While all this wet weather is a desert blessing, it’s also important to keep an eye out for moisture loving pest problems in your garden. If you have tomatoes, here are a few fungi to keep an eye out for.
Early Blight, caused by the fungus Alternaria solani, is common on garden tomatoes and potatoes, and also occasionally infects eggplants and peppers
Symptoms typically appear soon after fruit set, starting on the lower leaves as tiny dark brown spots. The spots enlarge to over 1/2 inch in diameter and develop a grayish-white center with a darker border. As the spots enlarge, they develop concentric, target-like rings. Spots may also develop on fruit and stems. Stem spots may enlarge to girdle the plant.
With the progression of the disease, leaves turn yellow and the spots make them appear “freckled.” Eventually the leaves turn brown and drop off. Black pycnidia (fungal fruiting bodies that appear as pinhole sized black dots) form in the center of the spots as they mature.
Septoria leaf spot is caused by a fungus, Septoria lycopersici. It is one of the most destructive diseases of tomato foliage and is particularly severe in areas where wet, humid weather persists for extended periods.
Septoria leaf spot usually appears on the lower leaves after the first fruit sets. Spots are circular, about 1/16 to 1/4 inch in diameter with dark brown margins and tan to gray centers with small black fruiting structures. Characteristically, there are many spots per leaf. This disease spreads upwards from oldest to youngest growth. If leaf lesions are numerous, the leaves turn slightly yellow, then brown, and then wither. Fruit infection is rare.
So you have blight/septoria, now what?
Here are some immediate and long term pest management strategies:
1. Remove diseased leaves. If caught early, the lower infected leaves can be removed and burned or destroyed. However, removing leaves above where fruit has formed will weaken the plant and expose fruit to sunscald. At the end of the season, collect all foliage from infected plants and dispose of or bury. Do not compost diseased plants.
2.Improve air circulation around the plants. If the plants can still be handled without breaking them, stake or cage the plants to raise them off the ground and promote faster drying of the foliage.
3.Mulch around the base of the plants. Mulching will reduce splashing soil, which may contain fungal spores associated with debris. Apply mulch after the soil has warmed.
4.Do not use overhead watering. Overhead watering facilitates infection and spreads the disease. Use a soaker hose at the base of the plant to keep the foliage dry. Water early in the day.
5.Control weeds. Nightshade and horsenettle are frequently hosts of Septoria leaf spot and should be eradicated around the garden site.
6.Use crop rotation. Next year do not plant tomatoes back in the same location where diseased tomatoes grew. Wait 1–2 years before replanting tomatoes in these areas.
7.Try a copper based fungicide spray.Fungicides will not cure infected leaves, but they will protect new leaves from becoming infected. If it rains, you will need to reapply the spray.