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Evaluation of Pheromone Disruption in Combination with Insecticide Applications for Control of Peachtree Borers in Peaches (Year 1) 2000

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Project Leaders: A. Agnello and D. Kain, Dept. of Entomology, NYSAES, Geneva, NY 14456

Abstract:

The effectiveness of three different treatments were compared in the control of infestations and damage by peachtree borer and lesser peachtree borer in commercial peach orchards: (1) pheromone disruption dispensers combined with directed trunk insecticide applications; (2) pheromone disruption dispensers only; (3) directed trunk insecticide applications only. Pheromone dispensers were placed in large blocks (2–3 acres) of peaches on two farms in Wayne Co., and insecticide treatments were applied to single-tree plots in each block. These insecticide sprays were also applied to comparable trees in another planting at each farm not containing the pheromone dispensers. The effectiveness of the different treatments was evaluated by comparing adult male trap catches in pheromone traps in each block, and excavating around the trunks to search for borers and damage in the fall. Pheromone trap catches of both borer species were completely suppressed by the pheromone dispensers in the disrupted plots. Fall trunk inspection revealed no damage attributable to peachtree borer infestation in either the test trees or the untreated checks. In spring 2001, adult emergence of both species will be assessed by enclosing infested cankers with sleeve cages before adult flight begins, and bark surfaces will be examined for empty pupal cases (exuviae). Results will be used to assess the advisability of using pheromone mating disruption as a borer management strategy in commercial peach orchards.

In New York, there are two species of sesiid (clearwing) moths that attack peaches — the peachtree borer (PTB), Synanthedon exitiosa, and the lesser peachtree borer (LPTB), Synanthedon pictipes. The adult borers are striking clear-winged moths with yellow and steel-blue body markings. The adults of these insects have from one to four yellow-orange stripes across the abdomen, depending upon species and sex. The PTB enters the tree near soil level and does not require the presence of wounds or breaks in the bark for entry, but the LPTB nearly always enters the tree at a pruning scar, canker, mechanical injury, or winter-injured area. Both species pass the winter as borers inside the tree, and in the spring emerge as moths that lay eggs on or in the trunk during the summer. In New York, the LPTB moth emerges first, in late May, and the PTB doesn't show up until mid-June; both stay active (laying eggs) through August. When the borer stages hatch, the PTB tends to crawl down the tree to soil level and burrow in there, but the LPTB will move to the nearest injured area, which may be on the lower trunk or just as easily up in the scaffold limbs. LPTB completes its development in one year, but some PTB larvae take two years to develop, so any control measure a grower would elect will require repeating for at least 2–3 years.

Injury is caused by larval feeding on the cambium and inner bark of the trunk close to the soil level (PTB) or on the upper trunk and lower scaffold branches (LPTB). Occasionally, larger roots are also attacked by PTB. Areas attacked often have masses of gum, mixed with frass, exuding from the bark. All ages of trees are injured. Young trees are at times completely girdled and subsequently die. Older trees are often so severely injured that their vitality is lowered and they are rendered especially susceptible to attack by other insects or by diseases. Although both species may be found in infested trees, younger plantings and those not afflicted by extensive cankers or other bark splits are attacked primarily by PTB. Control is difficult, owing to the concealed habit of the larvae, and most growers must rely on one to several coarse insecticide sprays of the trunks and lower scaffold branches to deter egg laying and kill newly established larvae. Because this is a labor-intensive measure that often fails to completely control these pests, many growers choose not to elect treatment, or else do an incomplete job, with the intention of getting what they can out of a planting until infestations combine with other peach production factors to warrant tree removal. This approach has been common in the recent past, during which there has been little demand for New York stone fruits outside of local farmstand markets. However, with a recent increase in the planting of new peach varieties and short-range distribution to other markets, there is now more interest in examining currently available pheromone disruption tools for the control of these perennial pests.

This research involves trials testing the efficacy of pheromone disruption with and without directed trunk sprays, and here we report our findings after the first of what is intended to be at least a 2-year period, in order to establish reliable guidelines for the use of mating disruption against these pests in commercial New York plantings.