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Codling moth, the fruit worm

Three apples infected with codling moth fruit worms
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The damage is hidden until the fruit is cut open: a caterpillar tunnelling through the flesh of an apple, pear, plum, nut or chestnut. This is the codling moth, the pest gardeners call the fruit worm, and because it spends almost its whole life inside the fruit, well-timed watchfulness achieves far more than brute force.

It is actually a type of caterpillar that feeds on the fruit’s flesh.

Most often it is found in apples, but also appears in:

  • pear,
  • nuts,
  • chestnut,
  • and plum.

When and how to treat against fruit worm?

When should one treat against this enemy of apple trees and pear trees, and how?

Four ways to fight codling moth, compared

The article describes four complementary lines of attack against the fruit worm. Use this table to see what each one does and when it belongs in the season.

Four ways to fight codling moth, compared
Method When How it works
Bacillus thuringiensis spray Late spring, repeated two weeks later Organic microbe-based insecticide that acts specifically against worms
Pheromone traps Late spring Attracts male moths, so fewer females are fertilized
Sexual confusion Whenever moths are flying Artificial pheromones mimic female scents so males cannot locate females, cutting egg-laying
Picking up dropped fruit As soon as fruits fall before maturity Removes the caterpillars hidden inside the fallen fruits

Combining trapping with well-timed spraying and strict clearing of dropped fruit is what keeps numbers down.

Eliminating codling moth, the fruit worm

Getting rid of this pest isn’t an easy task, because the span of time wherein this caterpillar is not inside a fruit is very short, and difficult to pinpoint.

It seems more relevant to sacrifice a few damaged fruits on the tree, to track the parasite’s developmental stage, without necessarily aiming to eliminate it entirely.

Eliminating it entirely feels practically impossible for the above-mentioned reason, anyway.

How to treat effectively against codling moth larvae

Codling moth
The adult moth; its caterpillar is the fruit worm
  • Beginning of May, spray an organic insecticide containing Bacillus thuringiensis (organic microbe-based insecticide) which works specifically against worms, and repeat this spraying two weeks later.
  • During the month of May, place pheromone traps to attract male moths, and reduce female fertilization rates.
  • Pick fruits up that have fallen before having reached maturity, since they have most often been invaded by codling moth caterpillars.
  • Sexual confusion is a technique that aims to mimic female hormonal scents with artificial pheromones. It makes it difficult for males to locate the females, which considerably reduces egg-laying.

Other fruit tree diseases and pests

  • Fruit flies, how to fight them – fruits turn brown and shrivel up.
  • Rust – brownish orange blisters appear on the underside of leaves, with yellow spots to match on the topside.
  • Root crown canker – trunk starts growing into twisted irregular bulges and turns brown.
  • Powdery mildew – white velvet covers branches and then leaves.
  • Scab – brown stains appear on leaves and then on fruits.

Smart tip about codling moths or fruit worms

Codling moths are a nuisance, but it’s possible to limit their numbers by being watchful. Cull any fruits that might be housing worms.

 


Image credits (edits Gaspard Lorthiois):
CC BY 2.0: Patrick Clement
CC BY-SA 2.0: Alan Cann

Written by Gaspard Lorthiois | Loves helping out, especially when it comes to growing things. Worked in herbal medicine, runs a farm, and dabbles in tech. Master's degree and engineer.

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