Codling Moth

Codling moth (Cydia pomonella) is one of the worst orchard pests. The larval stage of these moths burrows into the core of apples and pears, and the nut meat of English walnuts, leaving a tunnel filled with frass (bug poop).

Damage to apple caused by codling moth larva (USDA) Public Domain

​Codling moth identification

Codling moths are mottled gray in color, so they are camouflaged when on tree bark. If a codling moth is trapped, a copper band can be seen along the outer edge of the wing. Codling moths rest with their wings held like a tent over the body. Adults are 1/2-3/4” long. The larvae are white to pink worms with a black head and they are usually only seen when you bite into an infested apple or pear. Yuck!

Uncontrolled codling moth infestations can damage 20-90% of a crop. Infested fruit can be eaten, but the damaged parts should be cut out because they can contain mold toxins (aflatoxin).

Female codling moth (Simon Winkley & Ken Walker, Museum Victoria) CC BY 3.0 au

​Codling moth lifecycle

In late April and early May, adult moths emerge from cocoons that have overwintered in the soil and leaf litter around host trees. These moths have only one thing on their minds: sex. After mating, female codling moths lay 30-70 eggs on leaves, spurs and fruit. When this abundant family hatches, the only thing on their mind is your apples and pears. Larvae burrow into the fruit to eat and eat and eat. Then, they leave the fruit (hopefully, before anyone took a bite) and drop to the ground. Here, they hide in the soil or leaf litter, where they enter a pupal stage. Depending on the weather, there can be as many as four generations a year.

Adult codling moth Olaf Leillinger CC BY-SA 2.5

Codling moth controls

Since the lives of codling moths are all about reproduction, managing their courtship has been one of the best control methods. Since most insects find mates by the sense of smell, pheromone traps are very effective. Pheromones are sex hormones. When a male codling moth gets near a pheromone trap, he becomes too confused to find a mate. Also, these traps feature a sticky substance that traps the moths. These can be found at most garden supply stores. Pheromone traps work best in solitary trees, when several traps are used. According to companion planting lore, codling moths are said to avoid areas where garlic and wormwood are planted.

To prevent codling moths from laying eggs on fruit, individual fruits can be protected with paper lunch bags. To bag apples and pears, wait until the fruit is 1/2-1” in diameter. Thin fruit to one to a cluster (which generates bigger fruit). Simply lift the bag over the fruit and fold the edges over and staple the bag shut. This will protect your pears and apples, but it interferes with color development. Many gardeners remove the bags 1 or 2 weeks before harvest to allow fruit to reach its normal mature color.

Some commercial growers use insecticides to kill codling moth eggs, but the timing and temperatures must be exactly right for it to be effective. Once the larvae enters the fruit, it’s too late. A biological insecticide, codling moth granulosis virus (CYD-X), is now available in California. This virus attacks coddling moth larvae when they eat it.  

Gardeners can also dust fruit with kaolin clay to prevent coddling moth infestation, but coverage must be complete to be effective. Kaolin clay is very fine clay used to make porcelain. While it doesn’t hurt people or animals, it is deadly to insects. Being so fine, it clogs their breathing holes. As an added benefit, kaolin clay improves photosynthesis and helps keep trees a little cooler through the summer!