Glirus Section Proc. Fla. State Hort. Soc. 100:58-61. 1987. GLUFOSINATE (IGNITE): A NEW PROMISING POSTEMERGENCE HERBICIDE FOR CITRUS Megh Singh and D. P. H. Tucker ported that the pattern of plant responses to glufosinate University of Florida, IFAS and glyphosate was distinctly different. Glufosinate has li Citrus Research and Education Center mited translocation to rootstocks and rhizomes, etc. of per 700 Experiment Station Road ennial weeds as compared to glyphosate. Therefore, even Lake Alfred, FL 33850 tual regrowth from these plant parts will occur. Glufosinate may be a useful herbicide for weed control Additional index words. Basta, Buster, Conquest, Finale, in no-tillage systems, for orchards and vineyards, and for HOE-00661, HOE-39866, glufosinate-ammonium. general weed control in rangeland and non-cropland situ ations. Kapusta (6) reported effective control of several weed species using glufosinate in no-till fields. Glufosinate Abstract. Glufosinate [ammonium (3-amino-3-carboxypropyl) at 1.0 to 2.0 kg/ha provided effective control of several methyl phosphinate] is a non-selective postemergence her annual and perennial weeds in vineyards, citrus, and other bicide for the control of a broad spectrum of grasses and fruit orchards as well as in uncultivated areas (3). Lawson broad leaf weed species. It is known worldwide by various names such as Basta, Buster, Conquest, and Finale. Glufosi and Wiseman (9) reported satisfactory runner control in nate controls both annual and perennial weeds. The activity strawberries without the adverse effect on the growth and of glufosinate is somewhat slower than paraquat but dis yield of the crop. Glufosinate at 4.0 kg/ha provided tinctly faster than that of glyphosate. The effect on perennial adequate control of cogangrass (Imperata spp.) (10) and at weeds is longer lasting than paraquat but not as long as the 2.0 kg/ha provided 93% control of purple nutsedge (7). control exhibited by glyphosate. Glufosinate inhibits the syn Wilson et al. (11) reported the control of rye and horse- thesis of glutamine synthetase which is required for the fixa weed with glufosinate. Glufosinate at 1.0 kg/ha controlled tion of ammonia in plant cells. Without the activity of a broad spectrum of annual and perennial weeds in or glutamine synthetase, ammonia (NH3) concentration in chards in Europe, though some species required higher creases to toxic levels in the plants. Glufosinate is a herbicide rates. In most cases two applications were adequate to pro of relatively low toxicity; the oral LD50 in female rats is 1620 vide full season weed control. The summer application in mg/kg. It is rapidly degraded biologically in soil. Glufosinate many cases was more effective than the spring one. This is being developed in the United States for no-tillage crops, may be due to weeds which were not fully emerged at the orchards, vineyards and for non-cropland situations. Evalua time of early application. The leaves of stone and pome tion of glufosinate for the control of bahia (Paspalum fruit trees which were directly sprayed showed necrotic notatum Fluegge), bermuda [Cynodon dactylon (L) Pers.], symptoms but no signs of translocation were found (8). guinea (Panicum maximum Jacq.), para [Brachiaria mutica Glufosinate shows excellent potential as a herbicide for (Forsk.) Stapf], torpedo (Panicum repens L.) and signal weed control in citrus. Thus, it is appropriate to review the [ Brachiaria piligera (F. Muell.) Hughes] grasses indicated that information from the manufacturer's technical informa glufosinate will be a useful herbicide for weed control in cit tion bulletins (1, 2) for the benefit of citrus industry per rus. Further work needs to be done on its compatibility as a sonnel. tank mix with residual herbicides. Chemical and Physical Properties Glufosinate is a primary amine with an extended car Chemical Name: Ammonium (3-amino-3-carboxypropyl) bon chain. The parent acid of glufosinate was first discov methylphosphinate ered as a microbial metabolite of Streptomyces viridoc- Common Name: Glufosinate hromogenes in 1972 and was named phosphinothricin or Chemical Structure: bialophos (5). Glufosinate is a non-selective, foliar applied herbicide for the control of a broad spectrum of grasses and broadleaf weeds. Glufosinate controls both annual and perennial weeds (1). In general, lower rates of glufosinate are needed to control dicot weed species. NH, CH - p - CH-CH-CH - COOH Glufosinate acts more slowly than paraquat and faster 5 I 2 d\ than glyphosate. It controls perennial weeds longer than paraquat but not as long as glyphosate. Bellinder and Wil son (4) reported the effective control of several weed species using glufosinate. The symptom response to glufosinate occurred within 36 hr, whereas response to Trade Name: The trade name in the U.S.A. is IGNITE. glyphosate was observed after 4 to 7 days. They also re- Molecular Weight: 198.19 Appearance: Crystalline powder Florida Agricultural Experiment Station Journal Series No. 8630. Color: White to light yellow 