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Friday, December 21, 2018

Using Pheromone Traps to Control Wormy Apples

Q. We have six apple and two pear trees in Ely, Nevada. This year all the fruit had worms in them. The damage started when the apples were only about 1 inch in diameter. Every single fruit had worms in them. I am suspecting a moth but I’m not sure. We sprayed with Neem Oil before they blossomed and after the fruit set. Any ideas?

A. This “worm” is the juvenile or immature form of a moth called the codling moth. They ruin the apples or pears by devouring the inside of the fruit leaving their feces and allowing for the fruit to start rotting. Hence, “wormy apples” which can look disgusting later. In commercial apple and pear production, as many as eight “cover sprays” are applied to the trees every year to prevent wormy apples.
An early sign your apples may be wormy. The codling moth lays an egg on the outside of immature apple or pear fruit. The warm hatches and tunnels inside the apple. Conventionally, insecticides are sprayed on the trees and fruit to kill the warm before it enters the fruit.

Codling moth is the most destructive insect of apples and pears in the world. We see codling moth damage to apples and pears in the Las Vegas area as well. But because we are in the Mojave Desert, this pest is not as damaging as it could be. As more homeowners plant more fruit trees however, we will see more of this pest creating damage to these fruits in the future.
This is a winged sticky trap with a reddish brown rubber lure that was impregnated with a pheromone. This sex hormone is released into the air and one gender of the past is lured to the trap where it is stuck. When the sticky bottom of the trap is full or no longer sticky, it is replaced. In a dusty environment this can be weekly. The lure weakens over time and is replaced to keep the scent at its maximum filling the air.
            As I mentioned in passing, one method of control is using insecticides as a “cover spray”. A cover spray is an insecticide sprayed over the entire tree, not just the fruit. Sprays are applied often enough to create a poisonous barrier for the female codling moth. Neem oil will not work in this way against this pest.
This is a Delta trap used mostly for monitoring when the moth is flying. It does a great job telling you when sprays are needed. I like the trap better when relying only on disrupting the mating of insects for control.
            If you choose to use an insecticide, it must be something other than Neem oil and it must be sprayed frequently over the entire tree. There are insecticides you can purchase from the store but the secret is to apply it often beginning when the fruit first begins to develop.
            Another option, pheromone traps, can either reduce the number of times the tree is sprayed or even eliminate spraying altogether. Pheromone traps are cardboard traps which contain a sex hormone released into the open air. This pheromone prevents the male codling moth from finding a female and, instead, gets stuck in a sticky mess inside the trap.
            Under some circumstances, these pheromone traps may catch enough males to prevent female moths from laying their eggs. This interruption in mating can prevent wormy apples from occurring.

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