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Bio-control of Pests and Diseases, II

© Geoffrey Ian Miller

Predators

Predators include animals such as frogs, lizards, birds, dragonflies, and spiders. Provide places for them for shelter and breeding, such as hollow logs with food (insects, nectar, pollen) and water. Attract insect-eating birds by establishing plants native to your area. Many insects themselves are predators. Here are some of them:

Ladybird beetles and their larvae eat aphids. They are called ladybugs in North America.

Hover flies (Syrphid) eat aphids.

Lacewing control mites, caterpillars, aphids, thrips, mealy bugs, and certain scales.

Certain mites predate on other mites.

Praying mantis.

The Ichneumon wasp lays her eggs in armyworms, cutworms, and other insects.

Attracting Parasites

Plant chamomile, celery, hyssop, tansy, dill, and yarrow in the garden to encourage wasps which parasitise caterpillars. (Editor's warning: Tansy is poisonous to cattle and is therefore a banned plant in some US states. It is also invasive and may take over your garden.)

Clover attracts woolly aphid parasites.

Sunflowers attract lacewings.

Goldenrod (Solidago sp.) attracts praying mantis and other predators.

Buckwheat attracts hoverflies.

Beneficial Effects of Plants

A range of plants was tested to attract beneficial insects. The most promising plants included tansy, caraway, dill, white cosmos and buckwheat. Adapted from Organic Gardening May/June 1991.

Here are the tested plants and the reported effect:

Basil: Repels flies
Buckwheat: Attracts beneficial insects
Caraway: Attracts beneficial insects
Cosmos, White Sensation: Attracts beneficial insects
Dill: Repels aphids, red spider, attracts beneficial insects
Fennel: Repels fleas and ants
Horseradish: Deters chewing beetles
Leek: Deters carrot fly
Marigold: Controls root nematodes, attracts hoverflies and parasitic wasps
Peppermint: Deters many insects and rodents, e.g. ants
Petunia: Repels bean flies and some bugs
Rosemary: Deters bean beetle, carrot fly, cabbage grubs, attracts bees
Tansy: Deters ants, flies, mosquitoes and attracts beneficial insects.
Wormwood: Deters many insects, slugs and snails. (Editor's note: Wormwood is the #1 deterrent against flying insects.)

Beneficial Plants

Certain plants aid the growth and health of other plants. For example legumes (i.e. peas and beans) relate symbiotically with soil microorganisms. Nitrogen is absorbed from the air into solid nodules on the plant roots to be utilised by other plants.

Decoy Plants

These attract insects away from your desired plants. Plant decoys away from your main crop, otherwise pests will increase or move to your crop. Here are the plants and the insects which they attract:

Datura: Chewing beetles
Hibiscus: Harlequin Beetles
Hyssop and mustard: Cabbage white butterfly (Editor's note: Wormwood is far more effective, and so are chamomile and tansy.)
Nasturtium: Aphids

Pheromone Traps

Female insects produce scents known as pheromones which attract males for reproduction. Scientists have developed pheromone traps for pests such as fruit fly and coddling moth to show the pest populations in a given area.

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