Lepidoptera:Tortricidae

Oriental fruit moth is generally considered a problem only in stone fruits. In recent years, it has become an important pest of commercial apples, yet, for the most part, has nonetheless gone unrecognized. Oriental fruit moth can exist and become a problem in apple orchards when there are no nearby stone fruit orchards. Peach orchards in the vicinity will increase the probability and intensity of Oriental fruit moth infestations.

The first-generation larvae bore into apple shoots as they do into peach terminals, but in apple branches, the pests do not cause bushiness. Some apple varieties, including Red Delicious and Empire, appear to be more susceptible than other varieties to twig infestations. Investigations have shown that in some cases, the incidence of Oriental fruit moth infestations in apples is equal to or greater than the codling moth infestations.

Oriental fruit moth is generally considered more difficult to control than codling moth, especially with organophosphates. Emergence peaks of the two generations of codling moth occur at different times than the peaks of the three generations of Oriental fruit moth. The first generation of Oriental fruit moth, for example, usually peaks at apple's pink stage, so if spray is omitted for the fruit's pink stage, Oriental fruit moth could attack the apple terminals.

Peak emergence of the Oriental fruit moth sprays at second cover, they may omit the third cover spray. The Oriental fruit moth has a chance to cause further damage if the fourth cover spray is delayed until apple maggot appears, usually mid-to late July.

The third generation of Oriental fruit moth usually peaks about two weeks later than the second generation of codling moth. Thus, sprays applied for this generation of codling moth may not help control the third generation of Oriental fruit moth. Growers who wonder why they are having trouble controlling codling moth during this time may be surprised to learn that what they thought was poor timing or ineffectiveness of sprays was instead mismanaged infestations of the Oriental fruit moth.

The presence and emergence of Oriental fruit moth generations in apple orchards can be detected by using Oriental fruit moth pheromones. Braconids-especially those from the genus Macrocentrus-are important parasites of Oriental fruit moth larvae.

Egg: The egg looks like a small, flat scale adhering to the leaf or fruit. It is the size of a pinhead, 0.5 to 0.7 mm across, usually white, often semi-transparent and faintly reticulated.

Larva: The newly hatched larva is white with a black head and measures about 1.4 mm in length. When full grown, the larva has a brownish head and a pink body and measures 10 to 11 mm long. The head capsule is 1.1 mm wide.

Pupa: The pupa is brownish, turning nearly black just before the adult emerges. It is about 6 to 7 mm long.

Adult: The adults are small, grayish brown moths, with wings silvery on the undersurface and figured with light, wavy lines above. They are inconspicuous when the wings are folded. The male and female are similar, but the male's abdomen is more slender than the female's. The wingspread is 12.5 mm; body length is 4 to 5 mm.

The Oriental fruit moth attacks peach, apricot, nectarine, almond, apple, quince, pear, plum and cultivated cherry. It also attacks many woody ornamental plants. The Oriental fruit moth is found in all areas where peaches and nectarines are grown.

The larva attacks the twigs and fruits of most host plants and is now a common pest of apples, regardless of whether peaches or nectarines are grown in the area.

During May, June and July, when the terminal parts of rapidly growing twigs are succulent, they are frequently attacked by the Oriental fruit moth. Succulent peach twigs are exceedingly attractive to the larvae. Plum, apple and cherry may occasionally be moderately infested. Young trees are usually more heavily attacked than old bearing trees, and rapidly growing trees have more injured twigs than stunted trees.

In peach, a newly hatched larva usually enters the tender growing twig at its tip near the base of a young leaf, whereas a half grown larva that has abandoned an old injured twig may enter a new one at the axil of a fully developed leaf. After entering the twig, the larva consumes the central part and gradually works its way down the shoot for 2 to 6 inches. When a twig is no longer desirable as food, the larva makes an exit hole somewhere along the gouged-out channel and emerges. If it needs more food to complete its development, it may enter another twig or a fruit. One larva may enter two to five twigs or even more. On emerging from a twig, a full-grown larva will seek a place to spin a cocoon.

