characteristic, pungent odor. Adults overwinter 

 in plant debris or in hedgerows. Adults, depend- 

 ing on which species is present, appear from 

 petal fall to harvest. 



Damage to peaches by stink bug feeding can 

 be dimpling, scarring, catfacing, or gummosis 

 (oozing scars). 



Populations of stink bugs are higher in peach 

 orchards that are weedy or are bordered by 

 wooded areas. A grassy orchard floor and weed- 

 free understory help reduce stink bug popula- 

 tions. Mow after an insecticide application, as 

 mowing drives stink bugs up into trees. 



Although there are numerous insect pests 

 that cause catfacing damage, often the causal 

 agent can be determined by noting the time at 

 which the injury occurred, and narrowing the 

 source to one or two insect species. 



Insects Whose Larvae Tunnel 

 in Fruit 



Plum Curculio. The plum curculio 

 (Conotrachelus nenuphar) is a small, brown, 

 bumpy snout beetle about 1/4 inch long. Larvae 

 are white to yellow, legless, brown-headed 

 "grubs" about 3/8 inch long. 



Adult plum curculios overwinter in ground 

 litter, hedgerows , or other protected areas . They 

 become active after several warm days (>55°F), 

 usually at or around bloom. Adults begin feed- 

 ing on flowers and their activity peaks at about 

 12 to 14 days after petal fall. At this time, 

 feeding injury appears as small, round holes 

 which expand with growing fruit. Also, female 

 curculios deposit their eggs in small peaches, 

 after which they make crescent-shaped cuts 

 around the egg-laying sites. If eggs hatch, larvae 

 bore into the fruit, usually feeding around or 

 near fruit pits for up to three weeks. Full-grown 

 larvae drop from fruit to pupate in the soil. 



Monitor for plum curculios by scouting for 

 adults or fresh fruit damage. Watch trees in 

 border rows and rows near wooded areas. Beat- 

 ing traps may also be used to monitor for adults. 



Oriental Fruit Moth. The oriental fruit 

 moth (Grapholitha molesta) is a grey, 1/4-inch 

 long bug with dark brown wing bands. Early 



season damage occurs on growing shoot termi- 

 nals, but second and third generation larvae 

 feed on and develop in peach fruits. 



Oriental fruit moths overwinter as full- 

 grown larvae in crevices on trees or in the 

 ground cover. Adults emerge around the time of 

 peach bloom or in early May. Small, flat, oval, 

 disc-shaped eggs are laid on upper leaf surfaces 

 on terminal foliage. Full-grown larvae are 1/4- 

 to 5/16-inch long, pinkish in color with a brown 

 head and legs. Second- and third-generation 

 (early July to early August) larvae enter fruit, 

 resulting in gummosis and a black blotch on the 

 fruit at harvest. Half of the third generation 

 larval damage occurs when the larvae enter a 

 peach stem and move into fruit. Larvae, once 

 inside the fruit, feed to the pit. Oriental fruit 

 moth larvae leave peaches through holes 

 chewed in the sides of the fruit. These exit holes 

 are often marked by the presence of "gum" and 

 dark-colored blotches. 



Oriental fruit moths can be monitored by 

 using pheromone traps. Pheromone disruption 

 techniques have been used to control this pest. 

 Good orchard sanitation — mainly removal of 

 fruit drops and shallow cultivation of the or- 

 chard floor before bloom to destroy overwinter- 

 ing larvae - will decrease the incidence of this 

 pest. 



Walnut Husk Fly. The walnut husk fly 

 (Rhagoletis suavis) is a small picture-winged fly, 

 somewhat larger than the apple maggot, and 

 with a browner body. This insect feeds primarily 

 on native nuts such as shagbark or pignut 

 hickory, and occasionally is troublesome on 

 nearby peaches in years when native nut popu- 

 lations are low. 



Adult walnut husk fly females lay eggs in 

 peaches, leaving an injury that is about two mm 

 round, depressed and retaining a green color as 

 the fruit develops. Often ooze is present. If 

 injured peaches are cut open, tunnelling is evi- 

 dent. 



This minor pest occurs in peach orchards 

 with neighboring nut trees, especially during 

 years with poor nut crops. Adults have been 

 captured on several types of sticky traps, but no 

 economic threshold level has been determined. 



Fruit Notes, Spring, 1992 



15 



