Cyclamen mite in Mesabi.  The oldest leaf on the right has no symptoms, while the younger leaves in the middle and left of the picture have severe symptoms.

Cyclamen mite damage can be confused with a number of other problems including nutrient deficiencies, viruses, and thrips.  When strawberry leaves emerge from cold soils this time of year, the leaves often exhibit the same symptoms of cyclamen mites.  Cyclamen mites cause the leaves to be small, yellow, crinkled and stunted.  In an individual crown, the oldest leaves may be normal while each successive leaf is smaller with more symptoms.  Mites reduce yield both by reducing leaf area and feeding on the developing fruit.  Fruit damaged by cyclamen mites are small, orange, crunchy and unmarketable.  The only sure way to determine if cyclamen mites have infested a field is to inspect the leaves under a 20X or greater microscope.  Cyclamen mites rarely cause economic losses to plants in their first year of production, but if left uncontrolled, they can destroy a field in its second or third year of production.

Cyclamen mites have a number of traits that make them difficult to control.  They are very small and hide in the crown where they feed on developing leaves.  By the middle of summer, the mites are protected by several layers of leaves, which protect them from sprays for tarnished plant bugs.  Like all mites, cyclamen mites love hot, dry weather.  Fields with cyclamen mites may show no symptoms until shortly before picking.

Scouting for cyclamen mites should be done shortly before renovation and in late summer.  Currently, the only option for control is dousing the fields with harsh insecticides.  Although you can’t see symptoms of mites at this time of year, they should be controlled before the leaves become too big.  Currently, I am recommending people spray for cyclamen mites shortly after the first flower buds emerge from the crown, so that you can control mites and clipper weevils at the same time.  The primary insecticide for cyclamen mites is endosulfan, but endosulfan should be alternated with either diazinon or dicofol.  Endosulfan gives poor control of clipper weevils and works poorly at cool temperatures, so other insecticides should be used in early spring.

Many people have avoided cyclamen mites by using short rotations and only keeping their fields in production for one or two seasons.