Codling Moth

Codling moth has a 0.5 to 0.75 inch wingspan. The tip of each forewing has a coppery-tinged, dark brown band that distinguishes codling moth from other moths found in apple orchards. Females lay eggs singly on leaves and sometimes on fruit later in the season. The eggs are smaller than a pinhead, disk-shaped, and opaque white when first laid. Just before hatching the black head of the larvae becomes visible. Newly hatched larvae are white with black heads. Mature larvae are 0.5 to 0.75 inch long, pinkish white, with mottled brown heads. Depending on climatic conditions and location in the state, there are two to four generations of codling moth each year.

Codling moth has the greatest potential for damage of any apple pest, yet it can be effectively controlled with properly timed treatments. It causes two types of fruit damage: stings and deep entries. Stings are entries where larvae bore into the flesh a short distance before dying. Deep entries occur when larvae penetrate the fruit skin, bore to the core, and feed in the seed cavity. Larvae may enter through the sides, stem end, or calyx end of the fruit. One or more holes plugged with frass on the fruit's surface are a characteristic sign of codling moth infestation. Calyx entries are difficult to detect without cutting the fruit.

An IPM program uses a combination of tools for codling moth management, including insecticides, mating disruption, and cultural controls. Mating disruption is the preferred tool because of its low toxicity to people, natural enemies, and the environment, but it may need to be supplemented with insecticide sprays, especially during the first few years. In orchards where codling moth is managed primarily with insecticides, alternate insecticides that have a different mode-of-action Group number to avoid the development of resistance. If you see trap catches increasing and suspect insecticide tolerance or resistance, combine the use of mating disruption with the insecticides. All codling moth management programs should be supplemented with cultural controls.

Alone, natural enemies are not able to keep codling moth populations below economic levels. Augmentative releases of the egg parasite Trichogramma platneri have been applied to reduce codling moth populations, but research has shown that this technique has limited effectiveness and is too expensive for practical use.

Remove host trees in nearby abandoned orchards (apple, pear, and walnut) to destroy reservoirs of codling moth. Also remove props, picking bins, and fruit piles from the orchard. Proper pruning and orchard sprayer calibration will improve spray coverage. An option for small, organic orchards is hand thinning to remove all infested fruit during each generation, before worms leave fruit, and removal of dropped fruit.

Organically acceptable tools for the control of codling moth include cultural control in conjunction with mating disruption and sprays of approved oils, codling moth granulovirus (Cyd-X), the Entrust formulations of spinosad, and kaolin clay (Surround). Check with your certifier about the exact status of all materials.

Mating disruption works best in large, uniform orchards that are relatively square in shape. It is not recommended for orchards less than 3-5 acres in size. The larger the contiguous block of mating disruption, the more effective it will be. In orchards with moderate-to-high populations of codling moth and/or in the first year of mating disruption, insecticides or other supplemental controls will likely be needed in addition to the mating disruption program. Using mating disruption successively over a number of years can effectively lower the codling moth population so that alternative, reduced-risk chemical treatments can be effectively used to supplement control when needed.

Pheromones are deployed as either hand-applied dispensers or in an aerosol canister (puffer). Sprayable pheromones are available but not currently recommended for pome fruit orchards because of their very short residual.

Using historical biofix dates to time the application, hang all pheromone products shortly before the first moth emergence in early March to early April. It is important to put out pheromone products early in order to disrupt the mating of overwintering moths as soon as they emerge. A late pheromone application will require supplemental spray treatment.

Place hand-applied pheromone dispensers in the upper third of the tree canopy. When placing puffers, put them on the inside of the canopy of edge trees or on the outside of trees in the second row. Upwind placement is one puffer every 50 to 65 feet, and downwind placement is one every 100 to 130 feet, or an average of 20 units per quarter mile. For large blocks, also place a few puffers towards the middle of the orchard on the upwind side. Reapply the dispensers according to the manufacturer's guidelines if the product residual will not last through harvest or through the end of the last generation.

Monitoring with Traps

Monitor pheromone-treated orchards with traps carefully to help ensure that mated moths have not moved in from adjacent orchards and that the pheromone is successfully disrupting mating.

