Soil samples with and without a past history of dimethyl-2,3,5,6-tetrachloroterephthalate (DCPA) treatment were obtained from New York. A third sample was obtained from a field in Colorado where DCPA had been ineffective as a herbicide. The populations of bacteria and actinomycetes in these soils were determined and the actinomycetes were more prevalent in the samples with previous DCPA treatment than in untreated samples. Subsequent treatment resulted in an increase in actinomycete population and little change in bacterial population. In pure culture and in soils, the addition of DCPA had no adverse effect upon microbial growth, and several microorganisms appeared to utilize the herbicide as a carbon source. Two degradation products were methyl-2,3,5,6-tetrachloroterephthalate and 2,3,5,6-tetrachloroterethalic acid.

Absorption, translocation, and metabolism of 14C-labeled 2,4-bis (isopropylamino)-6-methylmercapto-s-triazine (prometryne) from solution cultures by cotton (Gossypium hirsutum L., var. DPL smoothleaf) and soybean (Glycine max Merr., var. Lee) were investigated. Cotton (moderately tolerant) and soybean (sensitive) absorbed essentially equal amounts of prometryne. Whereas 14C was uniformly distributed in soybean, it was concentrated in the lysigenous glands and in the root primordia of cotton. Soybean had a considerably higher concentration of radioactivity in shoots than in roots, whereas the reverse was true in cotton. The major methanol extractable 14C-labeled component in the roots and shoots of both species was prometryne. Both species converted some prometryne to the derivative, 2,4-bis(isopropylamino)-6-hydroxy-s-triazine (hereinafter referred to as hydroxypropazine), but cotton shoots had a slightly higher percentage of the latter than the soybean shoots. The concentration of prometryne in soybean shoots was about four times greater than in cotton shoots. Differential translocation of prometryne appeared to be a major factor contributing to the difference in susceptibility between cotton and soybean.

Fall treatments with 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) as opposed to cultivation during the growing season reduced hand labor requirements more than 70% for weed control in Japanese holly (Ilex crenata Thumb. Rotundifolia Hort.). The response of Japanese holly to simazine varied from superior growth and quality to severe injury and death. Simazine plus 3-amino-1,2,4-triazole (amitrole) resulted in better control of small weeds than simazine alone in late winter or early spring. Dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), and 2,6-dichlobenzonitrile (dichlobenil) reduced labor requirements for control of annual weeds without any visual response on the Japanese holly. In certain instances, rotations of herbicides were effective for broad spectrum weed control.

Simultaneous treatment with certain carbamate insecticides inhibited degradation of 3-(p-chlorophenyl)-1,1-dimethyrurea (monuron) in cotton (Gossypium hirsutum L.) leaf discs. Monuron degradation was strongly inhibited by 1-naphthyl methylcarbamate (carbaryl) and 4-benzothiophene-N-methylcarbamate, but 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate was ineffective. Effective carbamates did not prevent the metabolism of monuron to 1-(p-chlorophenyl)-3-methylurea (hereinafter referred to as monomethylmonuron), but they inhibited subsequent degradation of monomethylmonuron.

Three experiments were conducted in the greenhouse to study the effect of 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat) when sprayed directly on seeds at the soil surface. Germination of alfalfa (Medicago sativa L., var. DuPuit) and red clover (Trifolium pratense L., var. Kenland) was not affected at 1 1b/A paraquat, but germination of Kentucky bluegrass (Poa pratensis L., var. Newport) and perennial ryegrass (Lolium perenne L., var. Linn) was severely reduced at that rate. A protecting layer of soil approximately 0.25 inch thick was completely effective in protecting the seeds from the effect of paraquat. Germination of seven other grass species was reduced by 0.5 1b/A paraquat.

