Kelly Hamby, Associate Professor and Extension Specialist, Department of Entomology, University of Maryland, kahamby@umd.edu
Cyclamen mites (Phytonemus pallidus) and spider mites (usually twospotted spider mites, Tetranychus urticae) can become a problem soon after planting in strawberries. Because these mites may come into fields on contaminated transplants, transplants should be carefully inspected for mites before planting. If conditions are favorable, mite numbers can rapidly increase to levels of concern.
Figure 1. 20x magnified cyclamen mite and eggs.
Cyclamen mites are very rarely a problem for Mid-Atlantic strawberries.1 Cyclamen mites overwinter as adult females in the crown of the plant and are usually found along the midvein of young leaves that are starting to unfold.2 They are not visible to the naked eye and require 20x magnification by a hand lens or dissecting microscope to see (Figure 1). Heavily infested leaves become stunted and crinkled (Figure 2). It is difficult to manage cyclamen mites, so planting transplants that are free of mites is critical.2,3
Figure 2. Cyclamen mite damage to leaves.
Spider mites (Figure 3) are much more common, and are particularly favored by hot, dry weather. Inspect transplants for spider mites prior to planting, and also scout fields a few weeks after planting by selecting a random sample of at least 10 leaflets per acre to count mites on the underside of leaves. Plants can be treated before or after transplant if mites are found. Twospotted spider mite feeding is particularly damaging in the first 2 to 5 months following transplanting.4 Therefore, treatment is recommended if early spring populations reach 5 or more mites per leaflet (1/3 of a leaf). Tolerance to mite damage increases as the plants begin to fruit4,5. Practices that favor vigorous plants, such as vernalization of transplants and appropriate fertilization (excessive nitrogen favors spider mite outbreaks) minimizes damage from spider mites.
Figure 3. Slighly magnified twospotted spider mites and eggs on the underside of a leaf. Two mites and an egg are circled. Orange mites are nonreproducing overwintering females.
References and Further Resources:
1Brust, J. 2016. Mites (Two Types) Found in Strawberries. https://sites.udel.edu/weeklycropupdate/?p=9109
2University of California Extension. 2018. Strawberry Pest Management Guidelines: Cyclamen Mite
https://www2.ipm.ucanr.edu/agriculture/strawberry/Cyclamen-mite/
3North Carolina State Extension. 2014. Strawberry Insect Pests.
https://entomology.ces.ncsu.edu/strawberry-insects/
4University of California Extension. 2018. Strawberry Pest Management Guidelines: Spider Mites
https://www2.ipm.ucanr.edu/agriculture/strawberry/spider-mites/
5North Carolina State Extension. 2013. Twospotted spider mite. https://content.ces.ncsu.edu/twospotted-spider-mite-3