Supercharged (10 mg) pheromone traps.

Place pheromone traps with supercharged (10 mg) pheromone lures in the orchard when pheromone dispensers are set out. Put these traps in trees at the same level as the pheromone dispensers. These traps serve to help set the biofix point for degree-day accumulation, which is used to time both fruit sampling and supplemental treatments. Check traps one to two times a week until biofix is set and once a week thereafter. Biofix is the first date that moths are found in traps for three consecutive checks and sunset temperatures have reached 62°F. (Replace lures at the frequency recommended by the manufacturer.)

Supercharged traps do not attract moths from far, so place as many traps as you can monitor in areas of the orchard that are known hot spots and areas vulnerable to wind where pheromone concentration is likely to be reduced. Examples include high spots and orchard edges; five to six rows inside the orchard is a good location. If the supercharged traps consistently catch high numbers of moths, monitor fruit in the surrounding area for eggs and damage to determine if a supplemental treatment is necessary. No thresholds have been established for these supercharged traps but 5 moths/week can be considered a relatively high trap count.

Regular (1 mg) pheromone traps

Another tool in a mating disruption program is the use of pheromone traps with the regular (1 mg) lures to verify the effectiveness of the mating disruption dispensers. A good idea is to pair a 1 mg trap with a supercharged one. Check traps weekly and replace lures at the frequency recommended by the manufacturer. The supercharged traps should catch a few moths, but the 1 mg traps should not catch any. If moths are caught in the 1 mg traps, check the fruit in the surrounding area. If eggs or damage are found, apply a supplemental treatment to prevent further damage. Traps with regular lures can also be used in upwind border trees (placed in trees in the second row) to monitor the influx and development of codling moth. When moths are caught in these edge traps, it signals the need to monitor fruit.

DA lures

A plant-derived chemical (kairomone) lure has been developed to assist in monitoring codling moth populations. This lure is sold commercially as the "DA" lure and is available alone and in combination with pheromone ("combo lure"). The DA lure has been shown to catch both female and male moths, whereas pheromone lures catch only male moths. The sex of moths caught in traps using the DA lure can be determined by observing the tip of the abdomen. If the moth is female, the abdomen can be squeezed to eject the bursa pouch and give some idea of whether the moth is unmated, mated once, or more than once. Generally, if the female's abdomen feels hard to the touch, the moth is most likely mated.

The DA lure appears to work best in mating-disrupted apple orchards early in the season. The DA and DA/pheromone combo lure may also be used to assess the success of mating disruption in an orchard, similar to using a supercharged (10X) pheromone lure. Because these lures are relatively new to the market and there appears to be some variability in these lures from one season to the next, use them in conjunction with standard 10X and 1X pheromone lures in order to become familiar with them.

Fruit Sampling

Fruit damage can occur even when no moths are caught in traps, so always check fruit for damage towards the latter half of each generation (900 to 1000 degree-days from biofix) and whenever moths are being caught in traps. Examine at least 200 fruit from throughout the orchard as well as in known hot spots and areas vulnerable to wind (edges, high spots), which can reduce pheromone concentration.

If fruit damage exceeds 0.5%, supplemental sprays should be used for the next generation. If the damage is quite light and very localized along a border, treating five to ten rows along the problem border may be adequate. However, if damage is not clearly localized, or is localized but more than a few percentages, then a larger area or the entire orchard may need to be sprayed.

Supplemental Treatments

First generation
In orchards with moderate-to-high codling moth populations or if the orchard is in the first year of mating disruption, supplement the mating disruption with an insecticide spray of Altacor, Delegate, Assail, Imidan, or Warrior at 250 degree-days after the biofix to target hatching eggs from the first peak of the overwintered moth flight. If monitoring indicates continued flight, apply a second application about 600 to 700 degree-days from the biofix to suppress egg hatch from the second flight peak of the overwintered moths.

