Combating the webbed moth in apple trees: this is how you do it organically

In this series , Gardeners' World magazine and Rootsum, experts in biological solutions, give advice on how to control and prevent pests. This time we talk about controlling and limiting the web moth in the apple tree.

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We often hear about the nuisance of web moths ( Yponomeutidae ) in apple trees and it is quite possible that you will also find these animals in your garden. The pest is usually harmless and a tree can cope with it just fine. If it is a real invasion, and that can sometimes happen, then the apple harvest can fail.

Where possible, prune away the affected leaves and remove the caterpillars. If you have a lot of ermine moth in your apple tree and natural enemies cannot clear them completely, you can spray Carpo-care nematodes on the caterpillars in the evening to combat them biologically. These nematodes penetrate the body of the caterpillar and the bacteria they excrete will eliminate the caterpillars.

Never use chemicals. You will also poison the many natural enemies, such as parasitic wasps and garden birds, which will make the problem worse.

In some years, ermine moths can occur in large numbers. Not only on apple trees, but also on wild cardinal hats, willows, bird cherries and other tree species. Trees can change into complete 'ghost trees' when invaded. No matter how bad this may look - because not a single leaf remains - the tree always recovers. When the caterpillars pupate, new leaves will grow again. If a tree is (very) sick, such a heavy invasion can exhaust the tree too much, causing it to not survive.

With a normal amount of caterpillars, and that can still be hundreds, the plague does not pose any problem for the tree. It is actually a very important food source for, for example, blue tits and great tits. Countless parasitic wasps and other useful insects also eat the caterpillars. The chance is therefore great that the plague will resolve itself and that your garden animals will actually benefit from it.

Is the plague very severe every year? See if you can attract more natural enemies to the garden, for example by making it more bird-friendly. Adding native plants and 'rough' corners in the garden will attract many more insects, such as very small parasitic wasps. These can then tackle your caterpillars.

For 30 years, the Belgian family business Rootsum from Leuven (formerly known as BioGroei) has been developing natural solutions for pests in organic gardening. 'In search of beastly creatures', as they also call it. They do this by offering organic alternatives to poison, improving the soil and focusing on creating biodiverse gardens throughout Flanders and the Netherlands.