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Effect of Crop Sequence, Previous Peanut Blackhull Severity, and Time of Sampling on Soil Populations of Thielaviopsis basicola. David C. H. Hsi, Professor of Plant Pathology, New Mexico State University, Plains Branch Station, Clovis, NM 88101; Phytopathology 68:1442-1445. Accepted for publication 3 May 1978. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1442.

The selective medium of Tsao and Bricker (19) was used to determine soil populations of T. basicola. No significant differences in the mean populations were found between or within fields that had been cropped in four different sequences. However, blackhull severity was higher in fields under peanut monoculture than in fields under a rotation of peanuts and sorghum. Blackhull severity was lower in the middle portion of each field than at either end. The mean populations of T. basicola were significantly greater in fields where blackhull had been severe, than in those with low disease incidence. Populations of T. basicola during June and August were significantly lower than those determined in December or March.