How to Manage Pests

UC Pest Management Guidelines

Eggs are spherical and translucent when first laid, becoming opaque before hatching. Immature mites molt three times before becoming adults; under ideal conditions, a generation can be completed in 7 days.

DAMAGE
Light infestations result in yellow or brown spots between leaf veins. Clusters of dried, brown leaves and profuse webbing indicate a heavy infestation, which if compounded by water stress, could result in leaf and fruit drop.

MANAGEMENT
The twospotted spider mite is an occasional pest on citrus, particularly in the San Joaquin Valley. Its damage potential varies from year to year and is related to water stress and heat. Monitor for twospotted spider mite year round and treat with the most selective miticide to preserve populations of natural enemies.

Biological Control
A number of predators provide substantial control of twospotted spider mites. These include the sixspotted thrips, Scolothrips sexmaculatus, the spider mite destroyer, Stethorus picipes, minute pirate bugs, Orius spp., and the beneficial mite, Euseius tularensis.

Cultural Control
Adequate irrigation will reduce the impact of spider mite feeding.

Organically Acceptable Methods
Cultural and biological controls and petroleum oil sprays are organically acceptable methods.

Selectivity
Miticides available for controlling twospotted spider mite include dicofol (Kelthane), propargite (Omite), fenbutatin oxide (Vendex), and oil; of these miticides, some are more selective than others. Dicofol and pyridaben are of intermediate selectivity because they act primarily against mites with minimal impact on beneficial insects such as lacewings, lady beetles, and Aphytis melinus, which help control worms, scale, thrips, and other pests. However, these materials are toxic to beneficial mites such as Euseius tularensis. Propargite is even more selective than dicofol because, when used at low rates, it is relatively nontoxic to beneficial mites. Petroleum oil sprays are relatively nontoxic to insect natural enemies but suppress Eusieus tularensis. Fenbutatin oxide has the least effect of all on natural enemies.

Monitoring and Treatment Decisions
In the San Joaquin Valley, check for twospotted mites when you monitor citrus red mite in late winter and early spring. Continue monitoring twospotted mite occasionally during summer and more closely in late summer and fall. Look for yellow-brown spots on foliage, particularly in the last growth flush, indicating feeding by twospotted spider mites. High populations in summer and fall may require treatments, but thresholds have not been established.

PUBLICATION

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Insects, Mites, and Snails
E. E. Grafton-Cardwell, Kearney Agricultural Center, Parlier
J. G. Morse, Entomology, UC Riverside
N. V. O’Connell, UC Cooperative Extension, Tulare Co.
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura Co.
C. E. Kallsen, UC Cooperative Extension, Kern Co.
D. R. Haviland, UC Cooperative Extension, Kern Co.
Acknowledgments for contributions to the insect, mite, and snail section:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E. S. I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E. S. I., Corona, CA
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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