Blight is a general term for plant diseases that cause rapid leaf and fruit damage, severely impacting tomato harvests. A common concern for gardeners is whether fruit from an infected plant remains safe for consumption. The safety of eating blighted tomatoes depends entirely on the specific type of blight and the extent of the damage to the fruit itself. This guide clarifies how to identify common forms of blight and determine when a tomato can be salvaged.
Identifying Common Tomato Blights
Two primary diseases cause blight symptoms in tomatoes: Early Blight and Late Blight. Early Blight is caused by the fungus Alternaria solani and typically appears earlier in the season, often starting on lower leaves. On the fruit, Early Blight manifests as dark, sunken lesions near the stem attachment point. These spots are leathery, black, and have characteristic raised concentric rings, giving them a “target-spot” appearance.
Late Blight, caused by the water mold Phytophthora infestans, is generally more destructive. On tomato fruit, Late Blight usually begins as firm, irregular, dark brown or greasy-looking spots. These lesions become sunken and leathery, sometimes appearing mottled or golden brown. Unlike Early Blight, Late Blight lesions do not typically have distinct concentric rings.
Determining If Blighted Tomatoes Are Safe to Eat
The blight organisms (Alternaria solani and Phytophthora infestans) are not considered human pathogens. The primary risk associated with consuming blighted tomatoes comes from secondary invaders, not the initial infection. When blight damages the skin, it creates entry points for bacteria, molds, and decay organisms that can produce harmful toxins or cause spoilage.
For tomatoes with Early Blight, if the damage is superficial and localized, the fruit is generally safe to eat after trimming the affected area. The fungus is localized and does not spread throughout the entire fruit. However, if the blight spot has penetrated deep into the flesh, or if the tomato is soft or has a foul odor, it should be discarded immediately.
Late Blight poses a higher concern because the lesions often lead to rapid, widespread decay. If a tomato exhibits signs of Late Blight, especially if the lesions are large or the fruit feels soft and water-soaked, it must be discarded. The disease process can also lower the acidity of the tomato flesh, creating an environment favorable for the growth of harmful microorganisms.
Proper Handling and Preparation of Usable Fruit
For tomatoes with minor, localized blight damage, safe preparation requires careful attention. First, thoroughly wash the fruit under running water to remove surface spores or soil contaminants. Use a sharp, clean knife to excise the blighted area entirely.
Cut away all damaged tissue plus a generous margin of healthy tissue surrounding the lesion, ideally at least half an inch. If the blight lesion is deep or close to the center of the fruit, discard the entire tomato. This trimming ensures that any secondary decay or mold that may have begun to penetrate the fruit is completely removed.
Salvaged tomatoes should be used immediately and are best reserved for cooked preparations, such as sauces or pastes. Cooking provides an added measure of safety by destroying potential bacterial contaminants. Experts advise against using any tomato harvested from a blighted plant for home canning, even if the fruit appears unblemished, because the disease can compromise the fruit’s acidity.
Managing Blighted Plants to Avoid Future Contamination
Addressing the source of the infection is necessary to protect the garden and future harvests. Blighted plant material (leaves, stems, and fruit) should never be placed in a home compost pile. The spores of both Early and Late Blight can survive over winter in debris, and home composting temperatures are insufficient to kill the pathogens.
The best disposal method is to place all infected plant debris into a sealed bag and remove it as household trash. At the end of the season, remove and destroy the entire plant. Sanitation practices extend to garden tools; pruning shears or stakes used on blighted plants must be cleaned and disinfected before use on healthy plants.
Practicing crop rotation is recommended to break the disease cycle. Since blight pathogens can survive in the soil for at least a year, tomatoes should not be planted in the same spot for a minimum of two to three years. To further reduce contamination risk, avoid planting tomatoes near potatoes or other Solanaceae family members that host the pathogens, such as nightshade weeds.