Immunochemical techniques offer many advantages over chromatographic methods used for pesticide trace analysis of substrates such as soil, water, plants, urine, and blood. These advantages include speed of processing samples, high specificity for detecting a pesticide, reduced amount of preparation and cleanup of the sample before analysis, and a dramatic increase in the number of samples that can be analyzed. Immunoassays are based on the principle that antibodies to pesticides can be prepared, in animals, that can recognize and attach with exquisite specificity to certain chemical configurations displayed on the surface of a molecule. Small molecules such as herbicides usually are not immunogenic but can be made so by chemically bonding them to a large immunogenic protein such as bovine serum albumin before injection into an animal. Development of herbicide-specific antibodies and their use in direct and indirect enzyme-linked immunosorbent assays (EIA or ELISA) as well as radioimmunoassays (RIA) are discussed. The principles behind monoclonal antibody production are outlined, and immunoassays using polyclonal and monoclonal antibodies are compared. Specific reference is made to the development and use of indirect ELISA and RIA procedures for trace analysis of 2,4-D and picloram.

Picloram was applied to leafy spurge using flexible and rigid ropewick applicators for 3 yr at each of two upland pasture sites. The ropewick applicators were a cost-effective way to apply picloram to control leafy spurge compared to broadcast application, but minimal advantage was demonstrated for the segmented, flexible unit compared to the rigid applicator. Picloram applied as an 80 g ae/L solution through ropewick applicators controlled leafy spurge equal to broadcast picloram at 1.1 kg/ha while using 36% as much picloram.

Field studies were conducted from 1985 to 1987 to evaluate postemergence herbicide systems with preemergence systems to control Texas panicum, Florida beggarweed, sicklepod, and pitted morningglory in peanuts. Adding paraquat at 0.14 kg ai/ha to postemergence herbicide systems reduced fresh weight of Florida beggarweed 92% (18% increase over the same systems without paraquat), sicklepod 95% (21% increase), and pitted morningglory 95% (11% increase). Herbicide systems containing paraquat improved peanut yields by 230 kg/ha and net returns by $52/ha over herbicide systems not containing paraquat. Fluazifop-P and sethoxydim systems reduced Texas panicum fresh weight (at least 96%) more than a preemergence system (92% reduction) that used benefin applied preplant incorporated and alachlor plus naptalam and dinoseb applied at cracking (GC) or a postemergence system that used alachlor and naptalam plus dinoseb GC and paraquat applied early postemergence (86% reduction). Systems containing fluazifop-P provided greater yields (4190 kg/ha) and net returns ($383/ha) than systems containing sethoxydim (4010 kg/ha, $305/ha) when averaged across all rates of application.

Barnyardgrass, large crabgrass, and Texas panicum were evaluated in field experiments over 3 yr to measure their duration of interference and density on grain sorghum yield. When grain yield data were converted to a percentage of the weed-free control, linear regression predicted a 3.6% yield loss for each week of weed interference regardless of year or grass species. Grain sorghum grown in a narrow (61-cm) row spacing was affected little by full-season interference; however, in wide (91-cm) rows, interference increased as grass density increased. Data from the wide-row spacing were described by linear regression following conversion of grain yield to percentages and weed density to log10. A separate nonlinear model also was derived which could predict the effect of weed density on grain sorghum yield.

Fenoxaprop applied between late winter and mid-spring selectively controlled roughstalk bluegrass in perennial ryegrass grown for seed in Oregon. Fenoxaprop applied after the arrival of warmer weather in late March had enhanced effectiveness against roughstalk bluegrass compared to earlier application. However, additional delay into April increased damage to perennial ryegrass. Optimum application date coincided with a 15- to 18-cm perennial ryegrass canopy height. Mixed stands of seedling and established roughstalk bluegrass were more consistently controlled by 0.28 kg ai/ha fenoxaprop than by lower rates.

Hereford cows and their spring-born calves grazed an irrigated grass pasture containing about 13% dandelion based on dry weight yield. Grazing treatments were 1) no grazing, 2) 4 days of grazing just before clipping, and 3) long-term grazing just before clipping. In clippings taken in June and July after the grazing treatments, the percentage dandelion in the forage was similar in all three grazing treatments, indicating that cattle used dandelion as readily as grass. The protein and mineral contents of dandelion were at appropriate levels to meet the established requirements of beef cattle.

