Samunder Singh

Effect of growth stage on trifloxysulfuron and glyphosate efficacy in twelve weed species of citrus groves

Efficacy of trifloxysulfuron with and without surfactant was evaluated against balsamapple, cats claw vine, Florida beggarweed, hairy beggarticks, ivyleaf morningglory, johnsongrass, prickly sida, redroot pigweed, sicklepod, strangler vine, tall morningglory, and yellow nutsedge at 21, 42, and 63 g ai/ha applied at the four- or six-leaf stages and compared with glyphosate at 280, 560, and 840 g ae/ha. Delayed application from the four- to six-leaf stage significantly reduced trifloxysulfuron efficacy; reduction was less with glyphosate. Trifloxysulfuron plus 0.25% X-77 was more effective on the four-leaf stage than on the six-leaf stage plants of redroot pigweed, johnsongrass, hairy beggarticks, strangler vine, and prickly sida; effect was similar on yellow nutsedge, sicklepod, Florida beggarweed, balsamapple, ivyleaf morningglory, and tall morningglory. Trifloxysulfuron at 63 g/ha plus surfactant reduced the fresh weight of all test plants more than 80% compared with control, except prickly sida, strangler vine, and cats claw vine. Glyphosate was less effective than trifloxysulfuron plus surfactant against tall morningglory, sicklepod, ivyleaf morningglory, and yellow nutsedge but was significantly better against balsamapple, prickly sida, and cats claw vine. None of the herbicides provided satisfactory control of cats claw vine, strangler vine, and prickly sida. Nomenclature: Glyphosate; trifloxysulfuron; X-77; balsamapple, Momordica charantia L. #3 MOMCH; cats claw vine, Macfadyena unguis-catsi (L.) A. Gentry # BIGUC; Florida beggarweed, Desmodium tortuosum (Sw.) DC. # DEDTO; hairy beggarticks, Bidens pilosa L. # BIDPI; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; sicklepod, Senna obtusifolia L. # CASOB; strangler vine, Morrenia odorata (H & A) Lindl. # MONOD; tall morningglory, Ipomoea purpurea (L.) Roth. # PHBPU; yellow nutsedge, Cyperus esculentus L. # CYPES. Additional index words: Herbicide efficacy, stage of application, surfactant. Abbreviations: NIS, nonionic surfactant; POST, postemergence; WAT, weeks after treatment.

Role of Management Practices on Control of Isoproturon-resistant Littleseed Canarygrass (Phalaris Minor) in India

Littleseed canarygrass is a major weed of winter-season crops, although it is most dominant in wheat-growing regions in the Indo-Gangetic Plains of India, Pakistan, Nepal, and Bangladesh. Resistance in this species to photosystem II–inhibiting herbicide isoproturon was first recorded in 1992, and has since spread to several Indian states covering more than a million ha. Genetic studies and resistance characterization from multiple locations indicate independent evolution of resistance due to continuous use of isoproturon and monoculture rice–wheat-cropping system. Isoproturon-resistant biotypes were found cross-resistant to diclofop, but not to chlortoluron, which has the same mode of action as isoproturon. The isoproturon-resistance mechanism is metabolic degradation, mediated by P-450 monooxygenase enzymes. This type of resistance could become serious and lead to the evolution of multiple resistances to herbicides of different modes of action. Adoption of fenoxaprop-P, clodinafop, and sulfosulfuron in isoproturon-resistant areas since 1997 initially led to high yields, but resulted in a weed flora shift which eventually reduced yields and increased the cost of weed management. Although isoproturon recommendation has been withdrawn from rice–wheat cropping zones, resistance in littleseed canarygrass is spreading in other areas where isoproturon has been used for several years because it is inexpensive and has broad-spectum weed control. Management factors, such zero or minimum tillage, early planting after rice harvest, and alternative herbicides provide effective control of resistant biotypes. However, lower efficacy of these herbicides has been observed in the field, although multiple resistances have yet to be confirmed. Herbicide rotations, mixtures, and sequences are beneficial, but only in the short term. Improved cultivation practices are also helpful; however, no current single system is sustainable. An integration of tillage method, planting time, varietal selection, crop rotation, timing and method of herbicide application, optimum dose, and sanitation practices is crucial in managing herbicide-resistant littleseed canarygrass. Nomenclature: Chlortoluron; clodinafop; diclofop; fenoxaprop-P; isoproturon; sulfosulfuron; littleseed canarygrass, Phalaris minor Retz. PHAMI; rice, Oryza sativa L; wheat, Triticum aestivum L.

