Evaluation of biological fungicides to control diseases of spinach in winter high tunnels
In 2015, UMass Extension partnered with Danya Teitelbaum of Queen’s Greens to evaluate five biofungicides, alone or in rotation, for efficacy in reducing impacts of plant disease on yield and quality of overwintered spinach. The crop has been planted and the field experiment is underway. So far we have applied treatments up to nine times, depending on the spray interval for the material tested, and have collected data on stand establishment and crop vigor at eight time-points. The first harvest has not yet occurred. We will continue to make treatment applications and collect data on growth and yield through February or until the final harvest, whichever comes last. Meanwhile, biofungicides are also being cultured in the laboratory at UMass in order to assess differences in growth at low temperature between products. Each of the biofungicides being tested in the field study (Rootshield, Actinovate Ag, Mycostop G, Double Nickel) plus three additional biofungicides (Serenade Max, Sonata ASO, Taegro) have been successfully cultured on solid and liquid media in the lab. We are now in the process of evaluating growth rate at a set of temperatures ranging from 4-22 degrees Celsius to assess whether or not some of these organisms would be better suited for use in winter growing systems.
Our specific objectives were to: a) determine if there is a lower temperature limit past which the biocontrol organisms become inactivated and other control strategies should be used, or if certain biocontrol organisms are more cold tolerant and would thus be better suited for use in winter production systems; and b) if any of the products evaluated can significantly increase crop yield and quality.
For objective A, we experienced some setbacks in acquiring materials and developing culture methods and protocols in time to conduct this study before the busy field season started in May and so were unable to conduct the lab study from April-June 2015, as stated in the project timetable. However, we are now making quick progress on this objective: we have successfully cultured all of the biofungicides being tested in the field study (Rootshield, Actinovate Ag, Mycostop G, Double Nickel) plus three additional biofungicides (Serenade Max, Sonata ASO, Taegro) so that we have a total of seven products to evaluate in the lab assay. We are prepared to run the assay in January, giving us plenty of time to troubleshoot, re-run the assay if need be, and analyze our results and summarize findings in plenty of time.
Objective B is being completed on schedule and the field experiment is underway. Soil tests were taken 04 September and soil in the high-tunnel was amended with lime to increase pH from 5.5 to 6.5, and with potassium sulfate, per soil test instructions. Nitrogen was applied according to grower discretion, as her experience growing long-season spinach indicates that a large amount of N is needed up-front to get the crop through to March, and ~780 pounds of nitrogen/A in the form of organic feathermeal was applied prior to seeding. Danya seeded the entire tunnel with ‘Gazelle’ spinach (Johnny’s Selected Seeds, ME) on 02-03 October into 11-row beds seeded at ~0.5” in-row spacing. A randomized complete blocks design was used in which each treatment was replicated four times, with each block consisting of one bed, and buffer beds on each edge. Replicate plots consisted of 20 bed feet with 5’ buffers between plots. Dataloggers were deployed throughout the tunnel to collect information on ambient temperature and light intensity as well as soil temperature over the course of the winter season. Spinach began to germinate on 09 October and emergence was rated on 13 October. Biofungicides were applied just after seeding on 05 October and we have continued to apply them weekly, biweekly, or less frequently depending on manufacturer instructions (see Table 1). To date, treatments have been applied on nine dates. Plots have been rated for symptoms of damping off such as reduced or delayed plant emergence resulting in patchiness and uneven stands and reduced overall vigor at eight time-points. We have rated plots by visual estimation of the following parameters: emergence (plant number 1-100%), plot vigor (0-100%) and on the following ordered categorical scale from 1-6, designed to asses variability in plant size and plot patchiness, where: 1 represents small plants with large patches where plants did not germinate or germinated very slowly; 2 represents small plants with small patches; 3 represents small plants with no patches; 4 represents large plants that germinated as expected but the plot has large patches present; 5 represents large plants but small patches; and 6 represents large plants and no patches, with good plant stand and vigor (see Figure 1). We will continue to apply treatments as described in Table 1 and measure changes in plant vigor until the final harvest. We will also continue to scout for other diseases such as Cercospora and Cladosporium leaf spots, which if detected will be evaluated in terms of disease severity (0-100%). Yield will be quantified by measuring wet weight of the crop harvested from the whole plot at three to five dates to be determined by the grower.
The project period will run from April 1, 2015 through February 28, 2017.
April through June of 2015: Conduct lab experiment. As predicted in the project proposal, this proved too difficult to squeeze in before the field season started and this piece of the project is now being conducted and we anticipate it will be completed in January and results analyzed and summarized in February.
April 2015: Planning of the field experiment will be done collaboratively by the farmer and UMass Extension staff and will include ordering seed, determining planting strategy and crop production practices, and procuring biopesticides from chemical companies and specifying methods of application, and solidifying methods for data collection. This milestone was accomplished as stated.
August-September 2015: Soil testing and amendment with compost, fertilizers, and lime. UMass Extension staff will assist with soil sampling and interpretation of results, while the farmer will be responsible for applying and incorporating any soil amendments deemed necessary. This milestone was accomplished as stated.
Mid-late September 2015: The first biopesticide applications will be made and crop seeded. This milestone was accomplished as stated.
September 2015-April 2016: The farmer will be responsible for maintaining the crop in terms of insect pest management, weed management, irrigation, and fertility for the duration of the experiment. The spinach crop will be monitored by UMass Extension staff for pre- and post-emergence damping-off and other diseases. This milestone is underway and as anticipated.
December 2015- April 2016: Collection of yield data will occur at two to five time-points throughout the growing period, depending on crop growth and the number of cuttings achieved. The first harvest is yet to occur but we are on target to achieve this milestone as anticipated.
April-May 2016: Data will be analyzed for statistically significant treatment differences. We are on schedule to achieve this milestone as anticipated.
Summer 2016: Written outreach materials including an article for Vegetable Notes and a factsheet for the UMass Extension Vegetable Program website will be drafted over the summer of 2016 for publication in August or September of 2016, to coincide with planting of the next years’ winter spinach crop. We are on schedule to achieve this milestone as anticipated.
August 2016: Results will be presented by UMass Extension staff and the farmer at the Frozen Ground Winter Grower’s Conference in August 2016 if possible. We are on schedule to achieve this milestone as anticipated.
October 2016: Results will be presented by UMass Extension staff at the regional meeting of the American Phytopathological Society. We are on schedule to achieve this milestone as anticipated.
January 2017: Results will be presented by UMass Extension staff and the grower at the NOFA-MA Winter Conference in January 2017. We are on schedule to achieve this milestone as anticipated.
February 2017: A final report will be written collaboratively by the farmer and UMass Extension staff. We are on schedule to achieve this milestone as anticipated.
Impacts and Contributions/Outcomes
Analysis of the data collected so far has not yielded significant differences in plant emergence, plot vigor, or in our rating of overall stand. We still see patchiness and poor stand establishment in the high tunnel, and the use of biofungicides as soil drenches has not proven to improve plant stand relative to the untreated control. We will continue to observe plants weekly, and perhaps the treatments will have an effect on later season diseases such as Rhizoctonia seedling blight or Cladosporiumn leaf spot, both of which have been diagnosed in this tunnel in previous years. We also may see treatment differences once harvest occurs and we can collect data on yield. In conducting this study we have identified a potential new pathogen of spinach in New England and are conducting lab and greenhouse studies to properly identify the fungus and determine if a new pathogen is present in the area. In discussing winter growing challenges at a major winter conference in New England this month, we learned that patchy germination and poor stand establishment is considered one of the major challenges to winter spinach growing in the Northeast and there remains much support for this type of research.