Several types insects affect pears, attacking the trunk, bark, foliage and fruit of the tree. These pests range from tiny, soft-bodied aphids and scale insects that usually cause only minor injury, to more damaging insects, such as codling moth larvae, grasshoppers, fruitworms and pear psylla, which can threaten both the tree and the crop it produces. Several insecticide sprays are available on the market to help treat insect pest infestations in pear trees.
Coating insects with horticultural oils smothers them to death. Some insect pests, such as pear psylla larvae, are sensitive to horticultural oils when used during the tree's dormant period. Spraying both the surrounding soil as well as the trunk and branches of the tree will help prevent hatch-out infestations in the spring. Summer foliage can also be treated with horticultural oils. When using oils in the summer, spray the foliage thoroughly for total coverage. Horticultural oils are often mixed with other insecticides, such as malathion or permethrin to increase the kill rate.
Malathion is effective in treating a wide range of insect pests, including codling moth, Oriental fruit moth, aphids, leaf rollers, pear psylla, thrips and other damaging insect species. The Colorado State University Extension recommends applying malathion when the trees are dry at seven-day intervals. Not all products containing malathion are rated for use on fruit trees, including pears. Check the information on the package labelling to determine if the specific type of malathion product is appropriate.
A synthetic form of naturally-occurring pyrethrin, which is derived from a type of chrysanthemom, permethrin is significantly more stable and also more toxic to insect populations. Aphids, codling moth, Oriental fruit moth, leaf hoppers, pear psylla and plum curculio are all controllable using permethrin in pear tree plantings. Permethrin is often mixed with horticultural oils to improve contact with insect pests. Do not spray permethrin on pear crops within 14 days of harvest.
Adversely affecting the nervous system of insects, Carbaryl, sold under several names, the most familiar of which is Sevin, interferes with neurotransmitter function to kill insects. Carbaryl should be used with caution on pear trees only as a knock-down treatment early in the season. Later applications can reduce drop yields, according to the Colorado State University Extension.
Insect Growth Regulators
Some Insect growth regulators are rated for use on pear trees. This form of insecticide does not immediately kill pests. Instead, it interferes with the ability of young insects to mature, eventually killing them and preventing them from breeding. Pyriproxyfen, sold under the brand names Esteem and Knack, is a typical example of this type of insect spray which, according to Cornell University, is non-toxic and safe for use around people and pets.
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- Environmental Protection Agency: Types of Pesticides
- Cornell University: Pyriproxyfen--Registration of a Major Change of Label for Esteem
- Colorado State University Extension: Backyard Orchard: Apples and Pears
- Washington State University: Apple & Pear Orchard Pest Management Chart
- University of California: Pests in Gardens and Landscapes, Pears