“Worms” in apples are a familiar sight, often depicted in cartoons and stories. However, the squiggly creatures found tunneling through an apple are not actually worms, but rather the larval stage of specific insects. This common misconception often leads to questions about how these invaders get inside the fruit and what their presence means.
Unmasking the Apple Invaders
The primary culprits behind “wormy” apples are the larvae of two insect species: the codling moth (Cydia pomonella) and the apple maggot fly (Rhagoletis pomonella). Codling moth larvae are cream-colored to pinkish with a dark brown or black head, growing up to about 15-20 mm long. They are caterpillars, the larval form of a moth.
Apple maggot larvae, also known as railroad worms, are legless, cream-colored maggots that are typically smaller, reaching about 7-8.5 mm in length when mature. They have a blunt posterior and a tapered front end with small black mouthparts, distinguishing them as fly larvae.
The Entry Point: How Pests Get Inside
The presence of these larvae within apples directly results from the adult insects’ egg-laying behavior. Adult codling moths, grayish-brown with distinctive coppery-tinged bands on their forewings, emerge in spring around the time apple trees bloom. Female moths lay tiny, disk-shaped, opaque white eggs singly on apple leaves or directly on the fruit skin.
Once hatched, the newly emerged larvae bore into the fruit, commonly entering through the calyx (blossom end) or areas where apples touch. They tunnel towards the core, feeding on the flesh and seeds, leaving behind characteristic tunnels filled with frass.
Apple maggot flies, slightly smaller than houseflies with distinctive “W”-shaped black bands on their clear wings and a white spot on their back, typically emerge in mid to late summer. Unlike codling moths, the female apple maggot fly uses a specialized egg-laying organ called an ovipositor to deposit eggs directly under the skin of the apple. Once the eggs hatch, the tiny, legless larvae begin to tunnel throughout the fruit’s flesh, creating winding brown trails. The larvae develop faster in softer, riper apple varieties.
Dealing with Infested Apples
Finding larvae in an apple can be unappetizing, but consuming these insect larvae is not harmful to humans. They do not carry diseases and are composed of protein and lipids. However, their tunneling can cause the fruit to bruise, decay, and drop prematurely. Severely infested apples may become mushy and unpalatable.
Managing these pests in orchards and home gardens involves several strategies. Good orchard hygiene, such as removing fallen fruit promptly, can help reduce pest populations by eliminating sites where larvae can complete their development. Physical barriers, like bagging individual fruits on the tree, can effectively prevent egg-laying and larval entry. Traps, such as sticky red spheres for apple maggots or pheromone traps for codling moths, can also be used to monitor pest activity and sometimes reduce populations. These methods help protect the apple crop while minimizing the need for chemical interventions.