Land availability and topography in Puerto Rico dictated the development of a method for evaluating herbicide foliage sprays on individual trees and small plots. A pneumatically operated aluminum mast with six telescoping sections, capable of extending from 12 to 50 ft and mounted on a swivel base, was fitted with two different spray delivery systems. A spray boom consisting of two 10-ft sections of 0.75-inch aluminum pipe and equipped with 12 diaphragm nozzles was mounted on the top of the telescoping mast. An alternate spray system was developed by attaching a modified Spraying Systems BoomJet unit to the top of the telescoping mast. To spray with the above systems, the mast is erected and guyed to a vertical position, the spray unit raised to the proper height, and the mast uniformly rotated through an arc of 240° during which the spray is delivered to opposite 180° portions of a circle. The spray coverage for both systems was similar for an area 20 ft in diam, but the droplet size and distribution was more uniform with the boom than with the Boomjet.

Shoots of naturally established specimens of turkey oak (Quercus laevis Walt.) 3 to 6 ft high were treated with 4 to 8 lb aehg of a commercial concentrate formulation of the butoxyethanol ester of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) on or about May 1, June 1, July 1, August 1, and September 1. Foliar applications were made to the point of run-off and foliar-basal treatments were made first to the basal 8 inches of the main stem and then to the lower four-fifths of the remainder of the shoot. The objective was to assess the utility of number two diesel fuel as an additive for such treatments when the oil was used at rates of 0, 5, 10, and 20% in the final formulations. The experiment was repeated in 3 different years. Responses measured approximately 11, 14, and 23 months after initial treatment were percent control of original shoots, percent control of new shoots, shoot height, and number of live stems/plant. Foliar treatments without oil were progressively less effective as they were made later in the growing season. The addition of oil to foliar treatments provided more effective control of the original shoots and greater reduction in shoot heights, especially when the oil concentration was 20%. The foliar-basal method was notably ineffective in the absence of oil. Addition of oil to the foliar-basal treatments provided marked improvement in the original shoot, total shoot control index, shoot height, and stems/plant responses, especially at the 20% level of oil. Diesel fuel is useful as an additive for 2,4,5-T sprays to be applied to turkey oak, especially where treatment is to be made in the latter half of the growing season and in particular where the lower stems can be treated.

Flax (Linum usitatissimum L., var. Bolley) was susceptible very early, when less than 2 inches tall, 1965 only, and during flowering, to 3,6-dichloro-o-anisic acid (dicamba) as determined from 9 consecutive weekly applications in the field in 1965 and 1966. Dicamba decreased flaxseed yield, percent oil and iodine number of the oil, seed size, seed germination, and plant height, and increased the days to maturity by application at either one or both of the susceptible stages of flax.

Field experiments were conducted for 2 years at Urbana, Illinois, to evaluate the response of soybeans (Glycine max (L.) Merr., var. Harosoy 63) to soil and foliar applications of 3,6-dichloro-o-anisic acid (dicamba), 4-amino-3,5,6-trichloropicolinic acid (picloram), and (2,4-dichlorophenoxy)acetic acid (2,4-D). Soil incorporated applications of 2,4-D or dicamba at rates up to 8 oz/A or 4 oz/A, respectively, just before planting soybeans did not reduce soybean yields significantly. Picloram, applied under the same conditions, reduced soybean yield almost 40% at ½ oz/A. Picloram at rates from ½ to 2 oz/A caused slight to moderate leaf malformation on soybeans planted the following year but did not reduce yield. Foliar applications of 2,4-D up to 2 oz/A on soybeans had little effect on yield when applied at the prebloom stage and only slightly reduced yield when applied during flowering. Dicamba and picloram injured soybeans at the prebloom stage considerably more than did 2,4-D. Dicamba and picloram severely restricted soybean development, and reduced yield markedly when applied during flowering; ½ oz/A of dicamba or ⅛ oz/A of picloram reduced soybean yield about 50%.

A miniature sprayer designed for primary screening of herbicides is described. It uses a drift-free flat fan nozzle at low pressure. It has negligible dead volume and a minimum of wetted surface. Total cost was about $10.00 in 1967.

Soil samples were collected from 107 locations following the commercial application of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) for 1, 2, 3, or 4 consecutive years. Analyses of soil samples indicated that trifluralin does not accumulate with repeated annual application and that a steady and continuous decline in the level of trifluralin present in the soil occurred with time.

