Efficacy of compost tea on Septoria leaf spot in field and greenhouse studies

View the project final report

• 2007 annual report

Commodities

• Vegetables: tomatoes

Practices

• Pest Management: compost extracts

Compost teas (CTs) are gaining popularity as a disease control agent in many areas of plant production, particularly in the realm of organic farming. CTs are brewed with a composted organic material as a base with a brewer’s choice of amendments to build microbial populations in the final product. In this experiment, we plan to use vermicompost as a base for the extraction process. Examples of common amendments include: fish emulsion, humic acid, alfalfa, and molasses. It is with these amendments that this research aims to clarify some of the confusion surrounding CT recipes. We plan to continue ongoing research on CT by investigating the properties of several different blends of amendments (recipes) in an effort to identify an optimal recipe for use against a primary foliar disease of tomato in Kansas: Septoria Leaf Spot, caused by the fungus Septoria lycopersici. Preliminary investigation into the efficacy of the recipes of interest will take place in the laboratory and in departmental greenhouses on the K-State campus in Manhattan, KS. It is in this phase of the research that we plan to identify recipes that have the potential to be used on a larger scale. After conclusions are drawn from the preliminary investigation, use of these recipes will be tested on site at the K-State Research Station near Olathe, KS, and at local conventional and organic farms near the Kansas City metropolitan area. With control groups and the necessary statistical set-up of this project, we will be able to identify which recipes perform the best against the diseases of interest as well as which recipes work as well as or better than those pesticides that conventional farmers are using today. With the success of this project will come information that will both provide more specifics in the area of CT recipes and provide growers with interest in using CTs a report of efficacy versus those pesticides which they currently use.

This research is aimed directly at simplifying ideas about the use of CT in the farming of food crops, particularly tomato. Intermediate-term outcomes will include an understanding in compost tea (CT) recipe building and a listing of which ingredients are recommended over others. Short-term outcomes will lead to a more complete understanding of variables such as dilution, rates and timing of application. This information will provide more recognition on the part of growers to the use of CT and will be used to assist those growers who choose to try CT. Long-term outcomes will lead more growers to the prospect of regularly using compost teas. By being able to compare disease suppression and yield statistics from controlled field trials, growers will sooner appreciate the potential of CTs on organic and traditional farms. Involving growers from the region in this experiment will help in ensuring the practicality of the methods of the proposed research and allow for easier adoption. Ultimately, this project and others like it will lead to a more widespread acceptance of CTs in the production of food crops. This promotes the key purposes of the SARE program by increasing farmer profitability by forgoing investments in chemical pesticides, improving the environment by reducing the amount of chemical pesticides used and enhancing the quality of life of farmers by reducing the need to react to foliar diseases due to the suppressive characteristics of CT.

In an effort to make easy the process of adopting a compost tea regimen, this research is aimed at simplifying the choice to use CT as a part of farming. This will include: 1) Providing research that gives organic growers more options in fertilization and the promotion of crop health; 2) offering a method for conventional farmers to decrease pesticide use and maintain plant health; and 3) Optimizing an already tested CT recipe. Finding at least one dynamically important recipe for CT is especially critical for there to be a chance for CT to gain widespread acceptance.

A previous NCR-SARE project (# GNC03-019) was conducted by Chandrappa Gangaiah to investigate the efficacy of CTs against Septoria lycopersici and Alternaria solani. This project is designed to follow-up this research in an effort to provide further data. Preliminary data from this project has given us a foundation to build upon. One major plan of action that this proposed research aims to address is the on-farm aspect of the research. Gangaiah failed to investigate the effects of CTs on field plots located on-farm due to the overwhelming attention that the research station-based trials required. One recommendation that he made for further studies of CT was to apply his techniques to larger, on-farm sites in order to eliminate possible effects from his small plot design. We also plan to work more on the recipe itself since results from his study gave inconsistent, but promising results. In order to decrease the variability of CT treatments and the plant’s responses to them, work needs to be done in the area of recipe building.

Many studies have been done to show that there is evidence that CT can have an effect on fungal pathogens and yield on food crops. In an attempt to maximize anti-fungal and nutritional characteristics of CT, we plan to investigate these two variables in the production of an optimal CT recipe. With the success of this goal, CTs will be better aimed at increasing the profitability of both organic and traditional farmers.

Organic farmers are in need of options to deal with plant health issues. With this in mind, more attention is being paid to the potential of compost tea (CT) as a biological control agent. CTs can be classified into two different categories:
1) aerated, and
2) non-aerated.

Most studies have found that reliable control of foliar diseases was only achieved using an aerated CT due to the enhancement of microbial populations during the aeration process (Scheuerell, 2004; Welke, 2004). In addition to this primary categorization, compost teas can include a number of different components. The base for the tea is usually a composted organic material which is combined with a brewer’s choice of additives in order to maximize its efficacy. One study using several types of compost found that the choice of additives is more critical than the source of the compost (Scheuerell, 2004). Therefore, research is needed to identify an optimal blend of these components to benefit organic farmers.

