Peach growers combat several insects that harm their crop, usually using chemical pesticides to do so. Agricultural Research Service (ARS) scientists in the Southeastern Fruit and Tree Nut Research Laboratory in Byron, Ga., are seeking environmentally friendly alternatives.
ARS entomologists David Shapiro-Ilan and Ted Cottrell, along with colleagues at the University of Florida and the University of Georgia, are evaluating two tiny, soil-dwelling nematodes as possible biological controls. They were used to thwart damage caused by the plum curculio weevil (Conotrachelus nenuphar), and two clear-winged moths, the peachtree borer (Synanthedon exitiosa), and the lesser peachtree borer (S. pictipes).
Shapiro-Ilan and Cottrell used the Steinernema riobrave nematode to defend against plum curculio larvae—producing a suppression rate of 78 to 100 percent.
For the peachtree borer, the researchers used another beneficial nematode, Steinernema carpocapsae. They found that a single field application of S. carpocapsae provided 88 percent suppression when applied to mature peachtree borer infestations in springtime. In a recent field trial, three applications of S. carpocapsae during the peachtree borer's fall egg-laying season completely suppressed all damage.
The scientists knew from lab studies that another peach pest, the lesser peachtree borer, is also highly susceptible to S. carpocapsae. But the researchers also realized that controlling the lesser peachtree borer would be more difficult because they attack trees aboveground—where the nematodes dry out and are less effective.
To deal with this problem, the researchers applied S. carpocapsae nematodes to tree wounds and then covered the wounds with moisture-holding bandages. In the first trial, 100 percent lesser peachtree borer mortality was attained in five days.
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