PDC LESSON 6.12 COMPANION PLANTING DEFENSE PLANTS Part -2-

 

PERMA COURSE AGRO-ECONOMY

PDC LESSON 6.12 COMPANION PLANTING DEFENSE PLANTS Part -2-

 Trap cropping uses alternative plants to draw pests away from a main crop. For example, nasturtium (Tropaeolum majus) is a food plant for some caterpillars that feed primarily on members of the cabbage family (Brassicas); Some gardeners claim that planting around brassicas protects food plants from damage, as the pests prefer to lay eggs on the nasturtium. However, while many trap plants divert pests from burn crops in small greenhouse, garden, and field experiments, only a small fraction of these plants reduce pest damage on larger commercial scales.

Trouble finding hosts

Flying pests are far less successful when their host plants are surrounded by other plants or even green coloured "decoy plants".  Pests find hosts in stages, initially recognizing plant odours that prompt them to land on the host plant while avoiding bare ground. When the plant is isolated, the insect simply lands on the green patch near the smell and makes a "reasonable landing". If it is on the wrong plant, an "improper landing", it will take off and fly to another plant; it eventually leaves the area when there are too many "inappropriate" landings. Companion planting of clover as a ground cover equally disturbed eight pest species from four different insect orders. In one test, 36% of cabbage root flies laid eggs next to cabbage growing in bare ground (and destroying the crop), compared to just 7% next to cabbage growing in clover (allowing for a good crop). Simple green cardboard decoys worked just as well as the live ground cover.