Garden innovations - nematodes (garden pest destroyers)

Using biological pest controls rather than chemicals is a fast-growing and fascinating field of study and it is nature's way of keeping things in balance. All that's new is the technology that allows us to bring pest destroyers into our gardens.

Naturally occurring enemies of pests are often present but not in large enough numbers to control pests effectively, so biological pest control injects more of the pest's enemies into your greenhouse or garden. The reason that pests and their predators may be out of kilter in this way is often the chemicals, pesticides and other products that we've used - all of which tend to harm or suppress the smallest and most fragile soil organisms. Oddly enough, these same organisms may be the death knell to our most pernicious garden nuisances, because size and fragility have nothing to do with their ability to infest, and wipe out slugs, bugs and grubs.

There are things to remember about these microscopic creature though: the first is that they only affect the targeted pest, not any other bug and the second is that their effectiveness is temperature dependant - use them when it's too cold and they won't proliferate in your soil and water and so they can't kill off the pest. Each organism comes with its own set of instructions, including temperature, so you may want to invest in a soil thermometer to make sure you get the best from each product. Nematodes are the least fragile of all the organisms, as they can actually be refrigerated as long as you use them before their expiry date!

• Scientific research in many parts of the world has shown that an autumn application of anti-slug nematodes can significantly reduce slug populations the following spring, which allows your plants a good start to the growing season. Phasmarhabditis - snappy name! - is the nematode and they rest in the soil until the slug eats them, but once inside the slug, they release a bacteria. Infested slugs will stop feeding and won't lay eggs, thus massively reducing the population.
• Another nematode, steinernema kraussei, kills vine weevil larvae in the soil as long as the earth temperature is at least 5 degrees Celcius. And steinernema feltiae, yet another nematode has been show to reduce the problems caused by leatherjackets which are the larvae of daddy longlegs.
• It's not all microscopics though; you can also buy eggs from adalia bipunctata (adult ladybirds) to increase your population of this aphid loving predator, and a home and feed for them, to encourage them to stay in your garden.

Garden innovation pest destroyer photograph by David Prior, used under a creative commons attribution licence