When diseases or fungus attack the foliage on your tomato plants it is rarely fatal. Tomatoes suffer from pests and diseases like most other plants in the garden. When a disease does attack it is however important to catch and treat it early to prevent it from spreading to throughout the garden. Knowing the different diseases and being able to spot their symptoms will help you to determine the correct and proper treatment as well as maintain the proper management of the disease.
One of the most common knows diseases to tomatoes are called “Early Blight”. When a plant is infected with early blight its leaves will have small circles and spheres in the middles and dark spots on the older leaves while the leaves surrounding them will begin to turn yellow. Early blight not only affects the foliage but the stems and fruit as well. The disease can be transferred from new transplants, and since it is soil born, it can over-winter in your garden from residue of the previous year.
Another form of foliage disease is also blight, this one is called “Late Blight” which also affects the leaves and fruit of the tomato and it spreads very fast. If you suspect that your tomatoes have late blight, look for greasy irregular shaped gray spots on the leaves with a white mold if the weather is or has been extremely wet. The spots will turn paper-like and dry with blackened areas appearing on the stems. If you think the blight has attacked your fruit, look for large greasy irregular shaped spots as a symptom, this is what will distinguish it from “Buckeye Rot”, another type of tomato disease.
The third tomato disease to look for is called “Gray Leaf Spot” which affects only the leaves of the tomatoes. It will usually begin with the older leaves and they will have small dark spots in both sides of the leaves and they will grow larger then begin turning a grayish-brown as the center of the spots start to crack and fall out while the leaves on surrounding plants will turn yellow, dry up and drop off. Gray leaf spot will also inhibit the plants fruit production.
“Septoria Leaf Spot” is often mistaken for late blight because it also attacks the older leaves first. Leaves infected with this common tomato disease will have paper-like patches which will later develop tiny dark specks inside. “Southern Blight” will have a white mold at the stem near the soil line accompanied with round spots on the inner and outer stems that eventually become discolored. Once this fungus takes hold on the stems it prevents the plants from absorbing much needed water and nutrients. Small newly planted plants if infected will simply die at the soil line.
The last disease that can literally ruin your garden is called “Verticillium Wilt”. The leaves will often turn yellow, dry up and seem to wilt. This is another soil born fungus that affects not only tomatoes but a variety of vegetables. The plants will literally wilt during the hottest part of the day and only seem better at night only to begin to turn yellow then brown in the leaf veins. The older leaves will be show signs of this first, then the lower leaves will develop a discoloration inside the stems. This type of disease will inhibit the plants ability to absorb water and nutrients also which will eventually kill the plant.
If symptoms of any of theses diseases start to appear on your plants either a copper or a sulfur spray can be prevent its further development, but know which disease you plant has first. As for management of these fungi it is best to buy disease resistant plants, rotate you crop, when you fertilize try and use a fertilizer that contains ammonium and or calcium and in the fall remove all remains of an infected plants and any other garden debri remember also that some diseases are soil born. Remember to watch your plants carefully when the weather is consistently and extremely wet, wet weather stresses many plants and warm humid weather will worsen many fungus problems. Before you use any fungicide spray, always read and carefully follow the manufacturer’s suggestions.
Eudora DeWynter offers tips on Common Tomato Foliage Diseases on her blog at http://www.gardentoolguru.com