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(Art Agnello, ama4@cornell.edu, Entomology, Geneva)

Pear Psylla

Originally introduced accidentally from England into Connecticut about 1832, the pear psylla has 3—4 generations a year, depending on the length of the growing season for the area. The overwintering adults pass the winter in litter on the ground or in cracks in the tree bark. On warm spring days, prior to the trees breaking dormancy, these adults can be found on the trunks, twigs, and branches. The first eggs in the spring are laid prior to bud burst, on the terminals and spurs. As the foliage appears and for succeeding generations, the eggs are laid on the new leaves.

Pear psylla eggs

First egg hatch occurs about the time the foliage appears. The pear psylla is a "flush feeder", meaning that the nymphs feed and develop primarily on the newer, more tender growth. By midway through the growing season, the majority of leaves are hardened off and psylla development then may be limited primarily to the water sprouts.

Once the nymph begins to feed, a honeydew drop forms over the insect; the psylla develops within this drop for the first few instars.

Pear psylla eggs

Pear russetting caused by sooty mold growing on psylla honeydew

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Honeydew injury occurs when excess honeydew drips onto and congregates on lower leaves and fruit. Under bright sunlight and dry conditions, the honeydew can kill the leaf tissue and produce a symptom called "psylla scorch". The honeydew is a good medium for sooty mold growth. When it occurs on the fruit, it russets the skin and makes the fruit unsaleable. Excessive feeding and the injection of toxic saliva by large populations of psylla can cause a tree to wilt and lose its leaves prematurely. This reduces tree vigor, which can take the tree several years to recover.

Ladybird beetles, lacewings, syrphids, snakeflies, and predatory bugs have been recorded feeding on the psylla. There are also two wasp parasitoids of pear psylla in the U.S. However, to obtain commercially acceptable fruit in New York, pear psylla must be controlled with insecticides.

Registered insecticides for summer use on pears are historically unreliable in controlling pear psylla because of the development of resistance in psylla populations to materials that were once effective. In addition, N.Y. growing conditions necessitate management practices for fruit size attainment (vigorous fertilization and significant canopy pruning) that are favorable for the rapid buildup of psylla populations. Contributing to this situation of incomplete control is the widespread use of materials for other pests that are highly destructive to natural control agents, such as pyrethroids and carbamates.

Current management recommendations call for prebloom oil applications, and insecticide sprays to manage nymphal populations that build beyond 1—2 per leaf, starting anytime after petal fall and throughout the summer. Agri-Mek used shortly after petal fall has given good control if applied correctly (well-timed, adequate coverage, combined with an oil adjuvant), and Dick Straub's trials in the Hudson Valley have shown the utility of split applications of Pryamite or Provado, also starting soon after petal fall. In some orchards, Mitac retains its effectiveness as the standard rescue material during the summer, although its usefulness has been decreasing as local populations develop tolerance or resistance.

Pear Midge

The pear midge is an old pest not commonly seen in blocks under a "standard" spray schedule. This insect is usually controlled by chemical applications for other pests, and in most cases of fruit infestation (whether commercial or homeowner), the problem comes down to the proper timing of an insecticide spray. The pear midge overwinters as a pupa in the soil, and the adults emerge in the lake plains area of N.Y. in early May. The first flies will generally appear when Bartletts and Clapps are in the tight cluster bud stage, but no successful egg-laying occurs until the flower buds are a little more developed. The critical period for chemical control begins when the sepals have spread apart enough to show the first appearance of pink (the folded petals underneath), and continues until just before most of the blossoms are open. The flies disappear by the time of Bartlett full bloom. Larvae may be present inside the fruitlets on the tree, and do not affect fruitlet color. Full-grown larvae may leave the fruit or remain inside until it drops to the ground. In June and July, the maggots exit from the fruit (on the tree or the ground) and burrow into the soil as much as 3 inches to pupate later.

We know of no practice, either chemical or cultural (such as roto-tilling), that is effective enough to recommend for controlling the insects in the ground. These insects emerge in very large numbers, especially in a block continuously infested from year to year, and it is much easier to protect the fruit than to eliminate the pests at their source. If your pear block has a history of midge infestation and you wish to limit the area requiring chemical sprays, concentrate on those portions of the orchard most protected from the wind by trees, high ground, or buildings, as the midges tend to be most numerous in these spots. The most effective materials to use for midge sprays are organophosphates like azinphos-methyl; at least 2 sprays are recommended, one at first separation of the sepals, and one 7 days later (or at white bud, whichever comes first).

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