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Replacing Methyl Bromide for Preplant Soil Fumigation With Telone®, Chloropicrin and Tillam® Combination Treatments
This is an update of a July 1995 EPA report (Alternatives to Methyl Bromide, Ten Case Studies) entitled "Telone C-17 and Tillam Use on Florida Fresh Market Tomatoes". Considerable work has been done since that report with regard to these materials, and new data from field tests is reported here. This report contains information on the use of these pesticides in the production of tomatoes and other crops where methyl bromide is currently used.
Telone® C-17, a DowElanco product registered for preplant fumigation, contains 77.9 percent 1,3-dichloropropene (1,3-D) and 16.5 percent chloropicrin (an effective fungicide). Telone® C-17 and other Telone® products are recognized as effective preplant nematicides (Youngson et al. 1981) and have been proven to suppress some plant diseases (e.g., Fusarium wilt of cotton, Verticillium wilt of mint, and southern stem blight) (Melichar 1994, Dickson 1996). Tillam® 6E, a selective herbicide containing the active ingredient pebulate, is often used in conjunction with Telone® products for control of weeds (especially nutsedge) (Gilreath 1994, Gilreath 1996). Used together, these chemicals can achieve control of nematodes, weeds and a variety of diseases at levels comparable to those achieved with methyl bromide and chloropicrin combinations (Melichar 1994, Gilreath 1994, Olson et al. 1996, Gilreath 1996).
In a recent study, Telone® C-17 controlled root-knot nematodes and several diseases, and achieved yields similar to those obtained by fumigation with methyl bromide for tomatoes, peppers, and strawberries in Florida (Melichar et al. 1996b). Another study conducted at the University of Florida found that a combination treatment of Telone® C-17 and Tillam® on Florida tomatoes produced a significantly higher yield of medium and large fruit than methyl bromide/chloropicrin (67/33). There were no significant differences among treatments for yield of extra large fruit or for total yield in the study (Olson et al. 1996). In these and at least 4 other recent studies, Telone® C-17 was found to be as effective as, if not more effective than, methyl bromide and chloropicrin in controlling nematodes and certain soil-borne diseases (Chellemi et al. 1996, Dickson 1996, Noling et al. 1996, Duniway and Gubler 1996).
Telone® C-17 is a restricted use pesticide licensed for control of nematodes, symphylans, wireworms and certain soil borne diseases in the preplant fumigation of tomatoes, peppers, strawberries, melons, grapes, and 112 other crops. Telone® C-17 is also approved for use on nursery crops. This fumigant may be broadcast or row applied and should be sealed immediately after application. Sealing may be accomplished by uniformly mixing the soil to a depth of 3 or 4 inches and compacting the soil surface (broadcast fumigation) or by disrupting the chisel trace using press sealers, ring rollers or by reforming the beds and then using such equipment (row fumigation). In both application techniques, sealing can be improved by applying polyethylene film over the entire area or in strips (DowElanco 1994).
Research Summary
Several studies have been conducted comparing control of soil borne pests obtained with methyl bromide fumigation to that obtained by formulations containing Telone® products. Highlights of 1,3-D/chloropicrin research are presented in the two subsections below. The first section describes other formulations of Telone®, and the second section presents information on combination treatments consisting of Telone® C-17 with certain herbicides or integrated pest management (IPM) techniques.
Other Formulations of Telone®
Researchers have been investigating formulations of Telone® with varying percentages of chloropicrin for control of root-knot nematode, soil-borne diseases, and weeds. For example, Telone® C-25, Telone® C-30, and Telone® C-35 contain 25, 30, and 35 percent respectively in combination with Telone®, while Telone® II contains 1,3-D as the sole active ingredient. Increases in the percentage of chloropicrin are intended to raise the level of disease control achievable. In general, these formulations have compared favorably with methyl bromide and chloropicrin formulations, as described in the following bullets:
- Experiments compared the efficacy of Telone® C-17 and Telone® C-35 to methyl bromide/chloropicrin formulations. These experiments were conducted in 1996 at the Agronomy Research Farm at the University of Florida, Gainesville on tomatoes. Researchers found root-knot nematode galling indices to be lower in soil treatments of methyl bromide/chloropicrin (98/2), Telone® C-17 (1,3-D + 17 percent chloropicrin) and all treatments containing Telone® C-35 (1,3-D + 35 percent chloropicrin) than in the control. The study also found wilt caused by Sclerotium rolfsii (southern stem blight) was reduced to one or fewer plant hits per plot by methyl bromide/chloropicrin (98/2) and by all but one of the Telone® C-35 treatments (Dickson 1996).
