Low Volatile Ester Research Articles

Great Plains Yucca (Yucca glauca) Control on Shortgrass Rangelands

AbstractGreat Plains yucca is a native species that competes with forage plants for space and water and at high densities may warrant control. The objective of this study was to determine the efficacy of seven herbicides applied in the spring or fall for Great Plains yucca control. Six foliar herbicides applied by ground application at 187 L ha−1 spray volume, one herbicide applied to individual plant whorls, and a nontreated check were established in June and September of 2009 and 2011. Percent mortality was determined 12 to 16 mo after herbicide application. Most herbicides gave similar control between the 2 yr, with triclopyr in diesel applied to individual plant whorls at 10 g L−1 providing the greatest control at 83%. Most herbicides applied in June near the blooming stage of Great Plains yucca were more effective than September treatments. June treatments providing the greatest reduction in yucca densities were metsulfuron + dicamba + 2,4-D amine + 2,4-D low volatile ester (LVE) at 21 + 113 + 325 + 431 g ae ha−1, metsulfuron + aminopyralid + triclopyr at 49 + 9 + 227 g ha−1, metsulfuron + chlorsulfuron + 2,4-D LVE at 34 + 11 + 431 g ha−1, and metsulfuron + aminopyralid + 2,4-D LVE at 49 + 9 + 431 g ha−1. A single application of a foliar herbicide provided a maximum of 72% mortality of Great Plains yucca, suggesting that repeat application may be necessary to achieve optimum control.

Volatility of Broadleaf Weed Herbicides When Applied to Turfgrass

Laboratory and field studies were conducted in 2010 and 2011 to evaluate the volatility of commonly used turfgrass broadleaf herbicides when applied to tall fescue (Lolium arundinaceum Schreb.). Herbicides were applied at the highest label rate for dandelion (Taraxacum officinale G.H. Weber ex Wiggers) control. Turfgrass flats treated with herbicides were placed in enclosures containing tomato plants. In laboratory experiments, tomatoes exposed to turfgrass treated with products containing amine formulations of synthetic auxin herbicides exhibited minimal injury, but exposure to products containing low-volatile ester formulations caused significant negative effects on tomato quality, epinasty, and callus formation. Generally, products containing low-volatile ester formulations of synthetic auxin herbicides exhibited less volatility, compared to 2,4-D butyl ester (volatile standard). A subsequent field study corroborated the laboratory results, although injury symptoms were less severe. Turfgrass managers should avoid herbicides containing low-volatile ester formulations when vulnerable non-target plants are nearby, and/or when environmental conditions such as high temperature favor volatility.

Control of Common Sunflower (Helianthus annuus) in Artillery Range Trials at Ft. Riley, Kansas

Military bases in the United States were mandated to reduce the amount of pesticide used to 50% of 1993 levels by 2000. Historically, 2,4-D was applied to control common sunflower, which establishes itself in disturbed soils and obstructs gunners' views of targets. A 25-ha lowland field in Camp Forsyth was selected to compare efficacy of alternative herbicides with that of 2,4-D low-volatile ester (LVE), with the goal of reducing the amount of herbicide applied by at least half. Site vegetation was mostly native tallgrass prairie dominated by warm-season C4 grasses (e.g., big bluestem, Indiangrass, little bluestem, and switchgrass) and including less abundant C3 species in the Asteraceae, Fabaceae, Brassicaceae, and other families. Initially, the site had a high population of common sunflower. All herbicide treatments from 3 yr of field trials were highly and equally effective at reducing common sunflower, decreasing stem density by 83 to100%. Treatments that offer substantial reductions in the amount of herbicide applied are chlorimuron (0.01 kg ae/ha), dicamba + 2,4-D amine (0.07 kg ae/ha + 0.20 kg ae/ha), clopyralid + 2,4-D amine (0.06 kg ae/ha + 0.28 kg ae/ha), 2,4-D LVE (0.56 kg ae/ha), and metsulfuron + 2,4-D amine (0.002 kg ai/ha + 0.28 kg ae/ha). Use of these herbicides at Ft. Riley would reduce total active ingredient applied by 73 to 99% and lower chemical costs for this particular use by as much as 88%.

