Soilborne Disease Research Grant Progress Report –January 2005

Project Title: Effective Rotation Crops for Control of Powdery Scab and Other Soilborne Diseases

Principal Investigator: Robert Larkin¹, Plant Pathologist

Co-investigators: Dave Lambert², Plant Pathologist,

Tim Griffin¹, Agronomist, and

John Halloran¹, Agricultural Economist.

Address/Affiliation: ¹USDA, ARS, New England Plant, Soil, and Water Lab, University of Maine, Orono, ME 04469. ²Dept. Plant, Soil, and Environmental Sciences, University of Maine.

Project Objective: To evaluate the effects of selected rotation crops on multiple soilborne diseases, tuber yield and quality, and economic viability.

Executive Summary: Numerous soilborne diseases are persistent, recurrent problems in potato production, resulting in reduced plant growth and vigor, lower tuber quality, and reduced marketable yield. These diseases include Rhizoctonia, common scab, white mold, pink rot, Pythium leak, silver scurf, and powdery scab. Powdery scab, in particular, has emerged as a difficult and increasing problem, with virtually no effective control options available. The objective of this project is to evaluate the effects of selected rotation crops on multiple soilborne diseases, tuber yield and quality, and economic viability, with special emphasis placed on the efficacy of Brassica crops (canola, rape, and mustard) in managing serious soilborne disease problems. The project focuses on the establishment and assessment of various green manure, cover, and rotation crop treatments in on-farm trials at multiple locations with a history of soilborne disease problems. 2004 represented the very beginning stages (first few months) of this multi-year project. Accomplishments in 2004 included the selection and hiring of the graduate student whose primary responsibility will be conducting many aspects of this project, and establishment of replicated rotation crop treatments (barley, canola, and mustard) in research plots at Aroostook Farm with a history of pink rot and Rhizoctonia diseases, which will be planted to potato and evaluated for disease in 2005. Ryan Lynch (graduate student) has just recently started working on the project, and we are currently obtaining and doing greenhouse evaluations of numerous different varieties of mustard for potential use in field studies this year. However, due to the late initiation of the project in 2004, we were not able to coordinate and implement activities before the start of the 2004 field season, meaning we were not able to establish the rotation crop treatments in on-farm trials for the summer of 2004, as we had initially proposed. Thus, on-farm field initiation will be conducted in Spring 2005. This will allow us to be better prepared and fully ready to implement the field trials in 2005. We are currently preparing and planning for the establishment of these on-farm trials. The potential for use of rotation crops in the reduction of soilborne diseases has already been established in the literature and through previous research. Continuation of this project will provide documentation on the best rotation crops to use, extent of disease reduction, methods of implementation, and the economic consequences of these rotations when implemented under real field conditions on Maine potato farms.

class=Section2>

Project explanation. In this research project, we are continuing our previous research on the control of powdery scab and other soilborne diseases through the use of Brassica rotation crops by further evaluating specific crops and varieties for their disease-reducing potential. This project focuses on a series of replicated on-farm field trials, conducted at sites with a history of powdery scab or other soilborne disease problems. The researchers are working with grower-collaborators in identifying appropriate sites and establishing the particular rotation treatments and procedures to be conducted at each site. Rotation crops will include Brassica crops, such as canola, rapeseed, and mustard, compared with a standard rotation crop, such as barley, in a two-year rotation cycle. Different combinations of treatments will also investigate the effectiveness of using these crops as green manure, fall cover, or conventional rotation crops. Different handling of the same Brassica crop (harvested vs. not harvested, fall incorporation vs. spring incorporation, fall cover crop, etc.) may also impact efficacy in reducing diseases, and these factors will be evaluated, where possible. Potato would be planted the following year after the rotation crops, with disease monitored throughout the season, and tuber yield, quality, and disease symptoms assessed at harvest. At the same time the potatoes are planted in the rotation sites, additional adjacent field sites would be planted to the same rotation crops as the previous year, followed by potatoes the next year. Thus, two full two-year rotation cycles (rotation crop-potato) could be accomplished within three years. The following spring after the rotation crop treatments, potato will be planted and evaluated. The project will also include economic analyses of the rotation sequences to determine the effects on profitability and risk.

