European Red Mite

Life History

Overwintering eggs occur in clusters on roughened areas of bark on twigs and smaller branches, often on the undersides of fruit spurs and at forks of small branches. Eggs hatch at the pink bud stage, and young mites feed upon the opening flowers and developing leaves. The mites continue to feed upon leaves during the spring and summer, increasing in numbers in response to warm temperatures. There may be as many as 6-7 generations per year. Populations generally decline by mid-August, and females lay overwintering eggs during August and September.

Monitoring

Dormant season - Collect 5 fruit spurs per tree on 20 trees selected at random from each hectare of orchard. Count or estimate the number of eggs on the terminal 4-cm of each spur, starting at the base of the bud.

Summer Monitoring is especially important if you apply Sevin thinning sprays and either Assail or Admire, or both, each season. The combination of Sevin thinning sprays and more that 2 applications of either Assail or Admire, or both, can greatly increase the risk of mite flare-ups in the current or subsequent year. Assail and Admire increase egg production in mites. Examine leaves throughout the orchard to assess average numbers of active European red mites and predatory mites. Inspections every week or two are desirable to evaluate population trends and tree response. Numbers of both plant-feeding and predatory mites may be determined either by hand lens examination or through one of the mite counting services. Check with your crop management advisor for addresses of these monitoring services.

Control

Cultural - Healthy, well-maintained trees will tolerate higher mite populations than weak or stressed trees.

Biological - Several species of predatory insects and mites attack all stages of plant-feeding mites to keep populations below damaging levels in most tree fruits. Pear trees cannot tolerate high enough numbers of plant-feeding mites to support the predatory mites needed in integrated control. Chemicals applied for controlling other pests and diseases may upset the ratio of plant-feeding to predatory mites, reducing the effect of biological control. Therefore all pesticides and application rates recommended for integrated mite control in apple are selected to conserve predatory mites.

Chemical - If predatory mites are present in orchards and not exposed to harmful sprays (such as pyrethroids and many Sevin thinning sprays), summer sprays of miticides are not usually necessary.

Pesticide resistance management - It is important to alternate products from different chemical classes or with different modes of action to avoid the development of resistance.

Early season - If an average of over 50 European red mite eggs per spur is present in the dormant sample, apply dormant oil during the 15 mm green-bud to tight-cluster bud stage. This spray is especially important to integrated control because it favours survival of predatory mites and apple rust mite. Oil has a physical effect on mite eggs. A physical control method is not susceptible to resistance development. A well-applied oil spray will keep European red mites at a low level until summer.