Control of Ragweed Parthenium (Parthenium hysterophorus) and Associated Weeds1

Field experiments were conducted to evaluate control of 90- to 100-cm-tall ragweed parthenium in a noncropped situation in Haryana State, India, during 2000 and 2001. Atrazine, 2,4-D ethyl ester, atrazine plus 2,4-D, metribuzin, metsulfuron, chlorimuron, glufosinate with and without surfactant, glyphosate with and without surfactant, and glyphosate formulations MON 8793 and 8794 were sprayed on ragweed parthenium. Also, the effect of water quality was studied with flat-fan and flood-fan nozzles using glyphosate and its formulation MON 8793 against ragweed parthenium and associated weeds. Glyphosate MON 8793 and 8794 at 3.6 kg ae/ha provided excellent control of ragweed parthenium followed by glyphosate at 2.7 or 5.4 kg/ha, with no recovery until 18 wk after treatment (WAT). Addition of 0.1% v/v surfactant (MON 0818) to glyphosate at 2.7 kg/ha provided similar control to that of glyphosate alone at 5.4 kg/ha. Other herbicides failed to provide satisfactory control of ragweed parthenium. In the water quality study, glyphosate at 2.7 and 5.4 kg/ha and glyphosate MON 8793 at 2.7 and 3.6 kg/ha provided similar control of ragweed parthenium at 18 WAT. Glyphosate was antagonized less by tap water (0.45 mM Ca) than canal (0.7 mM Ca) and hand-pump water (1 mM Ca). Neither glyphosate nor glyphosate MON 8793 provided good control of purple nutsedge, velvetleaf, garden spurge, threelobe false mallow, jimsonweed, giant milkweed, Indian jujube, or tropical spiderwort, but crowfootgrass, green foxtail, sprawling signalgrass, and spiny amaranth were controlled. Glyphosate at 5.4 kg/ha and glyphosate MON 8793 at 3.6 kg/ha provided more than 80% control of bermudagrass at 8 WAT, which was significantly better than the 2.7 kg/ha rate. Flat-fan nozzles provided better efficacy of applied herbicides than flood-fan nozzles at 4 WAT on ragweed parthenium. Nomenclature: Atrazine; chlorimuron-ethyl; glufosinate; glyphosate; glyphosate MON 8793; glyphosate MON 8794; metribuzin; metsulfuron-methyl; 2,4-D; ragweed parthenium, Parthenium hysterophorus L. #3 PTNHY; bermudagrass, Cynodon dactylon (L.) Pers. # CYNDA; crowfootgrass, Dactyloctenium aegyptium (L.) Beauv. # DTTAE; garden spurge, Euphorbia hirta L. # EPHHI; giant milkweed, Calotropis procera (Ait.) R. Br.; green foxtail, Setaria viridis (L.) Beauv. # SETVI; Indian jujube, Zizyphus nummularia (Burm. f.) Wight. & Arn.; jimsonweed, Datura stramonium L. # DATST; purple nutsedge, Cyperus rotundus L. # CYPRO; spiny amaranth, Amaranthus spinosus L. # AMASP; sprawling signalgrass, Brachiaria reptans (L.), Gard. & Hubb.; threelobe false mallow, Malvastrum coromandelianum (L.) Garcke.; tropical spiderwort, Commelina benghalensis L. # COMBE; velvetleaf, Abutilon bidentatum L. Additional index words: Application stage, glyphosate formulations, nozzle types, surfactant, water quality. Abbreviations: DAT, days after treatment; WAT, weeks after treatment; EC, electrical conductivity.

