Cyclamen Mite

At low numbers, cyclamen mites (Family: Tarsonemidae) are usually found along the midvein of young, unfolded leaves and under the calyx of newly emerged flower buds; when numbers increase, these mites can be found anywhere on nonexpanded plant tissues. They are not visible to the naked eye, and when mature, they only measure about 0.01 inch (0.25 mm) long. Mature mites are pinkish orange and shiny. The hind legs are thread- or whiplike in the female and grasping or pincerlike in the male. Eggs are translucent and comparatively large.

Adult females lay about 90 eggs, 80% of which develop into females. During summer, newly hatched mites develop into mature adults within 2 weeks. Cyclamen mite numbers increase rapidly soon after a field becomes infested. They overwinter as adult females in the strawberry crown and can be present on transplants if the nursery field was infested.

Cyclamen mite can be distinguished from nondamaging tarsonemid mites in the genus Tarsonemus through microscopic examination, by examining the fourth femur of male mites. The cyclamen mite has a "flange" or distinct bulge present while the males of both Tarsonemus species do not.

Cyclamen mites are primarily pests in fall-planted and second-year plantings, but they can be transplanted into first-year fields and the damage symptoms become apparent on leaves as the season progresses. Leaves heavily infested with cyclamen mites become severely stunted and crinkled, resulting in a compact leaf mass in the center of the plant. Feeding on flowers can cause them to wither and die. Fruit on infested plants is dwarfed, and the seeds stand out on the flesh of the berry. When uncontrolled, this mite can prevent plants from producing fruit.

Management of cyclamen mite requires carefully timed sprays of miticides that do not harm natural enemies. Prevent its introduction into strawberry fields by following good cultural practices. Propagating nursery stock free of cyclamen mites is essential to prevent their introduction to fruit-producing fields. This mite may survive in furrows of fields that have been bed fumigated. Because other nondamaging tarsonemid mite species, including Tarsonemus setifer and Tarsonemus confusus, occur in strawberry fields and it is very difficult to distinguish one species from another, focus control efforts in those fields where damage symptoms occur.

Two naturally occurring predatory mites of cyclamen mite are Typhlodromus bellinus and T. reticulatus, but their numbers increase too slowly to provide economic control. Early season releases of the commercially available predatory mite, Amblyseius californicus, may be able to control this pest mite. Amblyseius cucumeris releases have not proven to be effective.

When pest numbers are high, the sixspotted thrips, minute pirate bugs, and western predatory mite (Galendromus occidentalis) all feed on cyclamen mite.

Pickers, bees, birds, and equipment, including strawberry freezer trays, can easily transfer cyclamen mites from one location to another. It may be worthwhile to dip trays of long-term cold storage (28°F) transplants into a hot water bath for 7 minutes right before planting to prevent infestation. (Infested nursery plants are the major source of this pest in annual plantings; be sure to use uninfested nursery stock.) To prepare plants for this treatment:

1. Thoroughly wash them to remove all dirt.
2. Place them in a circulating water bath that is held at a constant temperature of 120°F.
3. Submerge them in very cold water.
4. Plant them as soon as possible.

(This treatment is not recommended for fresh-dug transplants that have only been stored at 33°F.)

Avoid second-year plantings in problem areas. To slow the spread of infestations, rogue infested plants as soon as symptoms appear.

Use biological and cultural control methods on organically certified strawberries.

If any damage symptoms are observed, be sure to monitor the rest of the field carefully to determine the extent of the infestation.

• Monitor newly unfolding leaves.
• Spray the area of the field where infestation is expected when densities of one cyclamen mite in 10 leaves are found.

To control cyclamen mites, a high volume of water per acre (300–500 gal) is necessary to soak the folded leaves and immature flower buds located in the crowns. Effective control requires a high rate of kill because numbers of this mite can increase rapidly. Roguing and spraying infested hot spots with a hand-sprayer can be useful in suppressing infestations without having to spray the entire field. In nurseries, early season control before plant canopy closes over is critical.