Greenhouse studies on control of saltcedar (Tamarix pentandra Pall.), a problem phreatophyte, showed that when one of three hygroscopic compounds, polypropylenediol (a mixture of polypropylenediols with molecular weights ranging from 375 to 425) was added to water solutions of phenoxy herbicides, it significantly increased injury from most treatments. Injury to foliage from all herbicides tested, except the oil-soluble amine formulations (a mixture containing 80% tertiary dodecyl and 20% tertiary tetradecyl amine) of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4,5-trichlorophenoxy) propionic acid (silvex), and 2,4-D plus 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) (1:1), increased when polypropylenediol was added to the spray solution at 5% by volume. The increased activity was affected by the rate of the additive, temperature, humidity, and herbicide formulation.

Emulsions of aromatic solvent or dimethylbenzene (xylene) are used to control submersed aquatic weeds in irrigation systems. A procedure was developed for analyzing the concentrations of xylene in irrigation water. Samples of xylene emulsions were collected in glass bottles containing tetrachloromethane (CCl4). Xylene and emulsifier were partitioned into the CCl4. After addition of sodium chloride (NaCl) to remove the emulsifier from the CCl4, aliquots of the CCl4 were analyzed for xylene content by gas chromatography. Extraction of xylene from the water was complete and quantities of xylene as small as 10 ng were readily detected.

We evaluated 214 lines of wild oat (Avena fatua L.) for response to S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate), S-2,3,3-trichloroaHyl N,N-diisopropylthiolcarbamate (triallate), and 4-chloro-2-butynl m-chlorocarbanilate (barban). We found large differences among the lines in response to these herbicides and some lines that might not be controlled by recommended rates of these herbicides. Frequency distributions of response to herbicides suggest that reaction to these three herbicides is quantitatively inherited. We were unable to establish a relationship between morphological characteristics and plant response to these herbicides.

In a 3-year study on four soil types, subsurface application just ahead of a planter with a device that removed the top from the bed, applied a band of spray, and covered the band with soil reduced weed control in cotton (Gossypium hirsutum L.) obtained with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne), 3-(hexahydro-4,7-methanoindan-5-yl)-1,1-dimethylurea (norea), dimethyl-2,3,5,6-tetrachloroterephthalate (DCPA), and 1,1-dimethyl-3(α,α,α,-trifluoro-m-tolyl)urea (fluometuron) compared to applications on the soil surface. This machine improved weed control with α,α,α,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). Shallow incorporation, with two helical blades, after planting increased weed control with trifluralin, diuron, and DCPA by 10% or more over the surface applications. This incorporator increased weed control obtained with prometryne and norea 5%. Very shallow incorporation, with metal tines, after planting improved weed control obtained with trifluralin and DCPA 18 and 11%, respectively. Weed control with norea was increased 7%, but metal tines did not appreciably affect weed control obtained with prometryne, diuron, or fluometuron. Compared to surface applications, incorporation increased cotton injury with diuron, norea, prometryne, and fluometuron on sandy loam soil.

Ethylene production was stimulated by 2,4-dichlorophenoxyacetic acid (2,4-D) from light-grown corn (Zea mays L., var. XL-15) and soybeans (Glycine max Merr., var. Hawkeye). Ethylene had an inhibitory effect on the growth of corn and soybeans, but a reversal of the ethylene effect could not be clearly demonstrated using the competitive inhibitor, carbon dioxide. Ethylene did not mimic the ability of 2,4-D to cause growth curvatures. It was concluded that ethylene played a role in the activity of sublethal amounts of 2,4-D.

Wild oat (Avena fatua L.) competition severely reduced flaxseed (Linum usitatissimum L.) yield. Averaged over two locations and two fertility levels, 80 wild oat plants/sq yd reduced the yield 9.4 bu/A (60.1%) in 1964 and 160 wild oat plants/sq yd reduced the yield 21.5 bu/A (82.1%) in 1965. At Fargo, 160 wild oat plants/sq yd reduced flaxseed yield 16.1 bu/A (86.1%) in 1966. Flaxseed yield components, including bolls/sq ft, seeds/boll, plants/sq ft, and weight/1000 flaxseed were determined. Although all components were reduced by wild oat competition, a reduction in the number of branches and flax bolls/sq ft accounted for 90.7% of the yield loss. A reduction in weight/1000 seed and the number of flax plants/sq ft contributed 7.0% and 4.6% to the yield loss, respectively. Competition from wild oat also reduced flaxseed quality. The percent oil was reduced in all 3 years of the experiment. Iodine number of the oil was reduced, primarily because of an increase in oleic acid and a decrease in linolenic acid.

