Codling moth
Codling moth is the caterpillar found inside apples and pears. The larva bores in soon after hatching and tunnels to the core, leaving a hole filled with reddish-brown frass. UC IPM reports 20–90% of fruit infested on untreated trees, depending on variety and location. For a backyard grower the options that work are bagging the fruit, which UC IPM calls the only non-chemical method effective enough to use on its own, and well-timed sprays of codling moth granulovirus or spinosad. The virus does not harm bees; spinosad is toxic to bees, so keep it off open blossom and anything flowering where bees are foraging. Pheromone traps do not control it; they tell you when the eggs will hatch. Mating disruption, the commercial mainstay, does not work on a few trees.
Cydia pomonella larva in its tunnel at the core of an apple. Photo: pending.
Identification
The larva is the stage people find: a white to light pink caterpillar with a dark brown head, up to about ¾ inch long when full grown. It is one of the few caterpillars likely to be found inside an apple or pear. Oriental fruit moth larvae look almost the same and also attack apples; they have a small comb under the last abdominal segment that needs a hand lens to see.
The adult is a small grey moth, about 3/8 inch long at rest according to the University of Kentucky (UC IPM gives ½–¾ inch). The wings are mottled grey with a dark, coppery-brown band at the tips. The eggs are tiny flat discs laid singly on fruit, leaves or spurs, 30–70 per female.
Easily confused with
- Oriental fruit mothAlso a pestThe larvae look almost the same. Oriental fruit moth has an anal comb, a small toothed plate under the last segment, which needs a hand lens or microscope to see.
Damage symptoms
Damage is inside the fruit, so the first thing most people notice is a hole with frass at the entrance. Extension sources separate two kinds of injury: a "sting" is a shallow entry where the larva died or gave up, and a deep "entry" is a tunnel to the core. Infested fruit tends to ripen and drop early.
- A hole in the side or the calyx end of the fruit, plugged with reddish-brown, crumbly frass
- A tunnel running to the core, filled with frass
- Shallow, healed "stings" on the skin where a larva failed to get in
- Fruit that colours and drops early, with a larva or an exit hole inside
- Silk cocoons under loose bark on the trunk in autumn and winter
Lifecycle & degree days
Codling moth spends the winter as a full-grown larva in a silk cocoon under loose bark, in the soil or in debris, and pupates in spring. In California the moths emerge from mid-March to early April; in Kentucky in late April or early May; in the UK in late May and June. Egg hatch is predicted with degree days counted from biofix, the date moths are first caught steadily in pheromone traps. The figures below are UC IPM's commercial apple model; they are how the virus and spinosad labels time the first spray.
- Thresholds
- Lower 50 °F / 10 °C, upper 88 °F / 31 °C
- First egg hatch
- About 250 degree days (°F) after biofix in UC IPM's apple model; UC IPM's pages range from 200 to 300, and 160 where trap catches are high
- Second generation
- Spray from about 1,100–1,200 °F degree days after biofix (Cyd-X label)
- Generations / yr
- 2–4 in California; 3 in Kentucky; 2 plus a partial third in northern Utah
- Overwinters
- Full-grown larvae in cocoons under bark or in debris
Host crops
Apples and pears are the main hosts, and English walnut in California. The RHS adds quince, occasionally. UC IPM says late-maturing varieties are more likely to suffer severe damage than early ones, and suggests early-maturing apples and pears as one way to cut losses.
Monitoring & action thresholds
Extension sources give no numeric threshold for backyard trees. UC IPM's commercial figure is 0.5% fruit damage, above which growers add sprays for the next generation, and the University of Kentucky calls codling moth a pest that needs managing in every orchard in the state. UC IPM notes that a population allowed to build up over a season or two is much harder to bring down, so if last year's crop was wormy, plan to act before this year's first egg hatch.
Hang a codling moth pheromone trap as high in the canopy as you can reach by mid-March in California's Central Valley, or early May in the UK, and check it every few days. The trap catches males only; it is a clock, not a control. The date you start catching moths steadily is biofix, and first egg hatch comes about 250 degree days (°F) later (UC IPM's pages give 200–300): check your state's degree-day service, or start looking for the first stings three to four weeks after bloom and check the fruit twice a week. The RHS notes that on an isolated tree a trap may catch enough males to reduce mating, and Kentucky mentions homeowners trying to trap out males with 2–4 traps per tree, but UC IPM says trapping is not a reliable way to reduce damage.
Biological control
Natural enemies do little to codling moth on their own. UC IPM says naturally occurring biological control isn't effective, and that Bt, pyrethrum and pyrethrin–rotenone mixes have been tested and found ineffective. Trichogramma platneri egg wasps are released in some commercial walnut and pear orchards alongside mating disruption, but UC IPM says the method has not been successful in commercial apples, has limited effectiveness, and has not been tested in backyards; Utah State is more hopeful, saying Trichogramma has shown potential combined with other low-toxicity tactics. The one biological product that works is the codling moth granulovirus (Cyd-X, Madex HP), which UC IPM found as effective as carbaryl in backyard trees.
Cultural controls
Bagging is the backbone of a spray-free programme. The other cultural methods reduce numbers but will not save a crop on their own. Mating disruption is not on this list because it does not scale down: UC IPM says it is ineffective in orchards under about 5 acres and can increase damage on single trees, and Utah State puts the minimum at 10 acres.
- Bag the fruit 4–6 weeks after bloom, when it is ½–1 inch across: thin to one fruit per cluster, slip it through a 2-inch slit in the bottom of a No. 2 paper lunch bag and staple the open end shut (UC IPM). Paper or cotton bags work; UC IPM says nylon bags do not. Kentucky suggests removing bags about 3 weeks before harvest so red fruit colours, though UC IPM warns that fruit opened early can still be attacked while moths are laying eggs
- Thin to one fruit per cluster even if you do not bag; it cuts down the places larvae can enter unseen
- Every week or two from 6–8 weeks after bloom, pick off fruit with frass-filled holes and rake up drops before the larvae crawl out
- Wrap 2–6 inch corrugated cardboard bands round the trunk to trap larvae looking for a place to spin cocoons, and destroy the bands before the moths emerge. Utah State and Kentucky recommend them; UC IPM says they catch only a very small share and no longer recommends them for control
- Grow early-maturing varieties where codling moth is bad, and remove neglected apple, pear and walnut trees nearby that act as a reservoir
Chemical, last resort
- Codling moth granulovirusREI 4 h
- Horticultural oil (narrow range)REI 4 h
- SpinosadREI 4 h
Sources
UC IPM Pest Notes 7412, Codling Moth (Caprile & Vossen, updated 05/2011)
UC IPM Pest Management Guidelines: Apple — Codling Moth (Wunderlich et al., text 12/09)
UC IPM, Relative Toxicities of Insecticides Used in Apples to Natural Enemies (10/15)
Univ. of Kentucky ENTFACT-203, Codling Moth (Bessin, rev. 1/26)
Univ. of Kentucky ENTFACT-218, Bagging Apples (Bessin & Hartman, rev. 1/26)
Utah State University Extension, Codling Moth (IPM fruit pest page)
RHS, Codling moth (advice page)
CYD-X master label, EPA Reg. 70051-44 (EPA-stamped 2025-07-07)
Madex HP master label, EPA Reg. 69553-1 (EPA-stamped 2026)
UC IPM Pest Management Guidelines: Peach — Oriental Fruit Moth
Univ. of Kentucky ENTFACT-212, Oriental Fruit Moth (Bessin, rev. 1/26)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Codling moth by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.