Identification of Vegetable Plant Diseases

Early Blight

• When growing potatoes or tomatoes in your garden, you may encounter black or brown spots or rings on the stems and leaves. Some of the spots appear angular. The fungus Alternaria solani "Early Blight" can kill your seedlings or older plant leaves starting from the bottom of the plant. Rainfall and high humidity encourages the fungus to spread throughout your tomatoes and potatoes. Other vegetable plants at risk of early blight include parsley, beans, vegetables in the cabbage and squash family and carrots.

Pink Root and Bacterial Soft Rot

• The onions in your garden may attract diseases such as the fungus Pyrenochaeta terrestris "Pink Root." Pink root turns the onion roots pink and they will die. Since this fungus lives in the soil indefinitely, all other onion roots will also die. Soil and moisture help this disease to thrive. The fungus Erwinia caratovora "Bacterial Soft Rot" starts in the garden, but you will notice it when you store your onions by the dripping of water from the onion neck when you press the neck tissue. Observe also the foul odor and slimy, wet tissue on the neck. Peppers in your garden may also get this disease through a wound. Maggots in the soil along with moist conditions help spread bacterial soft rot while your onions grow.

Root Rot

• Root rot can occur in your vegetable garden in numerous vegetable plants, including bean and pea plants, which can result from poor water drainage and excessive moisture. Assume root rot as the culprit when you see the leaves of your plants looking stunted, the leaves becoming yellow and dropping off or when your plants wilt, fall over and die. Different fungi in the soil cause root rot, including Thielaviopsis basicola "Thielaviopsis Black Root Rot" -- a condition where the taproot or primary root of your beans turns into dark brown or black rot. Ascochyta spp. "Ascochyta Root" occurs in peas as purple streaks on the stem below and above the surface, mainly around the nodes.

Southern Blight

• This fungal disease Sclerotium rolfsii "Southern Blight," affects a wide range of vegetables in your garden including onions, potatoes, tomatoes, lettuce, peppers, eggplants, beets, corn, bean, carrots and peas. For instance, if your pepper plants suddenly wilt, then turn yellow and brown, they may have this soil-born, sclerotium fungus, which invades the plant's crown. Note the soft mold with little brown fungus on the crown and root tissues, which grows over the stem base and nearby soil. Running water can spread Southern blight, as well as garden tools, high humidity and high temperatures. You will see this fungus in warmer states without cold winters.

Dampening-Off

• Suspect Sclerotinia spp. "Dampening-Off" if you plant your seeds to germinate them and they never appear, or your plant seedlings topple over and die from dark stem rot near the soil surface or your plant cuttings rot. The seedling or surface of the seedling potting media may have white or brown growth of fungus. Some seedlings have just a portion of their stems affected, and they live a bit longer, but appear pale and stunted, dying a while later. Dampening-off affects all plant species, and a few other fungi can also cause this plant disease.