A Worm in the Apple

Just as you bite into that big, juicy apple, fresh off your tree, you catch sight of something that shouldn’t be there; that worm in the apple is no cute cartoon. Most likely it’s the larvae of the codling moth, a serious pest of apples that also attacks pears and walnuts.

This insect pest can be a curse in the home orchard.  The moth larvae tunnel into the fruit and as it feeds, pushes out brownish excrement called “frass” that accumulates around the entrance hole making the fruit unfit to eat.  The point where the larva chews a short distance into the apple is called a “sting.”  At this point they either die, enter at another place, or continue to munch their way through the apple to the core.

To keep this pest in check start with good garden sanitation; rake up and destroy dropped fruit as soon as it falls, especially in May and June. Limit shelter for cocoons by removing debris around the base of the tree and eliminate flaps of bark that may develop on older trees.  Look closely at maturing fruit and destroy apples that have stings or any telltale frass. 

Thin fruit were two apples touch. After thinning, when fruit is one-half to one inch in diameter, “brown bag” it. Place a small brown paper bag over each apple, cut a slit in the bottom of the bag large enough to fit over the fruit so the stem is in the slit and the little apple is in the bag, then fold and staple the opening of the bag shut. At about ten to fourteen days before harvest, remove the bag and allow the apple to ripen.

Natural enemies like spiders or carabid beetles might feed on codling moth larvae or pupae, but due to the nature of codling moth injury where a single larva can destroy a fruit, natural enemies on their own are generally not sufficient to provide acceptable control.