UC Delivers

Reducing environmental impacts of foothill citrus orchards

The Issue

Pest management is a key concern for small-scale foothill citrus growers, but few pest control advisers serve Placer and Nevada counties. Integrated pest management requires a high level of knowledge as well as careful monitoring. Growers must be able to identify pests, assess available tools and develop an effective combination of management methods.

Citricola scale has been a major foothill citrus pest for many years, often requiring several sprays per year. In 2003, California red scale began to emerge as a problem in Placer County mandarin orchards.

What Has ANR Done?

UCCE farm advisor Cindy Fake worked with mandarin growers and the Placer County Ag Department to launch a strategic pest management effort. Growers were trained how to monitor for and identify Citricola and California red scale. Six to eight field meetings per season provided opportunities to demonstrate pruning to help control Citricola scale, and teach monitoring to assess parasitism by natural enemies.

Since 2003, UCCE has coordinated seasonal releases of Aphytis, a tiny parasitic wasp which controls California red scale. Growers release two to three million wasps per season in 25 local orchards. UCCE has also helped growers establish insectary hedgerows to encourage natural enemy populations, coordinated trapping to monitor red scale, and collected weather data to help growers plan IPM programs.

The Payoff

Sustainable pest management helps the environment and the bottom line

More growers use traps, weather data and monitoring to time sprays, resulting in more effective pesticide use. Many growers have turned to alternative management tools - such as pruning, natural enemy releases or insectary hedgerows to augment natural enemy populations. These methods reduce the risk of pesticide impacts on water quality, beneficial insects and human health.

Aphytis wasp releases have become standard practice for managing red scale, and most growers manage Citricola scale through pruning. These practices were included in the 2008 foothill mandarin cost study, a significant change since 2002. By coordinating wasp releases, growers share the shipping costs, making it a cost-effective practice at about $72 per acre per year, as compared to about $145 per acre for a pesticide spray. Red scale populations are well managed and few growers have found it necessary to spray.

Contact

Supporting Unit: Placer-Nevada Counties

Cindy Fake, (530) 889-7385, cefake@ucdavis.edu