Apple Tree Maggots

Answered by Harrod Horticultural Posted in Category Pest Control & Nature

Dear Martin

I moved into a house last year with a lovely apple tree in the back garden. When it came time to harvest the apples most of them had to be thrown away due to maggots.  I have not done anything to the tree since, apart from prune it.  I have been looking at all the different items you can buy I am a novice gardener and I am not sure what action I should take to get fruit without the dreaded maggot. What would be the best course of action?  

Many thanks for any advice given.  

Jodi Bowman

Dear Jodi

Many thanks for your recent message concerning the damage that maggots are causing to your apple crop. The first step to eradicating the problem is to find out what type of maggot has chosen to burrow into your apples – and I’ve got a sneaking suspicion it could be the caterpillar larvae of the Codling moth. You can check this is the case by examining the fruits; if they have tunnels where the caterpillars have eaten through the flesh, then the Codling moth is the guilty party!   There are a few methods – both organic and otherwise – that you can implement to certainly lessen the caterpillar population, and hopefully obtain some edible apples;  

CODLING MOTH MONITOR This pheromone-based monitor is often labelled a trap; technically it does catch adult male moths but not in any number to significantly reduce the egg-laying activities of the female. The monitor is hung from the branches of the apple tree (one monitor will cover 5 average sized trees) in mid-May, as the adults take to the air on warm evenings around this time. The male moths are attracted to the monitor by the pheromone scent of the females and although some are caught, it really is to give an indication of the numbers. As a guide, if 15 or more adult moths are trapped in one night, it’s time to spray within a week!   The most effective sprays will contain the active ingredients of either permethrin or bifenthrin – just check the labelling on products at your local garden to find one of these sprays, which should be applied to the fruitlets where eggs are laid and subsequently hatch. It’s essential to spray promptly as if you leave it too late, the caterpillars will have tunnelled into the fruit (by the calyx, or stalk) and will be safe from chemicals.  

CODLING MOTH KILLER A much more environmentally friendly method of controlling the caterpillars, the nematodes are sprayed onto the trunk, branches and soil beneath the tree in September and October. The nematodes – which are naturally occurring microscopic worms – will seek out the non-feeding caterpillars which are preparing to spin cocoons and hibernate for the winter, and kill them. This causes a break in the lifecycle of the moth as the caterpillars quite clearly cannot emerge as adults in the spring if they are dead! However, this method of control does not affect any females which almost inevitably will fly into your garden the following spring, so although organic is not completely foolproof.        You’ll probably obtain the best results by employing a combination of the above treatments, although I can understand if you are unwilling to apply chemical sprays. There are some other cultural methods of control which will also help you in your quest – for example, tying small (7-10cm) strips of sacking or corrugated card to around branches or tree trunks during the summer gives caterpillars a place to hide and form cocoons. You can then collect and dispose of the caterpillars from these sites but you’ll only see the benefits the following year, as the caterpillars will already have caused more than enough damage to apples on the tree. You might also want to remove any apples immediately you see any damage occurring; the chances are the caterpillars are still inside and disposing of the fruit will put paid to few more potential adult moths!  

I do hope this helps; I know it’s rather a lot to take in, but just think of the lovely, fresh, crunchy - and unblemished - apples you could be tucking into!