Pear Psylla

Pear psylla (PP) is the most important insect pest of pear in all pear-growing regions (Asian pear species are less susceptible). It is responsible in large part (along with fire blight) for the decline of cultivation of pear in the eastern states of NY, NJ and Connecticut.

It is the only one of several European pear psyllids to have been introduced into North America. It was first introduced into Connecticut around 1832, and reached Virginia . The length of adults to the tip of folded wings is about 8/100 – 11/100 inch . The color is light orange to red brown, with darker markings . The legs and antennae are mostly light brown to orange.

Wings are clear with a conspicuous black spot on the hind edge (at the midline when at rest). Winter form: The length of adults to the tip of folded wings is 13/100 – 16/100 inch . The body color is now very dark red-brown to black . The wing veins are very dark and conspicuous, and the wing spot is now more pronounced. In both forms, the head is a little over half as long as wide. The antennae are 1 1/2 times as long as width of head.

Life Cycle: Pear psylla adults look like small, dark reddish brown, 1∕10-inchlong cicadas. Eggs, just visible to the naked eye, are pear-shaped, yellowish, and are laid in cracks in the bark and around the buds. They become dark yellow before hatching. Nymphs have sucking mouthparts and feed on plant sap. The young nymphs are soft-bodied and creamy yellow. As they mature they become dark brown and more oval in shape, with distinct wing pads present on the late instars. These late instar nymphs are commonly referred to as “hard shells.There are generally four generations per year.

The adults, which overwinter on trees or other sheltered places, become active anytime the temperature is above 40°F. Females begin laying eggs in late March and continue through the white bud stage. One female can produce as many as 650 eggs. The peak of egg laying is green tip to green cluster bud. Eggs hatch begins at the green cluster bud to white bud stage, with peak hatch occurring about petal fall. Nymphs move to succulent stems and developing leaves to feed, with the heaviest concentration along the midveins of leaves and at the calyx end of fruit.

They pass through five instars, each subsequent stage becoming more difficult to control. The early nymphal stages produce more honeydew than the later, larger stages. The first summer adults mature about 20 to 25 days past full bloom. They begin laying eggs on growing shoots as the population shifts from spur leaves to the more succulent shoot leaves. Late season infestations are typically found on water sprouts.

Damage: Generally, pear psylla is a greater problem on European varieties than on Asian varieties. Pear psylla damages pears in several ways. Loss of crop and tree vigor, and sometimes loss of trees, can occur from pear decline disease, caused by a phytoplasma organism that psylla injects into pear trees. Pear decline has varying effects on the trees depending on variety, rootstock, quality of the growing site, and pear psylla numbers. Honeydew, produced by psylla nymphs as they feed, drops onto fruit. A black sooty mold grows on the honeydew and the fruit skin russets, which downgrades fruit for fresh market use. Psylla feeding and injection of a toxin into the tree causes portions of the leaf blade to blacken, and leaves to yellow and sometimes fall. Growth and productivity of the tree can be severely reduced for one or more seasons.

Control: There are many naturally occurring predators and parasites of pear psylla including green lacewings, brown lacewings, and minute pirate bugs. Nonselective codling moth materials destroy many of these beneficials, resulting in outbreaks of this pest. Orchards in a codling moth mating disruption program generally have greatly reduced levels of pear psylla. In addition, some codling moth materials and some psylla materials destroy mite predators and chronic mite problems will develop. Although predators and parasites do not provide complete control in commercial orchards, they may maintain psylla populations below economically damaging levels when supplemented with a year round program of oil treatments.

Predation is probably occurring when top shoot samples show only one to several psylla nymphs per infested shoot; in the absence of effective predation there are apt to be 10 or more psylla nymphs on a shoot because each female psylla lays 10 to 20 eggs at a time.To reduce the effects of pear decline, use Winter Nelis, Old Home X Farmingdale, or Pyrus betulaefolia seedlings for rootstock and maintain pear psylla populations at low levels.

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