Anybody who's ever grown apples or pears will tell you that keeping away codling moths and their larvae is one of the hardest and most important daily tasks they face. The eggs that codling moths lay on the fruits and leaves, and the burrowing larvae that hatch from them, can cause enormous damage and financial loss to orchards. Besides apples, pears and crab apples, codling moths will also lay their eggs upon quinces and walnuts, and they are capable of destroying most kinds of stone fruit, with soft-fleshed fruits such as plums and nectarines particularly at risk.
So what can you do to stop the infestation before it starts?
All fruit growers, whether professional or amateur, should follow basic precautions to keep codling moths away, even if infestations in your area are rare or nonexistent. There are a number of ways to go about this without resorting to pesticides:
- Setting hanging traps in your trees will attract and kill moths before they can lay their eggs. Specialised traps for moth capture are widely available, but even a simple tin can filled with treacle or molasses will be effective. These traps will also kill other unwanted insects, such as fruit flies. Unfortunately they also pose a risk to beneficial insects such as bees, so try to find bee-safe traps when possible.
- Thin your fruit crop. Not only does this benefit the tree, and give you larger, riper fruit, but it also provides less cover for moths to lay their eggs in.
- Remove potential cover for larvae, such as loose bark and branches around the base of the tree, and any debris or disused structures near your fruit. Disused nest boxes are a prime suspect for harbouring larvae and cocoons.
- Applying a horticultural glue in bands around the trunks of your trees will trap both moths and larvae as they attempt to climb them.
What should I do if I find signs of infestation?
Regularly inspect your fruit, ideally once a week. The most obvious sign of infestation is one or more boreholes in the flesh of the apple, surrounded by brown detritus. These are usually near the stalk or base of the fruit, but can be anywhere on its surface.
1. If you find infested fruit, destroy it immediately. Under no circumstances should you dispose of the fruit in compost heaps, as the larvae can still thrive in such warm, nutrient rich conditions. Burning the fruit is one option, but if you keep any livestock such as pigs or chickens, feeding the fruit to them is a less wasteful course of action.
2. If you have a large number of fruit trees and are willing to sacrifice one or two to destroy the infestation, trunk banding may be the answer. Trunk banding involves attaching a strip of corrugated cardboard or burlap around the middle of the sacrificial tree's trunk. This is an easy way to destroy the vast majority of larvae in one fell swoop.
3. Possibly the most effective method of moth removal that doesn't involve pesticides or chemical sprays is the introduction of predatory insects. A number of species are suitable moth killers, but the trichogramma genus of micro-wasps is ideal for these purposes, and is sold commercially in egg form. However, to maintain a steady population of these little moth-terrors, you should plant smaller, nectar producing plants for them to feed on around your fruit.
For more tips or assistance, consult local experts such as Ranger Pest Control.