Applications of various compost teas can induce antifungal activity in plants (Singh, 2003), and inhibit fungal disease spread (Scheuerell, 2004; Welke, 2004; Singh, 2003). We know of some recipes that allow for foliar disease control comparable to that of many fungicides currently available to organic growers (Tsror, 1999; Gangaiah, 2005). Other studies have demonstrated the potential of compost tea as a nutritional supplement noting increased yields (Parikka, 2002; Tsror, 1999; Gangaiah, 2005). This means that the use of compost teas could prove useful for conventional farmers as well as those growers in the organic industry.

Gangaiah reported that inconsistencies in the efficacy of CT are likely due to a number of factors including added nutrients. His recipes, which were primarily composed of vermicompost, alfalfa pellets, unsulfured molasses, fish emulsion and humic acid, also gave inconsistent results, but did show promise in disease suppression (Gangaiah, 2005). It is with these recipes, Gangaiah states, that further work is needed in order to evaluate their potential efficacy.

By taking preliminary data derived from Gangaiah’s research to a larger schematic, we will be able to eliminate errors from small plot research and be able to address farmer concerns in the application of our proposed methods. With the results from the research station and greenhouse trials from his project, we will be better suited to approach our goals with tailored information and we will ultimately have a greater opportunity to investigate the various aspects of CT use that need attention.

Full-scale implementation of this project will occur in August, 2006. This will mark the initiation of the first phase of research which will focus on CT recipe investigations. The recipes from the previous study will be scrutinized for their ability to increase anti-fungal microbial populations and for their nutritional contribution for yield maximization. This phase of the research will be conducted in laboratory and greenhouse facilities on the K-State campus in Manhattan, KS where we will be able to customize CT recipes for use against the foliar disease of interest. Further consultation appointments with resident plant pathologists will be used in determining schematics for this investigation. Inputs for this phase of research will be intensive graduate student labor and recipe constituents as well as laboratory fees for conducting investigations of efficacy.

The second phase of the research will begin in late spring, 2007. It is with this leg of the research that we plan to actively facilitate the use of those recipes deemed suitable in the first phase of research for trial in larger-scale experiments. In an effort to minimize spatial variability among test plots, we plan to use a schematic that will allow for more separation between plots which will allow us the opportunity to focus our investigation on the timing aspect of CT application. The on-farm and on-station field trials of these recipes will be accomplished with the input of farmer and researcher dedication to the end result of the studies. We plan to use existing resources to produce CT on the large scale and will use graduate student labor as a means of implementing and evaluating the project’s progress. Due to this and the distance from campus to the research station and farms near the Kansas City metropolitan area, a large part of the budget request is dedicated to travel and labor. It should be noted that the principal investigator is a non-stipend student and resources allocated to said student will provide both the means to focus on the project on the whole and allow for travel as mentioned above.

A total of two cropping cycles will be facilitated through the summer and fall of 2007 allowing for greater staying power of statistical findings. Farmer cooperators will be given the opportunity to participate in further studies should their interests be peaked by the proposed research, giving them the option of remaining as an integral part of sustainable agriculture research.

Primary outputs of this research are expected to be extension publications on the topic of compost tea recipes and their efficacy against fungal pathogens on tomato and its extrapolation to other vegetable crops. A master’s thesis will be developed by the principal investigator for academic and scientific journal publication purposes. Other outputs will include presentations to interested grower audiences and field day presentations at the research station near Olathe, KS. Further studies into the use of CTs as a suppressive fungal pesticide will no doubt be needed to fine-tune the science of CT brewing, and this research will serve as both a continuum of that research and a basis for further investigations related to CT.

Disease indexing will play an integral role in the evaluation of field plots and in determining efficacy of tested recipes. Indexing will be done on a scale of 0 to 4 with 0 = no infection, 1= 1-5% infection, 2= 6-15% infection and 4= 16-95% infection. This scale is similar to other scales used in determining levels of fungal infestation by other researchers (Welke, 2004). In an effort to build upon the previous research funded by NCR-SARE, we will evaluate whole rows and whole plots on the basis of disease severity as the previous researcher found that evaluating single plants was possibly flawed due to the fast-acting systemic properties of fungal pathogens. He also found that careful whole plot assessments of disease severity were just as credible as individual leaflet and single-plant assessments. This will prove to be a valuable, time-saving tool.

Further investigation into process and outcome indicators will lead us to the choice of which indicators we will facilitate as the research progresses. However, we know that key indicators at each stage of the cropping cycles will allow for uniform comparisons among trials and that controlled experiments will give the best data. In an effort to maximize our effectiveness in data collection, we plan to meet with department statisticians for experimental design consultation.

This research will not include genetically modified plant varieties. No aspect of the proposed research will be affected by GMOs.