Codling moth has between one and four generations per year, depending on temperature and other climatic factors.
Adult codling moth females lay single eggs on the fruit or leaves of their host. Although some larvae feed on the surface of the fruit, most larvae bore directly into the fruit within 24 h, continue to feed briefly under the surface of the skin, and then move through the flesh of the fruit to feed on the seeds. There are five larval instars. Mature larvae exit the fruit and most frequently pupate under the bark. As daylength shortens with the approach of winter, mature fifth instars spin overwintering cocoons under bark, in debris, or wood fruit. The mature larvae spend the winter in a state of arrested development until spring conditions trigger development.
Management of codling moth populations in orchards traditionally has relied on synthetic pesticides. Although newer, more selective pesticides provide effective control of codling moth, older pesticides have been associated with nontarget environmental and human health risks. In addition, the evolution of resistance in codling moth to many different groups of insecticides (the chlorinated hydrocarbons, organophosphates, carbamates, pyrethroids, and newer insect growth regulators) has made the long-term reliance on these compounds more problematic.
A recent alternative to insecticides relies on the disruption of codling moth mating using sex pheromones. Artificial emitters of the female attractant interfere with the male's ability to find females. The most common dispensers are variations on different reservoir designs, which are tied or placed in orchard tree canopies. Synthetic pheromone from these emitters then permeates the orchard canopies. Although the exact mechanisms explaining this approach are unclear, program efficacy has been demonstrated in almost all growing regions of the world. However, mating disruption is often not efficacious initially in orchards with high pest densities, so that some use of conventional insecticides may be required. Mating disruption has been widely implemented in some areas such as the western United States, where up to 40 to 50% of the pear and apple acreage (e.g., in northern California) uses this technique.
Although management of codling moth based on control by natural enemies has proven elusive, significant reductions in population densities have been made by using both native and introduced natural enemies of codling moth. One of the more thoroughly studied natural enemies in North America, Europe, or the former Soviet Union is the Trichogramma egg parasitoid. Large numbers of these minute wasps are periodically released into an orchard to seek out and kill the eggs of codling moth. The eggs of Trichogramma are laid into the eggs of codling moth; the death of the egg occurs as the Trichogramma larvae develop. Other parasitoids that attack larval or pupal stages have also been introduced or accidentally released into new regions, including Pimpla pterelas and Ascogaster quadridentata. However, parasitism levels rarely reach more than 5%, except for some regions in central Asia where levels are as high as 50%. Nonspecialized parasitoids of egg, prepupal, or pupal stages comprise the majority of the natural enemies in North America; more specialized larval parasitoids are found in Europe and Central Asia.
General predators such as birds, predaceous insects, and spiders have been reported as suppressive agents of codling moth; these include woodpeckers, carabid beetles, and mirid bugs.
Although codling moth is susceptible to several diseases, a granulosis virus that can be applied in water, similar to insecticide applications, can cause significant reductions in codling moth densities. However, problems with production, formulation, and the short residual activity of the virus restrict its usage. Some reductions in codling moth populations also have been associated with applications of the bacterium Bacillus thuringiensis, but its efficacy is limited.
See Also the Following Articles
Agricultural Entomology • Biological Control of Insect Pests • Integrated Pest Management • Pheromones
Aliniazee, M. T., and Croft, B. A. (1999). Biological control in deciduous fruit crops. In "Handbook of Biological Control: Principles and Applications of Biological Control" (T. S. Bellows and T. W. Fisher, eds.), pp. 750—753. Academic Press, San Diego. Barnes, M. M. (1991). Codling moth occurrence, host race formation, and damage. In "Tortricid Pests: Their Biology, Natural Enemies, and Control" (L. P. S. v. d. Geest and H. H. Evenhuis, eds.), Vol. 5, pp. 313—328. Elsevier, Amsterdam. Calkins, C. O. (1998). Review of the codling moth areawide suppression program in the western United States. J. Agric. Entomol. 15, 327—333. Cardé, R. T., and Minks, A. K. (1995). Control of moth pests by mating disruption: Successes and constraints. Annu. Rev. Entomol. 40, 559—585. Cross, J. V., Solomon, M. G., Babandreier, D., Blommers, L., Easterbrook, M. A., Jay, C. N., Jenser, G., Jolly, R. L., Kuhlmann, U., Lilley, R., Olivella, E., Toepfer, S., and Vidal, S. (1999). Biocontrol of pests of apples and pears in northern and central Europe. 2. Parasitoids. Biocontrol Sci. Technol. 9, 277—314.
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