High concentrations of arsenic (As) may be expected on Coastal bermudagrass forage harvested soon after application of organic arsenicals for weed control. Stage of plant development at treatment, rainfall between treatment and harvest, rate of application of arsenical herbicides, and the amount of growth between treatment and harvest are factors influencing As residue levels in harvested material. Regrowth following removal of treated growth had a lower As concentration. Treatment application on short grass and removing and discarding the treated foliage appeared to be the most effective means of reducing As residues.

Many acid herbicides must be methylated before analysis by gas-liquid chromatography. Several reagents were evaluated for the esterification of substituted acid herbicides. Esterification by the different methods was determined on 2,3,6-trichlorophenylacetic acid [fenac], 2,3,6-trichlorobenzoic acid [2,3,6-TBA], 4-amino-3,5,6-trichloropicolinic acid [picloram], 2-methoxy-3,6-dichlorobenzoic acid [dicamba], and 3,6-dichlorosalicylic acid, a possible metabolite of dicamba. The effect of substituent size and position is discussed in relation to esterification. The best methylating reagent for acid herbicides was diazomethane although it is toxic, explosive, and more costly than the other methods. BF3-methanol was equally as good when the compound was not sterically hindered. Water interfered with the esterification efficiency of all reagents. Diazomethane esterified the ammonium salt but not the sodium salt of the acids used.

Herbicide-application equipment was combined with a sled tool-carrier to plant a test crop and apply a herbicide simultaneously to single rows as surface, subsurface, incorporated, and injected sprays. Results obtained, using the methyl ester of 3-amino-2,5-dichlorobenzoic acid (amiben), indicated the equipment can facilitate the evaluation of the influence of method of application on the activity of herbicides applied to soil.

Prior to planting of birdsfoot trefoil (Lotus corniculatus L.), stony soils were sprayed with ethyl N,N-dipropylthiocarbamate (EPTC) at 0, 2.0, or 4.0 lb/A and were tandem-disked or harrowed 0, 1, 2, or 3 times or rotary-tilled to incorporate the herbicide. Rotary tillage was the best incorporation method where stones were not numerous. Tandem disking was the most practical. Annual grasses were controlled by 2.0 lb/A EPTC and one incorporation. Higher rates of EPTC and more incorporations resulted in better annual broadleaf weed control and increased yields of birdsfoot trefoil.

Corn was grown in soils containing root residues of giant foxtail (Setaria faberii Herrm.), yellow foxtail (Setaria glauca (L.) Beauv.), and crabgrass (Digitaria sanguinalis (L.) Scop.). The effect of these residues on corn root growth was studied using a new technique which measures root response to soil properties with a single plant. Giant foxtail was the most inhibitory. Implications of these data are discussed in terms of the dominance and competitive ability of giant foxtail.

Preemergence applications of 5-bromo-3-sec-butyl-6-methyl-uracil (bromacil) and mixtures containing bromacil controlled both broadleaf and grass weeds best, and increased seed production and quality in side-oats grama [Bouteloua curtipendula (Michx.) Torr.] fields. Other herbicides significantly reduced broadleaf weeds but did not control grass weeds. The most troublesome grasses were foxtails; bristly foxtail [Setaria verticillata (L.) Beauv.] was the most prominent. Weed competition, in plots where herbicides were ineffective, significantly lowered seed production. Excessive rainfall after treatment was probably responsible for decreased weed control and increased crop damage from some of the herbicides. Applications of 2,3,5-trichloro-4-pyridinol (pyriclor) resulted in early crop chlorosis.

A new method for taking soil samples was devised. Vacuum is used to move the soil in an air stream from the sampling site into a sealed bag. Much of the hard, time-consuming work can be eliminated with this new method of sampling. No differences were noted in bioassay plants grown in samples of soil taken in the conventional manner, as compared to plants grown in samples taken with the vacuum device.

The herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and 2-methoxy-3,6-dichlorobenzoic acid (dicamba) each labeled in the carboxyl position were sprayed on a pasture consisting of a mixture of silver beardgrass (Andropogon saccharoides Swartz.), little bluestem (A. scoparius Michx.), and dallisgrass (Paspalum dilatatum Poir.) and a sideoats grama (Bouteloua curtipendula [Michx.] Torr.) pasture over a 3-year period. Plant samples were harvested at intervals between 1 hr and 16 weeks after treatment and residues determined by radioassay. No important differences were found in the persistence of herbicides or of different formulations of the same herbicide. Rainfall was the most important factor influencing the persistence of the herbicides. The little bluestem-silver beardgrass-dallisgrass samples harvested 1 hr after treatment with the butoxyethyl ester of 2,4,5-T contained both this ester and the acid of 2,4,5-T. One week after treatment, the acid of 2,4,5-T and unknown metabolites were found but no ester.

Visible symptoms of injury in susceptible oat plants were not apparent until 4 days after initial exposure to 1 ppm 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) solution. However, the herbicide affected normal absorption and translocation over this period of time. The expected translocation and uniform distribution of xylem transported atrazine-C14 was stopped after 2 days of exposure to atrazine. The reduction in translocation of atrazine-C14 to the shoot apices in early stages of herbicidal injury was not due to reduced asborption but very likely to some other factor such as reduced transpiration. Reduction in atrazine-C14 absorption reduced translocation to the shoot apices, but this probably was not an important factor in the early stages of injury. Absorption of atrazine-C14 by oat plants was not reduced until 3 days of exposure to atrazine. A reduction in carbohydrate concentration, resulting in injury to root tissues, may be responsible for reduction in total atrazine-C14 absorption.

Plots planted to corn (Zea mays L. var. Mo. 880) were treated with 0, 2.5, 5, and 10 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) or 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) plus 0, 100, or 200 lb/A of nitrogen fertilizer. Yields of corn forage harvested 5 weeks after planting were significantly reduced by herbicidal treatments. Reductions were more pronounced on corn treated with simazine than with atrazine. In a given year, yields of corn forage from each successive harvest were reduced less, percentagewise, than the previous ones. Yields of corn grain generally were unaffected by herbicidal treatments, except when 10 lb/A of simazine were applied. Herbicides caused an increase in percent nitrate in forage approximately 5 weeks after treatment. Percent of nitrogen in corn forage rose sharply, approximately 5 weeks after planting, due to herbicidal treatments, especially on plots not treated with nitrogen fertilizer.

Five rates of 1-(2 methylcyclohexyl)-3-phenylurea (siduron) were applied to Cohansey and IaGreen cultivars of creeping bent-grass (Agrostis palustris). Siduron had no effect upon leaf respiration or photosynthesis of either cultivar. Cohansey was tolerant to 100 lb/A of siduron while top growth of IaGreen was reduced 90% at 1.5 lb/A. Siduron inhibited new root growth of the IaGreen cultivar and decreased root respiration.

The influence of pH and incubation time on the detoxication of 11 herbicides incorporated into high organic matter soils was investigated. Five of the chemicals were detoxified at different rates at the various pH levels. Optimum pH levels for the detoxication of these chemicals were (a) pH 5.3 for 2-methoxy-3,6-dichlorobenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D), (b) 6.5 for 2,2-dichloropropionic acid (dalapon) and 3-amino-1,2,4-triazole (amitrole), and (c) pH 7.5 for S-propyl dipropylthiocarbamate (vernolate).

Slow positive detoxication, without pH influence, was observed for 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and 3-amino-2,5-dichlorobenzoic acid (amiben). No detectable detoxication was observed for 4-amino-2,5,6-trichloropicolinic acid (picloram), α,α,α-tri-fluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), 5-bromo-3-isopropyl-6-methyluracil (isocil), or 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone).

Virginia chain fern (Woodwardia virginica (L.) Smith) was controlled by 2,6-dichlorobenzonitrile (dichlobenil) in cranberry bogs on a St. Johns soil at Chatsworth, New Jersey, in experiments conducted during 1960, 1961, 1962, 1963, and 1964. The treatments were applied at emergence of the weed. Stalk counts of the fern were recorded the year following treatment. Excellent control was obtained at either 4 or 8 lb/A of dichlobenil. No re-growth occurred in subsequent years.

