California walnut farmers compete with pests and diseases to produce an economically viable crop. Current control strategies work reasonably well for most pest and diseases. However, the future of these techniques is a matter of speculation. This presentation describes current production practices and potential alternatives to “traditional” pest and disease control. Codling moth, walnut husk fly, mites, navel orangeworm, aphids, and scale are typical insect pests that have an impact on California walnut production. Spray decisions using Integrated Pest Management, beneficial insect releases, mating disruption, insect growth regulators, and orchard sanitation offer potential alternatives. Major diseases include: Phytophthora crown and root rot, crown gall, oak root fungus, and walnut blight. Control options include careful site selection and orchard management, resistant rootstocks, competitive bacteria for crown gall control, and copper compounds for walnut blight suppression. Weed growth is related to the amount of light reaching the orchard floor. Mature trees often shade the orchard floor, subsequently reducing the need for weed suppression. Herbicides are typically used for vegetation control. Choice of irrigation system, cultivation, mowing, cover crops, and flaming offer potential alternatives either alone or in combination with conventional herbicides.
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