In this issue:
Strawberries…brief alert for spider mites
| Vol 4 No. 6 | August 2, 2002 |
Strawberries and Two-Spotted Spider Mite
Suzanne Wold and Bill Hutchison, Dept. of Entomology, University of Minnesota
Although most berries have been harvested, growers should still be
careful to watch for continued activity of the two-spotted spider mite.
This species should not be confused with the more common “Cyclamen
mite,” which is much smaller in size and does more direct damage to the
fruit. Two-spotted spider mites appear to feed primarily on the leaves,
resulting in wilted leaves and stunting of vegetative growth; their activity
increases with hot, dry weather. Cyclamen mites also feed on the leaves, but
feeding is limited to the new unfolding leaves near the crown.
The predatory mite,
Neoseiulus (Amblyseius) fallacis, which is an important predator of
2-spotted spider mites, may also be present on leaves. N. fallacis is
similar in size to 2-spotted spider mites, but has a longer abdomen, and moves
more rapidly than its counterpart. Currently, it is recommended that a ratio of
1:10 predatory to 2-spotted spider mites, should adequately control 2-spotted
spider mite populations.
As part of our IPM research in southeastern MN, we observed a mite outbreak this year, as hot, and sometimes dry, conditions dominated. The following tables summarize mite infestations for three varieties as well as the impact of the pyrethroid, bifenthrin (labeled for strawberry as Brigade). Not much is currently known about the impact of continued mite pressure following harvest. However, if spider mite activity increases (e.g., 50% of the plants infested), an insecticide application may be needed. Lorsban also provided excellent control (data not shown).
| Table 1: Mite abundance on strawberry. | |
| Variety | Mites/Leaflet |
| Brunswick | 138.3 a |
| Mira | 9.8 b |
| Northeaster | 2.2 b |
| Means followed by a different letter are significantly different (P=0.05); mean of 3 sample dates (6/6 - 6/13/02). | |
| Table 2: Efficacy of Brigade for mite control. | |
| Treatment | Mites/Leaflet |
| Brigade (1 app.) | 12.9 b |
| Untreated Check | 138.3 a |
| Means followed by a different letter are significantly different (P=0.05); mean of 3 sample dates (6/6 - 6/13/02). | |
Co-Editors: Bill Hutchison, Department of Entomology,
University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture,
jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota,
ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Assistant, University of
Minnesota, woldx018@tc.umn.edu
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Last Revised August 2, 2002.
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