Pear Psylla (Cacopsylla pyricola)

    Pear Psylla

    Adult pear psylla.
    Pear psylla adult.
    Pear psylla damage.
    Pear psylla damage.
    Pear psylla late stage nymph.
    Pear psylla late stage nymph.

    HOSTS

    • Pear
    • Quince

    DESCRIPTION

    Pear psylla is a very small sap-feeding insect and is considered the most serious insect pest of pear in the United States. Serious infestations can stunt, defoliate, and even kill trees. Psylla feeding produces copious amounts of sticky honeydew that can cause fruit russeting. All commercial pear varieties are attacked, although smooth skinned pears are more injured than russeted varieties, and Asian and red pears are less prone to injury than European and green pears.

    BIOLOGY

    Nymphs are about 1.6 mm long and light yellow, they're cylindrical, but appear flattened.

    Adults are 2.5 mm long, and tan to light brown with clear wings.

    Eggs are minute, oval, and creamy white to yellow.

    SYMPTOMS

    • Large amounts of honeydew, making the tree sticky and promoting the growth of sooty mold.
    • Dark russet blotches or streaks on fruit.
    • Stunted shoots.
    • Small or curled leaves.
    • Reduced fruit size.
    • Twig dieback.
    • Premature leaf drop.
    • Stunted growth, wilting, defoliation, and fruit drop.

    GENERAL MANAGEMENT

    Insecticides:

    Chemical control is difficult because the pear psylla rapidly develops resistance to insecticides. It has already developed localized resistance to pyrethroids all across its range. As such, it is very important to alternate between pesticide classes to prevent or slow resistance.

    Cultural and Mechanical Controls:

    As populations of psylla increase rapidly on highly vigorous trees, avoid practices that overstimulate tree growth.

    • Apply the minimum amount of nitrogen fertilizer necessary to achieve adequate fruit set and good fruit size.
    • Avoid summer pruning which encourages shoot growth.
    • Pull off water sprouts or suckers growing from scaffold limbs through the center of the trees in order to remove tender foliage that psylla feed on and also to allow sprays to penetrate better. Pull water sprouts by hand rather than cutting them with loppers to minimize regrowth.

    Biological Control:

    A number of predators and at least two parasitoid species attack pear psylla in Washington. The common predators include:

    • anthocorid bugs
    • predaceous plant bugs
    • lacewing adults and larvae
    • ladybird beetle adults and larvae
    • spiders

    Two parasitoid wasps—Trechnites psyllae and Prionomitus mitratus—lay eggs inside the bodies of psylla nymphs where the wasp larvae consume the psylla host as they develop.

    Effectiveness of biological control increases in orchards where fewer codling moth treatments are applied such as in mating disruption blocks.


    Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.