USDA/EPA MeBr Working Group Report
on Efficacy and Regulatory Issues of Telone

By Ken Vick (1), Peter Caulkins (2) and Barbara Zapp (3).

(1) Co-chair, Agricultural Research Service, USDA (2) Co-chair, Office of Pesticide Programs, EPA (3) Program Assistant, Agricultural Research Service, USDA.

The USDA/EPA Methyl Bromide Working Group was established in 1994 by USDA Deputy Secretary Rominger and U.S. Environmental Protection Agency (EPA) Administrator Browner to coordinate the USDA's research program with the EPA's registration programs. This Working Group was referred to in a letter from Deputy Secretary Rominger which appeared in the October 1999 issue of this newsletter. Recent activities of this group were also reviewed in that issue.

A Working Group meeting was held in Orlando, Florida, May 11, 2000, to discuss efficacy and regulatory issues of the Dow AgroSciences product, Telone. Many scientists report that Telone in combination with a herbicide to control weeds and chloropicrin to assist with soil pathogens provides efficacy approaching or equal to that of methyl bromide/chloropicrin. There are serious regulatory impediments to its use in Florida and this meeting was held to discuss strategies for Telone use which might enable farmers to make more extensive use of Telone as a methyl bromide alternative. Approximately 60 people attended the meeting, including: farmers; Federal, State and university agricultural scientists; extension agents; Federal, state and county environmental protection agency personnel; commodity representatives for the major horticultural crops in Florida; Dow AgroSciences technical representatives; and several members of the USDA/EPA MB Working Group.

Major Telone issues summarized by two major growers in Florida and southeastern states are as follows (the importance of each issue may vary with local conditions):

1. Personal Protection Equipment: Telone recently completed the USEPA reregistration process—which took over a decade to complete. The label for Telone requires that workers in the field wear complete protective clothing (moon suits), and full face respirators while fumigation is in progress. In the Florida farming system, plant beds are raised at the same time that fumigation takes place. This activity requires that as many as 40 workers be in the field during fumigation—all required to wear moon suits. Fumigation normally takes place in late summer when temperatures are often in the mid 90's (F). The required protective clothing is very hot under these conditions and OSHA regulations will limit each worker to a few minutes of work per hour. Growers find this restriction to be economically unfeasible.

2. Broadcast Fumigation: This method involves fumigating the entire field (rather than just the plant beds) and forming the beds after the field entry waiting period is over. This has the advantage of greatly reducing the personnel (2 or 3) needed in the field during fumigation. This method was found to be less effective than bed fumigation (up to 40 percent reduction in efficacy). Research continues to determine the cause for the loss of efficacy.

3. Buffer Zone: For Telone, a 300 foot buffer zone (untreated area) between the treated area and any occupied dwelling is required. The Florida strawberry industry seems particularly vulnerable to the buffer zone restrictions because fields are typically small (averaging about 20 acres) and population densities are relatively high in the strawberry producing area. A 20-acre strawberry field with adjacent housing would only be able to treat about 8 acres due to buffer zone requirements. It is economically unfeasible with the cost of land and farming overhead for a strawberry farmer to fallow 12 out of 20 acres.

4. Consistent Efficacy: Tests in research plots and grower fields give results comparable to methyl bromide/chloropicrin in some tests but other tests show somewhat lower efficacy. A grower with an extensive alternatives testing program estimated the efficacy reduction to be about 4 percent for his tests. Also, one methyl bromide/chloropicrin fumigation is typically used for 2 crops (double cropping) but there has been little research on effectiveness of Telone-based systems for effectiveness on the second crop. Application through drip irrigation has been effective in California and more research is planned for Florida to increase effectiveness and possibly reduce atmospheric emissions. But cost of the drip tape, poor quality of the water (water emmiters tend to stop up when water quality is not good) and different soil types in Florida, may make this procedure less workable than in California.

5. Herbicide Partner: Telone has minimal effect on weeds and will not control nutsedge, probably the number one problem in Florida. There is no effective herbicide registered to partner with Telone/chloropicrin for peppers, a major crop in Florida. Weed control will also be a problem in strawberries, cucumbers and eggplants.

6. Label Changes for Tillam: On a brighter note, data collected from research plots using Telone/chloropicrin along with Tillam for weed control indicates this system provides efficacy approaching that of methyl bromide/chloropicrin for tomatoes. Tillam, however, is only provisionally approved for hand-transplanted tomatoes contingent on research by the registrant (registrant has 2 years) to produce data to address worker safety issues for Tillam.

These issues serve to illustrate the complexity of replacing methyl bromide in an era of low farmer profits and intense competition from commodities imported from Mexico and elsewhere. Telone has some pronounced advantages: it is an excellent nematicide—probably better than methyl bromide—and nematodes are a major pest in Florida with its warm winters and sandy soils; and Telone has completed the reregistration process—many alternatives being investigated by researchers are not registered—a process that even with a willing, well-financed registrant, requires multiple years.

The goal of the USDA/EPA Methyl Bromide Working Group is to make available to growers and other methyl bromide users the widest array of alternatives possible within the time constraints of the phaseout period and the requirement that pesticides be useable in a environmentally friendly manner. Research will continue to develop methodologies that will allow a greater use of Telone and other chemical and non-chemical alternatives to methyl bromide. Future updates of the MB Working Group will focus on other alternatives and research efforts to make them more effective and available to farmers.

Last Updated: July 24, 2000