European Red Mite

HOSTS

• Apple
• Cane and Bramble Berries
• Cherry
• Peach
• Pear
• Plum
• Prune
• Many Trees and Shrubs

DESCRIPTION

European red mite (Panonychus ulmi) eggs are 1/160 inch in diameter, dark red, and oval with small ridges running top to bottom and a slender tassel or stalk.

Larva are slightly larger than the egg, orange-red, and has three pairs of legs. They move to young leaves and begin feeding, usually on the undersides. 

Protonymphs and Deutonymphs are larger than larvae, red, and have four pairs of legs. They're greenish-red just after molting, and turn bright red as feeding resumes.

Adult females are about 1/72 inch long, brick red, and oval shaped with white hairs on their back and white spots at the base of the hairs. Males are 1/80 inch long, red tinged with yellow, and more slender and tapered near the hind end. Adults first appear around petal fall.

BIOLOGY

Eggs: overwintering stage - overwintering eggs are deposited during August and September and hatch the following spring between cluster and bloom. They are found on rough bark at the bases of buds and spurs, on small limbs and twigs, and in limb crevices and forks. Summer eggs hatch throughout the summer and are found along leaf veins predominantly on the undersides of leaves and sometimes on fruits if populations are high.

Nymphs: damaging stage - sex is distinguished at the deutonymphal stage as femals grow larger and more oval than females. They feed on the undersides of leaves.

Adults: damaging stage - Feeds maily on the undersides of leavs, moves to upper leaf surfaces when populations are crowded. Females begin laying eggs after two days, live up to 20 days, and lay an average of 30 to 35 eggs. One generation can be completed in 10 to 25 days, depending on the temperature. Typically there are five to eight overlapping generations per year. 

SYMPTOMS

• Light infestations cause leaf speckling
• Bronze and pale leaves
• Undersized and poor quality fruit
• Reduced tree vigor
• Decreased yield they year after significant June and July infestations
• Extremely heavy infestations can cause leaf drop

GENERAL MANAGEMENT

Delayed Dormant: 

If overwintering eggs are present, applying a delayed dormant oil spray (half-inch green to tight cluster) each year is the most important management tactic for the European red mite. Eggs are most vulnerable to control just before hatching. If a delayed dormant spray is missed, later sprays may be required to keep European red mite populations below damaging levels. This may result in the destruction of beneficial mites and insects and the outbreak of secondary pests, such as twospotted and McDaniel spider mites. Although a delayed dormant spray may not provide season long control, it can prevent early summer buildup of the mite.

Post Bloom: 

If European red mites are present later in the season, the grower will need to make a decision about whether to use a miticide or rely on natural predators for control. Use the treatment thresholds for web spinning  spider mites as a guideline, but have a higher tolerance for European red mite because its populations do not build as rapidly during the hot summer months as do populations of web spinning mites.

Biological Control: 

The major predators of European red mite are: the predatory mite, Zetzellia mali; the small black lady beetle, Stethorus picipes; green lacewings, Chrysopa spp.; brown lacewings, Hemerobius spp.; minute pirate bug, Orius tristicolor; and campylomma bug, Campylomma verbasci.

The more common predator, western predatory mite (Typhlodromus occidentalis), will feed to some extent on immature stages, but it prefers twospotted and McDaniel spider mites over European red mite. Relying on predators for natural biological control of European red mite is not as reliable as the biological control of web spinning spider mites by the western predatory mite. Therefore, the presence of predators in orchards should be considered in any management decision, but be aware that biological control of European red mite is generally less effective than that of twospotted and McDaniel spider mites.

Chemical Control: 

If European red mite reaches economically damaging levels early in the summer, using a miticide before predators begin moving into trees is preferable to waiting until mid to late summer when predators are more abundant. Midsummer miticide applications can upset the biological control of web spinning spider mites and insects.

From petal fall through summer, if chemical control of European red mite is required, the following materials are registered for tree fruit crops in Utah:

• abamectin (Agri-Mek)^R
• clofentezine (Apollo)
• fenbutatin-oxide (Vendex)^R - not on apricot
• hexythiazox (Onager, Savey)
• insecticidal soap (M-Pede, Safer’s, others)^O,H
• summer-weight oil (horticultural mineral oil, canola oil, soybean oil, others)^O,H

^OOrganic (OMRI-approved) products available
^HHomeowner products available
^RRestricted use insecticide; requires a pesticide applicator license to purchase and apply

Use lower label rates if predators are present. To avoid selecting for resistance, rotate different types of miticides. Once a miticide is applied, mite densities should be monitored 1 week later. A second application may be required in 7 to 10 days following the first application if a large number of eggs and hatching larvae are present.

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