WSU Tree Fruit Research & Extension Center

Pear Entomology

Monday, March 25, 2019

Pressure from pests is the chief management concern of pear growers in Washington. Under otherwise optimal conditions, a variety of strategies have been employed to bring excellent and environmentally safe fruit to the market. WSU scientists have been globally at the forefront of research.

Pear pest management

Pear pest management has been forced to rely heavily on chemical control tactics because of low pest thresholds on the high value crop. High pesticide inputs lead to rapid evolution of pesticide resistance in insects and mites, and Washington pear growers have faced resistance problems in key pests over the past 40 years. Research is directed at development of pesticide resistance management programs, reducing resistance or slowing the rate of resistance evolution. This is primarily accomplished by reducing the use insecticides through IPM practices and developing tactics to use pesticides in rotations.


Resistance in pear psylla

Resistance management programs for pear psylla are currently being developed and tested in the laboratory as well as in the field. The use of insect growth regulators (IGRs), which are environmentally friendly, is helping change pear agroecosystems by allowing more predators to survive. However, the efficacy of IGRs is currently so high that if they are used frequently resistance will rapidly evolve, and then the products will no longer work. Developing alternative pest management programs, using biological control as well as other pesticide chemistries, will stabilize IGR use.


Spider mites

Spider mites also rapidly develop resistance in pear orchards. Because many insecticides applied for pear psylla also control spider mites, both pests must be considered in developing a pear IPM program. A pesticide rotation program has been developed which controls both spider mites and pear psylla, yet reduces the likelihood of resistance evolution to any one pesticide. The efficacy of a resistance management program for spider mites and pear psylla is currently being tested by  Dr. Elizabeth Beers.


Grape mealybug

The recent increase in pest status of grape mealybug in pears in Washington makes this pest a problem which requires immediate attention. Development of an IPM program for grape mealybug is necessary to successfully implement a stable pest management system for other pear pests. High rates of organophosphate insecticides, which are highly disruptive and prevent biological control of grape mealybug and other pests, are required to obtain control. Research is currently underway to investigate new grape mealybug biological control agents from other parts of the world. Also, some endemic predators, such as earwigs and lacewings, are being examined for their potential in augmentative biocontrol, much like using a biological pesticide.


Resistance in codling moth

Resistance in codling moth is not present in Washington pears to the extent that it is in other parts of the world.Research has measured the dispersal ability of codling moth using an elemental marker. The results of this research will better address the need for areawide management of codling moth and determine the likelihood of the movement of pesticide resistance.

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