Walnut-Codling moth

Cydia pomonella

Pest description and crop damage A gray torticid moth with coppery spots on the wings and white or pink larvae up to 0.625 inch long that can damage walnuts. While codling moth is an important pest of walnuts in California, it is rarely a problem on walnuts grown in the Pacific Northwest. The type of injury varies with the time of infestation. Early season infestations arrest nut development and may result in heavy nut drop. Later in the season, feeding within the husk may stain nut shells but does not affect kernels, or larvae may enter the shell and destroy the kernel.

Biology and life history Codling moth overwinters as mature larvae in silken cocoons (hybernaculi) spun under loose bark, in the soil, or in litter at the base of the tree. Pupation takes place in the early spring, and adults emerge around the time of bloom. Adults are active only at dusk and dawn and lay eggs on leaves or occasionally on fruit. The larvae emerge from the eggs and search out the nuts to begin feeding. Sprays are typically applied to target the eggs and the young larvae before they enter the husk. Larvae may bore to the center of developing nuts to feed on the kernel. As they mature, they push frass out of the entry hole. After 3 to 4 weeks the nut may drop, and the larvae may leave the nut to seek a sheltered spot on the tree to spin cocoons. The larvae may overwinter in the cocoon, or they may emerge in 2 to 3 weeks as a new flight of adults. These adults are active in July and August. In warm areas, there may even be a third flight of moths. Larvae produced by the late moth flight may penetrate nuts but they often do not complete development before harvest or winter.

Pest monitoring Pheromone traps can be used to monitor populations. They can be used to set damage thresholds and they can also be used to set phenology models. Check with your Extension agent on moth levels in your area. There is a very low threshold for damage, as minor infestations one year can turn into a major problem the next.

Management-biological control

A number of natural enemies have activity against codling moth so conservation biological control is important for maintaining low pest populations. However, insect biological controls have not proven effective in controlling outbreaks of this pest. Sprays of Bacillus thuringiensis serotype kurstaki (Btk) have not proven effective. Insecticidal granulosis virus (OMRI-listed) is effective against larvae and there are several commercial formulations including Cyd-X. Application of virus should be timed to egg hatch, or approximately 200 to 250 degree days.

Management-cultural control

Black-light traps have shown some efficacy in small orchards for trapping the adult moths. Remove any infested fruit well before harvest, and destroy them to eliminate larvae. Remove brush and debris from the orchard, and remove bark scales from the tree to eliminate overwintering sites. Wrap the trunk with corrugated cardboard or burlap to trap migrating larvae. Periodic removal of these tree wraps to destroy cocooning larvae can help. A number of hand-applied and aerosol pheromone release devices are available for mating disruption of codling moth. This management tactic can be very successful on large orchard blocks (>10 ac) and moderate to low codling moth populations.

Management-chemical control: HOME USE

Spray timing depends on moth emergence. The first spray is usually when the average nut size is 0.375 to 0.5 inch in diameter.

  • acetamiprid-Do not apply until after trees have flowered or when bees are actively foraging. Do not make more than one application a year. PHI 7 days.
  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • carbaryl
  • esfenvalerate
  • gamma-cyhalothrin
  • horticultural oil-Some formulations are OMRI-listed for organic use.
  • insecticidal soap-May require several applications to be effective. Some formulations are OMRI-listed for organic use.
  • kaolin clay (Surround® at Home®)-Applied as a spray to leaves, stems, and fruit, it acts as a repellant to some insect pests. Some formulations are OMRI-listed for organic use.
  • lambda-cyhalothrin
  • permethrin
  • pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
  • spinosad-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

Spray timing depends on moth emergence. The first spray is usually when the average nut size is 0.375 to 0.5 inch in diameter.

