Developing Alternatives to Methyl Bromide: A Focus on Acrolein (2-Propenal)

Abstract

Methyl bromide, a soil fumigant with biocidal action, is used in agriculture to control weeds, fungi, bacteria, nematodes, and arthropods. Due to methyl bromide’s active role in atmospheric ozone depletion, its usage will be phased-out according to the guidelines of the United Nation’s Montreal Protocol. Acrolein is currently labeled as an aquatic herbicide for use in irrigation canals, however little has been done to explore the nematicidal effects of acrolein or to develop strategies and methods to use it in agriculture as an alternative to methyl-bromide. Herbicidal efficacy: In greenhouse trials, morningglory (Ipomoea lacunose L,/I.hederacea Jacq.), sicklepod (Senna obtusifolia (L.) H. S. Irwin and Barneby), jimsonweed (Datura stramonium L.), large crabgrass (Digitaria sanguinalis (L.) Scop.), and yellow foxtail (Setaria glauca L. P. Beauv.) were controlled with acrolein rates = 100 mg/ kg soil, while yellow nutsedge (Cyperus esculentus L.) required rates = 250 mg for complete control. Combinations of acrolein with halosulfuron, s-metolachlor, EPTC, and propionic acid were successful for reducing rates; however, it was also found that when applied in the same drench, metam sodium and acrolein were antagonistic. Nematicidal effects: Results from greenhouse trials indicated that drench applications of acrolein at rates 50 to 100 mg/ kg soil effectively controlled the reniform nematode. Control of root-knot by drench application in greenhouse studies required rates of 60 to 200 mg/ kg soil. Acrolein was also effective at controlling stubby-root (Paratrichodorus minor (Colbran) Siddiqi) and spiral (Helicotylenchus dihystera (Cobb) Sher.) nematodes. Rates required to control plant parasitic nematodes did not drastically affect microbivorous nematode populations. Soil Enzymatic Activity: In general, as acrolein doses were increased, there was a reduction in soil catalase, a-glucosidase, ß-glucosidase, a-galactosidase, ß-galactosidase, sulfatase, phosphatase, urease, and chitobiase activity. Acrolein treatments resulted in a slight decrease in soil pH and a slight increase in soil electrical conductivity. Effects on Fungi, Bacteria, and Actinomycetes: Bacterial colonies decreased as rates of acrolein increased to 200 mg/ kg soil. In contrast, the number of actinomycetes and fungi increased as rates of acrolein increased. Furthermore, while the number of fungal colonies increased, diversity decreased to nearly one fungal genus: Trichoderma. Conclusions: Acrolein exhibits potential as an alternative to methyl-bromide; however, high rates or combinations with other pesticides are needed to obtain equivalent pest control to that of traditional methyl-bromide/chloropicrin applications.