Before the advent of modern pesticide/insecticide regimen, farmers used natural methods to control pests in their crops. These natural methods have long being forgotten; however now scientists are working on bring back that lost knowledge. One such method of controlling harmful insects and pests is by growing such plants that repel such pests. Companion planting of these plants with other plants can serve a dual purpose of repelling pests as well as prevent the use of harmful pesticides that kill insects indiscriminately. This pest repelling ability of plants can be attributed to the fragrances or aromas released by the plant that pests do not like. Listed below are a few such plants.

Different aphids repelling plants:
• Catnip or Nepeta cataria is said to repel aphids. The leaves of Catnip resembles the mint leaves and is most used in perfumes, food flavours as well as a insect repellent
• Chives also repel aphids. These are perennial plants belonging to the onion group of plants. Chives are aggressive plants, so remove the flowers to prevent fruit formation. Once the seeds are formed they get scattered around, producing hundreds of plants!
• Coriander is another aphid repelling plant. It has a strong smell and is used as a garnish in Asian dishes.
• Aphids also to do not like the Nasturtiums. Nasturtiums are edible annual plants; both the leaves as well as flowers are eaten.
• Spearmint is another aromatic herb that repels aphids. It is also used as a garnish or dip.
• Dill is one more herb that aphids hate. Both leaves and seeds are used as flavouring agent in many dishes.
• Clovers (also called trefoil) cover the soil quickly, if provided with adequate water. They thus not only prevent soil erosion but repel harmful aphids as well.
• Then we have the annual petunias, these are said to be among the best aphid repellent plants. But these plants are susceptible to waterlogging.
• Unlike the delicate petunias, the perennial Fennel is hardy and is also said to repel aphids.
• Marigold is another annual flowering plant that can repel aphids.
• Another plant that aphids do not like is peppermint. This is an aromatic herb used in flavouring dishes.
• Did you know that Eucalyptus also repels aphids?
• Larkspurs or Delphinium, a perennial plant repels aphids, but it needs careful consideration when growing this plant, as it is toxic to our animals and us.
• Other strong smelling plants like garlic can also be tried.
• Spraying Neem oil or water-mixed leaf extract can also be used as an effective aphid repellent.
• Other herbs like basil, cumin (its essential oil) has also been recommended by researcher for aphid control.

Note: This pest repelling ability of plants can be attributed to the fragrances or aromas released by the plants that are not liked by the pests. Many of the plants mentioned above have sometimes been reported to attract insects instead of repelling. In this case, I came across a very useful advice from a commercial grower that is to burn the plant once it is full of insects. Poof… and all the pests are gone (not discussing the smoke effect, though!).


Resources
• Isman, M.B. 2000. Plant essential oils for pest and disease management. Crop Protection, Vol. 19(8 -10): pp 603-608.
• Khan et.al. 1997. Intercropping increases parasitism of pests. Scientific correspondence in: Nature, Vol. 388: pp631-632.
• Batish et. al. 2008. Eucalyptus essential oil as a natural pesticide. Forest Ecology and Management. Vol. 256 (12): pp2166-2174.