Selected clones of field bindweed (Convolvulus arvensis L.) differing in susceptibility to foliage applications of 2,4-dichlorophenoxyacetic acid (2,4-D) were used in testing some of the various mechanisms proposed for the selective action of this chemical. The differences found in external morphology, such as degree of pubescence and number of stomata, showed no relationship to the selective action of 2,4-D. Entry of the chemical into the plant and translocation within the stem also were not critical factors.

The most pronounced physiological differences between resistant and susceptible clones of bindweed occurred at the cellular level. When incubated in a nutrient agar containing 2,4-D, excised stem sections of both clones produced callus tissue, but the callus of the susceptible clone, as compared to the resistant, was approximately double in volume, dry weight, and degree of hydration. With increasing age, stem sections of the susceptible clone became even more responsive to 2,4-D; the reverse was true for the resistant. The differential response of the two clones was less pronounced when 2,4-D was applied to the roots than when it was applied to the foliage.

The herbicide 0-(2,4-dichlorophenyl) 0-methyl isopropylphosphoramidothioate (DMPA) applied either as a preemergence spray or in mixture with the alkanolamine salt of 4,6-dinitro-orthosec-butylphenol (DNBP) at the “ground-cracking” (emergent) stage increased the yield of peanuts from 1960 to 1965. Average yield increases from DMPA treatments for the 5-year period were highly significant statistically if DMPA treated peanuts were compared with peanuts either cultivated, handweeded, or sprayed with standard herbicide mixtures.

A 0.25-mil mylar film was used as a part of an in-situ autoradiographic technique for studying 14C-labeled compounds in soil containing growing corn (Zea mays L., var. WF9 X Hy) roots. This technique facilitates herbicide movement studies in soils and plants while plants grow undisturbed.

Damping-off of pea (Pisum sativum) seedlings in autoclaved soil subsequently inoculated with Pythium debaryanum ATCC 9998 grown in potato dextrose broth in presence of 75 ppmw O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramidothioate (DMPA) was not different than in soil inoculated with the fungus grown in potato dextrose broth without DMPA. Damping-off of pea seedlings was less in autoclaved soil subsequently inoculated with Pythium debaryanum ATCC 9998 and to which DMPA (100 ppmw) had been added than in inoculated soil with no DMPA present. Damping-off of pea seedlings germinated in soil from plots that had received annual applications of DMPA, 15 lb/A, was nearly as great as that in the control plots.

Encroachment of woody species reduces the productivity of sphagnum moss (Sphagnum sp.) in acid bogs. Leatherleaf (Chamaedaphne calyculata (L.) Moench) and black chokeberry (Aronia melanocarpa (Michx.) Willd.) were major species of concern to moss harvesters. Black chokeberry was controlled by spray applications in spring of 4-amino-3,5,6-trichloropicolinic acid (picloram) at 1 lb/A. Leatherleaf was controlled by either fall or spring applications of picloram at 1 lb/A. No control was obtained with eight other herbicides tested. Sphagnum moss carried phytotoxic residues three growing seasons after picloram application.

The U.S. Department of Agriculture World Collection of Flax Germ Plasm was screened for resistance to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine). A single plant selection of CI 719 was the most resistant. It produced dry matter equaling 33% of the control in soil treated with atrazine at 1 lb/A while Amy produced 10%. In another experiment, the selection of CI 719 produced 44% as compared to only 11% for Koto. The atrazine-resistant selection was not resistant to 2-chloro-4,6-bis(ethylamino)-s-triazine [simazine]. Seed of this selection of CI 719 have been entered in the World Collection and assigned the number CI 2484.

Experiments were conducted to evaluate the preplant incorporation and preemergence activity of several herbicides for weed control in southern peas (Vigna sinensis (L.) End.). The selectivity of 4,5,7-trichlorobenzthiadiazole-2,1,3 and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline has been demonstrated. Eight other chemicals generally gave good weed control but resulted in injury to the peas.