How to Avoid Blight

Plant certified seed potatoes and purchase tomato seeds or seedlings from reputable sources. Because pathogens can survive in the potato tuber and can be transmitted via tomato seeds, saving your own seeds or purchasing from an unknown source may put you at risk.

Provide good air circulation. Overcrowding your vegetable plants sets the stage for disease and creates a breeding ground for a host of pathogens. Follow the recommended spacing for all vegetable plants.

Keep insects under control. Insects weaken your plants, making them more susceptible to diseases, and insects may carry blight spores from plant to plant. Handpick insects or control them with insecticides to lessen the risk of blight and other diseases.

Rotate your crops, and do not plant members of the nightshade family, such as tomatoes and potatoes, in the same location for at least three years. Pathogens may survive in the soil or on plant debris, and quickly infect a new crop.

Remove and destroy rogue or volunteer plants that spring up in your garden. These may carry the pathogens and spread infection to your plants. Keep weeds under control, as some may carry the pathogens that cause blight.

Destroy plant material if blight is suspected. Remove the plant, including the roots, and tie it tightly in a garbage bag. Throwing plant material in the compost bin may infect the compost or release pathogens into the air, posing further risk to your plants.

Apply preventative fungicides to your garden. The University of Maine Cooperative Extension recommends chlorothalonil applied every seven to 10 days to control early blight. Craig Cramer of Cornell University recommends chlorothalonil and copper-based products for control of late blight.