Organic Insect Control Methods

Examples of predators

Ladybird larva eating wooly apple aphids
Lacewings are available from biocontrol dealers.Ladybugs, and in particular their larvae which are active between May and July, are voracious predators of Aphids, and will also consume Mites, Scale Insects and small Caterpillars.

Hoverflies are another very welcome garden predator. Resembling slightly darker Bees or Wasps, they have characteristic hovering, darting flight patterns. There are over 100 species of hoverfly whose larvae principally feed upon greenfly, one larva devouring up to fifty a day, or 1000 in its lifetime. They also eat fruit tree spider mites and small caterpillars. Adults feed on nectar and pollen, which they require for egg production. Eggs are minute (1 mm), pale yellow white and laid singly near greenfly colonies. Larvae are 8-17 mm long, disguised to resemble bird droppings, they are legless and have no distinct head. Semi-transparent in a range of colours from green, white, brown and black.

Hoverflies can be encouraged by growing attractant flowers such as the poached egg plant (Limnanthes douglasii), marigolds or w:phacelia throughout the growing season.

Dragonflies are important predators of mosquitoes, both in the water, where the dragonfly nyads eat [[mosquito larvae, and in the air, where adult dragonflies capture and eat adult mosquitoes. Community-wide mosquito control programs that spray adult mosquitoes also kill dragonflies, thus removing an important biocontrol agent, and can actually increase mosquito populations in the long term.

Other useful garden predators include Lacewings, w:Anthrocorid bugs, rove and ground beetles, w:aphid midge, Centipedes, Horticulture/Predatory Mites, as well as megafauna such as frogs, toads, hedgehogs, slow-worms and birds. Cats and rat terriers kill field mice, rats, june bugs, and birds. Dogs chase away many types of pest animals. Dachshunds are bred specifically to fit inside tunnels underground to kill gophers and rabbits.

Parasitic wasps
A diverse range of wasps lay their eggs on or in the body of an insect host, which is then used as a food for developing wasps. Parasitic Wasps take much longer than predators to consume their victims, for if the larvae were to eat too fast they would run out of food before they became adults. Such parasites are very useful in the organic garden, for they are very efficient hunters, always at work searching for pest invaders. As adults they require high energy fuel as they fly from place to place, and feed upon nectar, pollen and sap, therefore planting plenty of flowering plants, particularly buckwheat, umbellifers and composites will encourage their presence.

Three of the most important groups are;

Ichneumon Flies: (5-10 mm). Prey mainly on Horticulture/Caterpillars.
Braconid Wasps: Tiny wasps (up to 5 mm) attack caterpillars and a wide range of other insects including greenfly. A common parasite of the cabbage white caterpillar- seen as clusters of sulphur yellow cocoons bursting from collapsed caterpillar skin.
Chalcid Wasps: Among the smallest of insects (<3 mm). Parasitize eggs/larvae of Aphids, Horticulture/Whiteflies, cabbage caterpillars, Scale Insects and strawberry tortrix moth.