Wild oat (Avena fatua L.) competition increased the losses in yield of both wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) with increased densities of seedlings. At Fargo in 1965, wild oat densities of 70 and 160 seedlings/sq yd reduced the wheat yield 22.1% and 39.1%, respectively, compared to the wild oat-free check. Similar wild oat densities reduced the barley yield 6.5% and 25.9%, respectively. The addition of nitrogen and phosphorus fertilizer reduced the yield loss caused by wild oat 2 out of 3 years of the experiment. Although a considerable yield reduction occurred in barley and wheat, percent protein and seed size were not influenced noticeably.

Wild oat (Avena fatua L.) was removed at several stages of growth from flax (Linam usitatissimum L.) plots in 1964, 1965, and 1966. The flaxseed yield was reduced as the period of competition increased during each year. In 1965, competition from wild oat until the 4 to 5-leaf stage reduced the flaxseed yield 15.1% while competition until maturity reduced the yield 74.9%. The number of bolls/sq ft also was reduced as the period of competition increased; but the number of seed/boll, plants/sq ft, and the weight/1000 seed were not affected consistently by wild oat competition. Both the percent oil of flaxseed and the iodine number of the oil were reduced by wild oat competition, but not until the wild oat was in the heading stage and the flax was in the boll stage.

Seed of corn (Zea mays L., var. Texas 28) and cotton (Gossypium hirsutum L., var. Deltapine smooth leaf) were planted in sand and subsequently drenched with solutions of α,α,α trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). The levels of herbicide used inhibited growth of roots and shoots in both crops, but cotton proved more tolerant than corn. The roots failed to elongate normally, but the lateral growth that continued gave the radicle a “club-shaped” appearance, especially in corn. Stained sections of the roots were mounted as permanent slides for study. The cells at the extreme tip of the treated roots were small and dense; many were multinucleate. Immediately behind this region, the cells were abnormally large, thin-walled, and aberrant. A disorganized type of nuclear division was evident. Cell plate and cell wall formation were apparently rare. Although we found no normal sequence of mitosis in cells of treated roots, all stages of mitosis were seen in the untreated roots.

The fate of the potassium salt of 2,4-dichlorophenoxyacetic acid (2,4-D) when applied to birdsfoot trefoil (Lotus corniculatus L., var. Viking) and an intercross resistant to 2,4-D was studied. No difference in spray retention per mg fresh weight between the two trefoils was detected and more than 98% of 2,4-D-2-14C was absorbed within 2 days after application. Herbicide moved from treated leaves to young leaves, stems, and roots in about equal quantities. Seven days after treatment, 70% of the 14C activity of 2-propanol extracts of both trefoils was 2,4-D-2-14C; the remaining activity of the extract was from unknown metabolites of 2,4-D. The total activity recovered from the tolerant selection and Viking, respectively, was 57% and 50% of that applied. The methods used failed to establish a clear basis for the difference in reaction of the two birdsfoot trefoils to 2,4-D.

