Ten Years of Plant Pathology Research at the Cook Agronomy Farm: What Have We Learned?

Authors: Paulitz, Timothy; Schroeder, Kurtis; Okubara, Patricia

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2009
Publication Date: 6/20/2009
Citation: Paulitz, T.C., Schroeder, K.L., Okubara, P.A. 2009. Ten Years of Plant Pathology Research at the Cook Agronomy Farm: What Have We Learned?. Meeting Abstract. Timely Solutions for Shifting Economics. Department of Crops and Soil Sciences Technical Report 09-1

Interpretive Summary:

Technical Abstract: The Cook Agronomy Farm has provided important information for understanding root diseases under directseeded conditions in the higher rainfall annual cropping zones of the Palouse, at a landscape scale. This farm has served as an important outdoor laboratory to test disease management techniques such as chemical fallow, residue management and precision N application. The primary Rhizoctonia species on the farm is R. oryzae, which has an aggregated, patchy distribution and is not influenced by crop rotation. On the other hand, R. solani AG 2-1, a brassica pathogen, was strongly influenced by rotation, and was found almost exclusively in the plots that had either spring or winter canola the previous 1 or 2 years. Surprisingly, R. solani AG-8, the cause of bare patch, is almost completely absent from the farm, despite 10 years of direct-seeding. Chemical fallow reduced R. solani AG-2-1 but not R. oryzae, only after 3 years in the absence of a host, although the fallow was not completely weedfree. This indicates that Rhizoctonia can survive for long periods in intact roots in chemical fallow, or as microsclerotia, in the case of R. oryzae. The predominant Pythium species on the farm are P. irregulare group IV and P. rostratafingens. The most virulent species, P. ultimum, is very rare on the farm. Unlike Rhizoctonia, Pythium is more evenly distributed across the landscape. P. irregulare group I is also less prevalent, but highly pathogenic on legumes such as lentils, peas and chickpeas. Fusarium crown rot probably has been the most yield-limiting disease on the Cook Farm, especially since the wheat varieties were hard red, managed with high N levels to attain protein. This disease is exacerbated by drought and excess N fertilizer levels. We have been able to see crown rot every year, especially on dry sites and in low rainfall years. F. culmorum is the predominant species, with less F. pseudograminearum. Rotation does not have a large effect on these pathogens, which mainly infect grassy hosts. Splitting N application in the fall and spring, as opposed to all in the spring, did not consistently reduce Fusarium crown rot averaged across the entire landscape. Precision application of N, based on landscape position and amount in the soil, also did not consistently reduce disease when averaged over the entire field, but may reduce disease at specific locations. Take-all, caused by Gaeumannomyces graminis var. tritici, has occurred at very low levels on the Cook Farm. This disease is primarily controlled by rotating with non-host broadleaf crops such as pea or canola every 3rd year.