Effects of a 28% N solution containing urea and ammonium nitrate (28% UAN) and a nonionic surfactant on efficacy, uptake, and translocation of chlorimuron ethyl ester in soybean and broadleaf weeds were investigated. Chlorimuron applied postemergence at 8.8 and 13 g ai/ha with either nonionic surfactant at 0.25% (v/v), 28% UAN at 9.4 L/ha, or nonionic surfactant plus 28% UAN controlled weeds better than without additives. Chlorimuron with nonionic surfactant and with 28% UAN controlled weeds similarly but with 28% UAN injured soybeans least. Chlorimuron with nonionic surfactant plus 28% UAN controlled velvetleaf best but injured soybeans most. Less than 2% of applied 14C-chlorimuron was absorbed in velvetleaf 84 h after treatment (HAT) when no additive was present, but adding nonionic surfactant, 28% UAN, and nonionic surfactant plus 28% UAN resulted in 21, 9, and 32% uptake, respectively, 84 HAT. Nonionic surfactant plus 28% UAN also increased translocation (primarily acropetal) of the 14C. Adding 28% UAN increased 14C-chlorimuron uptake in velvetleaf grown at low fertility but had no effect under high fertility.

Experiments were conducted in Massachusetts and New York to evaluate the potential influence of plant growth stage, spray volume, nozzle type, additional surfactant, and herbicide formulation on smooth and large crabgrass control in turf with fenoxaprop. At a well-watered site, crabgrass control with fenoxaprop was equal to or greater than with MSMA. On an irrigated, fertilized site, crabgrass growth stage did not influence fenoxaprop efficacy. Excellent control of up to 5-tiller smooth crabgrass was obtained with 0.20 kg/ha of fenoxaprop. On nonirrigated turf, fenoxaprop was less effective on tillered crabgrass than on 2- to 5-leaf weeds. Under very dry conditions, fenoxaprop was ineffective regardless of growth stage. Control with MSMA was less affected by drought than was fenoxaprop. Spray volumes, between 140 and 1120 L/ha, did not affect fenoxaprop efficacy; however, high volume applications (1120 L/ha) with floodjet nozzles were less effective than flat fan nozzle treatments in two of three tests. Added surfactant did not improve efficacy except with floodjet nozzles on a droughty site. No differences were observed between the water-based and the emulsifiable concentrate formulations of fenoxaprop. Fenoxaprop caused temporary phytotoxicity (≤20% reduction in turf quality) to established Kentucky bluegrass and perennial ryegrass.

Field experiments were conducted on six loam and sandy loam soils to study the influence of various soil parameters on atrazine, cyanazine, alachlor, metolachlor, and pendimethalin efficacy. Herbicidal activity was highly correlated to the soil organic content. Humic matter content was equally or better correlated (r = 0.70 to 0.91) with herbicide bioactivity than was organic matter content (r = 0.66 to 0.84). Regression equations were determined which allow herbicide rate recommendations for 80% weed control to be calculated based on soil humic matter or organic matter levels.

Growth room and field studies were conducted to determine if increasing use of forage aeschynomene may lead to new weed problems in rice and soybeans and to identify possible control measures in these crops. In a growth room study, flooding of ‘Florida Common’ and ‘LSU 1147’ forage aeschynomene did not reduce yield. However, forage aeschynomene seedlings did not emerge from a flooded seedbed, and 1-week-old seedlings were killed by 2.5 or 7.5 cm of flooding. Competition from interseeded forage aeschynomene reduced ‘Centennial’ soybean yields by 81%. Acifluorfen, fomesafen, and lactofen, labeled for soybeans, control forage aeschynomene. Acifluorfen, labeled for rice, may control forage aeschynomene in that crop. Forage aeschynomene might become a weed problem in rice if plants are past the seedling stage when flood water is applied and could cause weed problems in soybeans; but, in most situations, cultural and chemical control practices should provide adequate control.

Imazamethabenz is a selective herbicide used to control wild oat in small grains. The effects of rate, volume of carrier, and surfactant concentration on the efficacy of this herbicide in controlling wild oat were studied in field experiments. As each of the variables increased, wild oat control increased; the greatest degree of wild oat growth inhibition occurred at the highest herbicide rate, highest volume of carrier, and highest surfactant concentration.

The response of giant burreed to bentazon, propanil, 2,4-D (amine salt), and 2,4-D plus crop oil (0.5% v/v) was evaluated at the 2-aerial-leaf stage of wild rice. Bentazon, 2,4-D, and 2,4-D plus crop oil at 1.1 kg/ha or more in 1984, and propanil and 2,4-D plus crop oil at 4.5 kg/ha in 1985 reduced giant burreed dry weight. Generally, herbicide rates above 1.1 kg/ha injured wild rice and reduced yields compared to weed-free controls. None of the study treatments resulted in effective giant burreed control without unacceptable injury to wild rice.

