Grantee Research Project Results
Final Report: Ozone Biocidal Properties and Stimulation of Trichoderma harzianum (Strain T- 22) When Applied in Combination as an Environmentally Benign Alternative for Methyl Bromide
EPA Contract Number: 68D99035Title: Ozone Biocidal Properties and Stimulation of Trichoderma harzianum (Strain T- 22) When Applied in Combination as an Environmentally Benign Alternative for Methyl Bromide
Investigators: Hayes, Christopher K.
Small Business: BioWorks Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Description:
The purpose of the research was to examine the use of a commercially available biofungicide in conjunction with ozone as a possible replacement for Methyl Bromide. Methyl Bromide use is rapidly being phased out in agriculture because of concerns about its long-term effects on the environment. By 2005, Methyl Bromide will no longer be commercially available. Alternatives need to be tested to determine the most effective options for the grower.In this study, ozone and a commercially available biofungicide were used in various combinations to determine their effectiveness as a replacement for Methyl Bromide. One or two applications of ozone at various concentrations applied alone or in combination with a registered biofungicide was used to treat strawberry plots at two sites. The parameters used to measure effectiveness included yield and total plant death, as a measurement of disease control. The chemical, Telone, as well as nontreated plots were added as a check.
The gas ozone was applied either once, as a pre-plant treatment, or applied a second time during midseason. The amount of ozone used varied, from low (25 lbs./A) to medium (100 lbs./A) to high amounts (400 lbs./A). Two different formulations, a granular and a wettable powder, of a commercially available biofungicide, Trichoderma harzianum, were used with the various ozone applications.
The overall objectives of the research were to examine the conditions under which ozone and a commercially-produced biofungicide would protect against soil pathogens in strawberry plots. Originally, the following research objectives were proposed:
- Determine the optimal range of rates under which the biofungicide was stimulated by ozone applications.
- Compare ozone and a commercial biofungicide combination against replacement chemicals to be used in strawberry production.
- Perform laboratory surveys of the possible effects of ozone and the biofungicide on other soilborne microflora.
- Extrapolate the field trial results to verify the economics of the process on a larger scale.
Summary/Accomplishments (Outputs/Outcomes):
In general, a limited positive yield response was observed with the biofungicide applied alone when compared to untreated control. One application of ozone, in conjunction with the biofungicide, showed a uniformly positive response in No. 1 berry yields and total yields compared to untreated controls. Midseason applications of ozone showed a positive response when compared to untreated controls at one site, but had a negative response when compared to untreated controls at the other site. Telone treatments consistently gave the best yields, both in No. 1 berry yields and total yields, regardless if the biological was applied. Telone treatments more than doubled yields compared to untreated controls.The single application of ozone caused only a slight decline in microbial populations of aerobic bacteria, anaerobic bacteria, actinomycetes, nitrogen-fixing bacteria, yeasts and molds, and Verticillium spp. The biofungicide was found to be present on the roots, but its concentration was low. The concentration of the biofungicide did not increase with a mid-season ozonation, which contrasts to what has been observed in past studies. Plant death was reduced for most treatments when compared to nontreated controls. The least amount of plant death was recorded on the Telone treated plots.
Conclusions:
Tests were conducted to determine if ozone, when used as a biocide, followed by a commercial biofungicide could be used as an alternative to methyl bromide. In the past, this combination of products has been shown to be highly effective. The chemical, Telone, was included in the test as a control since growers have commercially used it. Ozone was applied at three different rates either once or again during mid-season. In all plots, biofungicide application followed ozonation. The biofungicide was applied as a granule in the planting hole, or roots were dipped into a dry powder before placement in the field.In all cases, yield and percentage plant survival was greatest in the chemical treated plots. Some of the plots receiving ozone and the biofungicide also gave yield increases and increased plant survival when compared to the untreated controls, but fell short of the levels recorded for the chemical.
Root washings demonstrated that the biofungicide had colonized the roots by both methods of application. Root washings after mid-season ozonation showed no increase in the level of the biofungicide on the roots, a direct contradiction to earlier trials. Using ozone alone or in conjunction with the biofungicide were not as favorable as we have seen in prior years' trials at the same site. We believe the differences were primarily due to the much lower ozone injection flow rate used when injecting ozone in this year's trials. This year ozone was injected at the rate of 30 cfh/20 ft of bed through 0.5 gph drip tubing. In prior years' trials in Watsonville, ozone was injected at the rate of 280 cfh/20 ft. of bed through "modified" 4.0 gph tubing. It was decided to use lower flow rates at MBA this year based on the desire to integrate the ozone technology with current farming practices which primarily use 0.5 gph tubing or tape for irrigation. Also, 3 straight years of successful trials injecting ozone at these lower flow rates in sandy soils in tomato, carrot, and broccoli trials have been done in trials conducted with Dr. Becky Westerdahl of UCD at the UC Extension Research Station in Irvine California. Laboratory trials had also been conducted that indicated that lower ozone gas flow rates were equivalent to higher flow rates in killing nematodes in sandy soils. However, all of the work was done with nematodes and in very sandy soils. Also, in retrospect it was observed that all of these crops are fairly rapidly growing compared to strawberries. It may very well be that the zone of effect of ozone has to be much larger in strawberries to provide a longer period of protection and this could not be completely provided with the lower flow rates used this year.
Since the biofungicide is most effective as a preventative against soil phytopathogenic fungi, it must be used in conjunction with something else especially in high disease conditions, which occurred at the test sites. Record rainfall during the trial period favored the development of high disease pressure. This, in combination with suboptimal kill by the ozonation, reduced protection by the biofungicide.
In this study, ozone was used to first reduce or eliminate most of the microflora in the plots. Following ozonation were treatments with the biofungicide. In most cases, this combination gave increased yields and a decrease in plant loss when compared to the nontreated plots. In all cases, the chemical treated plots had better yields and lower plant loss than the combination treatment. In lab studies, it was shown that the use of the smaller diameter pipe restricted ozone movement in the soil. Improper initial knock-down, followed by the high disease pressure created by the excessive rain observed after planting were too much for the combination technique. Even the chemical plots experienced plant loss due to high disease pressure.
The results of this study suggest that the combination technique employed in this study is a viable alternative to the commercial use of Methyl Bromide. Indeed, they warrant additional research to determine the optimum method to introduce ozone into the soil profile and to optimize the amount of the biofungicide needed in field situations. Passed performance with the ozone/biofungicide combination has been shown to be effective at controlling root rot and increasing yield. Additional studies are needed to optimize the system.
Supplemental Keywords:
Biocontrol, Methyl Bromide, Ozonation, Strawberries, Telone., Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Toxics, Water, Ecosystem Protection/Environmental Exposure & Risk, Sustainable Industry/Business, National Recommended Water Quality, cleaner production/pollution prevention, Ecosystem/Assessment/Indicators, Contaminant Candidate List, New/Innovative technologies, Agronomy, Biology, Engineering, Engineering, Chemistry, & Physics, Economics & Decision Making, Futures, ozone, Methyl bromide, soil, fungicide, agriculture, irrigation, agrochemcial, nematode parasites, pollution prevention, diseaseThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.