Blight spores can survive in the soil for three or four years. Only plant tomatoes in the same bed every three to four years, and remove and burn tomato refuse in the fall.

The key is solarizing the soil to kill the bacteria before they get to the plants. As soon as you can work the soil, turn the entire bed to a depth of 6″, then level and smooth it out. Dig a 4-6″ deep trench around the whole bed and thoroughly soak the soil by slowly running a sprinkler over it for several hours.

Baking soda has fungicidal properties that can stop or reduce the spread of early and late tomato blight. Baking soda sprays typically contain about 1 teaspoon baking soda dissolved into 1 quart of warm water. Adding a drop of liquid dish soap or 2 1/2 tablespoons vegetable oil helps the solution stick to your plant.

Blight spreads by fungal spores that are carried by insects, wind, water and animals from infected plants, and then deposited on soil. The disease requires moisture to progress, so when dew or rain comes in contact with fungal spores in the soil, they reproduce.

What does potato blight look like? Blight turns the leaves brown and fungal spores develop. Dark brown blotches appear around leaf tips and edges, spreading towards the middle, shrivelling and rotting the leaf. The leaves and stems rapidly blacken and rot, and the plant collapses.

Symptoms

1. The initial symptom of blight on potatoes is a rapidly spreading, watery rot of leaves which soon collapse, shrivel and turn brown.
2. Brown lesions may develop on the stems.
3. If allowed to spread unchecked, the disease will reach the tubers.

Yes, it is possible to get rid of late blight disease on tomato and potato plants using proven, organic and natural methods. Unlike other fungal diseases, this plant problem does not overwinter in the soil or on garden trash. Instead the spores are introduced by infected tubers, transplants or seeds.

Symptoms of common bacterial blight first appear on leaves as small, water-soaked spots, light green areas, or both. As these spots enlarge, the tissue in the center dies and turns brown. These irregularly shaped spots are bordered by a lemon yellow ring, which serves as a diagnostic symptom of common bacterial blight.

Late blight is caused by the oomycete Phytophthora infestans. Oomycetes are fungus-like organisms also called water molds, but they are not true fungi. There are many different strains of P. infestans.

Spraying fungicides is the most effective way to prevent late blight. For conventional gardeners and commercial producers, protectant fungicides such as chlorothalonil (e.g., Bravo, Echo, Equus, or Daconil) and Mancozeb (Manzate) can be used.

Probably the most common plant disease, blight can wreck whole crops in a matter of a few weeks, as it did so devastatingly during the Irish potato famine in the 1840s where 1 million people died and a further 1 million emigrated.

Late blight of potatoes and tomatoes, the disease that was responsible for the Irish potato famine in the mid-nineteenth century, is caused by the fungus-like oomycete pathogen Phytophthora infestans. Severe late blight epidemics occur when P. infestans grows and reproduces rapidly on the host crop.

Late blight affects both leaves and fruit. Leaves develop blue-gray spots which turn brown. Spots on both leaves and fruit may develop a white, cottony ring of mold. Late blight can overtake an entire plant quickly (within a week) if untreated.

Late blight, a plant disease caused by the water mold Phytophthora infestans, on a potato tuber. The disease was responsible for the Irish Potato Famine of the mid-19th century.

Late blight-infested plants may put off an unpleasant odor that smells like decay. Tubers frequently become infected, filling with rot and allowing access to secondary pathogens. Brown to purple skin may be the only visible sign on a tuber of internal disease.

Early blight is caused by two different closely related fungi, Alternaria tomatophila, and Alternaria solani, which lives in soil and plant debris. Late blight is caused by Phytophthora infestans, a microorganism which prefer moist and cool environments.