Propargyl Bromide and Other Fumigants for Nematode Control

J.W. Noling¹ and J.P. Gilreath² University of Florida, Institute of Food & Agricultural Sciences
¹Citrus Research & Education Center, 700 Experiment Station Rd., Lake Alfred, FL 33850
²Gulf Coast Research & Education Center, 5007 60th St. E., Bradenton, FL 34203

Although early stage field and laboratory investigations showed promising results as a broadspectrum fumigant for soilborne pest control (patent application results, 1953), propargyl bromide was apparently never fully pursued because of the explosiveness of the compound and because of the manufacturing cost differential between propargyl bromide and methyl bromide (methyl bromide is, after all, a waste product of the halogen fire extinguishers). In contrast, field research at the CREC Lake Alfred was initiated with the assumption that propargyl bromide would not ultimately be characterized as an ozone depleting substance and that formulation problems contributing to its explosiveness could be resolved. Cost factors were not a consideration. To reduce or eliminate the explosive nature of propargyl bromide, it is currently formulated with toluene (20%). Given that toluene is a known carcinogen, an alternative stabilizer will undoubtedly be required to survive the registration process. Soil-borne pest and disease control in Florida tomato production had been achieved for over 25 years with the broadspectrum soil fumigant methyl bromide. The objectives of the studies reported herein were to evaluate the use and efficacy of various alternatives as preplant soil treatments for control of the southern root-knot nematode, Meloidogyne incognita, yellow nutsedge, Cyperus esculentus, and to measure resultant impacts on tomato plant growth, development, and yield. During the spring of 1999, a single replicated field experiment was conducted to compare nematode control and tomato yields in response to broadcast equivalent propargyl bromide application rates of 150 and 300 lb/a compared with Basamid (400 lb/a), methyl bromide 98/2 (400 lb/a), Telone C17 (35 gal/a), and an untreated control. Propargyl bromide and Telone C17 soil injections were made using a Hamilton Gas Tight syringe installed with a 25 cm-long stainless steel needle. After a two week soil aeration period, tomato plants were grown to maturity and harvested twice. At each harvest fruit was sorted and weighed into three size categories including medium, large, and extra large tomatoes. Following harvest, these same plants were cut at the soil line and the foliage weighed. Immediately after foliage removal the plants were uprooted and the root systems evaluated for root gall severity based on a visual rating scale of zero to ten. Final soil population density samples were then removed after root gall assessment.

The results of this study showed that all fumigant treatments significantly (P=0.05) reduced final harvest soil population density of Meloidogyne incognita and tomato root gall severity compared to the untreated control. No differences (P=0.05) or dose response relationship between application rates of propargyl bromide, Telone C17, or methyl bromide were observed in these parameters. Tomato yields were significantly (P=0.05) increased by all fumigant treatments compared to the untreated control. Both propargyl bromide (150 lb/a) and Telone C17 increased (P=0.05) tomato yields compared to the Basamid treatment. In summary, propargyl bromide proved to be a compound which was easy to handle and apply, demonstrated excellent nematicidal and herbicidal activity, and produced tomato yields equal to or superior to that of methyl bromide.

Field research with propargyl bromide is continuing, however other factors and regulatory concerns must be addressed before being realistically considered a potential alternative to methyl bromide. In addition, to effectively reduce field application rates of propargyl bromide because of cost considerations may require the coapplication (synergism) of other fumigants such as chloropicrin. In this regard, future field testing may require further expansion. Methyl bromide is commonly used with chloropicrin when soilborne disease constitutes a problem. This suggests that future testing of propargyl bromide should be done in combination with chloropicrin.

Last Updated: February 24, 2000