Decision-support tools for determining when chemical control programs are needed to supplement naturally-occurring biological control for spider mites in California almonds


Abstract: Pacific and twospotted spider mites (Tetranychus spp.) are considered significant pests of the approximately 400,000 ha of almond production in California, USA. Spider mites feed on the leaves and cause defoliation that results in reduced photosynthesis and reduced yields. Spider mites are managed through a combination of chemical and biological controls, including Galendromus spp. phytoseiids and the six-spotted thrips, Scolothrips sexmaculatus. Decisions regarding the need to supplement biological control with miticide applications can be made using a presence-absence sampling program. However, due to recent increases in the value of almonds, many growers and pest control advisors are using more prophylactic approaches to spraying for mite control. This manuscript provides a brief overview of how spider mites are managed in California almonds with specific emphasis on work conducted during the last six years on methodologies for making treatment decisions based on field monitoring of spider mites and their natural enemies.

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