alternatives to pesticides - plant disease - blight
The term blight is used to refer to a great number of plant diseases that affect a number of plants in one area, rather than isolated cases. Most blights are caused by pathogenic organisms, generally fungi, but sometimes bacteria, and are manifested by browning foliage, reduced vigor and death of the plant. Early and late blight, which strikes potatoes and tomatoes, and brown rot blossom blight, which affects cherries, peaches and plums, are common in the region. Blights spread readily when plants are wet. A warm, humid spring increases the chance of blight problems. Warmer, drier weather may check the spread of blight.
Most diseases – including blights – are almost impossible to eliminate once they have taken hold of a plant. The best we can hope for is to try to prevent them from starting and, if that fails, to prevent them from spreading. Blight-resistant varieties of plants are available. Don’t water tomatoes overhead at night. The foliage can’t dry off and this increases the potential for blight problems.
As mentioned above, once the plant is infected with blight, it is virtually impossible to control. Pick off and destroy infected parts when you spot the first sign to prevent the disease from spreading.
Least-toxic chemical control
A fungicide spray of copper may be effective in preventing late blight on tomatoes and brown rot blossom blight on fruit trees.