With this nematode species (Steinernema kraussei), the larvae of the black wine weevil can be combated from soil temperatures of 5°C onwards.
Thus, the application can still be carried out in late October or already in March/April.
The nematodes are about 1 mm long and actively search for hosts (grubs) into which they enter through their orifices. Once inside the larva, they emit a bacterium which kills the larva/ the grub within 2-3 days. The success of the application can be seen by the discoloration of the grubs: they turn from white to a reddish brown. Subsequently, the nematodes reproduce in the host cadaver which afterwards gets decomposed. Pupas are only partially damaged, adult weevils aren't harmed at all.
At soil temperatures above 12°C Heterorhabditis bacteriophora should be used. In this case the best time for the apllication is in April/Mai and in August/September.
The nematodes are delivered in clay powder which is dissolved in water and poured over the soil. The treated area should be kept moist throughout the following 6-8 weeks to achieve a longterm effect.