. The actinomycetes. Actinomycetales. CAUSATION OF 1M>A\T DISEASES 269 100. pH Figure 105. Relation of soil reaction to the occurrence of potato scab (Reproduced from: Dippenaar B. J. Union of South Africa Dept. Agr. Sci. Bull. : 52, 1933). found difficult if not imposs^ible to do this. It has been obsen-ed in western Nebraska that potato seal:) is always severe following heavy, packing rains when the field cannot be cultivated sul)se(iuently. Scab was also commonly foinid in flooded areas, at the lower ends of irrigated fields, and in poorly drained portions of dry-land fields. This is
. The actinomycetes. Actinomycetales. CAUSATION OF 1M>A\T DISEASES 269 100. pH Figure 105. Relation of soil reaction to the occurrence of potato scab (Reproduced from: Dippenaar B. J. Union of South Africa Dept. Agr. Sci. Bull. : 52, 1933). found difficult if not imposs^ible to do this. It has been obsen-ed in western Nebraska that potato seal:) is always severe following heavy, packing rains when the field cannot be cultivated sul)se(iuently. Scab was also commonly foinid in flooded areas, at the lower ends of irrigated fields, and in poorly drained portions of dry-land fields. This is the reverse of what one might expect from the work of Sanford and Dippenaar on soil moistiu'e and of Sanford on the necessity of abundant aeration for the best development of the scab organism. A study was made to det(»rmine whether the effect of soil sterili;cation on the occur- rence of scab was due to chemical or physical changes in the soil or to lack of competing organisms. Sterilized soil was treated with an extract of unsterilized soil. The effect of the time of inoculation was determined ))y adding the inoculum either at the time of planting or at the begiiming of tuber forma- tion. In sterilized soil thei-e was a greater amount of scab. This was due to a lack of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Waksman, Selman A. (Selman Abraham), 1888-1973. Baltimore, Williams & Wilkins
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