Some studies have demonstrated beneficial effects. For instance, cabbage crops can be seriously damaged by the cabbage moth. It has a natural enemy, the parasitoid wasp Microplitis mediator. Companion planting of cornflowers among cabbages enables the wasp to increase sufficiently in number to control the moth. This implies the possibility of natural control, with reduced use of insecticides, benefiting the farmer and local biodiversity. In horticulture, marigolds provide good protection to tomato plants against the greenhouse whitefly (an aphid), via the aromatic limonene that they produce. Not all combinations of target and companion are effective; for instance, clover, a useful companion to many crop plants, does not mask Brassica crops.
some studies have demonstrated beneficial effects for instance cabbage crops can be seriously damaged by the cabbage moth it has a natural enemy the parasitoid wasp microplitis mediator companion planting of cornflowers among cabbages enables the wasp to increase sufficiently in number to control the moth this implies the possibility of natural control with reduced use of insecticides benefiting the farmer and local biodiversity in horticulture marigolds provide good protection to tomato plants against the greenhouse whitefly (an aphid) via the aromatic limonene that they produce not all combinations of target and companion are effective; for instance clover a useful companion to many crop plants does not mask brassica crops