Department of Entomology

Southeastern Apple Production ENTOMOLOGY

Oriental Fruit Moth

Grapholita molesta

Description

Adult Oriental fruit moths (OFM) are about 1/4 inch long and brownish gray with a faint 'salt and pepper' pattern. Full-grown larvae are about 1/2 inch long, pinkish white, and very similar to codling moth larvae except for the presence of an 'anal comb' structure visible only under a microscope. Pupae are reddish brown, and eggs are yellow-white and laid singly.

Adult

Larva

Pupa

Egg

Life History

OFM overwinters as a fully grown larva enclosed in a cocoon and located in tree bark or orchard debris. Larvae develop into pupae in early spring and emerge as adults in early April (before bloom). First-generation eggs begin to hatch at petal fall, and larvae feed on shoot tips and inside fruit (though variable spring temperatures can cause erratic emergence and egg-laying by first-generation moths). There are typically four or five generations per season in the Southeast. See also graph below.

Damage

Though common, RBLR is seldom economically damaging. Larvae can harm leaves by skeletonizing the underside close to the midrib, folding and webbing the leaf together. Second and (more often) third generation larvae may feed on the fruit surface, often beneath a white web or leaf that is webbed down to protect the feeding site. Larvae may also attack the cavities at the calyx and stem ends as well as the places where two fruit touch.

OFM shoot feeding

OFM entry with frass

OFM fruit tunnels

Monitoring and Control

Base a decision to spray insecticides against OFM on pheromone trap catches and a degree-day model. Traps should be placed in orchards near the green tip stage of bud development, and checked one to two times per week. Hang traps at eye-level at a density of one trap per ten acres of orchard. The 'biofix' date is established when pheromone traps sustain a catch of two or more moths. (It is only necessary to check traps once per week after biofix is determined.) Begin to accumulate degree days at biofix. The degree-day table at the bottom of the page uses daily maximum and minimum temperatures to determine daily degree-days for OFM (base 45º F). The degree-day model predicts adult emergence and egg hatch for the first three generations of the four or five generations that occur in the Southeast. Since generations overlap in the late season, the degree-day model becomes less useful at that time.

First-Generation OFM: Control of the first generation is often important to prevent first-generation damage and to reduce populations of subsequent generations. First-generation egg laying is usually low on apple, and only one insecticide application between 400 and 500 DD after biofix is necessary, which usually coincides with petal fall.

Second-Generation OFM: If first-generation control was successful, second-generation populations are usually very low. Extremely low-density orchards may not require an insecticide application (i.e., pheromone trap catches never exceed 3 moths per trap per week between 800 to 1,600 DD after biofix). In low-density orchards (3 to 7 moths per trap per week caught between 800 and 1,500 DD), make a single insecticide application at 1,400 DD. Moderate- to high-density orchards will have fruit damage, higher pheromone trap catches, or both, and may need two insecticide applications 14 days apart starting at 1,100 DD.

Third-Generation OFM: An insecticide is recommended at 2,200 DD after biofix if pheromone trap catches exceed 5 moths per trap per week at 1,900 DD after biofix and if there is fruit damage caused by the second generation.

Fourth-Generation OFM: Because of overlapping generations late in the season, it is difficult to predict when egg hatch of the fourth generation begins. However, continuous egg laying can occur from August through October, and the use of pheromone traps are the best method to determine the potential for late-season damage. Apply an insecticide within 7 to 10 days of a pheromone trap threshold of 10 moths per trap per week. Maintain spray intervals on a two-week (complete) or 5- to 7-day (alternate-row-middle) schedule for as long as the threshold is exceeded.

Typical Seasonal OFM Population Trends

Insect and Mite Management Overview
Insect and Mite Index

Southeastern Apple Production
Mountain Horticultural Crops Research & Extension Center
455 Research Drive
Mills River, NC 28759
Phone: 828.684.3562 ~ Fax: 828.684.8715
Email: jim_walgenbach@ncsu.edu

Web Crafters: Anne S. Napier and Steve Schoof
Email: steve_schoof@ncsu.edu

Updated March 9, 2007