ABSTRACT
In 1992 chemical analyses were conducted on soils from the Lower Rio Grande Valley, Coastal Bend, Blacklands, Edwards Plateau and South Rolling Plains of Texas to correlate the occurrence of Phymatotrichum root rot (PRR) with soil properties. Soil cores (2 x 36 in.) were collected from 21 counties in Texas with a history of PRR. Attempts were made to select cores from infested and noninfested soils, especially in the South Rolling Plains where there is a distinct region absent of PRR and a region where the disease is endemic. Each soil core was divided into three segments and separately packaged in plastic bags for transport to College Station for analysis. The samples were air dried, ground, extracted with ammonium acetate and analyzed for total calcium, magnesium, and sodium ions, as well as for pH and electrical conductivity. Three from each segment were assayed for their potential to produce sclerotia of Phymatotrichum omnivorum. With the exception of soils collected from Navarro county, soils in the Blacklands have less exchangeable sodium in the lower depths than soils from the Coastal Bend and Lower Rio Grande valley regions. In prior studies, Gerik found the preponderance of sclerotia resided in the upper 24 inches in these regions, but in the Blacklands we recovered the highest number of sclerotia 18 to 36 in. deep. Successful implementation of control strategies based upon disruption of the survival stage of the pathogen could be influenced by chemical properties of the soil that impact the location where sclerotia form. Soil analysis may provide a reliable predictor for making this determination.
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