Predators
- Insectivorous birds and many species of polyphagous predatory insects feed occasionally on winter moth larvae.
- However, their impact on populations of winter moth larvae in orchards is limited.
Parasitoids
Many species of parasitoid attack the larvae or cocoons of the winter moth and these are its most important natural enemies.
- The tachinid fly Cyzenis albicans is one of the most common.
- It lays up to 1000 eggs which are attached singly to leaves that already have some feeding damage by winter moth larvae.
- The eggs are ingested with the food and the parasite larva soon begins to consume the host tissue.
- Parasitism rates can be high (30-60%) when the density of winter moth larvae is high, but are much lower (<5%) in commercial orchards.
- The ichneumonid parasitic wasp Agrypon flaveolatum, which attacks winter moth larvae, is another common species which may play a role in reducing populations.
- Parasitic wasps are sensitive to broad-spectrum insecticides, which are especially harmful to adults.
Bacteria
- Bacillus thuriengiensis is a pathogen of winter moth larvae but infections are normally associated with applications of the bacterium as a biological control agent.
Viruses
- Nucleopolyhedroviruses and cypoviruses have been recorded from winter moth.