Alternaria Tomato Information – Learn About Nailhead Spot Of Tomatoes

(Image credit: Aksana Zavadskaya)

Each year early blight causes significant damage and loss to tomato crops. However, a lesser known, but similar, fungal disease known as nailhead spot of tomatoes can cause just as much damage and loss as early blight. Continue reading to learn about the symptoms and treatment options of tomato plants with nailhead spot.

Alternaria Tomato Information

Nailhead spot of tomatoes is a fungal disease caused by the fungus Alternaria tomato, or Alternaria tennis sigma. Its symptoms are very similar to those of early blight, however, the spots are smaller, approximately the size of a nail head. On the foliage, these spots are brown to black and slightly sunken in the center, with yellow margins. On the fruit, the spots are gray with sunken centers and darker margins. The skin around these nailhead spots on tomato fruits will stay green as the other skin tissues ripen. As the spots on leaves and fruits age, they become more sunken in the center and raised around the margin. Moldy looking spores may also appear and stem cankers may develop. The spores of Alternaria tomato are airborne or spread by the splashing up of rain or improper watering. In addition to causing crop loss, the spores of nailhead spot of tomatoes can cause allergies, upper respiratory infections, and asthma flare ups in people and pets. It is one of the most common fungal related allergens of spring and summer.

Tomato Nailhead Spot Treatment

Fortunately, because of regular treatments of fungicides to control early blight, tomato nailhead spot does not commonly cause as much crop failure in the United States and Europe as it used to. New disease resistant tomato cultivars also account for a decrease in this disease. Spraying tomato plants regularly with fungicides is an effective preventative measure against tomato nailhead spot. Also, avoid overhead watering which can cause spores to infect the soil and splash back up on plants. Water tomato plants directly at their root zone. Tools should also be sanitized between each use.

Darcy Larum