Codling Moth

Cydia pomonella

Insectalso: Apple worm

The classic cause of the wormy apple. Its caterpillar bores straight to the core of apples, pears, and walnuts to feed on the seeds, leaving a frass-plugged hole and a tunneled, inedible fruit. It is the single most important pest of backyard pome fruit.

🔎 How to spot it

The larva is a pinkish-white caterpillar with a dark brown head, found tunneling inside the fruit. From outside, look for the entry hole on the fruit surface plugged with reddish-brown crumbly frass, often at the blossom end. The adult is a small gray moth about three-eighths of an inch long with a coppery patch at each wingtip, active around dusk.

🥀 Damage it causes

Newly hatched caterpillars bore into the fruit and tunnel to the seed cavity, feeding there and packing the tunnel with frass; the fruit is left holed, brown-trailed inside, and unusable, and often drops early. There are usually two or more generations a year, so both early and late fruit can be hit. Apple, pear, quince, and walnut are the main hosts.

🛡️ Prevent it

Thin fruit so apples hang singly rather than touching, removing a hiding route between fruits, and pick up and destroy dropped fruit promptly to break the cycle. Bagging individual young fruit in paper or mesh bags physically excludes the moth on a small tree. Wrap the trunk with a band of cardboard to trap the larvae as they crawl down to pupate, then remove and destroy it.

🧯 If it is already here

On a backyard tree the non-chemical tools carry the load: fruit thinning, bagging, sanitation of drops, and trunk banding. If spraying, timing is everything and must be set by a pheromone trap and degree-day tracking to hit the brief egg-hatch window, since sprays do nothing once the larva is inside the fruit. Pheromone mating disruption helps over larger plantings.

💡 Good to know

Because the caterpillar spends almost its whole life sealed inside the fruit, calendar spraying rarely works; the value is in exclusion (bagging), sanitation (removing drops), and trapping. Pheromone traps are mainly a timing and monitoring tool, telling you when the moths are flying, rather than a control on their own.

🌱 Plants it attacks

26 plants in the library can be attacked by this pest

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.