Oriental Fruit Moth

The adult oriental fruit moth is small, grayish, and about 0.4 inch (10 mm) long. This moth normally flies in the evening, just after sunset, but occasionally flies between daybreak and sunrise. Eggs are usually laid on the tops of leaves and are disk-shaped, white to creamy when first laid, and about 0.03 inch (0.8 mm) in diameter. Just before hatching, the black head of the developing larva becomes visible. Larvae are white with a black head when first hatched. As they mature, they gradually turn pink with a brown head. Mature larvae are about 0.5 inch (12 mm) long. Use a hand lens to detect the presence of an anal comb under the last abdominal plate (sclerite), which helps distinguish oriental fruit moth larvae from other white or pink worms, such as codling moth, that may be found in stone fruits.

Oriental fruit moth usually produces five generations per year in California, although a sixth generation has been observed in years with warm weather in early spring and late fall. Oriental fruit moths overwinter as mature, inactive (diapausing) larvae inside tightly woven cocoons in protected places on orchard trees or in the debris near the bases of trees. In early spring, they pupate inside their cocoons and adults begin emerging in February or early March.

First- and second-generation larvae mine young, tender shoots, causing the shoots to wilt and die (symptoms known as shoot strikes or flagging). Subsequent generations may feed on shoot terminals and green fruit, but as fruit matures, it becomes this pest’s preferred site of feeding. Early-stage larvae generally enter the fruit at the stem end and may not leave noticeable entry marks, although entry can be made anywhere on the fruit, particularly where two fruits touch. Larvae immediately bore to the center of the fruit and feed around the pit. After reaching maturity, they exit from the fruit and pupate.

Mating disruption is the preferred management strategy for oriental fruit moth. Alternatively, insecticide sprays timed according to degree-day accumulations can be used. Selective insecticides can be integrated into an integrated pest management program. Careful monitoring is critical for success when using these management tools.

Macrocentrus ancylivorus is a common parasitoid of oriental fruit moth and peach twig borer larvae. In orchards where broad-spectrum insecticides are not used, parasitism can reach 80 to 90% by August and September, which helps provide long-term control of these pests. Studies indicate that growing a small plot (0.3 to 0.5 acre) of sunflowers within 25 to 50 feet of an orchard can provide Macrocentrus with an overwintering host (the sunflower moth, Homoeosoma electellum), which allows Macrocentrus numbers to increase more rapidly in the orchard the following season.

Provide habitat for natural enemies. Use mating disruption and a certified organic formulation of spinosad in certified organic orchards.

Establishing Biofix and Accumulating Degree-Days

Put pheromone traps in the orchard by February 7 to detect the first moth emergence (see Pheromone Traps). Once the first moth is found in a trap (biofix), accumulate degree-days to estimate the onset of the second flight. Use a lower threshold of 45°F and an upper threshold of 90°F. The second flight should begin about 920 to 1,010 degree-days (DD) from the beginning of the initial flight; in some areas, however, the second flight may be seen in as early as 800 DD. Calculate degree-days for oriental fruit moth in peaches for your location using the oriental fruit moth pest model or degree-days table. To learn more about using degree-days to time insecticide applications, watch the degree-days video. Continue using pheromone traps throughout the growing season until the crop is harvested to detect late-season peaks or migrations of moths from adjacent orchards.

Monitor shoot strikes (see Shoot Strike Monitoring) in late April, mid-June, and mid-July and sample fruit every week with an emphasis on the final 4 weeks before harvest (see Preharvest Fruit Samples). Although oriental fruit moth may damage green fruit, the fruit is most susceptible to damage after color break. Fruit is most heavily fed upon in the tops of the trees, so fruit samples should be picked and examined from that area.
 
Take a fruit damage sample at harvest to assess the effectiveness of the current year's integrated pest management program and determine the needs of next year's program (see Fruit Evaluation at Harvest). Record results for the harvest sample.

Mating Disruption

Before applying mating disruption, learn about the various formulations and their durations of effectiveness by closely reading label instructions and getting advice from your pest control adviser. For example, one application of a sprayable formulation is effective for one generation, while aerosol and passive dispensers can cover an entire season. Mating disruption interferes with the mate-seeking behavior of the male moths; therefore, mating disruption pheromone should be applied as soon as moths begin to emerge either in spring or in subsequent generations, depending on whether your selected formulation is targeting one generation or multiple generations.

Four types of pheromone mating disruption products are available for oriental fruit moth.

• Sprayable liquid formulations are designed to be applied with standard orchard sprayers and contain pheromones in microcapsules that release pheromones into the air once they are deposited on leaves.
• Hand-applied passive dispensers of various designs are hung in the orchard at rates ranging from 15 to 250 units per acre. Pheromones are released into the orchard continuously over a prolonged period to cover adults in multiple generations.
• Aerosol dispensers are hung in the orchard at low densities, typically one to two units per acre. These products mechanically dispense small amounts of pheromones into the orchard air at programmed intervals.
• Specialized Pheromone and Lure Application Technology (SPLAT) formulations are dollops applied directly to upper portions of the canopy, either manually or mechanically, with customized equipment that typically includes a hopper, pump, and output nozzles. It can be applied from the ground or aircraft.

Continue using pheromone traps to monitor the emergence of the second flight to get a biofix. Pheromone traps work only when a short-duration sprayable formulation has been applied for the previous generation. When using season-long mating disruption formulations, the biofix can be established by installing traps in nearby almond or peach orchards where mating disruption is not being used. Depending on the duration of effectiveness for each application type, a second application of pheromone may be needed in late July to early August for later-maturing peach varieties. Sprayable pheromones may be used for the first flight or substituted for the second application of pheromone dispensers.

Depending on the orchard history and seasonal pest density, one or two applications of insecticide may be needed. If a sprayable liquid formulation of pheromone is used, it can be tank-mixed with an insecticide. In orchards with high numbers of the parasitoid, Macrocentrus ancylivorus, frequent insecticide applications may not be necessary. This parasitoid will not be abundant, however, in orchards where a broad-spectrum insecticide has been used.

Insecticide Applications

Generally, do not apply insecticide to the first generation, except where numbers are excessive, because variable weather conditions during spring cause erratic emergence and egg laying (oviposition), and insecticides are less effective as a result.

Once the second flight has started, usually in May, accumulate degree-days. If you plan to apply insecticide with a relatively long-term residual effect (e.g., methoxyfenozide or chlorantraniliprole), treat at 400 DD from the first trapped moth; otherwise, apply insecticides from 500 to 600 DD.

In orchards with heavy infestations (an average of 3 shoot strikes per tree or if you find any larvae in the fruit), additional insecticide applications will be needed to treat the succeeding generation and prevent fruit damage at harvest. Sprays must be carefully timed to kill newly hatched larvae before they bore into shoots or fruit. If treatments are needed for the third and fourth flights, spray at 400 to 500 DD after the start of the flight.

• Degree-days
• Degree-day table
• Fruit sampling for pest damage at harvest (PDF)
• Using degree-days to time insecticide applications