated that moisture-retaining covers (placed over S. pictipes-infested wounds on peach limbs) increased the ability of the nematodes to kill the lesser peachtree borer on trees. We conclude that even when using highly virulent nematodes against the lesser peachtree borer, it is likely that an application of nematodes to tree trunks or limbs will require an environmental modification to increase and maintain moisture to allow the nematodes to kill the pest.

Technical Abstract: The lesser peachtree borer, Synanthedon pictipes (Grote & Robinson) (Lepidoptera: Sesiidae) is indigenous to eastern North America where it is a pest of commercially grown Prunus spp., especially to southeastern peach orchards where earlier regulatory changes affected pesticide usage on peach and facilitated populations. Pest management practices are now having a positive effect toward control of this pest but biological control solutions are sought that may be cost competitive and promote increased environmental stewardship. Here we tested species and strains of entomopathogenic nematodes against larval S. pictipes and consistently found that Steinernema carpocapsae strains provided better control than other Steinernema or Heterorhabditis spp. Additionally, we determined susceptibility of different size S. pictipes larvae, as occur simultaneously in orchards, and found that larvae rated as 'medium' and 'large' were more susceptible than 'small' larvae. Last, we conceptually demonstrated that moisture-retaining covers (placed over S. pictipes-infested wounds on peach limbs) increased efficacy of nematode treatments against larval S. pictipes. Even when using highly virulent nematodes against S. pictipes, it is likely that an above-ground application will require an environmental modification to remain efficacious.