Since 2007, a small, black-and-white butterfly and its numerous and voracious offspring have been spreading in Germany and the neighboring countries: we are talking about the box tree moth, which came here from East Asia through plant imports and is now threatening large stocks of box trees. The always hungry, green and up to six centimeters long larvae currently only feel ravenous hunger for boxwood and eat it bare within a very short time after an infestation. However, the conspicuous caterpillars are poisonous and should only be collected with gloves.
Box tree moth caterpillars should not be touched with bare hands
Caterpillars only become poisonous when they eat
However, the box tree moth larvae are not poisonous on their own, but because they absorb the toxic ingredients from their food - the poisonous box tree - and store them in their small bodies. More than 70 of the different toxins, including alkaloids in particular, could be detected in the caterpillars. The poison doesn't seem to bother them at all, quite the opposite: the caterpillars prefer to feed on the older leaves of the boxwood, which have a higher concentration of toxic substances than young leaves.
Natural predators of the box tree moth
The reason seems obvious: their secondary toxicity makes the caterpillars unattractive as food for domestic pesticides. In the first few years, it was observed that birds ate the larvae individually, but then spat them out again. For a long time, the box tree moth had no natural predators and was able to spread all the more undisturbed. However, this seems to be changing gradually, as more and more sparrows and great tits were sighted, not only eating the caterpillars themselves, but also feeding them to their nestlings. So there is still hope that the local beneficial fauna will discover the voracious caterpillar as a food source.
tips
Instead of collecting the caterpillars by hand - which can be very tedious due to the often heavy infestation with several hundred to thousands of animals - you can also vacuum them up or blow them out of the bush with a high-pressure cleaner.