Winter moth (Erannis defoliaris) is the name of the small brown-winged butterfly whose green caterpillars so greedily feast on the shoots and blossoms of fruit trees in particular (except peach trees) in spring.
However, fighting these pests begins now in autumn, from September, October – by attaching so-called caterpillar glue rings to endangered fruit trees, as after the first autumn frosts, the insects come out of their pupae in the soil. The flightless females then crawl up the tree, where they later mate and lay their eggs, from which the caterpillars then hatch in time for the budding of the trees.
Attach the caterpillar glue rings so tightly to the bark that no undulations occur. Otherwise the females can get through these tunnels onto the plant. Therefore, smooth coarse bark before attaching the glue ring if necessary. Crawling bridges over the caterpillar glue ring, for example made by leaves, grasses or pieces of twigs, should also be avoided. Caterpillar glue rings must be wrapped around other bridge formations, such as tree posts, to prevent the winter moth females getting into the fruit tree via such by-passes. The caterpillar glue rings should remain on the tree trunks until March and should not have lost their adhesiveness by then.
The insects gather here in the winter season, the time when the birds are particularly hungry for them. Therefore, the birds’ beaks may become stuck up when eating or the glue may even get into the oesophagus and the birds starve to death.
Therefore, preferably replace the caterpillar glue rings occasionally, when numerous insects have got caught on them.
Tip: Use green coloured glue rings in preference to yellow ones, as the latter also tend to trap more useful insects.