Effects of Glufosinate-Ammonium and Terbuthylazine on Germination and Growth of Two Weed Species
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Plant Protection Quarterly Vol.9(1) 1994 15 this study. The objective of this study was, therefore, to evaluate the effects of these Effects of glufosinate-ammonium and terbuthylazine two herbicides on germination and seed- ling growth of two weed species preva- on germination and growth of two weed species lent in plantation crops of Malaysia. Ismail Sahid and K. Kalithasan, Department of Botany, Universiti Materials and methods Kebangsaan Malaysia, 43600 UKM, Bangi, Malaysia. Weed seeds Seeds of a broadleaf weed, A. gangetica, Summary and a grass species, P. conjugatum, were Effects of glufosinate-ammonium and control 100% of the weed seed pop- collected from a rubber estate near Sungai terbuthylazine on germination and ulations. Clearly, a weed control measure Buluh, Selangor. After air-drying, har- growth of two weed species were evalu- has to severely reduce the weed seed vested seeds were kept under laboratory ated in the laboratory and in the green- population in the soil to be effective. Re- conditions in air-tight glass bottles until house. Germination of Asystasia gang- search on the effects of herbicide on seeds used. etica (L.) T. Anders. and Paspalum in soil may contribute to knowledge on conjugatum Berg. declined considerably the effective control of weed seed Herbicides when seeds were germinated in petri populations. Glufosinate-ammonium (ammonium-DL dishes containing either glufosinate-am- The effects of herbicidal treatment on -homoalanin-4-yl(methyl) phosphinate) monium or terbuthylazine at 250 mg L-1. seed reserves in the soil or on subsequent was obtained from Hoechst (Malaysia) Glufosinate-ammonium also caused a growth of weed seedlings form an impor- under the trade name Basta®; it contains marked reduction in radicle elongation tant aspect of weed control. However, not 150 g a.i. L-1. Terbuthylazine (2 tert. of Asystasia, whose fresh weight was many studies have reported on the effects butylamino-4-chloro-6-ethylamino-5- reduced proportionately with increasing of herbicide on seed germination; it seems triazine) was supplied by Ciba-Geigy concentrations of either glufosinate- that only paraquat, glyphosate, prona- (Malaysia) under the trade name ammonium or terbuthylazine. Terb- mide, propham and metribuzin (Young Gardoprim®; it contains 500 g a.i. L-1. uthylazine was more effective than et al. 1984, Salazar and Appleby 1982) glufosinate-ammonium in reducing ger- have been studied for such effects. Laboratory experiment mination and growth of both weeds Glyphosate or paraquat applied directly Fifty seeds each of the two weed species when applied either to seeds on the soil to seeds on the soil surface may reduce were placed on 9 cm filter paper in a se- surface or to the soil prior to sowing. germination and/or seedling growth of ries of petri dishes that contained 8.0 mL Storage of seeds after treatment with several grass species (Salazar and of the herbicide solution or distilled wa- either herbicide reduced the inhibitory Appleby 1982, Egley and Williams 1978, ter. The experimental design was a effect of the herbicide on germination Klingman and Murray 1976). randomized complete block with five rep- and growth of the weeds. Residual Glufosinate-ammonium is used in lications per treatment. The concentra- terbuthylazine in soil 14 days after treat- plantation crops such as cocoa, oil palm tions of glufosinate-ammonium or ment could still reduce germination and and rubber as well as in vegetable crops terbuthylazine used were 0 (control), 25, growth of the weeds. and on non-crop land to control a broad 50, 100 and 250 mg L-1. spectrum of grasses, broadleaf weeds, The petri dishes were placed in dark Introduction sedges and ferns (Kuah et al. 1989, germination chambers at a constant tem- Asystasia gangetica and Paspalum conjug- Rodrigo 1988, Kassebeer et al. 1983). It is perature of 27°C. On days 3 through 10 atum are two weeds common in cocoa, rapidly adsorbed to soil particles, effec- daily germination counts were made. rubber and oil palm plantations. A ma- tively preventing degradation of the her- Seeds were considered germinated when ture A. gangetica plant produces several bicide, or degraded by soil microorgan- the radicle had protruded through the fruits which contain four seeds each. The isms, releasing carbon dioxide (WSSA seedcoat. Radicle length and fresh weight ripe fruits usually burst with considerable 1989). of 10 seedlings were recorded after 10 force, scattering the seeds one to three Terbuthylazine, a broad-spectrum s- days. The experiment was repeated twice metres away from the mother plants (Lee triazine herbicide, is presently being and the means were averaged. All data 