Uptake of the herbicide [14C] 2,4-D iso-octyl in the vapour phase by tomato and lettuce plants and some effects on growth and phytotoxicity

Summary Tomato and lettuce plants were exposed to vapour of the herbicide [14C-phenyl] 2,4-D iso-octyl at concentrations in the range 0–450 pg litre-1 for periods of 6, 24 and 72 h in separate experiments using a flowing-air system. The rate of uptake, as indicated by plant content of radiolabel, was both linear with respect to the vapour concentration and independent of the duration of exposure. The uptake rate of tomato was greater than that of lettuce at any given vapour concentration. Uptake by the apical leaves of lettuce was higher than by the older leaves expressed on an area basis; tomato showed no effect of leaf position. Visible symptoms of phytotoxicity were shown by both species 40 days after exposure to the highest doses. Advantages of using the low-volatile ester (iso-octyl) of 2,4-D to reduce vapour drift damage are discussed in terms of plant uptake.

Buckbrush (Symphoricarpos orbiculatus) Control in Tall Fescue (Festuca arundinacea) Pastures

Field studies were established to evaluate several herbicides for buckbrush control in tall fescue pastures. Buckbrush was controlled most consistently by 2,4-D amine or low volatile ester, or package-mixes of 2,4-D plus dicamba or triclopyr. Two consecutive years of herbicide application was more effective for reducing buckbrush stem populations than one application.

Biological activity of 2,4-D esters on rubber vine (Cryptostegia grandiflora): dependence on vapour pressure and molecular weight and isomerism of the alcohol substituent

The relationship between molecular structure and biological efficacy was investigated for 16 esters of 2,4-D [(2,4-dich1orophenoxy)acetic acid] on rubber vine (Cryptostegia grandiflora). These included the normal (n) or straight-chain esters from C-1 (methyl) to C-8 (octyl), the n-decyl, n-dodecyl, isobutyl, amyl (iso-pentyl), 2-ethylhexyl (iso-octyl), and the methoxy-, ethoxy-, and butoxyethyl esters. For the normal series esters, biological efficacy was found to be a function of both the molecular weight and the vapour pressure of the esters. This relationship was linear for the higher molecular weight, low volatile esters, biological efficacy decreasing with increasing molecular weight and the accompanying decrease in vapour pressure of the esters. The low molecular weight, volatile esters were more active than the higher molecular weight, low volatile esters, and increases in the vapour pressure of these low molecular weight, volatile esters were sufficient to account for the deviation from linearity of those esters. When all esters are considered, the same relationships hold but the branched-chain (iso) and chemically substituted (alkoxy alcohol) esters are less effective than the corresponding normal esters. Possible reasons for these results are discussed.

A Survey of Herbicide Use in Canadian Forestry

The results of an across-Canada survey into the past, present, and future use of herbicides in forestry are presented. Based on a response of more than 60% return of 250 questionaires sent, herbicide use potential is not being met. In Ontario, the most commonly used herbicides are simazine, mainly for grass control, and the low volatile esters 2,4-D and 2,4,5-T, used either alone or in combination for conifer release from overtopping hardwood vegetation, for site preparation and weed control in young hardwood and conifer plantations, and for the general control of brush along roadsides.It is suggested that greater communication is necessary between the field forester and the chemical manufacturer before herbicide versatility can be realized and, for their use in the environment to be accepted, communication must also include the general public.

2,4-D Injury to Citrus Rootstocks1

Abstract Four commercial formulations of 2,4-dichlorophenoxyacetic acid (2,4-D), including 3 oil-soluble amines and one low volatile ester were tested at 2 rates in plots of established budded citrus nursery stock. Five rootstocks budded to ‘Pineapple’ orange scions were evaluated for damage from spray applications to trunks. All amine salt formulations caused varying degrees of damage to the bark (below soil line) and root systems, with little or none from the ester. Rootstock sensitivity to 2,4-D formulations was highly significant with trifoliate orange (Poncirus trifoliata L.) and the hybrid ‘Carrizo’ citrange being most tolerant and rough lemon (Citrus jambhiri Lush.), ‘Cleopatra’ mandarin (Citrus reticulata Blanco), and sour orange (Citrus aurantium L.) least tolerant.

