Description. Pear rust mite is a sporadic but serious pest of fresh-market pears. It may become a pest if pyrethroids are used at any time of the year. An increase in pear rust mite populations is seen in orchards that have been under mating disruption for several years where miticide use has been reduced. Rust mites are so small that you need a 14 to 20 X hand lens to see them. They are wedge-shaped, with the wider end at the head. Pale brown female mites overwinter in bark crevices or behind loose bud scales usually on 2- to 4-year-old wood. As buds open in spring they move to developing clusters, leaves, and fruit to feed. During the growing season, adults are pale white to cream-colored.
Damage. Pear rust mite feeds on the surface of fruit and foliage, causing a bronzing of the tissue. Injury to leaves may stunt the growth of young trees, but on older trees it is of minor importance compared to fruit damage. Soon after petal fall, damaging populations may develop on fruit around the calyx or stem end, giving a localized russetting to those areas. Feeding and russetting may spread over the entire fruit if mites are unchecked. Late-season feeding tends to be scattered more uniformly over the fruit surface, with the intensity of russetting determined by the number of mites and the length of their feeding period. Rust mites are not an economic pest of naturally russetted varieties and in these orchards are even considered beneficial because they serve as a predator food source.
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