Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
Cyclamen mites have been found in a few Maryland strawberry fields in the last few weeks. They are not much of a problem now but when we start to warm up, they may become more of a problem along with two spotted spider mites. The cyclamen mites (Phytonemus pallidus) have been found most often in plasticulture strawberries and less often in matted row systems. Adult cyclamen mites are usually never seen as they are only a quarter of a mm long and a 20X hand lens or dissecting microscope is needed to see them.
Adult mites are oval-shaped and a glossy creamy orange (Fig. 1) with males being smaller than females. The hind legs of females are thread-like and in males are pincerlike (the male uses these hind legs to transport female pupae to new locations on the plant). The eggs are translucent and comparatively large, about ½ the size of an adult (Fig. 1). Masses of eggs in leaf crevices can be so numerous that they look like tiny piles of salt. Female adults overwinter in strawberry crowns and also can be present on transplants. Female mites lay their eggs on strawberry leaves that hatch into tiny, white, six-legged larvae (Fig. 1). The entire life cycle of the cyclamen mite is less than 3 weeks and therefore populations can build quickly. Although there are multiple generations each year, populations tend to peak in early spring and again in late summer.
Cyclamen mites use their piercing-sucking mouthparts to feed on plant material. Symptoms of infestation can be found throughout the plant. However, at low populations cyclamen mites can usually be found along the midvein of young, unfolded leaves and under the calyx of newly emerged flower buds. As numbers increase mites can be found anywhere on the plant. The infested leaves will appear stunted and crumpled (Fig. 2), while flowers wither and die and fruit becomes shrunken with protruding seeds (Fig. 3). By the time these symptoms appear, it is too late to limit damage, so cyclamen mites should be managed preventively. Treatments should be applied when 1 leaf in 10 shows cyclamen mite damage.
Growers should watch for deformed leaves starting when new buds emerge from the crown and continuing until harvest. Older fields will most likely have more problems. In order to be sure of the presence of cyclamen mite, you need to examine the newest leaves in the crown, specifically the mid vein and lower part of a leaf where it joins the petiole. Magnification (20-40X) is recommended for confirmation of cyclamen mites.
Early detection of cyclamen mites is essential in achieving best control. Thorough spray coverage of the crown leaves is important for good control, so high volumes of water are needed (60-100 gal/a). Horticultural oils can be used if temperatures are below 88 °F. Agri-Mek SC or Portal also can be used for mite control. Predatory mites can be used and work best if cyclamen mite populations are small and confined to scattered hot-spots in a field.
Figure 1. Adult female cyclamen mite (yellow arrow), eggs (white arrows) and larva (red arrow)
Figure 2. Cyclamen mite damage to strawberry—crinkled deformed younger leaves
Figure 3. Cyclamen mite damage to strawberry fruit-protruding seeds