As we go into the Spring, the birds and flowers are starting to wake up.
And so are the slugs.
Here at the glasshouses, we manage them using nematodes.
Nematodes are one of the most abundant creatures in the living soil. They are an essential part of the soil food web. Some of them feed on plants, some feed on dead organic matter, and others are parasites of other living organisms. Just as there are “bad bacteria” and “good bacteria” from the human perspective, so there are “bad nematodes” and “good nematodes” in the soil The nematodes that feed on living plant material can be considered to be “bad nematodes” – eg the potato eelworm. However nematodes that kill other plant pests are considered “good nematodes” – eg the nematode that kills slugs.
Parasitic nematodes seek out suitable hosts by swimming in the thin film of water on soil particles, locating hosts by detecting carbon dioxide and other waste products. Once they find a host, they enter the body cavity through any hole they can find. They carry bacteria which kills the host within hours, and the nematodes grow and reproduce within the ‘broth’, which they produce. The next generation of infective juveniles leaves the dead host, and moves in search of fresh hosts.
Nematodes multiply and spread providing that they have plenty of food, and the soil is warm and wet. The slugs die within a few days, and their bodies decompose underground. I have never actually had the time to go spotting the dead ones – all you get is a decline in damage.
In the glasshouses we get slugs pretty well all year round – they biggest victims are the winter lettuce and pak choi. So we treat in the autumn and early spring – whenever we have time.
The slugs do come back over time – possibly the eggs come in on the compost, possible from the damp areas around the walls, possibly from another area. If we don’t treat regularily,because we don’t have the labour, then this is what we find.
You can buy nematodes in an inert paste which can be mixed with water and poured on the ground with a watering can or hose. You can order them here.
If you would like to know more about this you will enjoy this little video about nematodes and slugs.