For low populations, applying a supplemental spray to the first generation may not be necessary. Use trap catch information and monitor fruit to determine if a spray is needed. Using a reduced risk material such as the IGRs (methoxyfenozide-Intrepid) or an organically acceptable alternative (oil, spinosad-Entrust, or codling moth granulovirus – Cyd-X) may be sufficient for control of low populations.

Second and third generation
To determine if treatment is needed for subsequent generations, careful trap and fruit monitoring is essential. If treatment is needed, use the guidelines in the section below to determine the best time to spray.

In orchards where codling moth is managed primarily with insecticides, pheromone traps, in conjunction with degree-days and sunset temperatures, are used to determine egg hatch and proper spray timing. When using pheromone traps, keep in mind the many factors, such as tree size, trap density, type of trap, trap placement, brand of pheromone, as well as climatic conditions, that can affect trap counts.

Establishing Biofix and Accumulation of Degree-Days

Hang 1 mg pheromone traps in the orchard in mid-March (or at bloom in foothill orchards) about 6 to 7 feet high, with one trap every 10 acres and at least two traps per orchard. The first date that moths are found in traps for three consecutive trap checks and sunset temperatures have reached 62°F is first biofix. (Service traps one to two times a week until biofix is set and once a week thereafter. Replace lures at intervals specified by the manufacturer.)

Spray Timing

Once biofix is reached, calculate degree-days using a lower threshold of 50°F and an upper threshold of 88°F.

The most effective spray timing for each generation is outlined below. For all generations, if high levels of moths are being caught in traps, do not wait until 200–250 degree-days to treat, but apply the first spray at the beginning of egg hatch (160 degree-days).

Codling moth has two to four generations each season. Continue to monitor the generations with traps and accumulate degree-days until the crop is harvested or populations decline below damaging levels in September.

Two to three sprays may be necessary to adequately control the first generation particularly if the population is high or a short-residual insecticide is used. In addition, if rainfall exceeds 0.5 inch or an irrigation with overhead sprinklers is scheduled within 2 weeks after treatment, a second spray will be needed. Apply the first spray when 250 degree-days have accumulated from the first biofix, unless high levels of moths are being caught, in which case spray at 160 degree days.

Make the second and third, if needed, application when the residual effectiveness of the previous spray has ended; this will vary, depending on the chemical used. If trap catches are low or the weather turns too cool for moth activity, you can delay treatment, but continue to monitor.

Use pheromone trap catches to detect an increase in moth flight activity around 1060 degree-days from the first biofix, which signals the start of the next flight and is the second biofix. For low moth populations, a single application may be sufficient; make this application when 200 to 250 degree-days have accumulated from the second biofix. If you are catching high levels of moths per trap per week, spray at 160 degree-days. If needed, apply a second spray when the residual of the previous spray ends. These two sprays should provide control during the entire egg hatch period.

A third generation of codling moth eggs does not occur every year in every location. Codling moth larvae normally go into diapause (winter dormant state) around August 22, but in warm years and warm locations they will have already started pupation before August 22, and these pupae will soon emerge as adults to produce a third generation. If 650 degree-days have accumulated between the peak of the second generation flight and August 22, most of the codling moth will not go into diapause but will pupate and emerge in August to early September, depending on climate.

If degree-day accumulation data indicates a third generation will occur, use pheromone traps to establish a third biofix point around 1100 to 1200 degree-days from the second biofix. Apply a spray when 200 to 250 degree-days have accumulated from the third biofix unless trap catches are high, in which case treat at 160 degree-days. If needed, apply the second spray when the residual of the previous spray ends.

In the hottest growing regions of the state, such as the southern San Joaquin Valley, a fourth or partial fourth generation may occur in some years. When flight activity increases around 1100 to 1200 degree-days from the third biofix, establish the fourth biofix. Apply a spray when 200 to 250 degree-days have accumulated from the fourth biofix and, if needed, a second spray when the residual of the previous spray ends.

Degree Days

Calculate degree days for codling moth for your location using the codling moth pest model or degree-day table. To learn more about using degree days to time insecticide applications, watch the degree-days video. Use the online tool to find your sunset temperature.

• Degree-day table
• Degree-day calculator
• Sunset temperatures
• Using degree-days to time insecticide applications