‘Atlantic’ and ‘Russet Burbank’ potato cultivars were grown on mineral and organic soils either with or without weeds and were hilled at two stages of potato development (potatoes cracking through the soil and potatoes 30 cm tall). A single hilling procedure was not adequate in either year for full-season weed control. Early hilling suppressed weeds and increased tuber yields more than conventional hilling on mineral soils in 1988 only. Early hilling tended to increase the relative biomass of C4 weeds compared to C3 weeds for both soils. Weeds reduced aboveground potato biomass on mineral and muck soils. However, reduced aboveground potato biomass measurements did not predict tuber yield reductions. Marketable yield of Russet Burbank potato was reduced by weed interference more than the yield of Atlantic on mineral soils when planted according to conventional cultural practices. However, the marketable yield of Atlantic potato was reduced more than Russet Burbank yield by weeds on muck soils. Weed interference influenced tuber quality on both mineral and muck soil.

Field experiments were conducted to determine the influence of winter wheat seeding date and forage removal on the efficacy of cheat control herbicides, forage and grain yields, and net returns to land, overhead, risk, and management for the various cheat control strategies. Economic analysis showed that net returns were higher when wheat was seeded during the traditional seeding period (October) than when either seeded early (September) for increased forage production or delayed (November) for cultural cheat control. Some herbicides were economically beneficial at two of three locations where the initial cheat population exceeded 170 plants/m2.

Chlorimuron applied postemergence at 2.2, 4.4, 8.8, 18, and 35 g ai/ha to cotton at either the 4-leaf, pinhead-square, first-bloom, or full-bloom growth stage was evaluated for potential as a plant growth regulator. Chlorimuron did not reduce bolls per plant at any rate or time of application, but the proportion of open to closed bolls decreased as rate increased. Seed cotton yields decreased with increasing chlorimuron rate and cotton age. The use of chlorimuron as a plant growth regulator for cotton appears limited.

Primary tillage is an inexpensive method to control foxtail barley, a perennial bunchgrass which is an increasing concern to no-till cereal farmers in the Northern Great Plains. Moldboard plowing or chisel plowing in fall followed by field cultivation-harrowing in spring effectively controlled established foxtail barley on previously untilled sites before planting spring wheat. In contrast, chisel plowing in spring followed by field cultivation-harrowing did not control this weed completely.

Pronamide was applied to a ‘Tifway’ bermudagrass golf green overseeded with perennial ryegrass during 1988 and 1989 to determine how herbicide rate and date affected ryegrass injury on transition back to a bermudagrass monostand. In most instances, perennial ryegrass was injured less when pronamide was applied at 0.28 or 0.56 kg ai/ha March 30 or April 13 than when application was delayed until April 28 or May 14. Perennial ryegrass injury lasted longer when 0.28 kg/ha was applied twice (March and/or April) than when applied singly at 0.28 kg/ha March 30 or April 13. The optimum time and rate of pronamide for effective transition was April 13 and 0.56 kg/ha, respectively.

The weed sicklepod, a problem in the cultivation of soybean, cotton, and peanut, can be controlled by the mycoherbicide, Alternaria cassiae. However, the presence of water (dew) for an extended period is required by the fungal spores to germinate and infect the target weed. Preliminary tests with invert (water-in-oil) emulsions containing paraffin wax, paraffin oil, lecithin, and water indicated that about 10% (w/w) water, maintained over an 18-h period, was necessary under laboratory conditions for significant germination of the fungus. The ability to maintain that amount of water in the invert emulsion depended upon spray deposit size, adjuvants, and oil phase: water ratio. Paraffin wax was an effective adjuvant for reducing water evaporation and increasing sicklepod mortality in the greenhouse.

Field studies were conducted to compare preplant-postemergence-applied paraquat, glyphosate, SC-0224, and HOE-39866 on subterranean clover, crimson clover, and hairy vetch cover crops. Subterranean clover control with paraquat at 1.1 kg ai/ha was about 80 and 100% when applied in early April and early May, respectively, regardless of spray volume (190 vs. 370 L/ha). Glyphosate and SC-0224 at 1.7 and 2.8 kg ai/ha applied in April controlled about 53% of subterranean clover. Subterranean clover control with HOE-39866 at 0.8 kg ai/ha applied in April was excellent. Paraquat at 0.6 kg ai/ha and HOE-39866 at 0.8 kg/ha regardless of application time controlled both crimson clover and hairy vetch. Grain sorghum and soybean yields following the legume cover crops generally were similar for the herbicide treatments.