No one wants to pluck a fresh, ripe peach from a carefully nurtured tree and discover the delicious fruit is already being eaten by a worm. What's worse is knowing that a single worm on a peach tree means there are more worms on the tree. These worms are usually the larval forms of moths and other insects that lay their eggs on peach trees and sometimes just beneath the skin of the fruit. Successfully eliminating the pests requires identifying the species and knowing when to spray the tree to kill them.
Three types of leafroller larvae may infest peach trees. When disturbed, leafrollers often drop from the foliage on the end of long, silken threads. Leafrollers generally hatch in spring. Fruittree leafroller larvae are various shades of green with a black head, while obliquebanded leafrollers range from yellowish to brown with black heads. Omnivorous leafrollers have light-colored bodies and black or dark brown heads. The first generation of these larvae hatch in spring, followed by a second generation in summer. Control is three-pronged. Sprays of dormant oil, narrow range oil or pesticides formulated with spinosad while the peach trees are in their dormant stage should be followed by sprays in early spring that target the larvae. A spray of spinosad or Bacillus thuringiensis (Bt) while the tree is in bloom is effective on young larvae. A second spray of Bt is normally performed within 10 days of the first. Spinosad, Bt or carbaryl may be sprayed after bloom. Follow label directions carefully.
Peach Twig Borer
If the worms on your peach tree are tiny and white with a black head, they are probably the immature larvae of the peach twig borer. Older larvae are 1/2 inch long and cocoa colored, with light and dark bands. They overwinter in the crotches of peach trees, or in pruning wounds and cracks in the bark. Larvae emerge in early spring and feed in the shoots or inside the fruit. Dormant oil sprays that include spinosad may be used during the dormant season to kill overwintering larvae. Spray with Bt when shoots first appear, or use a formulation of spinosad. You may use these sprays at bloom time, too. After bloom, you may spray the tree again with Bt or spinosad.
Oriental Fruit Moth
White larvae with a black head are probably from the Oriental fruit moth. As the larvae age, they turn pink with a brown head and are about 1/2 inch long. They produce about five generations per year and hatch from eggs laid on the leaves. The larvae usually start out eating shoots, but some generations feed on fruit, entering the stem end and chewing their way to the pit. Mating disruptors used in spring can help control the moths before they get a chance to lay eggs. Mating disruptors combined with sprays containing spinosad or carbaryl work better than either option alone.
Prune Limb and American Plum Borers
The prune limb borer and American plum borer produce white larvae with dark brown heads that turn off-white or pinkish when mature. They hatch from eggs laid in spring and bore into graft unions and crotches of young trees. Limbs may become weakened and break or fall under the weight of a heavy crop of peaches. Spraying with a pesticide containing carbaryl or Diazinon from mid- to late April and repeating two or three times as instructed on the product label should provide control.
- UC IPM Online: Fruittree Leafroller
- UC IPM Online: Obliquebanded Leafroller
- UC IPM Online: Omnivorous Leafroller
- UC IPM Online: Peach Twig Borer
- UC IPM Online: Oriental Fruit Moth
- UC IPM Online: American Plum Borer
- UC IPM Online: Peach -- Year Around IPM Program
- UC IPM Online: Pests in Gardens and Landscapes -- Landscape and Garden Pesticides
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