1981). P. conjugatum spreads quickly by evaluated in plantation crops in Malaysia. were subjected to an analysis of variance means of its stolons as well as by seeds. With adequate rainfall or irrigation, with mean separation by Duncan’s multi- Approximately 1500 seeds are produced terbuthylazine is leached to deeper soil ple range test at 5% probability level. per plant (Dirven 1971). layers and is taken up by deep-rooted Such production of seeds contributes weeds. Terbuthylazine may move deeper Greenhouse experiments heavily to effective weed dispersal and es- into the soil, not necessarily because of its Four experiments were conducted in tablishment in plantations. Most agricul- greater mobility, but because it persists the greenhouse to determine the effect of tural soils contain a large reservoir of longer (Bowman 1989). In the soil it pre- glufosinate-ammonium and terbuthyl- weed seeds which germinate over a pe- vents the germination of seedlings for azine on seed germination and seedling riod of time. Weed seeds shed onto the several months after application (WSSA growth of the two weed species. The her- soil surface may remain there or be incor- 1989). bicide was sprayed using a laboratory porated into the profile by natural or arti- Past research evaluating the effect of sprayer that delivered a volume of 500 L ficial means (Pareja et al. 1985). Potential glufosinate-ammonium and terbuthyl- ha-1 at a pressure of 200 kPa. The dose ap- weed problems in most cultivated crops azine on the germination seeds of plied was 0 (control), 0.5 and 1.0 kg ha-1. including rubber and oil palm depend at A. gangetica and P. conjugatum is very lim- The soil used in the experiments was a least in part upon the weed seed bank. ited; most reports have considered only sandy loam (40% sand, 40% silt and 20% Norris (1985) suggests that weed control the control aspects at post-emergence clay) with an organic matter content of should exceed 99.99% efficiency to keep stages. Glufosinate-ammonium and 1.1% and a pH of 6.2. No artificial light the seed bank static and proposed that terbuthylazine, which have different ac- was supplied and the temperature in the an ideal weed control measure should tions on weed growth, were chosen for greenhouse was 27±3°C. 16 Plant Protection Quarterly Vol.9(1) 1994 Table 1. Germination, radicle length and fresh weight (% of control) of petri dish grown Asystasia and Paspalum 10 days after exposure to herbicides. Treatment Germination Fresh weight Radicle length (mg L-1) Asystasia Paspalum Asystasia Paspalum Asystasia Paspalum Control 100 a 100 a 100 a 100 a 100 a 100 a Glufosinate-ammonium 25 72 b 49 d 48 b 65 bcd 5 c 60 b 50 68 b 15 e 41 bc 55 cd 4 c 32 d 100 36 c 7 ef 33 c 30 e 3 c 12 e 250 11 d 1 f 20 d 5 f 1 d 3 f Terbuthylazine 25 95 a 100 a 100 a 75 b 84 a 52 bc 50 17 d 97 ab 95 a 70 bc 84 a 44 bc 100 15 d 93 b 41 bc 55 cd 84 a 40 cd 250 6 d 83 c 20 d 55 cd 52 b 52 bc Means within a column followed by the same letters are not significantly different at the 5% level by Duncan's multiple range test. The four experiments (methods of ap- Results and discussion The results of this experiment indicate plication) were as follows: that at higher concentrations, glufosinate- i. Herbicide applied directly to seeds. Laboratory experiment ammonium caused drastic reduction of Fifty seeds of each species were placed After 10 days, each herbicide reduced radicle elongation of both species, but es- in separate petri dishes, sprayed with germination of Asystasia proportionately pecially of Asystasia. Glufosinate-ammo- the appropriate herbicide solution and with increasing herbicide concentration nium not only reduced germination of dried at 20°C for three hours. The seeds (Table 1). Seed germination of Paspalum Paspalum and Asystasia at higher concen- were then placed firmly on an un- declined significantly in the presence of trations, it also consequently reduced treated, moist soil surface in individual 25 mg L-1 glufosinate-ammonium and fresh weight and radicle elongation. At plastic trays (30 cm × 30 cm × 10 cm). prevented seed germination at 250 mg L-1. concentrations as low as 50 mg L-1, ii.Herbicide applied to seed and soil. Terbuthylazine at 250 mg L-1 caused a terbuthylazine caused a marked reduc- Seeds of each species were placed on slight reduction in the germination of tion of germination of Asystasia. the surface of moist soil in similar trays Paspalum. In the case of Asystasia, terb- and then sprayed with the appropriate uthylazine at 50 mg L-1 caused a greater Greenhouse experiments concentration of either glufosinate- reduction in seed germination (reduced i. Herbicide applied directly to seeds ammonium or terbuthylazine. by 83% of control) than did glufosinate- Direct application of glufosinate-ammo- iii.Storage of herbicide-treated seeds.