“The most basic resolution is to rotate the crops,” said Bruce Crawford, director of Rutgers Gardens in New Brunswick. “Planting the same crop in the same location year after year not only reduces the minor nutrients in that area, it also allows for an increase in the number of insects and diseases in the soil."
“Always practice sanitary measures, and remove fallen leaves, fruit or any broken branches.”
Remember, though, that tomatoes, potatoes, eggplants and peppers are in the same family and cannot be rotated in the same soil. Blight is hard to eradicate once you’ve got it. Garden centers and websites offer fungicides and other suggestions.
Crawford said the most common problems in New Jersey are early blight, late blight and blossom-end rot.
Early blight: Alternaria solani fungus, which spends the winter in infected plant debris or the soil, causes lower leaves to show brown or black spots with dark edges. Where the stem connects to the fruit, large, sunken black areas with concentric rings develop.
Spray with a fungicide immediately, and follow directions. If unsuccessful, remove plant, bag it, and discard.
Late blight: Phytophthora infestans fungus occurs during periods of cool, rainy weather that may come at the end of a growing season. It looks like frost damage, causing irregular green-black splotches on the leaves. Fruits may have large, irregular-shape brown blotches that rot.
Blossom-end rot: A water-soaked spot at the bottom of the tomato, it is caused by a calcium imbalance in tomatoes, peppers, squash, cucumbers and melon fruits. Most common when the season starts out wet and then becomes dry when fruit is setting.
The water-soaked areas enlarge and turn dark brown and leathery. Will rot, so fruit should be picked and discarded.
Non-disease problems seen this Summer include:
Cracking: Occurs when warm, rainy periods are followed by a dry spell. The tomatoes expand too fast. Most crack when they’ve reached full size and are beginning to turn color. Keep the moisture consistent, and select crack-resistant varieties.
Sun scald:Occurs when green or ripening tomatoes get too much exposure to the hot sun. A yellowish white patch appears on the side of the tomato facing the sun, gets larger as the fruit ripens and becomes grayish white. Don’t remove foliage shading the fruits, and grow in cages where they develop protective foliage.Source: Asbury Park Press