Submitted to: Canadian Journal of Plant Pathology
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2004
Publication Date: September 20, 2004
Citation: Paulitz, T.C. 2004. Spatial distribution of rhizoctonia solani and rhizoctonia oryzae at three different scales in direct-seeded wheat.. Canadian Journal of Plant Pathology.26:419. Technical Abstract: A 36-ha farm north of Pullman, WA was cropped with a three-year rotation of spring wheat, winter wheat, and alternative crops (winter and spring cultivars of canola, barley, and pea). Twelve-ha plots of winter and spring wheat were sampled at GPS-located sites with 10 x 10 grids at three different scales- 30 m, 3 m and 0.3 m. Populations of R. solani Kühn and R. oryzae Ryker & Gooch were determined using a toothpick baiting technique. Spatial distribution was analyzed by fitting frequency distributions to a beta binomial distribution and maps were derived from inverse distance weighted interpolations. Both pathogens showed an aggregated distribution, but R. solani was more patchy than R. oryzae. In both crops, R. solani had a higher theta value, an index of aggregation. In spring wheat, high populations of R. solani were associated with previous rotations of winter and spring canola, but R. oryzae was equally distributed among the alternative crops. Frequency distributions and spatial patterns were similar at all three scales. At the 3 m and 0.3 m scale in winter wheat, R. oryzae exhibited anisotropy in the direction of tillage which last occurred 6 years ago. R. oryzae was more widely distributed across the landscape than R. solani, which was confined to patches 1 to 15 m in diameter.