Vapor Pressures of Low-Volatile Esters of 2,4-D

The vapor pressures of the four most common commercial low-volatile esters and a reference high-volatile ester of 2,4-dichlorophenoxyacetic acid (2,4-D) were determined by gas-liquid chromatography. The order of increasing volatility and the vapor pressure of these esters in mm of Hg at 187 C are as follows: isooctyl—2.7; 2-ethylhexyl—3.0; butoxy ethanol—3.9; propylene glycol butyl ether—3.9; and the reference, isopropyl—16.7. Extrapolations to 25 C support this ranking at working temperatures. Commercial esters of 2,4-D derived from long-chain hydrocarbon alcohols are in the same volatility range as the commercial esters containing an ether linkage.

Volatility of herbicides under field conditions

Herbicidal formulations of 2,4-D, 2,4,5-TP, and amino triazole were tested for volatility under high summer temperature conditions in the Coachella Valley, California. The herbicides were applied to plots in cotton fields and the degree and extent of injury to surrounding cotton plants served as a measure of the volatility of the herbicides. Formulations of 2,4-D were found to be increasingly volatile in the order amine salts, acid, and low-volatile esters. It was determined that vaporization of the herbicides occurred predominantly during the daytime. A low volatile formulation of 2,4,5-TP appeared to be as volatile as similar formulations of 2,4-D but produced only minor injury symptoms on cotton. Amino triazole appeared to be entirely free of volatility hazard.

STUDIES ON SEED DORMANCY, PLANT DEVELOPMENT, AND CHEMICAL CONTROL OF TARTARY BUCKWHEAT (FAGOPYRUM TATARICUM (L.) GAERTN.): III. CHEMICAL CONTROL AND EFFECTS OF COMPETITION

The effects on Tartary buckwheat and barley of various chemical treatments, applied at different stages of plant development, were compared in field plots. For control of Tartary buckwheat there was no advantage in using two applications of 2,4-D (2,4-dichlorophenoxyacetic acid, ethyl ester) or of MCPA (methylchlorophenoxyacetic acid, butyl ester), 12 days apart, rather than a single application at a correspondingly higher rate. At comparable rates a low volatile ester (butoxyethanol ester) was more effective than regular 2,4-D ester (ethyl ester), especially at the later growth stages, and both were much superior to MCPA.In competition between Tartary buckwheat plants, total production of vegetative matter and seed increased somewhat with increasing number of plants per square yard, but, as expected, the single-plant yields decreased sharply. In barley plots infested with Tartary buckwheat sprayed with LV 2,4-D when the plants had 2–3 leaves, up to 50 buckwheat plants per square yard had not yet, during the time before spraying, affected the ultimate yield of grain. On sprayed plots there was a balancing effect between herbicidal injury to the grain and decreased weed competition. The effect of the interaction between these two factors was manifested in the yield of grain.

THE EFFECTS OF 2,4-D SPRAY DRIFT ON SUNFLOWERS

At Saskatoon the effects of drift spray of the butyl ester, low volatile ester, and amine formulations of 2,4-D on growing sunflowers all resulted in distortion of the leaves and stems, and malformed heads. Effects decreased with distance but were clearly discernible at 120 rods. With a wind velocity of 9 miles per hour after 1 hour of spraying the total seed yield was reduced by 42, 38, and 37 per cent for ester, low volatile ester, and amine, respectively. Seed quality decreased with proximity to the sprayed area.Similar damage occurred at Morden when low volatile ester of 2,4-D was applied adjacent to a breeding nursery.

