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Description: The adult pear psylla looks somewhat like a tiny cicada. Early season adults are small, 2.12 mm (1/10th inch) in length, and are a dark reddish brown color with black bands on the abdomen. The wings are held roof-like over the sides of the body and are nearly translucent. Eggs are yellowish orange and may be seen with the aid of a hand lens in creases of the bark. Newly hatched nymphs are yellowish and only 1/4 mm (1/80 inch) in length! Late-stage nymphs are hard shelled and wing pads may be seen forming. Adults of summer generations may differ from those of the hibernating generation being about one third smaller and having brighter (tan to light brown) coloring and different wing markings.
Life Cycle: Adult psyllas overwinter on the trunks under flakes of bark or in crevices. If they are abundant, they may also be found under leaves on the ground. Adults emerge with the onset of warm weather (40 to 50 degrees F) in the spring, mate, and begin laying eggs when temperatures reach 50-60 degrees F. Yellowish-orange eggs are deposited in crevices in the bark and near the terminal buds. Most of the eggs will have hatched by the time the flower petals fall. Young nymphs migrate to the axils of leaf petioles and of forming fruit. As these sites become overcrowded, the nymphs move on to the undersides of the leaves. Five immature (nymphal) stages are passed through before the winged adults appear. There are three to four generations of the pear psylla per year. Females of the later generations will deposit most of the eggs along the leaf midribs. One female pear psylla may deposit up to 500 eggs. Damage: The pear psylla attacks all varieties of pears and may occasionally attack quince. It is a sucking insect and feeds on the plant sap. Heavy feeding plus the injection of toxic saliva by pear psylla may cause early defoliation and loss of the fruit crop. The nymphs secrete a sticky substance known as honeydew as they feed. A black sooty mold fungus forms on this honeydew and may cause damage by interrupting the normal process of photosynthesis. A roughening or 'russet' of the skin occurs on the fruit. Monitoring: Look for adults on the spurs and branches of the tree during warm days just prior to bud burst, and on the tender new shoots from green cluster through the remainder of the season until leaf drop. Eggs in the late dormant to bud burst stages are found singly or in rows on spurs and twigs, or around bud scales. Through the remainder of the growing season, look on tender new growth for rows of eggs along the leaf midribs and especially the undersurfaces. Small nymphs are found from green cluster throughout the season on tender new growth, larger nymphs are found on leaves that are hardening off. Control: Natural enemies such as lady bird beetles, lacewings, and syrphid fly larvae are often present but they seldom keep populations low enough to prevent injury. Apply oil as adults are emerging, but before egg laying has occurred (as soon as adults are present and temperatures exceed 50 degrees F.) Timing will vary each season. The most important times to treat for pear psylla are at the pre-bloom (white bud) and petal fall stages. Apply a multipurpose fruit tree spray mixture (note: multipurpose mixture often contains malathion, captan and methoxychlor) or insecticidal soap at white bud, at petal fall, and as needed based on monitoring during the growing season. Insecticidal soaps are made from biodegradable fatty acids and are contact insecticides that can provide suppression of pear psylla when used in a seasonal spray program. Their residual period is short, however, and uniform drying conditions are required to prevent droplet residues on the fruit surface.
Adapted from the Cornell Cooperative Extension, 1999
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