They are the quintessential worm in the apple and the bane of tree-fruit growers around the world. The worm is actually the immature caterpillar form of the codling moth (Cydia pomonella). Once it’s in the apple, it is very difficult to control the codling moth. This means that you need to think about treatment of this problem on a generational basis. They are most susceptible as eggs, when they hatch and crawl to the fruit, when they crawl out of the fruit and down the tree to pupate, and once they emerge as moths. Planning your treatments to have an effect on the moth at every step of the way will help to ensure that they won’t be a problem.
Identification of Codling Moths
Codling moths are grey in color with copper to brown stripes on the ends of their wings. As adults, their wingspan is around ⅔ of an inch. Unfortunately, the easiest way to know you have a codling moth problem is to look for small bore holes in your apples. Remove any affected fruit.
Best Ways to Get Rid of Codling Moths
Controlling codling moths is all about timing. Scientists have figured out the breeding habits and timing involved in the lifespan of the codling moth. It is mostly decided by minimum and maximum daily temperature ranges and the number of consecutive days at a particular temperature. Search for a “Codling Moth Degree-day Table” if you are interested in really figuring these moths out. Using the blooming of the tree as an indicator, you can generally assume that the moth’s eggs will hatch every ten to fourteen days after the petals fall and the fruit sets (if your sunset temperature is in the mid-sixties). You will want to treat sometime around there if you want to prevent the eggs from hatching and attacking your fruit.
Use lures to trap the moths. Professional fruit growers have large moth pheromone traps, which they can use to trap and monitor moth populations. Home growers can buy smaller versions which hang in trees and trap moths and recently hatched larva. They can work in two different ways—playing on the urges for food and sex, or a combination of both. The lure could contain a sweet-smelling food bait and also a feeding attractant like kairomone (called a DA Lure), or it could contain a synthesized moth pheromone. The pheromone lures will attract only male moths, while the food lures will attract both genders. If you catch moths more than twice a week and it’s above sixty degrees Fahrenheit, they have already laid eggs.
Kaolin clay spray helps repel infestations. This low-cost, poison-free pest repellent product is sold under the brand name Surround. It is essentially a super-refined clay powder. When mixed with water, it can be applied to the fruit and tree after the blossoms have dropped. The dried powder residue makes the surface of the tree inhospitable for the moths without affecting production much. The adult moths are less likely to find a place to safely lay their eggs; also, it clings to them and is an irritant. With time the clay will wash away, so you will need to reapply if the moth problem continues. Be sure to rinse the clay from fruit as it matures, as fruit needs some sunlight to ripen.
Time pheromone treatments for maximum mating disruption. Hanging pheromone-based lures in your trees before bloom (very early in the season) has been shown to cause some confusion amongst the male moths, which leads to fewer successful matings and eventually fewer moths. The cause is either that so many males are attracted to the pheromone lure that they don’t have time to mate with other moths, or that the smell is so overwhelming they have a hard time finding actual females, so fewer are mated. Whatever the case, it works—in the long term. We can’t buy the bulk pheromones available to professionals, but smaller home versions are available in several locations online.
Trunk banding will help capture immature moths. There are several ways to capture the larvae as they exit their (now worthless) apple and head down the tree to find a spot to pupate. First of all, it is suggested that you keep your tree’s trunk free of loose bark and debris around the bottom. Secondly, take a three-inch strip of corrugated cardboard, make sure it can wrap around the tree, cut it to length, and then tape it around the trunk. The idea is that the moth caterpillars will find that and think it is the perfect place to hide while they go through metamorphosis. Keep checking to see if they are in there and dispose of the cardboard accordingly.
Use a sticky horticulture glue to catch codling moths. This product is called tanglefoot glue. You choose a spot on the trunk or branches to apply the glue all the way around, forming a barrier in which the codling moth larvae will get trapped. This product would be good to use in concert with the cardboard trunk band. Paint a layer of tanglefoot under the band, just in case some decide to move on instead of choosing to hang out under there. This method won’t save this year’s crop, but it will cut down the codling moth population, and maybe next season won’t be so bad.
Chemical Codling Moth Control
In a commercial tree fruit-growing setting, insecticides need to be applied every couple of weeks to ensure a good crop of unblemished apples. Although a lot of work has been done to implement multi-tiered moth control programs utilizing the non-poisonous methods described in this article, it isn’t as cost-effective or foolproof as spraying insecticides with names like Guthion, Imidan, Lorsban, Penncap, Altacor, Delegate, Assail, or Warrior. Of course, you can do the same thing by just buying some orchard spray from your local hardware store. However, if you’ve only got a couple trees, it might not be too hard to try the alternative methods described here.
Biological Coddling Moth Control
There are a number of biological control methods available to the professional apple grower that just wouldn’t be affordable or practical for home use. I’ll mention them just because they are kind of cool:
- Trichogramma wasps lay their eggs in codling moth eggs, and the wasp larvae eats the young moths.
- Sterile male moths can be released into an orchard to trick females into thinking they are mated, but of course they aren’t.
- Baculoviruses are viruses which infect specific insects; they can be applied to fruit trees, and they will kill moth larvae.
Best Natural Methods to Get Rid of Codling Moths
Exclusion bags. If you have only a few apple trees in your yard, this method might be for you. Exclusion bags are fine mesh fabric bags which are placed over a young fruit and attached to the branch; this doesn’t allow any insects in to ruin your fruit. It is usually suggested to to spray the area with an organic insecticide before placing the bag—just in case the moths have already laid eggs.
Homemade moth trap. If you don’t want to spend the money buying fancy pheromone traps, moths are also attracted to sweet smells. One common recipe suggests mixing a dollop of molasses with a can of cheap beer in a bucket. Add a couple drops of oil or soap to the liquid to make sure they can’t escape, and you have a trap for codling moths (and other insects). If, though, you trust the commercial product more (because you drank all the beer), you can find codling moth traps on Amazon.
Organic pesticides. Spinosad is a broad-spectrum insecticide made by a rare soil bacteria. It must be eaten by the insect, so that means you need to spray this stuff on the leaves and fruit of your tree. Never apply before flowering, as it is highly toxic to bees, and they are having enough trouble already. You can get insect spray with Spinosad in it at Aamzon.