Cyclamen Mite: A Pest of Strawberries

What is cyclamen mite: Cyclamen mites are very small mites in the tarsonemid family; so small (< 0.3mm) that they are not visible to the naked eye. Mature mites are oval in shape, pinkish or amber coloured, and shiny. Eggs are oval, translucent and comparatively large. Cyclamen mites thrive in humid locations and are a common greenhouse pest. They are also a serious pest of strawberries.

Symptoms and damage to strawberry plants: Cyclamen mite feeding causes wrinkled, distorted leaves, slightly darker in colour than uninfested leaves. When populations are low, leaves grow to nearly full size. Leaves heavily infested with cyclamen mites become severely stunted and crinkled, resulting in a compact leaf mass in the center of the plant. Fruit on infested plants is small, bronzed, with prominent seeds. When uncontrolled, this mite can prevent new growth and severely affect fruit quality.

Life cycle and biology: Cyclamen mites overwinter as adult females in the strawberry crown. At low population densities, they are found along the midrib of folded leaves and under the calyx of the fruit. At higher population densities, they can be in any protected part of the plant. This mite prefers high humidity. When the leaflet unfolds, changes in temperature and humidity cause the mites to migrate down the petiole to new leaflets. There are multiple generations per season. Newly hatched mites develop into mature adults within 2 weeks if temperatures are favourable. Populations build rapidly soon after a field becomes infested, and tend to peak in late spring and again in early fall.

Mites can be spread to new fields on infested planting stock. The mites maybe also be transferred from plant to plant by routine cultural practices, by drafts of air, by close proximity of plants, or on clothes or hands. Females can produce eggs in absence of males; one mite can soon produce a mite colony large enough to cause damage and spread to surrounding plants.

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Monitoring techniques: Expect to find more problems in older fields. Monitor strawberry fields by walking a large portion of the field, looking for areas where the plants are slightly stunted and leaves are somewhat distorted or crinkled. Confirm the presence of cyclamen mite in these areas by pinching out the newest leaves in the crown. Unfold these leaves and examine the mid vein and lower leaf where it joins the petiole. Cyclamen mites and eggs are often found in this area. Masses of eggs look like piles of salt. A microscope or good handlens and trained eye are needed for identification of these mites.

Look-alike symptoms: Cyclamen mite injury is easily confused with winter injury, herbicide damage, virus disease.

Thresholds for control: There are no thresholds established for cyclamen mite control in Ontario or other northeastern regions.

• In California, 1 mite in 10 new leaves is considered a potential problem.
  
• In Manitoba: Treatment may be necessary if there are 1 to 15 mites per leaf. Densities of 45-65 mites per leaf can cause a 33 per cent yield reduction.

Control of cyclamen mite: Products for cyclamen mite control are listed in OMAF publication #360, Fruit Production Recommendations. New products are being evaluated for control of this pest.

Successful application of an insecticide or miticide for cyclamen mite control depends on thorough coverage and a high volume spray. Water volumes of 4000 L/ha are recommended.

The best timing for control is when there is little leaf canopy. Spring, when buds are extending from the crown, and after renovation, when plants are beginning to grow back after mowing, are two suggested timings for controls.

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Factors that affect control: Circumstantial evidence suggests that the use of pyrethroid insecticides (Decis, Cymbush, Ripcord), especially more than one application /year, increases the likelihood of cyclamen mite problems.

Beneficial mites, such as Amblyseius and other phytoseiids, feed on cyclamen mites. Research is needed to investigate the use of commercially available predators mites for cyclamen mite control in the field.

Spray coverage is important for control. Mites are present in the newest leaves in the crown. If non-systemic products are used, they should be applied in a high water volume to ensure the product actually contacts these small leaves.

Figure 1: Cyclamen mite eggs, along midrib of new leaf

Figure 2: Cyclamen mite adult with egg

Figure 3: Cyclamen mite eggs, nymphs and adults as they would appear at 40X magnification

Figure 4: Cyclamen mite damage to strawberry plants

Figure 5: Small patch of plants with cyclamen mite damage

Photocredits: Figure 1-3,:W. McFadden-Smith

Related Links

• OMAFRA Publication 360, Fruit Production Recommendations
• Cyclamen Mite Infosheet - Manitoba Agriculture
• Strawberry Cyclamen Mite - University of California

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