Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/1996
Publication Date: N/A
Interpretive Summary: Common root rot in peas and sugar beets caused by the Aphanomyces pathogen is widespread in the United States and Europe. The only control method in peas is to avoid the crop for up to 10 years and even then disease control is uncertain. Precrop green manures of corn (variety Jubilee) oats (variety Troy) and rape (variety Humus) all three markedly reduced disease in peas and inoculum (of the pathogen) in the soil as measured in rolled-towel bioassay. Measures of soil inoculum change are necessary and useful to the user. Four other crops as green manures did not suppress the disease. This information can be used directly by Extension and producer organizations to precede peas with any of the above three crops provided the residue is incorporated at a shallow depth late in the fall before pea planting in the spring. Shallow incorporation cannot be done with a moldboard plow. In fact growers could rely on these three crops in a crop rotation with peas for control of Aphanomyces so long as there is good wee control.
Technical Abstract: Five-wk-old green manure crops of sweet corn, soybean, alfalfa, snap bean, rape, pea and two cv. of oat 'Dane' and 'Troy' were incorporated back into soil in which the crop was grown. The soil was then evaluated for disease suppression of common root rot (Aphanomyces euteiches) on a subsequent pea crop grown in pasteurized and non-pasteurized soils in the greenhouse. Green manures of sweet corn cv. 'Jubliee', oat cv. 'Troy', and rape cv. 'Humus' reduced losses in pea biomass significantly more than pea biomass loss that resulted in the absence of these crops in both pasteurized and non-pasteurized soil. Oat cv. 'Troy' and sweet corn cv. 'Jubilee' green manures significantly reduced inoculum concentrations of A. euteiches in pasteurized soil by 87 percent and 76 percent, respectively, and by 67 percent and 66 percent, respectively, in non-pasteurized soil over the representative fallow controls. Only the green manure of one of the two oat cv. 'Troy', reduced inoculum concentrations significantly below fallow Thus, green manure crops of either 'Troy' oat, rape or sweet corn cv. 'Jubilee' has potential for reducing severity of common root rot of pea caused by A. euteiches.