Organic Pest Control
Organic Farming in South Africa

The most natural and cost-effective way of pest control is to protect the natural enemies of pests. In turn, these natural predators can help control pests in your crops. 

©Dr Pia Addison Winetech
This parasitic wasp of the Anagyrus sp is the natural enemy of the vine mealy bug.

An excess of one species can indicate that the biological balance of the environment is disturbed and can mean that the natural predators of the pest is not present and therefore that there is not enough biodiversity in the area.

Biodiversity is when many species of different creatures (e.g. plants, birds, insects, microbes) live in an environment. Natural predators thrive in areas with high biodiversity and where the farmer moves away from a monoculture way of farming where only one crop is planted.

Natural predators of pests include: Predatory insects such as ladybirds and parasitic wasps; reptiles (lizards) and amphibians (frogs); spiders Biodiversity can be improved by not spraying insecticides and by planting (or not destroying) natural habitat or plants that benefit natural predators.

This can be done by planting hedges as biological borders, keeping areas of natural plant growth as well as planting flowers to attract bees, for example.

Spraying insecticides not only kills the pests but also their natural enemies, develop resistance in pests and poisons water systems. There are two ways to control pests: natural pest control and biological pest control.

Natural Pest Control

Certain plants such as khaki bush (Tagetes minuta or mbanje in isiNdebele) keep insects away while marigold can suppress 14 genera of plant-parasitic nematodes with lesion nematodes and root-knot nematodes the most affected.

For marigold to successfully suppress nematodes, it should be planted at least two months before the susceptible crop is planted. Certain plants can regulate pests in the following ways: Masking the crop by companion planting. Insects can’t smell the crop or are repelled by the smell of the companion plant.

For example, rosemary repels cabbage flies. Establish plants (e.g. flowers) that attract beneficial insects (e.g. bees). Plant a biological border around the crop. In small gardens, pests can be controlled with an extract of khaki bush. A chilli and garlic extract can also be sprayed to ward off insects.

Biological Control

©Prof Piet Goussard Winetech
Ladybirds are known for eating aphids, but they also eat other soft-bodied insect pests such as mealy bugs.

Insects play an important role in nature and the smaller ecosystems on a farm and it must be remembered that not all insects are pests. Insects help to keep nature in balance and, as mentioned above, help limit pests through ‘biological control’.

Beneficial insects eat aphids, mites, caterpillars and other plant-consuming bugs and are harmless to people, plants and animals.

Beneficial insects such as ladybird beetles Chilocorus nigritus and Cryptolaemus montrouzieri and the parasitic wasps Aphytis lingnanensis and Coccidoxenoides perminutus are bred commercially and can be bought and used on the farm as biological control.

By Marinda Louw