  • acetamiprid (Assail 30SG) at 0.1 to 0.18 lb ai/a. No more than 4 applications and a maximum of 0.72 lb ai/a per growing season. Retreatment interval 14 days. PHI 14 days.
  • alpha-cypermethrin (Fastac EC) at 0.02 to 0.025 lb ai/a. Retreatment interval 7 days. Maximum 0.075 lb ai/a. PHI 7 days.
  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • beta-cyfluthrin (Baythroid XL) at 0.016 to 0.019 lb ai/a. Maximum per 14 day and per season 0.022 lb ai/a. PHI 14 days.
  • bifenthrin (Brigade WSB) at 0.05 to 0.2 lb ai/a. PHI 7 days. REI 12 hr.
  • bifentrin/abamectin B1 (Athena) at 7.5 to 20 fl oz/a. Retreatment interval 21 days. Maximum of 2 applications per season. PHI 21 days.
  • carbaryl (Sevin XLR Plus) at 2.5 to 5 quarts/a. PHI 14 days. REI 12 hr. Extremely toxic to aquatic invertebrates.
  • chlorantraniliprole (Altacor) at 3 to 4.5 oz. PHI 10 days. REI 4 hr.
  • chlorpyrifos-Generic labels for chlorpyrifos are also available.
    • Lorsban 4E at 4 pints/a. PHI 14 days. REI 1 day. Do not exceed two applications per season. Do not graze. Extremely toxic to fish. Toxic to birds and wildlife.
    • Lorsban 75WG at 2.6 lb/a. PHI 14 days. REI 1 day. Do not exceed two applications per season. Do not graze. Extremely toxic to fish. Toxic to birds and wildlife.
  • chlorpyrifos/gamma-cyhalothrin (Cobalt) at 26 to 57 fl oz/a. PHI 14 days. Do not make more than 2 applications per season of Cobalt or other product containing chlorpyrifos for walnuts.
  • cyantraniliprole (Exirel) at 13.5 to 20.5 oz. Retreatment interval 7 days. PHI 5 days. REI 12 hr.
  • cyfluthrin (Tombstone) at 0.031 to 0.038 lb ai/a. Maximum 0.044 lb ai./a per season. PHI 14 days.
  • deltamethrin (Delta Gold) at 0.02 lb ai/a. Maximum 0.165 lb ai/a. Retreatment interval 7 days. PHI 21 days.
  • diflubenzuron (Dimilin 2L) at 16 fl oz/a. Most effective if applied before egg-laying. Extremely toxic to aquatic invertebrates. Do not apply within 25 ft of bodies of water. Do not make more than 4 applications per season. PHI 28 days. REI 12 hr.
  • esfenvalerate (Asana XL) at 10 to 16 fl oz/a. PHI 21 days. REI 12 hr. Do not exceed 0.2 lb ai/a per season. Do not feed or graze livestock on untreated orchard floors. Extremely toxic to fish and aquatic habitat.
  • lambda-cyhalothrin (Warrior II) at 1.28 to 2.56 fl oz/a PHI 14 days. REI 24 hr. Do not exceed 0.16 lb ai/a per season or 0.12 lb ai post bloom.
  • malathion (Malathion 57% EC) at 0.4 to 0.6 oz/a. PHI 7 days. REI 12 hr.
  • methoxyfenozide (Intrepid 2F) at 0.19 to 0.38 lb ai/a. PHI 14 days. REI 4 hr. The higher rates in the recommended rate range may be required for extended residual effectiveness, high pest infestation levels, larger trees, or heavy dense foliage. Do not exceed 24 fl oz/a per application or 64 fl oz/a (1 lb ai/a) per season. Do not apply within 25 ft of an aquatic habitat, 150 ft if applied by air.
  • permethrin-
    • Ambush 2E at 16 to 24 oz/a. PHI 1 day. REI 12 hr. Extremely toxic to fish and aquatic habitat.
    • Pounce 3.2 EC at 8 to 16 oz/a. PHI 1 day. REI 12 hr. Extremely toxic to fish and aquatic habitat.
  • pyriproxyfen (Esteem 35WP) at 4 to 5 oz /a. PHI 21 days. REI 12 hr. Do not exceed two applications per season.
  • spinetoram (Delegate WG) at 3 to 7 oz/a. PHI 14 days. Apply no less than one week apart, with a maximum 4 applications per season.
  • spinosad (Entrust SC) at 4 to 10 oz/a. PHI 14 days. REI 4 hr. OMRI-listed for organic use.
  • spinosad (Success) at 4 to 8 fl oz/a. PHI 14 days. REI 4 hr. Do not exceed 29 oz/a per year or apply fewer than 14 days apart.
  • zeta-cypermethrin (Mustang, Mustang Max, Mustang Maxx) at 0.02 to 0.025 lb ai/a. Maximum of 0.125 lb ai/a per seaon. PHI 21 days.

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