Potato Common Scab
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Potato Scab  Potato scab is a widespread bacterial disease, most common in light sandy, alkaline soils, and encouraged by dry, hot weather. Serious outbreaks of potato scab can occur on newly cleared grassland. Following the initial infection the scab lesions produce further spores, which persist in the soil. The disease is present in most soils but is only active when the proper conditions occur.Susceptible Plants- Potato, (Russets are more resistant to potato scab) Symptoms- Potato scab symptoms are quite variable. Usually roughly circular, raised, tan to brown, corky lesions of varying size develop randomly across tuber surfaces. Russet scab occurs as a rather superficial layer of corky tissues covering large areas of the tuber surface. Pitted scab occurs where lesions develop up to 1/2 in(1.25 cm) deep; these deep lesions are dark brown to black, and the tissues underneath are often straw-colored and somewhat translucent. More than one of these lesion types may be present on a single tuber. Although potato scab symptoms are usually noticed late in the growing season or at harvest, tubers are susceptible to infection as soon as they are formed. Small brown, water-soaked, circular lesions are visible on tubers within a few weeks after infection. Mature tubers with a well-developed skin are no longer susceptible, but existing lesions will continue to expand as tubers enlarge, increasing disease severity throughout the growing season. Potato scab is most severe when tubers develop under warm, dry soil conditions. Coarse-textured soils that dry out quickly are therefore more conducive to scab than are fine-textured soils. Prevention and Control- in the vegetable garden for the most part involves correcting the conditions most favorable for scab production. Do not apply lime as this will increase potato scab incidence. When pH 5.2 or below add sulfur to make the soil more acidic. Water potato crops during dry periods, particularly when the crop is in the flowering stage. If your soil is a very light sandy soil add organic soil improvers to increase the water holding capacity of the soil. Use a minimum 3 year crop rotation planting non-susceptible crops between potatoes. If possible grow potato scab resistant varieties. Fungicidal Control- 3-in-1 Garden Spray Fungicide, Insecticide, Mitacide
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