- Telone® II/chloropicrin formulations were tested against methyl bromide/chloropicrin in a study supported by the California Strawberry Commission and ARS-USDA. In this study, Telone® II/chloropicrin formulations were broadcast fumigated and covered with polyethylene tarpaulins for 5 days before raising the beds. Relative to yields (100%) obtained following standard fumigation with methyl bromide/chloropicrin (67/33 @ 325 lb/acre), total yields for 1994 and 1995 trials, respectively, were 98 and 108 percent with Telone® II (1,3-D)/chloropicrin (70/30 @ 454-461 lb/acre), and 109 percent with Telone® II/Chloropicrin (70/30 @ 410 lb/acre, 1995 only) (Duniway and Gubler 1996).
- Telone® C-17, Telone® C-25, and Telone® C-35 were compared with methyl bromide in field tests conducted by the manufacturer of Telone® products in Florida, California and North Carolina. Researchers compared these three formulations of 1,3-D and chloropicrin to methyl bromide for nematode and soil-borne disease control. Telone® C-35 performed similarly to methyl bromide based on measurements of nematode counts, root damage, disease incidence and disease severity (Melichar et al. 1996a).
- Research trials compared the efficacy of Telone® C-17 and Telone® C-30 with methyl bromide on tobacco and peppers in Georgia. Researchers applied Telone® C-17 (@ 20 gal/acre), Telone® C-30 (@ 20 gal/acre), and methyl bromide/chloropicrin (@ 9 lbs/300 linear feet) to tobacco beds. They found no significant differences between the treatments for control of soil borne diseases (Pythium spp., Fusarium spp., Rhizoctonia solani), nematodes (root knot larvae, ring, spiral), or weeds (purple cudweed, cutleaf evening primrose, and old field toneflax) (Melichar et al. 1995).
Combination Treatments with Telone® C-17
Studies have shown the importance of using an herbicide in conjunction with Telone® C-17 in areas where nutsedge is a problem. For example, a Florida study evaluated the efficacy of Telone® C-17 on nematodes (Meloidogyne spp.), diseases (fusarium wilt, Fusarium oxysporum f.sp. lycopersici, and fusarium crown and root rot, Fusarium oxysporum f.sp. radicis-lycopersici), and weeds (yellow nutsedge, Cyperus esculentus, and purple nutsedge, Cyperus rotundus). Telone® C-17 disease and nematode control was equivalent to methyl bromide, however, Telone® C-17 did not provide equivalent weed control (Melichar et al. 1996b).
Although combination treatments with Tillam® have been very effective against weeds, researchers have been looking into other herbicides and combination treatments for use with Telone®, because Tillam® is currently registered for only three crops -- tobacco, tomato, and sugarbeets (Helena Chemical Company 1997). Summaries of research results for herbicides including Tillam® and IPM practices that could be used in combination with Telone® products are presented below.
One of many studies in which a combination treatment of Telone® C-17 and Tillam® was proven to be as effective as treatment with methyl bromide/chloropicrin was conducted at the North Florida Research and Education Center. Telone® C-17 (@ 35 gal/acre) and Tillam® 6E (@ 4 lbs a.i./acre) were applied and covered with black polyethylene mulch immediately after fumigation. Telone® C-17/Tillam® produced the highest yield of medium and large fruit of all the treatments and significantly higher yield of these fruits than methyl bromide (Olson et al. 1996).
Researchers have also combined Telone® C-17 with Vapam®. Experiments conducted at the University of Florida in 1995 compared the efficacy of methyl bromide/chloropicrin (98:2 @ 400 lb/acre), chloropicrin (@ 350 lb/acre), and Telone® C-17 (@ 35 gal/acre). Each plot was then treated with 956 ml Vapam®. Although chloropicrin treatments resulted in numerically higher strawberry yields, no significant differences in January yields were identified in any of the fumigation treatments (Noling et al. 1996).
A 1996 study compared the efficacy of methyl bromide/chloropicrin on peppers to that of Telone® C-17 and Devrinol® (napropamide) herbicide, the only in-bed herbicide labeled for peppers. The trial was conducted late in the season, thereby allowing time for only 2 harvests. Telone® C-17 (@ 21 gal/acre) and Devrinol® (@ 3.4 lb a.i./acre) produced significantly more peppers than the methyl bromide treatment during the first harvest, and resulted in a minor cumulative yield advantage after both harvests (Mueller 1997).
Another study considered the effects of soil solarization in combination with Telone® C-17. This Florida study compared the efficacy of soil solarization/Telone® C-17 fumigation with those of standard methyl bromide application on tomatoes. Soil solarization in combination with reduced rates of methyl bromide plus chloropicrin or Telone® C-17 provided significantly greater control of root galling than soil solarization alone. In addition, rows treated with soil solarization reduced the incidence of southern blight (Sclerotium rolfsii) to less than 0.1 percent, whereas rows treated with only methyl bromide experienced a 3.7 percent incidence of disease (Chellemi et al. 1996).
