propyrisulfuron, a new sulfonylurea herbicide for rice - Wssp.org.pk

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230 Hajime Ikeda et al., Propyrisulfuron, a new Sulfonylurea…Table-1. Properties of Propyrisulfuron.Chemical and PhysicochemicalAppearance : White solidMelting point : >193.5 ºCWater solubility : 0.98 mg/L (20 ºC)Partition coefficient : Log Pow 2.9 (25 ºC)Acid dissociation constant : pKa 4.89 (20 ºC)ToxicologicalAcute oral : LD 50 > 2000 mg/kg, rat ♂Acute dermal : LD 50 > 2000 mg/kg, rat ♂♀Acute inhalation : LC 50 > 4300 mg/m 3 , rat ♂♀Skin irritation : Not irritant, rabbitEye irritation : Slightly irritant, rabbitMutagenicity : Negative (Ames test)Common carp : NOEC (96 hrs) >10 mg/LMATERIALS AND METHODSHerbicideThe herbicides used for testing were 0.5 g/L provisionalemulsions or 100 g/L suspension concentrate. The provisionalemulsions were prepared by dissolving the technical grade ofpropyrisulfuron in acetone including 20 g/L sorbitan monolaurate(TWEEN TM 20; Sigma, St Louis, USA), or in N, N-dimethylformamideincluding the 20 g/L sorbitan monolaurate.Weed controlPot tests were conducted in a greenhouse using 200 cm 2 × 19cm plastic pots or 100 cm 2 × 14 cm plastic pots filled with light claysoil (pH 6.1 - 6.5, organic matter 2.0 - 2.3 %) or sandy soil (pH 5.5,organic matter 1.9 %). After the soil was puddled and flooded, the
Pak. J. Weed Sci. Res., 18: 229-237, Special Issue, October, 2012 231seeds or tubers of weeds shown in Figure 3, Figure 4 and Figure 5were planted in the pots. The weeds were grown in a greenhouse up tothe leaf stages indicated in Figure 3, Figure 4 and Figure 5.For submerged application tests, propyrisulfuron at 25 - 100 g a.i./hawas applied directly into standing water. The flooding depth was keptin 3 - 5 cm during experiments. The weed control efficacy wasevaluated at 3 - 5 weeks after the application, using a visual ratingscale of 0 (no effect) to 100 (completely killed) compared to anuntreated control. Each test was conducted with three replications.For spray application tests, propyrisulfuron at 50 and 100 ga.i./ha was sprayed over the top of plants. The volume rate was 500L/ha. There was no flooding water at the application. Pots were floodedto 2 - 5 cm above the soil surface at 2 - 4 days after the application.The weed control efficacy was evaluated at three weeks after theapplication, using a visual rating scale of 0 (no effect) to 100(completely killed) compared to an untreated control. Each test wasconducted with two replications.Dose responses of Echinochloa oryzicola at different growthstages to propyrisulfuron by spray application were investigated.Propyrisulfuron at 7 - 55 g a.i./ha was sprayed over the top of plants.The volume rate was 154 L/ha. There was no flooding water at theapplication. Pots were flooded to 5 cm above the soil surface at a dayafter the application. The shoot biomass (dry weight) was evaluated atfour weeks after the application. The test was conducted with tworeplication.ED 90 value, the dose giving 90 % reduction of shoot biomasscompared to an untreated control, was calculated by non-linearregression using the model:f(x)=c+(d-c)/{1+9×(x/ED 90 ) b } ,where f(x) = shoot biomass, x = dose, c = lower limit of response, d =upper limit of response, b = slope (Scabenberger et al. 1999).Absorption site studyThe seedlings of Echinochloa oryzicola at 2.5 - 2.7-leaf stagewere prepared using a seedling box for rice transplanters. The plantswere transplanted in 100 cm 2 × 14 cm plastic pots filled with light claysoil (pH 5.5, organic matter 2.0 %). The soil was flooded at 1 cm,without making the water level reach the shoots.The activity of propyrisulfuron at 40 and 90 g a.i./ha wasevaluated under two different application practices as shown in Figure2: (1) Practice-1. Propyrisulfuron was applied directly into standingwater; (2) Practice-2. After the surface of soil was covered withpolyethylene sheet, propyrisulfuron was sprayed on the foliage of theplants with a volume rate of 1000 L/ha. The sheet was removedimmediately after the application.
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