Oriental Fruit Moth

Oriental fruit moth has three full generations and occasionally a partial fourth generation each year in the Midwest and the northeastern peach-growing regions. The moths overwinter as full-grown larvae in cocoons in tree bark crevices, weed stems, trash on the ground, fruit containers and packing sheds.

Oriental fruit moth (OFM), introduced in the U.S. on nursery stock from Japan between 1913 and 1916, is a serious stone fruit pest in the mid-Atlantic area. This species can be found in various stages during the entire growing season, and is the main reason for season-long, repeated insecticide applications. This pest, together with codling moth, has been causing the rejection of many truckloads of apples in the mid-Atlantic region in recent years.

The adult (pictured above) is a small grayish, mottled moth about 1/4 inch (6-7 mm) long and with a wingspan of about 1/2 inch (10-15 mm). Its wings are held roof-like over its body. Eggs are flat, oval and whitish, and are laid singly on twigs or the undersides of leaves near growing terminals, or on water sprouts. Newly hatched larvae are 1/16 inch (1.5 mm) long and are cream colored with a black head. Older larvae have a brown head capsule, are slightly pink, and grow to about 4/10 inch (9-13 mm) long. Larvae have three pairs of true legs and four pairs of prolegs, located on the third, fourth, fifth, and sixth abdominal segments. An anal comb with five “teeth” on the last abdominal segment sets OFM larvae apart from some other larvae which may feed inside fruit.

Life cycle:Full grown larvae overwinter in cocoons in bark crevices, orchard trash, weeds, ground cover, and in fallen or mummified fruit. The larvae pupate in March, with the first adults found by the pink to early bloom stage of bud development, depending on variety. There are four to five generations per year in the mid-Atlantic region. In southern New Jersey, flight peaks can occur during the first week of May, mid-June, mid-July, and late August.The adult female may lay up to 200 eggs in her lifetime.

The eggs may take up to three weeks to hatch during cool spring weather, but need only three to four days during hot summer weather. After egg hatch, first and some second brood larvae bore into new growth stems, and exit one and a half to five weeks later, depending on the temperature. Larvae will tunnel up to 6 inches (15 cm) into the shoot, or they may exit and enter one or more new shoots before maturing. Larvae of later generations of OFM lay eggs directly on the fruit, where the larvae bore in and feed. Most summer cocoons are formed on the tree.

Damage: The first generation, which is feeding when terminals are succulent and tender, develops almost exclusively in the vegetative growth. The larvae often enter the terminal at the base of a young leaf, and tunnel toward the base of the shoot. Infested terminals wilt and die back to the margin of feeding , and are commonly called “strikes” or “flagged shoots”. Heavy twig infestations of nursery stock can adversely affect the shape of the tree. Axillary buds often begin to grow when the terminal shoot is killed, causing the tree to have a bushy appearance.Fruit that are infested when very small often drop. Early-infested peaches that do not drop have obvious entrance holes with frass and gum exuding from them . Larvae attacking nearly ripe peaches usually enter the fruit near the stem, leaving only a very small, inconspicuous entrance hole. The larvae tunnel in the fruit, and frequently excavate cavities near the pit.Terminal feeding on apple is similar to that on peach.

Infested apples have a collection of frass at the exit hole of the insect’s feeding tunnel , or at the calyx end. It is difficult to distinguish between OFM damage and codling moth damage. OFM larvae feed randomly in the apple, and usually do not feed on the seeds , while codling moth larvae usually tunnel directly to the core of the apple and feed on the seeds. Later instar larvae of the two species may be distinguished by the presence or absence of the anal comb at the tip of the abdomen. The anal comb is present in the OFM and absent in the codling moth.

Control:More than 130 species of parasitoids have been reported attacking OFM; however, parasitism probably plays a very minor role in OFM control in today’s commercial orchards because of the sensitivity of many parasitoids to commonly used insecticides. Before the advent of DDT, attempts were made to supplement naturally occurring biological control of the OFM. Inundative releases of the braconid wasp Macrocentrus ancilivorus provided an average 50% reduction in number of infested fruit. However, because of the large pest complex on apple, biological control of one pest is difficult to achieve, since broad-spectrum insecticides are still needed for other pests.

Research has shown that if a synthetic sex pheromone is released in high concentrations in an orchard, male Oriental fruit moths cannot locate a female to mate. This control method, known as mating disruption, has proven effective in field tests.The OFM is rarely a problem in orchards with a regular insecticide program, but could become a more important pest as patterns of insecticide use change, or if insecticide resistance develops. Check local Cooperative Extension recommendations for the best materials and timing for OFM control in your area.

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