University of Vermont
Department of Plant and Soil Science

gmg logo   Spring News Articleline

TREE FRUIT PESTS   

Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont

Codling moth, plum curculio, and trunk borers are common pests on tree fruits in New England.  Being ready for these if you have crabapples, flowering cherries, and fruit trees, and knowing cultural controls, will help you have better fruit with the least harm to the environment. 

Codling moth larvae (small caterpillar stage) hatch in June and early July.  They seek newly developing fruit, which they tunnel into, usually feeding in the center of the fruit and on the developing seeds.  Look for piles of “sawdust” in July on the flower end of fruit.  They feed on apples and pears, and even the related landscape plants quince, hawthorn, and crabapple.  Affected fruits, if just with a bite on the surface, usually merely have a surface blemish.  Fruits in which larvae have tunneled inside drop prematurely. 

If using pesticides to control codling moth, follow label directions, especially in regard to proper timing of spring sprays.  Biorational pesticides—those with a biological base—although better for the environment may be less effective.  These include bacteria, insect growth regulators, viruses, and botanically-based products.  More on controls and timing can be found in a Penn State University leaflet (ento.psu.edu/extension/fruit/fact-sheets).

Plum curculio weevils lay eggs in spring on apple, pear, peach, plum, and cherry fruits once they are pea size.  The eggs hatch into larvae, which feed on fruit, causing them to drop.  Larvae feed on seeds of pome fruits (such as apples) but not of stone fruits (such as cherries). If fruits remain, they show D-shaped scars or deformities.  If spraying for other pests in the spring, this one usually will be controlled as well.  Especially watch for this pest in spring on trees near hedgerows or woods where this pest may be present.

The European apply sawfly lays eggs on the base of apple flowers during bloom, which hatch into larvae.  These feed on fruit, causing a winding scar, then tunnels and holes. As a result, many immature fruit fall off.  Controls for the plum curculio also control these sawflies.

There are several species of trunk borers that kill fruit trees.  Adult beetles lay eggs on lower parts of tree trunks in summer.  The larvae that hatch tunnel throughout the trunk, causing structural damage and a site for wood rot diseases to enter.  Especially susceptible are young, unsprayed trees, and those with close-fitting tree guards.  Such guards, put on to deter mammal feeding, provide an ideal site for these borers to lay their eggs.  Removing these guards in spring helps to lessen this pest. This insect, too, is usually controlled by sprays for others orchard pests so is most often found on wild or unsprayed trees.

One of the best controls for this pest is to keep trees healthy.  If planting new ones, or near landscapes, keep them at least 300 yards away from other host plants for this pest.  These include crabapples, hawthorns, and shadbush.  Keeping brush and grass mowed and away from trunks allows natural predators such as woodpeckers and parasitic wasps to find these pests.

Other potentially serious pests of tree fruits include various mites, aphids, and San Jose scale.  More on all these pests, and controls, can be found at the above Penn State website. Another extensive website with photos on not only tree fruit pests but all aspects of culture is from the University of Maine Extension (extension.umaine.edu/fruit).  If you’d like a book reference, a good one is the Fruit Gardener’s Bible by Lewis Hill and Leonard Perry.

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