An Areawide Concept of Codling Moth Management

Integrated Codling Moth Management

An Areawide Concept of Codling Moth Management

Smith and Van den Bosch (1967) introduced the concept of "key pests" as: a serious perennially occurring, persistent species that dominates control practices because, in the absence of deliberate control, the pest population will remain above economic injury levels. According to Cate & Hinkle (1993), the "Rosetta stone to the system is the key pest. Once this pest is identified and controlled by non-disruptive methods, such as biological control, host plant resistance, or some modification to the cultural practices, the pest management system for the crop begins to fall into place for all pests." The codling moth is the prototype key pest for pome fruit crops in most part of the world.

Codling moth is moderately dispersive. Efforts directed towards management of a dispersive pest are influenced by the density of alternative hosts in the surrounding area and the management practices of neighboring growers. An areawide, coordinated approach would likely be beneficial to managing this type of pest. In many parts of the world, phenology models have been implemented to time the first cover spray of insecticide. With this program, growers within a geographical districts generally apply the first spray during a narrow time interval. Thus, there is already, to some extent, an areawide approach to managing codling moth. Timing of subsequent sprays tend to be more variable and this coordinated approach breaks down during the season.

What are the benefits of adopting an areawide management program for codling moth that is not dependent on insecticides? To society, the benefits of developing alternatives to broad-spectrum insecticides for pest management include reduction of potential insecticide residues or the perception that there is a risk for residues to exist on foodstuffs, reduction of ground and surface water contamination, reduced risks of harmful human health effects, and increased penetration in diverse international and domestic markets. Additional benefits to growers should include more sustainable pest control at costs competitive with insecticide-based programs.

Mating disruption is a likely candidate for implementing areawide management of codling moth. The advantages of treating large acreages with pheromone, versus smaller distinct blocks, have been demonstrated. In Parker Valley, California (USA), 25,000 acres were treated with sex pheromone for control of pink bollworm in a patchwork design. Within this region, significant reductions in boll infestation in a given treated field were found to be a function of the number of surrounding fields also treated with pheromone. In tea, the levels of pheromone of a trotricid moth in the air was directly related to the size of the plantation treated. Levels of injury from the moth in the larger tea plantations were lower than in small plantations due to this higher level of pheromone and a reduced edge effect. In 1993, mating disruption of codling moth was tried in two large contiguous areas, 600 acres on Randall Island, California and 1,200 acres in Brewster, WA. In both areas, insecticides were used to a limited extent (first and second cover sprays and border sprays) and control of codling moth was rated excellent.

Adoption of mating disruption for codling moth control by individual growers is currently limited by its perceived higher cost and lower efficacy than current insecticide programs. Most growers who have used this technology have treated ca. 10 acres in one 'test' orchard to evaluate its performance. Many growers have discontinued their use of mating disruption because of its expense or lack of performance relative to their traditional use of insecticides. However, these perceptions may begin to change as growers realize the full cost of using insecticides. A recent survey of growers in the Washington (USA) found that conventional growers were using four to six sprays of Guthion® ($37 per application) and growers using mating disruption had a lower pest management input cost than those using insecticides. Advantages such as no reentry waiting periods, compatibility with overhead irrigation, lowered risk of incidence of insecticide resistance, improved worker safety, and no container disposal combine to make the use of mating disruption very attractive. The remaining hurdle for the adoption of mating disruption for codling moth may be its efficacy compared to insecticides, and the relative cost of the system, if only product and application costs are computed. If, however, environmental and social costs are factored, a pheromone based system should be highly economically competitive.

The pome fruit industry requires very high product quality, especially for the export market. Thus, the industry is not likely to establish higher economic injury levels for codling moth or lower cosmetic standards. The use of mating disruption suffers from the "edge effect" and will probably never serve as a stand-alone tactic, unless all other options become unavailable. An approach to minimize the "edge effect" is to expand the area treated with pheromone out to the natural boundaries of fruit production in a given area, i.e., non-hosts surrounding the pheromone-treated area for at least 100 m. Problems associated with noncommercial hosts (backyard trees) may have to be addressed through educational and regulatory means. Alternatively, borders and backyard areas can be treated with biological control agents, or selective insecticides can be used in the orchards.