Avoiding Potato Scab by Rob Sproule. As common as a cold, scab is a bacterial infection that results in nasty scabs across the potato. The good news is that scab damage is entirely superficial. Streptomyces scabies is a bacteria that typically gets into your garden via infected seed spuds.
Seed Potato Basics Inspect the potatoes you bring home carefully and only buy from vendors you trust. It can blow in from wind and rain, as well.
Once in the soil it can live indefinitely, overwintering under the cover of leaf litter and garden detritus. It thrives in slightly alkaline soil 5. Scab attacks the potato plant either via the stem or directly into the tuber.
Buy your seed spuds from trusted vendors and, if you have a history of scabby soil, look for varieties that are more resistant. The next issue of Edmonton Journal Headline News will soon be in your inbox. We encountered an issue signing you up. Please try again. This website uses cookies to personalize your content including ads , and allows us to analyze our traffic. Read more about cookies here.
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We apologize, but this video has failed to load. Within the range of pH 5. Warm and dry soil conditions can noticeably increase the incidence of the disease, particularly during the critical period of susceptibility to scab 2 and 5 weeks after tubers start to form. Use a combination of several control measures to prevent an outbreak of common scab.
This is more effective than using just one control measure. For example, controlled irrigation combined with a registered fungicide treatment results in better control than either treatment used on its own. The only economical means of long-term control is to use resistant varieties in soils where the problem recurs. While no popular variety is resistant, the early types Red Pontiac, Kennebec and Sequoia are more susceptible than the medium- to late-maturing types Sebago and Coliban.
Dry soil at the time when tubers start to form, and for the 5 weeks after that, will increase the chances of common scab occurring.
Compendium of Potato Diseases ed. The disease cycle of S. Inoculum on seed tubers, even those without visible lesions, seems to be important in disease outbreaks in New York. While low-pH soils provide good control of common scab, there are disadvantages associated with this management strategy. Plant nutrients are most available at soil pH levels near 6.
Since acid soils are unfavorable for most vegetable and field crops, the number of them that can be grown in rotation with potatoes is limited. Maintaining soils near pH 5. Potatoes grown in soils near pH 6.
Lack of crop rotation aggravates many pest problems, especially the Colorado potato beetle. Soil moisture. Soil moisture during tuberization has a dramatic effect on common scab infection. Maintaining soil at moisture levels above Bacteria that flourish at high soil moisture appear to outcompete S. However, maintaining high soil moisture may be difficult in some soils, and it is possible that other disease problems may be aggravated by excessive irrigation. Soil type and soil amendments.
Light-textured soils and those with high levels of organic matter are favorable to scab infection. Streptomyces are generally involved in the decomposition of soil organic matter, and therefore thought to be stimulated by its presence. Applying manure to potato fields can cause an increase in scab infection. Coarse-textured soils are conducive to scab, probably because of their moisture-holding capacity; thus, gravelly or eroded areas of fields that tend to dry out rapidly are often sites of heavy scab infection.
Crop rotation. Crop rotation reduces the inoculum levels in potato fields, but S. This may be due to saprophytic activity or an ability of S. Infection of seedlings of many vegetables and fleshy roots of beet, cabbage, carrot, radish, spinach, turnips and other plants has been reported.
Rotation with small grains, corn, or alfalfa appears to reduce disease in subsequent potato crops. Red clover, however, stimulates problems with common scab and should not be used in fields where scab has been a problem.
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