Bacterial diseases of plants are more than just unsightly; they are often destructive to plants. The University of Minnesota explains that there are more than 160 species of plant bacteria, each with its own growth rate. While some bacteria will quickly overwhelm your plant, others will slowly ravish your plant. Bacterial diseases are non aggressive and cannot penetrate the foliage or stems of plants. However, bacterial diseases do take advantage of your plant's natural state, entering the plant through its natural and man-made wounds and opening, such as with pruning cuts, cracks and stomata.
Bacterial Leaf Spot
Bacterial leaf spot is easily identified by the infected plant's foliage symptoms. Plants that are infected with bacterial leaf spot will develop dark-colored, water-soaked spots that are accompanied by encasing yellowing halos. Continuous rain and moisture will cause the coalescence of the spots. Severely infected leaves will defoliate prematurely. Bacterial leaf spot is a common nuisance of citrus and stone fruit trees and vegetables, as well as other indoor and outdoor foliage plants. There is no cure for bacterial leaf spot. However, the potential for bacterial leaf spot can be reduced by keeping the area free of decomposing debris and watering your plants at soil level. Planet Natural explains that the spread of bacterial leaf spot can be controlled with a copper-based fungicidal spray if applied at first signs of infection.
Crown gall is a root and stem disease that is most commonly found on woody plants. Roses and flowering fruit trees are common victims of crown gall. Still, the University of Maine Cooperative Extension explains that crown gall disease can infect more than 140 genera of plants and trees. Infected plants will develop smooth, light-colored galls on its roots and stems. As the galls age, they develop into hardened, discolored galls that eventually slough off to make room for new, secondary galls. These formations inhibit the plant's ability to transport nutrients and water throughout the plant. This lack of transport results in the plant's loss of vigor which is also accompanied by growth stunt and branch and twig dieback. Crown gall disease is a soil-borne bacterial disease for which there is no cure and the disease can thrive in the soil for several years without a host. Planting resistant plants is the best protection against crown gall disease.
Fire blight is a destructive bacterial disease that is especially threatening to rosebushes and pome fruit trees. This disease lies dormant in the plant and in decomposing matter that lies around the plant. The bacterium begins its growing season as your plant enters its growing season. It enters the natural openings of the plant through its twigs and branches and is often transported by insect and honey bee bites. Trees and plants that are infected with fire blight will display tan-colored, bacterial ooze near the points of infection. The University of California explains that the foliage and flowers of the plant are generally first to show signs of infection. The infected areas become necrotic, turn black, wilt and become deformed. Unlike many diseases, vigorously growing trees are more susceptible to fatal infections than slow-growing ones. The University of California explains that is because the spread of fire blight is directly related to the growth of the tree. Fire blight can be controlled by pruning away the diseased and infected areas of the plant. The pruning should be completed with sharp, sterile pruning shears that are sterilized between each cut. The potential for fire blight infections and repeat infections can be reduced by applying a copper-based fungicidal spread several times throughout the year.