DNA fingerprinting tests are also available in research laboratories to determine more details about the bacterial strains in question. This information will be helpful for developing long-term control strategies. At this time, there are few sources of resistance to these diseases available. Sprays of copper, or copper plus an EBDC fungicide, can reduce spread of bacterial spot and speck, but resistance to copper is common among strains of the causal bacteria isolated in this region, and thus copper sprays are not wholly effective. The best management strategy is to prevent the disease through exclusion of the bacteria from seedlings in the greenhouse, and through rotations away from peppers or tomatoes in the field.
Late blight is a disease that can destroy a tomato field in a few days.
Late blight appears on tomato leaves as pale green, water-soaked spots, often beginning at the leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly, and turn dark brown to purplish-black. When humidity is high and leaves are wet for an extended period, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. When conditions are dry, infected leaf tissues quickly dry up, and the white mold growth disappears.