Box moth caterpillars
The box moth has begun to make serious progress in recent years and is now common in Belgium and the Netherlands. This Asian moth was probably imported into Europe with boxwoods and was first spotted in Germany in 2006.
Life cycle
The box moth overwinters as a caterpillar and reappears in spring at temperatures of 10°C and above to feed immediately on the boxwood leaves. The box moth appears in April-May and lays new eggs on the underside of the boxwood leaf. The young larvae are dark yellow, the mature larvae are bright green with a black head and measure 4 cm. They have black dots and longitudinal stripes on their green bodies. Caterpillars develop into bright green pupae with dark stripes and spots, then turn brown as the moth develops into the pupa. The most significant damage is caused by the fact that the moth develops several generations per year, which means there are continually larvae feeding on the leaves of the boxwood tree.
Damage from the box moth
The larvae of the box moth eat the leaves of the boxwood tree. The result is eaten leaves, bare twigs, leaf skeletons and visible filaments between the leaves. At first, the damage is not very noticeable, but once the caterpillars start spinning the leaves together, the damage quickly becomes visible. Large numbers of caterpillars can lead to total denudation of the boxwood. If the box tree cannot stop this constant denudation, it will die.
Fighting box tree caterpillars with nematodes
The larvae of the box moth can be effectively eradicated with the nematode species Steinernema carpocapsae (Carpo-care). As soon as the larvae are present on the boxwoods and the daytime temperature reaches 14°C, they can be sprayed on the boxwoods with a foliar treatment. Use normal spray equipment for this purpose, provided that all filters <1mm are removed.
When sprayed on as a foliar treatment, Carpo-care acts as a contact agent, so it is necessary to directly come into contact with the caterpillars in order to infect them with the nematodes.
As not all caterpillars will be reached and destroyed by a single foliar application, several treatments are necessary. We recommend 5 successive applications at one week intervals.