We tend to want to protect our plants from any creepy crawlies, but the reality is that they’re not all that threatening. There are plenty of beneficial insects that won’t harm your plants at all, but will actually protect them. Some insects naturally hunt common plant pests which helps to keep their numbers under control.
Using beneficial insects is a type of organic pest control that doesn’t require chemicals. It depends on the natural function of insects in ecosystems. Usually, this method is not used alone but would be part of an integrated pest management plan.
There are two types of beneficial insects in pest control – predatory and parasitic. They control pest populations in different ways.
Predatory insects hunt and feed on garden pests. They will either eat the adult pests or their eggs; either way, they help to keep pest numbers down.
While they appear beautiful and unassuming, ladybirds are actually incredible predators. They are great at controlling aphids, with each ladybird eating up to 50 aphids a day. Their larvae can eat even more! Ladybirds will consume any type of aphid including blackfly and greenfly. Some places will sell ladybirds as pest control, but you could naturally attract them to your garden by planting calendulas and other pollen-rich flowering plants.
Another lover of aphids, hoverflies will also feast on thrips and caterpillars. Their larvae are especially efficient at controlling aphid populations. As well as their pest control abilities, hoverflies are also pollinators, making them doubly useful to have in your garden. You can attract them by planting dahlias, calendulas, and other flowering plants.
The common green Lacewing is also excellent at controlling aphid populations, especially blackflies. Lacewing larvae can each eat around 200 aphids a week, making them incredibly effective pest control. To introduce these predators to your garden, you could purchase Lacewing larvae or attract them by providing shelter for them to overwinter in.
Parasitic insects harm garden pests by laying their eggs in or on them. This could take place at different stages of the pest’s life: eggs, larvae, or pupae. The parasite will grow and feed on its host, killing the pest.
There are over 6,000 species of parasitoid wasps in the British Isles. Adult wasps will lay their eggs on or inside the body of their host. The eggs hatch into larvae which will eat the host from the inside out.
The most common in the UK are Braconid wasps, which target caterpillars of the cabbage white butterfly. One species – Aphidius – is commercially bred for organic aphid control.
Otherwise known as tachinid flies, these creatures come from the family Tachinidae. Most tachinid flies will use caterpillars or beetles (both adults and larvae) as their hosts, but other creatures could also fall victim to these insects. They lay their eggs inside the host’s body and the hatched larvae will eat their way out, helping to keep your pest populations controlled.
Nematodes are microscopic insects that use other types of insects as their host. Instead of laying eggs inside them or directly eating them, nematodes will release bacteria into the host. The bacteria will kill it, leaving the nematodes to eat it.
Nematodes are a popular method of biological pest control among gardeners. They are more pleasant to work with than some other beneficial insects because of how small they are.