Using Nematodes of the genus Heterorhabditis has proved an efficient way to control the black wine weevil. The nematodes are only about 1mm long and search actively for the weevil larvae. They enter the larvae through the body orifices and there emit bacteria which cause the death of the larvae within two to three days. Infested larvae turn from white to a reddish brown, so the success of the application can be seen. The nematodes continue reproducing in the corpse of the host which finally gets decomposed. However, pupa of the wine weevil won't be reduced sufficiently by the nematodes, adult beetles are not affected at all.
For a successful application, soil temperature shouldn't be below 12°C, otherwise the nematodes will be inactive. For cooler soil temperatures we recommend Steinernema kraussei, another nematode genus which is already active from 5°C upwards.
The most favorable time for the application of Heterorhbditis nematodes against wine weevils ist from early April to June and from the end of August till October; against garden chafers from mid July till late September. Depending on the weather conditions, those periods can differ. In the greenhouses, the nematodes can be used all year round.
Heterorhabditis can endure throuhgout months without host and even survive frost periods. However, the population will be reduced massively by the frost so they have to be applicated again in the following year.
The nematodes are packed in clay granule which has to be dissolved in water and poured evenly over the soil surface. The treated area has to be kept moist during the following 6-8 weeks so that a longterm effect can be achieved.