PEARLEAF BLISTER MITE

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July 17, 2008

Pearleaf blister mites (Phytoptus pyri) were reported in an earlier BYGL this season when the damage caused by these microscopic eriophyids was just becoming evident. PDA participants observed holes appearing in necrotic tissue on the underside of ornamental pear leaves meaning that the damage is now beginning to peak for the season. Feeding by the mites produces small, distinct blisters on the upper leaf surface and rough, irregular patches of necrotic tissue on the lower surface. The blisters are light-green at first, but later turn pinkish-red, and eventually brownish-black. The blisters may coalesce giving the leaf a blackened, gnarled appearance. The patches on the lower surface turn from dark brown to black and tiny exit holes appear as mites emerge.

The tiny, cigar-shaped blister mites overwinter under bud scales and initiate blister formation as leaves expand. They first feed on the lower leaf surface, causing the epidermis to rupture. The mites then crawl into the leaf and deposit eggs. As eggs hatch, the new mites continue feeding within the leaf, destroying more cells. Blister and necrotic patch symptoms become most evident after successive generations of mites have fed within the leaves. Although high populations of this mite may cause dramatic symptoms, damage is seldom significant relative to tree health. Control is generally not warranted since high populations on landscape trees seldom occur over successive years.

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Last Updated ( Thursday, 17 July 2008 21:27 )

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