Hazards of Bacteria

As mentioned earlier, some bacteria cause disease. Several diseases of potatoes are attributable to bacteria: Pectobucten'um curotovomm, Pseudomonas solanacearum (brown rot), and Corynebacterium sepedonicum (ring rot). Shot hole is a bacterial disease that produces numerous small holes in leaves. The second most common problem among cotton plants is a bacterial disease called leaf spot, or black arm. Sugar cane is prey to a bacterial infection called Bacterium uasculorum (gumming disease). Tobacco suffers from a similar disease.

Bacterial diseases, as well as viral and fungal diseases, are frequently carried by insects, and, thus, can often be brought under control by the use of insecticide sprays or dusts. Infected seeds can be treated with bichloride of mercury, with formaldehyde, or with hot water. Timing of the latter treatment is particularly important.

Figure 11-3 Roots of a bean family plant containing nodules of nitrogen-fixing bacteria.