Evaluation of Some Adjuvants for Improving Glyphosate Efficacy

Glyphosate is the most common non-selective post-emergence herbicide used under diverse conditions. The efficacy of foliar applied herbicides is greatly influenced by adjuvants, but not all adjuvants have a synergistic effect. Greenhouse experiments were conducted using weed species of Echinochola crus-galli, Panicum maximum, Bidens pilosa, and Abutilon theophrasti to evaluate glyphosate efficacy by tank mixing with 0.5 % of Blaze®, Condition®, Improve®, and Induce®. Glyphosate at 0, 0.14, 0.28, and 0.56 kg ae/ha alone and with adjuvants was sprayed at the 4 leaf stage of weeds. Surface tension and contact angle were measured under lab conditions. Adjuvants increased the activity of glyphosate by 15–29 % compared to glyphosate alone. Among the weed species, higher mortality was observed in P. maximum and B. pilosa followed by E. crus-galli and lowest in A. theophrasti. On mortality of grass and broadleaf weed species, significant differences were observed by tank mixing glyphosate with different adjuvants. Lowest Contact Angle (CA) and Surface Tension (ST) were recorded when glyphosate (Rodeo®, with no surfactant) was mixed with Improve and Blaze surfactants, which was significantly lower than glyphosate formulation pre-mixed with surfactant (Roundup UltraMax®). In the case of Condition, the relative decrease in CA was less than ST when added to glyphosate, compared to Improve and Blaze. Lower ST and CA of glyphosate tank mixed with Improve and Blaze correlated with improved weed mortality in the activity study.

Suitable Adjuvant to Maximize Trifloxysulfuron Efficacy and Early Assessment of Herbicide Efficacy Using Chlorophyll Fluorescence

Trifloxysulfuron 2.5, 5, and 10 g ai/ha mixed with non-ionic (0.25% Induce and X-77), organosilicone (0.1 % Kinetic and Silwet L-77), and crop oil concentrate (1 % Agridex and Meth-N-Oil) adjuvants was evaluated for efficacy, surface tension (ST), contact angle (CA), and chlorophyll fluorescence responses in redroot pigweed, prickly sida, and barnyard grass. The lowest ST and CA were recorded with L-77 mixed with trifloxysulfuron. Among the six adjuvants, ST and CA were highest with Meth-N-Oil; however, these differences did not greatly influence herbicide efficacy. No trifloxysulfuron-adjuvant antagonism was found for any weed species. Differences in activities were observed at 2.5 g/ha trifloxysulfuron with different adjuvants; however, activities were comparable when data were averaged over species and rates. All the adjuvants increased trifloxysulfuron efficacy; some differences were observed among the weed species, but adjuvants were equal in improving trifloxysulfuron efficacy. Redroot pigweed was more sensitive to trifloxysulfuron compared to barnyardgrass and prickly sida was least. Chlorophyll fluorescence 1, 4, 7, and 14 days after treatment (DAT) was not greatly inhibited by trifloxysulfuron mixed with different adjuvants. Reduction in chlorophyll fluorescence was recorded 4 DAT in barnyard grass, but the reduction was not proportionate to the mortality and lacked uniformity among different treatments.

Abundance, distribution and diversity of weeds in wheat in Haryana

Wheat (Triticum aestivum L.) crop is infested with both grassy and broad-leaf weeds. Losses caused by weeds in wheat vary from 30-50% depending upon type of weed flora, time, and intensity of weed infestation, but in extreme cases there could be complete crop failure (Malik and Singh 1995). Weed flora has been in a state of dynamism brought about by mankind for his benefits, thus paving the way for superior competitive species to gain the foothold in changed soil conditions. Species which have same ecological demands are inclined to occupy the same habitats with much rapidity. Crop type and soil properties have greatest influence on the occurrence of weed species (Streibig et al. 1984, Andreasen et al. 1991). The type of irrigation, cropping pattern, weed control measures and environmental factors have a significant influence on the intensity and infestation of weeds (Saavedra et al. 1990). Abundance measures the quantitative significance of a species in its habitat. It describes the success of weed in terms of numbers. Density and frequency are the two simplest and most popular methods of measuring abundance. Whereas, the distribution of weed species denotes its natural geographic range. It is the description of where the species naturally occurs or where it has been recorded. Weed flora distribution is a dynamic phenomenon because it changes over time as the result of climatic, anthropogenic or ecological factors. Changes in a weed distribution can provide critical information regarding the weed species expansion or contraction, predictability of occurrence, effectiveness of control measures, habitat preferences and dispersal mechanisms. In contrast, weed diversity can be explored at several different scales from number of species per unit area to genetic diversity. It represents the number of species present in an area and specifies the abundance of each species in a community. Therefore, knowledge of weed species associated with crops in a region is pivotal and necessary to plan and execute a sound and economical weed management schedule depending upon various factors affecting weed distribution in different areas. The present survey was planned to study the abundance, distribution and diversity of weed flora in wheat crop in 14 wheat growing districts of Haryana state.