Twigs infested by larvae usually have one or more wilted leaves. When an upright twig has one small wilted leaf, it means that a larva has recently entered it, probably 24 to 28 hours before the time of observation. As a larva progresses down into a twig, successive leaves become wilted, with the number depending on the distance the larva penetrates. Injured twigs with dark-colored or dry leaves and exudations of gum no longer harbor larvae.

The only fruit trees in which Oriental fruit moths are likely to cause conspicuous injury to the twigs are peach and apple. In young trees when terminal twigs are attacked, several lateral shoots will appear below them and grow rapidly. Some of these shoots may also be injured by later generations, and then secondary lateral shoots will be produced. Under severe and continued attack, the tree may become somewhat bushy. In nurseries, the rapidly growing shoots of recently budded peach trees are sometimes severely attacked. The result is crooked stems.

In harvested peaches, two distinct types of injury are visible. One is caused by feeding on or entrance into the side of the fruit early in the season when the fruit is small. Frequently called "old injury," this is usually caused by larvae that have abandoned the twigs and gone to the fruit. It may take place where two peaches are touching, where a leaf rests against a peach or on the open surface of the fruit. As the peach grows, gum exudes from the point of entrance. The exudations turn dark as the season progresses, and a black blotch will be present on the peach at picking time. The infested fruit of early varieties usually shows a high percentage of side entrances; other types of entrance are not so common.

Injury caused by entrance at the stem, sometimes called "new injury," occurs when the fruit is almost full grown, especially in late varieties. This injury is caused by newly hatched larvae that go directly to the fruit. As a larva wanders over twigs and leaves in search of food, the first part of the peach it reaches is likely to be tissue near the stem end. The outside skin surrounding the stem is tender, and the larva promptly enters at this point and leaves a small pile of frass, which is easily overlooked unless the fruit is examined carefully. When fruit is sorted in packing sheds, this type of injury goes unnoticed unless it is prominent. Stem entrance in late varieties may be found in more than half of the infested fruits. Generally, the later the variety of peach, the greater the percentage of stem entrances and the smaller the percentage of side entrances.

A type of injury characterized by no visible entrance is called "concealed injury." About half the injury in late peaches may be of this type. In orchards w here fruit injury is severe, it is possible to examine a peach with great care and find no external sign of injury, yet when the peach is cut open it contains a larva feeding on the inside tissue. The larva under these conditions entered the fruit through the green stem. In the orchard, it has been repeatedly noted that a newly hatched larva may enter the side of the stem and work its way down into the fruit without in any way injuring the skin. When the peach is picked, the short stem remains on the tree, and all evidence of how the larva entered the fruit is destroyed. Concealed injury is apparently produced by newly hatched larvae, not by larvae that have abandoned the twigs.

Once a larva has entered a fruit, it may make a long, irregular channel through the soft tissue or confine its activities to a small area. It frequently does much of its feeding around the pit and characteristically leaves much sawdustlike frass in this area. Its feeding in ripe or nearly ripe peaches is thus distinguishable from that of the plum curculio, which is more likely to cut cavities in which the frass is relatively inconspicuous. Unless the infestation is severe, there is usually only one larva to a fruit, though third-generation larvae frequently enter fruits through the conspicuous black, gummy side injury caused by an earlier attack. When a larva has completed its development in a peach, it tunnels to the surface and leaves the fruit through a clean hole.

So far as is known, a larva will not leave one partly consumed fruit to attack another and will not abandon a fruit to attack another and will not abandon a fruit to attack a twig. Early in the growing season, some of the larvae enter very small peaches. When infested at this stage, the fruit always drops, usually before the larva has issued from it. Brown rot infection in peaches frequently starts at the entrance or exit holes of larva.

Oriental fruit moths are most active on quiet, fair days toward sundown. Maximum egg production occurs at 70 F and above. A succession of days when the temperature is below 60 F will inhibit egg production; temperatures of about 80 F will retard egg deposition.

Wet weather following a dry spell kills many of the larvae in the twigs. They apparently drown in the flow of sap that occurs. Severe winters may kill up to 90 percent of overwintering cocoons, but usually enough survive to produce a normal spring generation.