The degradation of 14C ring-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) was studied in the laboratory with four Hawaiian soils selected for their wide range of organic matter contents (4 to 29%), pH values (4.4 to 6.3), and different mineralogies. Atrazine concentrations of 1, 5, 10, 50 and 100 ppmw in soils incubated at 30 C gave similar 14C-recovery curves. Degradation was rapid in all four soils; atrazine recovery at 34 days (30 C) ranged from 15 to 30% of the quantity applied. Degradation was accelerated by a temperature increase from 30 to 50 C, suggesting a chemical rather than a biological process. The loss of atrazine from soils approached a first order reaction rate at 30 C, and deviated from this at 50 C. Hydroxyatrazine was the main degradation product with only a slight amount of an unidentified “Product B”. It was concluded that chemical degradation (hydrolysis) was the major pathway of atrazine loss in these soils. This process was more closely related to pH, i.e. faster on low pH soils, than with organic matter content or adsorption. The fraction of atrazine adsorbed on soil increased with the decrease in total atrazine caused by degradation. Extraction of soils with both water and methanol and subsequent analysis of extracts by thin-layer chromatography showed that some of the methanol-extractable atrazine was not readily desorbed by water. These results indicate that some of the residual atrazine extracted chemically may not be available for uptake by plants and would be relatively immobile in soil water.

The concept of herbicide partition into adsorbed and solution phases in the soil was utilized to predict the effect of soil water content on the concentration of herbicide in solution. Calculated predictions based on measured partition coefficients and water contents were tested experimentally by equilibrating 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) with soil from three horizons of a latosolic soil at four water contents (45 to 60%). The effects of adsorption and water content were predicted with reasonable accuracy when only that water held at tensions less than 15 bars was considered available for equilibration with the applied herbicide. Only on low adsorption soils will water content variations alter significantly herbicide concentration in the soil solution. The principal effect of soil water content on herbicide phytotoxicity probably is associated with herbicide transport, which is more sensitive to changes in water content than is the concentration of herbicide in soil solution.

Wheat (Triticum aestivum, subspecies vulgare L.) straw, sawdust, peat, and cellulose pulp were mixed with Westmoreland silt loam in a 2 to 1 ratio (soil to organic matter) in a greenhouse study, on the influence of organic matter-interaction with 3-amino-2,5-dichlorobenzoic acid (amiben) on nodulation and growth of soybeans (Glycine max L., var. Clark). The dry weights of shoots and roots, harvested 1 week after flower initiation in the control, decreased with increasing rates of amiben in the unamended soil and in soil in which cellulose pulp and peat were mixed.

Photosynthetic 14CP2 fixation was significantly inhibited in the excised leaves of cotton (Gossypium hirsutum L., var. DPL smoothleaf) (moderately tolerant) and soybean (Glycine max Merr., var. Lee) (sensitive) by 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) and the degree of inhibition increased with increasing herbicide concentration. Prometryne produced no significant effect on 14CO2 fixation during the dark period in either species except for some changes in the concentrations of aspartic and glyceric acids in soybean.

Residual herbicidal action of 3-amino-2,5-dichlorobenzoic acid (amiben), the methyl ester of amiben, 3-acetamido-2,5-dichlorobenzoic acid (N-acetyl amiben), 3-propionamido-2,5-dichlorobenzoic acid (N-propionyl amiben), 3-benzamido-2,5-dichlorobenzoic acid (N-benzoyl amiben), and the methyl ester of N-benzoyl amiben after 0, 1, 2, 4, and 6 hr irradiation was measured by oats (Avena sativa L., var. Markton) bioassay. In a greenhouse study, amiben and N-benzoyl amiben were applied to the soil surface, exposed to sunlight for 7.5 hr, and similarly bioassayed. Amiben, the methyl ester of amiben, and N-acetyl amiben lost 40 to 60% of their original herbicidal activity after 2 to 4 hr irradiation in the laboratory. N-benzoyl amiben and its methyl ester retained over 90% of their activity after 6 hr irradiation. Solar illumination reduced the herbicidal activity of amiben applied to the surface of wet soil by 11 to 14% but had no effect on N-benzoyl amiben. On a dry soil, the losses of amiben and N-benzoyl amiben were not significant.

The compound 2-chloro-N-isopropylacetanilide (propachlor) and five analogs were evaluated for the control of matricaria (Tripleurospermum inodorum (L.) Schultz, syn. Matricaria inodora L.) and common lambsquarter (Chenopodium album L.) in turnip rape (Brassica rapa L.), rape (Brassica napus L.), kale (Brassica oleracea L., var acephala DC.), and rutabaga (Brassica napobrassica Mill). Chemicals were assayed by using nutrient solution culture techniques at rates of 10-4 through 10-8M. N-(butoxymethyl)-2-chloro-2',6'-diethylacetanilide and 2-chloro-N-(propoxymethyl)-2',6'-acetoxylidide appear useful for the control of matricaria in brassicaceous crops commonly grown in Scandinavia.

We studied changes in the concentration of 4-amino-3,5,6-trichloropicolinic acid (picloram) with time in roots, stems, and leaves of 20-day-old seedlings of huisache (Acacia farnesiana (L.) Willd.) and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Exposing root systems to aqueous solutions of picloram (1.0 ppm huisache and 10.0 ppm honey mesquite) for 24 hr killed approximately 60% of the treated plants. In honey mesquite, picloram was redistributed and eventually lost over a 5-day period, whereas neither redistribution nor loss occurred in huisache.