How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

These mites overwinter as eggs located at the base of buds and spurs on small branches, in wounds, or bark cracks. Eggs are red with a slender stalk arising from the center. Newly hatched mites are green, but with feeding, turn red. They have white spots at the base of the large hairs on the back. These mites have 5 to 10 generations per year.

DAMAGE

European red mites cause leaf stippling. Prolonged feeding causes leaves to pale and appear bronzed and burned at the tips and margins. Almond trees that are not stressed for water or by any other factor can tolerate high infestation levels (in excess of 50 mites per leaf) for extended periods without experiencing leaf drop. If the trees are stressed, however, these levels can cause defoliation. At low levels, this mite can be beneficial; it serves as an alternative food for mite predators. European red mites do not commonly reach damaging levels in almonds. Populations often decline when temperatures turn hot.

MANAGEMENT

European red mite is often kept below damaging levels by natural enemies and is an important food source for building up natural enemies of spider mites early in the season. Monitor this mite as part of your regular monitoring program throughout the season. The best time for treatment in an IPM program is an oil spray during the dormant season as determined by a dormant spur sample.

Biological Control

The western predatory mite feeds on the immature and adult stages, but is unable to break through the egg shell so it is not as effective in controlling European red mites as it is other mite species. The brown lacewing, Hemerobius sp., is an effective predator, but is not always present.

Organically Acceptable Methods

Biological control and oil sprays are organically acceptable methods.

Monitoring and Treatment Decisions

Monitor the European red mite eggs as part of the dormant spur samples during the dormant season as described in the DORMANT SPUR SAMPLING SECTION. A delayed dormant oil spray is the preferred treatment and is intended to control mite eggs and is suggested when 20% of spurs have mite eggs. During the growing season, monitor orchards once a week along with other pests. No treatment thresholds have been established, but almond trees are able to tolerate greater numbers of European red mites than webspinning spider mites per leaf.

PUBLICATION

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431
Insects and Mites
F. G. Zalom, Entomology, UC Davis
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
R. L. Coviello, UC Cooperative Extension, Fresno Co
R. A. Van Steenwyk, Insect Biology, UC Berkeley
M. W. Freeman, UC Cooperative Extension, Fresno Co.
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier
L. C. Hendricks, UC Cooperative Extension, Merced Co.

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