Natural parasites, such as Trichogramma minutum (an egg parasite) and Macrocentrus ancylivorus  (a larval parasite), may parasitize 50 to 90 percent of the Oriental fruit moth eggs or larvae. Growers cannot rely on parasites for commercial control of this insect, however.

The 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. Most of the larvae that overwinter on mature peach trees are found on lower 2 feet of the trunk; the remainder, on the upper parts of the tree.

In the spring, the larvae change into pupae. Pupation begins about mid-March. The adults begin to emerge about the time Alberta peach blossom buds show pink. Though they will continue to emerge for about two months, peak emergence of the first generation occurs about the last week in May or in early June. On peach trees, the great majority of the eggs are laid on the leaf surfaces; the rest are laid on fruit stems and bark.

The Oriental fruit moth, like the codling moth, has a marked daily flight period in the evening. That's when the eggs are laid. Females lay from 30 to 60 eggs. The incubation period averages about seven days in July and August, with a minimum of four days.

On hatching, most of the first-generation larvae bore into the twigs; only a few attack the fruit. First-generation larvae usually damage two or three twigs before reaching maturity. The length of the larval feeding period can vary from 10 days to 10 weeks, with an average of about three weeks. During the summer, the average length of the developmental period from newly deposited egg to adult emergence is about six weeks, with a minimum of 24 days during very hot weather.

The second generation of adults generally begins to emerge about July 1, with increases or decreases in numbers dependent on weather conditions. Larvae of this generation attack both peach twigs and fruits. As the twigs harden, the partially grown larvae leave them and enter the fruits. Fruit injury in July or early August is indicated by the exudation of large masses of gum mixed with frass. Second-generation larvae usually attack three or four twigs before reaching maturity.

Adults of the third generation emerge in early to mid-August, depending on weather conditions. The third-generation larvae appear about mid-August and may continue to hatch in large numbers until mid-September. This generation is the major cause of wormy fruit at harvest, often with little or no external sign of injury. The majority of the third-generation larvae grow to maturity, spin cocoons and remain in them over winter. In very warm seasons, a few may pupate and emerge as adults that may produce a few eggs and larvae late in the season.

Using 45 degrees F as a base, degree-days (DD) for Oriental fruit moth activity* are:

(NOTE: Only mature larvae should be examined for the anal comb, because the comb is difficult to recognize in immature larvae without a powerful microscope. In mature larvae, the anal comb is visible with a hand lens and easily seen under a binocularscope.)

The most convenient way to check larvae for anal combs is to cut open infested apples and preserve the larvae in alcohol to be checked later. If you wish to examine the larvae immediately, place them in boiling water to kill them before checking.

It is very important to note that both Oriental fruit moth larvae and lesser appleworm larvae have anal combs and are similar in size and color. It is nearly impossible to distinguish the larvae of the two insects, and growers may have to wait until larvae reach the adult stage before the insect can be correctly identified. Be aware that Oriental fruit moth males are attracted to often caught in lesser appleworm pheromone traps. Lesser appleworm males, however, are much less attracted to Oriental fruit moth pheromone lures.

Use pheromone traps to monitor adult activity and to time spray applications. Pheromone disruption of Oriental fruit moth is now legal in some states. Hang traps in early April and count and remove moths twice weekly. Use 10 traps for a 10-acre orchard, with two traps inside and the rest as border traps. Place traps at least 100 feet apart to prevent interference between traps. Sprays to control the first generation should be applied about six days after the first peak adult emergence. This application usually coincides with sprays for plum curculio control. Apply sprays for the second generation three days after peak adult emergence to coincide with peak egg laying of the second generation.

The braconid wasp Macrocentrus ancylivorus is an important parasite that destroys many of the first and second generation larvae.

Growers spraying for the third generation fruit moth need to take into consideration expected harvest dates of their cultivars. Because ripening peaches are most susceptible to fruit moth attack, third generation larvae are largely responsible for wormy fruit at harvest. To protect ripening peaches, sprays should be applied 10 to 12 days before harvest. If peak emergence of third generation adults occurs some weeks before harvest, sprays should be applied about three days after peak emergence of adults to coincide with peak egg laying. Additional sprays may be necessary, depending on harvest dates.