If your last crop of apples featured a worm inside that big, juicy fruit, it likely was the larvae of the codling moth, a serious pest of apples that also attacks pears, large-fruited hawthorns, and walnuts.

This insect pest can be a bane 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. In addition to the direct damage they cause, the fruit can subsequently be attacked by microbes that lead to fruit rot. To manage codling moths:

Choosing Resistant Varieties

  • Select early maturing apples like Jonagolds, Gravensteins, Galas, Macintoshes, and Red Delicious that are less susceptible to codling moth than late-maturing varieties.
  • Plant trees with semi-dwarf rootstocks; the smaller trees will make it easier for you to manage codling moths.

Focus on sanitation:

  • Check fruit on trees for signs of damage every week or two, beginning about six to eight weeks after bloom.
  • Remove infested fruit from trees; look for worm entry points (“stings”) marked by tiny mounds of reddish-brown frass.
  • Rake up and destroy dropped fruit as soon as it falls, especially in May and June.

Trap the pest: 

  • Hang codling moth pheromone traps to help reduce codling moth populations (though it isn’t a reliable way to reduce damage).
  • Put traps out by the end of March, as high as possible in the tree canopy.
  • Check them every few days for moths.

Thin your fruit:

  • Remove apples so that they do not touch; the female moth likes to lay eggs where two apples touch.
  • Thin when the fruit is about the size of a cherry or walnut.
  • Thin to have about six inches between the fruiting cluster, leaving just one apple

Protect your apples:

  • Bag when fruit is one half to one inch in diameter, four to six weeks after bloom.
  • Cut a two-inch slit in the bottom of a standard lunch bag, thin fruit to one per cluster, slip the fruit through the slit, and staple the bag shut.
  • Remove the bag and allow the apple to ripen, about 10 – 14 days before harvest,

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