Management of Verticillium wilt of potato with disease-suppressive green manures and as affected by previous cropping history

Authors: Larkin, Robert - Bob; Honeycutt, Charles; Olanya, Modesto

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2011
Publication Date: 4/6/2011
Citation: Larkin, R.P., Honeycutt, C.W., Olanya, O.M. 2011. Management of Verticillium wilt of potato with disease-suppressive green manures and as affected by previous cropping history. Plant Disease. 95:568-576.

Interpretive Summary: Vertcillium wilt is a major disease problem in potato production. In this research, the ability of potential disease-suppressive rotation crops to reduce Verticillium wilt and other soilborne potato diseases in a severely infested field was evaluated over three cropping seasons in Maine. A mustard blend (mix of white and oriental mustard) and sudangrass, both known for their biofumigation potential and grown as green manures, were compared with a standard barley rotation and barley followed by chemical fumigation with metam sodium as controls. Both green manure rotations significantly reduced wilt in the subsequent potato crop compared to the barley control, with average reductions of 25 and 18%, respectively, but were not as effective as chemical fumigation (35% reduction). In addition, mustard blend reduced other soilborne diseases (black scurf and common scab) to a greater extent than all other rotations, including chemical fumigation. Mustard blend and chemical fumigation treatments increased tuber yield relative to the barley control and sudangrass treatments by 12 and 18%, respectively. However, by the second potato crop, the green manures were less effective. This research indicates the potential for using disease-suppressive rotations for managing Verticillium wilt and other soilborne diseases, but also demonstrates the limitations of 2-yr rotations regarding the build-up of soilborne diseases over time. This research is useful for scientists, extension personnel, and growers, providing information on sustainable practices that can help reduce potato diseases and increase crop productivity.

Technical Abstract: The ability of potential disease-suppressive rotation crops to reduce potato disease problems and increase crop productivity in a field severely infested with Verticillium wilt was evaluated over three field seasons in Maine. Disease-suppressive rotation treatments consisted of 1) a high glucosinolate mustard blend (‘Caliente 119’), a mixture of white mustard (Sinapis alba) and oriental mustard (Brassica juncea) known for its biofumigation potential, and 2) a sorghum-sudangrass hybrid, both grown as green manures. These rotations were compared with a standard barley rotation and a barley rotation followed by chemical fumigation with metam sodium as controls. Both green manure rotations significantly reduced wilt in the subsequent potato crop compared to the barley control, with average reductions of 25 and 18%, respectively, but were not as effective as chemical fumigation (35% reduction). In addition, mustard blend reduced other soilborne diseases (black scurf and common scab) to a greater extent than all other rotations, including chemical fumigation. Mustard blend and chemical fumigation treatments increased tuber yield relative to the barley control and sudangrass treatments by 12 and 18%, respectively. However, by the second rotation cycle (second potato crop after initial rotations), disease levels were high in all rotations, and only chemical fumigation resulted in substantial disease reduction (35%). Rotations also had significant effects on soil microbiology and pathogen inoculum levels. This research indicates the potential for using disease-suppressive rotations for managing Verticillium wilt and other soilborne diseases, but also demonstrates the limitations of 2-yr rotations regarding the build-up of soilborne diseases over time.