The development of amylase activity controlled by the embryo in the distal halves of intact barley (Hordeum vulgare L., var. Larker) seeds during the first 2 days of germination was prevented by the presence in the culture solution of 10−4 M 7-oxabicyclo-(2.2.1)heptane-2,3-dicarboxylic acid (endothall), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 2,6-dichlorobenzonitrile (dichlobenil), or 3 amino-2,5-dichlorobenzoic acid (amiben) and was not overcome by the simultaneous addition of gibberellic acid. The aforementioned herbicides did not inhibit gibberellic acid-induced amylase synthesis in de-embryonated halved barley seeds. The amiben and bromoxynil inhibition of barley germination was slightly reduced by the simultaneous addition of 10−2 M glucose to the culture solution. Amiben and bromoxynil also inhibited the development of low levels amylase activity found in 2-day-old squash (Cucurbita maxima Duchesne, var. Chicago Warted Hubbard) cotyledons; however, added benzyladenine overcame the inhibition. In contrast to barley, benzyladenine was shown to induce the development of amylase activity in squash. Tolerance of squash and other seeds low in carbohydrates to amiben and bromoxynil during germination may be related to their independence from herbicide-inhibited carbohydrate degradation for energy and carbon source required for anabolic processes.

Excised leaves of Canada thistle (Cirsium arvense (L.) Scop.) ecotypes and bean (Phaseolus vulgaris L., var. Red Kidney) metabolized 3-amino-l,2,4-triazole-14C (amitrole) to the same radiolabeled products, but they were produced at different rates as shown by thin-layer and paper chromatography. Bean leaves metabolized amitrole to a metabolic product (Unknown II) probably β-(3-amino-1,2,4-triazolyl-1-) α-alanine approximately three times taster than Canada thistle leaves, while Canada thistle converted Unknown II to another product (Unknown I) about 10 times faster than did bean. Thus Unknown II accumulated in bean, and Unknown I in Canada thistle. This reaction sequence in Canada thistle was evidently an irreversible consecutive first order reaction. A difference in the rate of metabolism was observed between susceptible and resistant ecotypes of Canada thistle.

Several factors were studied which influenced 3-amino-1,2,4-triazole (amitrole) metabolism in excised leaves of bean (Phaseolus vulgaris L., var. Red Kidney) and Canada thistle (Cirsium arvense (L.) Scop.) ecotypes. Amitrole metabolism in the leaves of both species held in the light was greater than in leaves held in the dark. Increasing the temperature from 15 C to 28 C also stimulated the rate of metabolism of amitrole. However, this effect was much less pronounced when the temperature was increased from 22 C to 28 C. Dipping the leaves in 10−2M ammonium thiocyanate reduced the metabolism of amitrole, whereas similar pre-treatment with 3.5 × 10−3M 6N-benzyladenine enhanced the metabolism of amitrole.

Chemical-fallow experiments were initiated as a possible means of improving summer-fallow procedures for seedbed preparation and rehabilitation of abandoned croplands subject to wind erosion. Red threeawn (Aristida longiseta Steud.) and sand dropseed (Sporobolus cryptandrus (Torr.) Gray) are pioneer perennial grasses that have stabilized these sandy loam soils but are undesirable forage plants. Dimethylarsinic acid (cacodylic acid), 2-tert-butylamino-4-ethylamino-6-methylthio-5-triazine (GS-14260), and a mixture of 3-amino-l,2,4-triazole (amitrole) plus ammonium thiocyanate were ineffective, but 2,2-dichloropropionic acid (dalapon) applied at 6 lb/A or more reduced these pioneer perennial grasses 80 to 100%. Follow-up treatments, either mechanical or chemical, are needed to maintain control of competing vegetation while seeded species become established.

We studied the uptake of ethyl N,N-dipropylthiocarbamate (EPTC) by barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oats (Avena sativa L.), sorghum (Sorghum vulgare Pers.), and giant foxtail (Setaria faberii Herrm.) using a double plastic pot technique that allowed separate exposure of the shoot and root zones to treated soil. Barley was more tolerant than wheat, whereas oats, sorghum, and giant foxtail were the most susceptible to EPTC at 1/4 to 1 1/2 lb/A-inch. The roots were the major site of uptake in barley, but injury to the other species from root exposure was equal to or slightly less than that from shoot exposure. The seed, or first 2 to 4 mm of shoot or both, were more sensitive in wheat than in barley. Such differential sensitivity was not evident in the shoot zone of the other species. These experiments, coupled with 14C-EPTC studies, indicated that differences in tolerance can be associated with the sites of uptake.