Anything that eats or damages what we eat. Too many pests mean not enough predators, like fish or birds for mosquitos and gopher snakes for gophers, who also avoid daffodils, elderberry cuttings, and castor beans. Teas made of chamomile, stinging nettle, comfrey, or horsetail discourage harmful fungi. Marigolds control whiteflies, spearmint, tansy, and pennyroyal control ants, Mexican marigold controls nematodes and root pests, as do French marigolds; yellow nasturtiums decoy black aphids, which are repelled by spearmint, stinging nettle, southernwood, and garlic, and borage repels tomato worms while attracting helpful bees.