Biologically Integrated Orchard Systems

Alternative management of codling moth, navel orangeworm, and web-spinning spider mites in walnuts

The BIOS program was originally started by CAFF in the 1990s with transformative work by Robert Bugg and continued with work by Joe Grant and several collaborators. BIOS was relaunched in 2021, in collaboration with CDFA, UC Cooperative extension, the California Walnut Board, and Pest Control Advisors (PCAs). The Ecological Pest Management team is currently working on two projects: the use of mating disruption for codling moth and navel orangeworm management, and investigating the effects of cover crops and predatory mite releases for management of web-spinning spider mites. 

This project involves six BIOS demonstration sites where we implemented alternative pest management practices for CM, NOW, and spider mites in concert with a robust monitoring program for each using UC IPM models and action-based thresholds. Using the results from these demonstrations, the BIOS approach will be compared to the grower standard for these pests, and evaluated on the basis of pest management efficacy, economic feasibility and pesticide use and their environmental implications.

Mating Disruption for Codling Moth and Navel Orangeworm

It has become increasingly important to adopt selective, low-risk management practices, like mating disruption, to reduce the disruptive effects of commonly used pesticides. Especially for pests like codling moth and navel orangeworm, the commonly used pesticides can kill off natural enemies and cause secondary flare-ups of other pests like spider mites and aphids. Mating disruption utilizes synthetic pheromones to reduce populations of the target pest by preventing mating and reducing the reproductive success of females, thereby reducing pest populations in the long-term. The synthetic pheromone used in mating disruption can be applied in sprayable liquid form, aerosol dispensers, or plastic strips dispensers. Mating disruption works best when used in concert with intensive monitoring, in-season nut sampling, and harvest damage assessments.

Cover Crops for Spider Mite Management

Cover cropping is not only a cornerstone practice when it comes to improving soil health, but is also foundational to the biological control of pests. Natural enemies of pests thrive best when they have sufficient food and habitat, both of which can be provided by cover crops. A beneficial insect attracting mix might include brassicas, legumes, grasses, and flowering broadleafs. This is especially important early in the season, when the numbers of pests like spider mites are still relatively low and insufficient to maintain large predator populations. Cover crops also provide a number of co-benefits including improved soil infiltration, water holding capacity, and fertility. To compare the effects of cover crops, we monitored for web-spinning spider mites, as well as its natural enemies, predatory mites, six-spotted thrips, spider mite destroyers, and big-eyed bugs.

Predatory Mite Release

Mites of the Phytoseiidae family, or commonly known as predatory mites, are a key predator of web-spinning spider mites. When making treatment decisions, it is not only important to consider the population of spider mites, but also the ratio of spider mites to predatory insects. Maintaining an adequate ratio can help keep spider mite numbers low enough without having to spray a miticide. Releasing predatory mites can supplement the already existing predator population to keep the predator-to-spider mite ratio favorable. These releases can be done by hand, leaf blower, or drone. Photo Credit: Ryan Fillmore

Predatory mite release via leaf blower

Predatory mite release via drone (Video by Ryan Fillmore)

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