Availability and Regulatory Issues
Telone® products are currently available in Florida. Although regulatory issues (worker exposure health-related concerns) were once a limiting factor in California (Melichar 1995), Telone® II is now available in California. The California Department of Pesticide Regulation draft permit conditions restrict use of Telone® products to 5,000 gallons per township (i.e., 36 square mile range) for application depths less than 18 inches and 9,500 gallons for depths greater than 18 inches (Duniway 1997, Roby 1997).
DowElanco is considering drip irrigation as a means to deliver Telone®, while reducing 1,3-D loss to the atmosphere. Several field studies have proven 1,3-D/chloropicrin combinations to be effective nematicides when applied through drip irrigation. Drip irrigation of Telone® II (1,3-D) is registered for melons in Arizona and studies are underway to determine the extent of disease control achievable when using drip applied 1,3-D/chloropicrin combinations (Mueller 1995).
Costs
Because Tillam® is frequently used in combination with Telone® C-17 during tomato production and because both are applied in a manner similar to the application of methyl bromide/chloropicrin, alternative costs reflect the costs of the raw materials, only. Other costs associated with Telone® C-17/Tillam® or methyl bromide/chloropicrin fumigation include labor costs, machinery costs and the costs of time delays associated with protecting against phytotoxicity and addressing human health concerns. An analysis of the raw material costs associated with fumigation for tomatoes in Florida is presented in Table 1. Please note that application rates are presented in terms of bed fumigation rather than broadcast fumigation.
| Cost Factor | Telone® C-17/Tillam® | Methyl bromide/ chloropicrin (98:2) | |
|---|---|---|---|
| Telone® C-17 | Tillam® 6E | ||
| Application Rates | 17.5 gal/acre | 2 lb a.i./acre | 200 lb a.i./acre |
| Cost per Unit | $12.75-13.75/gal | $7.66/lb a.i.
($45.95/gal) |
$1.12/lb |
| Total Material Cost | $247/acre | $224/acre | |
References
- Asgrow Agricultural Supply, Collier County, FL, personal communication, 1995.
- Chellemi, D.; McSorley, R.; Rich, J.R. Presented at the Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 42. Dickson, D. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 46.
- DowElanco, Indianapolis, IN. Label Code 112-70-007, EPA Approval 4/93, 1994.
- Duniway, J.M.; Gubler, W.D. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 37.
- Duniway, J.M., University of California, Davis, CA, personal communication, 1997.
- Eger, J., DowElanco, Indianapolis, IN, personal communication, 1997.
- Gilreath, J., Gold Coast Research and Education Center, University of Florida, Braedenton, FL, personal communication, 1997.
- Gilreath, J.P.; Jones, J.P.; Noling, J.W. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 44.
- Gilreath, J.P.; Jones, J.P.; Overman, J. "Development of Alternatives to Methyl Bromide in Tomato Production"; report of Tomato Research: Supported by the Florida Tomato Committee 1993-1994; Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 1994.
- Helena Chemical Company, personal communication, 1997.
- Melichar, M.W.; Eger, J.E.; Huckaba, R.M.; Mueller, J.P.; Peterson, L.G. Presented at the 1995 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA, November 1995; paper 51.
- Melichar, M.W.; Huckaba, R.M.; Eger, J.E.; Mueller, J.P. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996a; paper 94.
- Melichar, M.W. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996b; paper 93.
- Melichar, M. Presented at the 1994 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Kissimmee, FL, November 1994; paper 15.
- Mueller, J.P. Presented at the 1995 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA, November 1995; paper 28.
- Mueller, T., Roger Seed Company, Naples, FL, personal communication, 1997.
- Noling, J.W.; Gilreath, J.P.; Chandler, C.K.; Legard, D.E. Presented at the Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November, 1996; paper 39.
- Olson, S.M.; Rich, J.R.; Chellemi, D.O. Presented at the 1996 Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 41.
- Roby, D., DowElanco, Indianapolis, IN, personal communication, 1997.
- Youngson, C.; Turner, G.; O'Melia, F. Control of plant parasitic nematodes on established tree and vine crops with Telone II soil fumigant. Down to Earth 1981, 37(3).
Please note that this publication discusses specific proprietary products and pest control methods. Some of these alternatives are now commercially available, while others are in an advanced stage of development. In all cases, the information presented does not constitute a recommendation or an endorsement of these products or methods by the Environmental Protection Agency (EPA) or other involved parties. Neither should the absence of an item or pest control method necessarily be interpreted as EPA disapproval.
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