A COMPARISON OF MCP AND 2,4-D FOR THE CONTROL OF ANNUAL WEEDS IN GRAIN CROPS

Oats, flax and barley were sprayed with various formulations of MCP (2-methyl-4-chlorophenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) at a number of Experimental Farms in Western Canada in 1954 and 1955. Each formulation was applied at 4 and 8 ounces of acid equivalent per acre at each of two dates, viz., Date 1, when the weeds were in the seedling stage less than 3 inches in height; and Date 2, at a stage coinciding with the first appearance of buds on the major weed species.Stinkweed (Thlaspi arvense, L.), wild mustard (Brassica kaber (DC.) L.C. Wheeler var. pinnatifida (Stokes) L.C. Wheeler), lamb's quarters (Chenopodium album L.), Russian pigweed (Axyris amarantoides L.), and ball mustard (Neslia paniculata L.), were effectively controlled by each of the MCP and 2,4-D formulations used. Russian thistle (Salsola kali L.), and red-root pigweed (Amaranthus retroflexus L.), were not satisfactorily controlled by MCP, whereas hemp nettle (Galeopsis tetrahit L.) was not controlled by 2,4-D. Wild buckwheat (Polygonum convolvulus L.) was not controlled by any of the treatments. Each treatment was more effective when applied during the seedling stage of the weeds.On the basis of wood control and yield of grain the results of this study favour the use of MCP over 2,4-D with either oats or flax. Oats was significantly more tolerant to MCP, particularly if treated during the early growth stages when weed competition was most critical. With flax, the difference in tolerance was most pronounced in favour of MCP at the later date of treatment. The 2,4-D ester and low volatile ester resulted in a preponderance of plant deformities, lowered the yields of both oats and flax and delayed the maturity of flax significantly. Barley yields in this study were not adversely affected by any of the treatments.

Chemical Control of Big Sagebrush and Its Effect upon Production and Utilization of Native Grass Species

A S EARLY AS 1946, a limited study conducted in Oregon (5) showed .t big sagebrush (Artemisia tridentata Nutt.) to be susceptible to the sodium salt of 2,4-D. Cornelius and Graham (3) stated that big sagebrush was highly susceptible or hypersensitive to 2,4-D. Kissinger, Hull and Vaughn (7), reporting on experiments conducted at the Beaver Rim area near Lander, Wyoming, found that the isopropyl and amyl ester of 2,4,5-T consistently gave higher kills for a given amount of chemical. One pound acid equivalent (hereafter referred to as pounds acid) of 2,4,5-T usually gave somewhat higher kills than two pounds acid equivalent of 2,4-D. Hull and Vaughn (4) stated that the type and amount of chemical which killed two-thirds or more of the brush plants varied with the carrier and the season. The butyl ester form of 2,4-D gave better results than mixtures of 2,4-D and 2,4,5-T or the contact sprays. Hyder (6), working in Oregon, stated that butyl ester of 2,4-D gave the best control for the money, even though the growth regulator, 2,4,5-T, killed more brush. Colorado workers (1) showed that volatile esters of 2,4-D gave more economical control of big sagebrush than the low-volatile esters. The herbicide 2,4,5-T made a poorer showing as an economical means of control, was less effective than 2,4-D, and more costly. Bohmont (2), observing the effects of chemicals 75 days after treatment, noted that a low-volatile (tetrahydro furfural) ester of 2,4-D, at two pounds acid per acre, caused the most observable toxicity. While 2,4,5-T treatments suppressed seed head development, the plants partially recovered and seed heads formed during the growing season, compared to the 2,4-D treatment which prevented seed heads from forming. Increase in production of native forage has been reported on all sites where chemical control has been used. Average air-dry herbage production near Lander (7) showed 222 pounds per acre on untreated land; 490 pounds per acre with 58 percent sagebrush control; 553 pounds with 66 percent sagebrush control; and 645 pounds with 97 percent sagebrush control. Native grass production, on an experimental area near Lander, was increased two to three times by killing 60 to 97 percent of the sagebrush. The increased production and more accessible forage supply on the sprayed areas were utilized almost twice as heavily as on unsprayed areas. Bohmont (2) stated