You can find out what you can do to keep the winter moth away from trees and how to recognize and combat it when it is infested.
The Winter Moth (Operophtera brumata) is polyphagous, which means it likes to attack all kinds of different trees and shrubs. Deciduous trees, fruit trees, berry bushes and roses are just as much on his menu as many ornamental shrubs. Fortunately, the insatiable caterpillars are easy to spot and fighting them is relatively easy - if you know how.
The Lesser Winter Moth (Operophtera brumata) is a butterfly found worldwide that can cause great damage to deciduous trees. The adult moths hatch - presumably depending on the ground temperature - between mid-October and early November. The flightless females climb the trunk of the host tree and are mated by the winged males on their way to the crown. The eggs are preferably laid in the immediate vicinity of buds and around the onset of the first night frosts. A female can lay up to 300 eggs. When the winter is over, the moth caterpillars hatch from the eggs at exactly the same time as the young buds burst, until the beginning of May. In the course of their caterpillar life, the moths eat buds, leaves, flowers and even young fruits. Once they have developed sufficiently, the caterpillars drop to the ground on a caterpillar silk thread and pupate in the soil - only to hatch as adult winter moths in October and father the next generation.
So that your plants do not fall victim to the voracious moth caterpillars, you will find below everything you need to know about recognising, preventing and fighting the winter moth.
Note on the winter moth: The winter moth (Erannis defoliaria) is far less common in the home garden. Its biology is similar to that of the lesser winter moth, although they are not the same genus. The control measures are also the same as for the Lesser Winter Moth.
Detect Frost Moth
If you check the buds of your trees, you can already find the red eggs of the winter moth, which are about half a millimeter in size, in autumn. The caterpillars that hatch are initially only about a millimeter long and dark gray. As they develop, they grow to two and a half centimeters and turn light green. The special way the caterpillars move is easy to recognize: Because tensioner caterpillars only have a single pair of rear abdominal legs, they make a very high "hump" with every step. In order to be able to eat undisturbed, the caterpillars like to spin themselves between the leaves of the host plant, which is where their German name comes from. If the infestation is very severe, the leaves can even skeletonize, so that only the leaf skeleton remains. However, the damage usually looks worse than it actually is. The frost moth caterpillar likes to eat half of the young fruit of sweet cherries - also called "spoon feeding". The caterpillars can be found between April and June. The finished moths show a clear sexual dimorphism - males and females differ greatly from each other. While the males are gray-yellow to beige-brown in color and have brown-yellow, fringed wings with a maximum width of two and a half centimetres, the females are brownish-grey and only have stunted stub wings of the same colour. Both have short, hairy antennae and a useless proboscis - the moths don't eat and die after a few days.
Prevent Frost Moth
Anyone who has often observed damage caused by the winter moth in recent years should ask themselves one thing above all: Is the damage relevant? Especially for hobby gardeners, where high yields are not a must, a regular, weak infestation can often be tolerated and is hardly worth the effort to combat.
Promote beneficial insects
Particularly in gardens that are close to nature, a lot of preventative plant protection is already being done - unconsciously: the promotion of beneficial insects and the avoidance of pesticides that are harmful to insects often ensures a large number of natural opponents that prevent severe yield losses. Setting up nest boxes is particularly worthwhile: great tits can eat several hundred caterpillars every day during the breeding season.
Glue Rings
Glue rings are a tried and tested means of preventively combating the winter moth. you will beattached to the trunk or trunks of the endangered trees by mid-October at the latest. Any support posts and neighboring trees that are very close should also be ringed. The females crawling upwards then stick to the sticky glue. Make sure the ring fits snugly so the caterpillars can't crawl underneath. You should check the rings after stormy weather: sometimes leaves or twigs that are blown in build “bridges” over the glue rings. In the spring, however, the rings should definitely be removed so that any beneficial insects are not prevented from climbing the trunk as well.
Fight Frost Moth
If your preventive measures were not sufficient and you notice a clear infestation in spring, you can also fight the moth directly. Well suited are preparations with the active ingredient Bacillus thuringiensis. They are very specific only against caterpillars and only if they are ingested. The application should be carried out in warm weather (at least 15 °C) - then the caterpillars have a big appetite and they take the drug safely. In the best case, the spray is applied early so that the damage caused by feeding is limited. One example of an officially approved Bt preparation against the winter moth is our Plantura Zünslerfrei XenTari®.
Tip: In the home garden you can speak of a stronger infestation if 10 out of 100 leaf clusters checked have caterpillars.