How to use companion planting to prevent disease?

Plant basil near tomatoes to deter aphids and thrips. Grow marigolds near cucurbits and brinjal to repel nematodes and whiteflies. Interplant garlic around roses to suppress powdery mildew. Mint deters aphids but plant in a separate pot — it spreads aggressively. These combinations reduce pesticide use in Indian terrace and kitchen gardens significantly.