Insect Note # S-2 (Revised)

The strawberry spider mite is often referred as "red spider". It is not a true insect but a spider like mite.

DAMAGE: Mites do not injure strawberries every year but appear in sporadic outbreaks. Their presence is most often seriously felt in hot, dry growing years when numerous mites retard the growth of strawberry plants which may result In plant death. Most severe losses to California varieties grown on black plastic have resulted from outbreaks starting in late fall or winter. In the spring, mites increase rapidly and do the greatest damage during or after the blooming period. Mite populations often rise rapidly following repeated applications of carbamate pesticides. Mites may come in on greenhouse propagated plants or move In from nearby weed hosts.

DETECTION OF OUTBREAKS: Strawberry fields should be inspected several times between fall and early spring. Both old and young leaves from many parts of the field should be examined. Close examination of undersides of leaves, pulled at random, with a magnifying glass or hand lens is essential. Mites can be verified by the presence of red specks upon pressing leaves on a white background.

Mites may be present all over the underside of the leaf or only in small colonies. Such colonies usually start in a hollow between leaf veins. Mites spin very fine webs over the places where they are feeding. Such webbing is easily visible when mites are abundant.

Spider mites are present in large numbers before casual symptoms can be recognized without close examination of the plant. Badly infested leaves gradually lose their normal color and take on a yellowish or brownish cast. Such an appearance is most often confused with plant diseases, nitrogen deficiency or dormancy of older leaves. Close examination revealing presence of mites or their webbing will establish the true cause of abnormal growth.

LIFE CYCLE: Spider mites never have a winged stage. They start from a globular egg bid on the underside of leaves. Young mites are pale yellow, while adult mites are a rich dark red. All stages are usually found on the same leaf. A general of mites may be completed in two or three weeks in warm weather. A much longer time is required during cool weather. As mites never become completely dormant, a mild prolonged winter allows for their buildup.

CONTROL AND MANAGEMENT: Consult N. C. Agricultural Chemicals Manual.

THE USE OF TRADE NAMES IN THIS PUBLICATION DOES NOT IMPLY ENDORSEMENT OF THE PRODUCTS NAMED OR CRITICISM OF SIMILAR ONES NOT MENTIONED.

Prepared by Kenneth A. Sorensen
August 1993
gah/60
Revised 02/17/05