CHARLESTON, W.Va. -- Recent heavy rains and a lingering period of high humidity have created perfect conditions for a disease that preys on tomato and potato plants.According to West Virginia University Extension Service plant disease specialist Mahfuz Rahman, conditions are just right for formation of Septoria Leaf Spot, a condition that can affect both tomatoes and potatoes.Septoria is characterized by leaf spots that can grow up to 1/8-inch in diameter. The spots may turn gray or tan in the center and develop a pimply fungus inside the circle. The disease eventually kills the leaf, but does not usually attack the tomato fruit.Mahfuz said the disease can be confused with Early Blight, another tomato condition that can spread to the fruit of a tomato. The disease usually shows up as five to 10 brown, circular spots that can grow to half an inch in diameter. Spots have concentric rings that are usually surrounded by a yellow halo.
Both conditions can be treated with similar chemicals. For organic tomatoes, copper hydroxide or Serenade can be effective. For non-organic plants, chlorothanolil or azoxystrobin may be used.For more information, call Kanawha County Extension Agent John Porter at 304-720-9887.