58 Proc. Fla. State Hort. Soc. 100: 1987. Odor: Slightly pungent duction, photorespiration and amino acid metabolism) is Solubility: Soluble in water bound to glutamic acid to form glutamine. This process is Vapor Pressure: Not determinable due to decomposition catalyzed by the enzyme glutamine synthetase. Glufosi- Stability: Two years in original sealed containers stored at nate-ammonium inhibits the activity of this enzyme. Am 25 ± 5 C. monium metabolism in the plant is disturbed shortly after Formulation: It is a blue color liquid containing 200 g/liter application of the product so that ammonia (NH3), a strong active ingredient. phytotoxin, accumulates and kills the cells. Photosynthesis is also inhibited. Toxicological Properties Since ammonia is produced mainly during the reaction linked with photosynthetic electron transport, its accumu Aute Oral Toxicity: LD50 Male Rat—2000 mg/kg body lation is higher in treated plants exposed to light than in weight those kept in darkness or shade. Exposure to light also Female Rat—1620 mg/kg body accelerates the development of phytotoxic symptoms, weight which begin with the development of pale yellowish discol Acute Dermal Toxicity: LD50 Male Rat—4000 mg/kg body oration of the green plant parts. Plants wilt and die within weight 1 to 2 weeks. Female Rat—approximately 4000 mg/kg body weight Metabolism in Soil and Plants Skin and Eye Irritation: No primary irritation of skin and eye mucosa was observed in rab Physical and chemical properties of the active ingre bits. dient glufosinate-ammonium are very similar to those of Subchronic Toxicity: This is based on a 90-day feeding test. protein compounds synthesized by living organisms. The No effect level—rats—18 mg/kg body weight/day active ingredient is highly stable as a chemical compound dogs—2 to 8 mg/kg body weight/day but its degradation is rapid in a microbiologically active Embryo Toxicity: No observable effect level— environment such as soil or surface water. Consequently, rats—10 mg/kg body weight there should be no accumulation of the substance in the rabbits—6.3 mg/kg body weight food chain. Model tests carried out in the laboratory Mutagenicity: Mutagenic tests in vitro and vivo did not suggested that the active ingredient could leach into the show any mutagenic activity. deeper layers of the soil. Field studies, however, de Neurotoxicity: No signs of neurotoxic effects in hens have monstrated that under natural conditions there is no been observed. movement into the soil layers deeper than 15 cm. Because Ecological Data: glufosinate is a relatively new herbicide, there are no de Toxicity to Fish: LD50 (96 hr) for Rainbow trout is > tailed studies on its mobility in different soils under differ 320 mg/liter water. ent environmental conditions. Such studies are needed to Bees: Non-toxic to bees. clearly establish its leaching behavior in soil. This suggests rapid biodegradation of glufosinate-ammonium. Further Biological Properties tests with radioactive labelled material showed that glufosi nate-ammonium is rapidly decomposed to 3-methyl phos- Glufosinate must be applied postemergence to the phinicopropionic acid and finally to carbon dioxide. No weeds. Annual grasses and broadleaf weeds should have residues of the active ingredient have been detected using developed sufficient foliage to allow uptake of the her the commercial formulation in any of the major crops bicide. Perennial weeds are most sensitive when treated at treated for weed control (fruits, grapes, vegetables, etc.); the time of maximum translocation of photosynthetic however, traces of the metabolite, 3-methyl phosphinicop- products to the storage plant parts, i.e., beginning of flow ropionic acid were detected. ering to full flowering stage. Favorable environmental con ditions for active plant growth are preconditions for effec Spectrum of Herbicide Activity tive weed control with glufosinate. Cold and dry weather reduce plant metabolic activity and thus, the product effi Glufosinate is effective against a wide range of monocot cacy. Lower light intensity may increase the activity of and dicot annual and perennial weeds. Generally, peren glufosinate. Since the spray deposit of glufosinate is likely nial weeds require a higher rate than annual ones. Major to be washed off by rain, no precipitation should fall dur weeds controlled by glufosinate are listed in Table 1 ing the first 6 hr after application to ensure adequate up (monocot) and Table 2 (dicot) (1). take of the herbicide (2). We have evaluated glufosinate for the control of annual and perennial grasses in citrus groves. The grasses in our study included bahia, bermuda, para, guinea, torpedo, and Mode of Action signal. The rates tested were 1.12 and 2.25 kg a.i./ha. The active ingredient of Ignite, glufosinate-am- Glufosinate provided excellent burn down of all grasses at monium, is a non-selective, partially systemic contact her both rates. Signal grass was most sensitive, para and tor bicide.
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