Project Initiation. Due to the lateness of approval of the project (approved by MPB in late March ’04 and final approval from ARS in late April ’04) and the lack of appropriate time to adequately meet, discuss, and work out the project plans and details with grower-collaborators and a grower advisory group prior to the Spring ’04 planting season, we missed the window of opportunity to establish the rotation treatments in on-farm trials for the summer of 2004, as was previously proposed. However, this gave us additional time to plan and create the potential for better field trials in 2005 (and beyond) by not rushing into any ill-conceived or improperly coordinated field work in 2004. Thus, the formal initiation of the project was postponed until the fall of 2004, when the recruitment, selection, and hiring of a graduate student dedicated to the project was conducted. However, rotation crop treatments were established in research plots with a history of pink rot and Rhizoctonia disease at UM’s Aroostook Farm in 2004 (as described below), and will be ready for disease assessments in 2005.

Project Accomplishments (2004):

Aroostook Farm Plots. Replicated treatments of three different rotation crops (barley, canola, and mustard) were established on research plots with a history of pink rot and Rhizoctonia diseases at the University of Maine Aroostook Farm (Dave Lambert’s pink rot plots). There were 4 replicates of each rotation crop (12 plots), with each plot being 12 ft wide (4 potato rows) by 36 ft long. Rotation crops were grown through the summer and incorporated in the fall. Next season (2005), all plots will be planted to Russet Norkotah, and rated for pink rot, Rhizoctonia, and yield among plots.

Graduate Research Assistant. Ryan Lynch, who recently completed undergraduate studies at The University of Maine with a background in Sustainable Agriculture and extensive undergraduate research and work experience, was selected to be the graduate research assistant working on this project. Ryan will develop this research into a Master’s thesis project, and will be primarily responsible for much of the implementation, data collection, and analysis of the results of this project. Aside from coursework responsibilities in the spring and fall semesters, Ryan will be dedicated full-time to the project. Ryan has only just officially started work on the project over the last couple months. He is currently in the process of assessing and evaluating several different Brassica spp. and crop varieties for growth characteristics, biomass, pathogen inhibition, disease reduction, and possibly glucosinolate content in greenhouse tests. He has obtained, or is in the process of obtaining, numerous new and different mustard varieties from various seed sources (many that have been used or tested in the Pacific Northwest) for testing to determine the varieties with the best combinations of attributes for inclusion in the upcoming on-farm field trials. Ryan also will be closely involved in the planning, preparations, and working with growers to coordinate the on-farm trials this coming year. Thus, with Ryan now aboard and beginning to actively work on the project, we can move forward in making the arrangements and preparations for the upcoming field trials.

Future Plans (2005 and beyond):

Detailed plans for the continuation of this research project will be outlined in the upcoming proposal for continuing support (2005 proposal, to be submitted January 28, 2005). Our overall plans are briefly summarized as follows. We are currently in the process of identifying and lining up grower-collaborators with fields having a history of soilborne disease problems that we may use in our on-farm field trials. We will work with the growers in determining the specific rotation treatments and plot designs to be used at each location. We anticipate two or more on-farm sites with 4-8 rotation treatments including different crops (barley, canola, rapeseed, mustard) and different usages of the Brassica crops (harvested crops, green manures, cover crops) to determine maximum efficacy and appropriate implementation. These rotation treatments will be established in 2005, and a subsequent potato crop in 2006 will be monitored and assessed for soilborne plant and tuber diseases, and yield among treatments. Additional rotation treatments will also be established in 2006 (preferably in nearby or adjacent areas to 2005 rotation treatments) to enable evaluations on potato crops to be conducted in 2006 and 2007, thus allowing potato disease and yield data from 2 separate field seasons conducted over three years at multiple locations. Economic analyses of the rotation sequences will also be conducted to determine the effects on profitability and risk. In 2005, we also will be planting potato in the Aroostook farm rotation plots for evaluation of rotation effects on disease and yield in those plots.

Conclusions:

Although we may have missed an opportunity to implement the rotation treatments in 2004, as originally proposed, I think that, in the long run, the project will benefit from this additional time to design, plan, and more effectively implement the on-farm field trails in 2005. With Ryan now on board, all the pieces are now in place, and additional preliminary experimentation and planning for the coming year will result in a better designed, implemented, and coordinated study. This project has tremendous potential to answer many of the questions growers have regarding the effectiveness of rotation crops in the management of soilborne diseases. In addition, this study will address the economic aspects of using these rotation crops, as well as better determining the best approaches for managing the rotation crops for maximum efficacy. The potential for use of rotation crops in the reduction of soilborne diseases has already been established in the literature and through previous research. Continuation of this project will provide documentation on the best rotation crops to use, extent of disease reduction, methods of implementation, and the economic consequences of these rotations when implemented under real field conditions on Maine potato farms.