Differential germination of corn chamomile (Anthemis arvensis L.) achenes was associated with achene size. Germination increased with reduction in achene size. Lower germination of large achenes was caused by a physical restriction of embryo expansion rather than by chemical inhibition or the preventive entrance of water or oxygen through the pericarp. This physical restriction was caused by lignified portions of the pericarp surrounding the seed.

Simulated rainfall at 0.1, 0.5, and 2.0 in applied to six crops in the field previously treated with 1.5 lb/A of the dimethylamine salt of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) resulted in an average herbicidal loss from the forage of 21, 60, and 93%, respectively. One inch of rain removed an average of 80% of 2,4-DB applied at 0.5, 1.5, and 2.0 lb/A to birdsfoot trefoil (Lotus corniculatus L.). Loss of the herbicide was attributed to the dissolving of herbicide in water and subsequent runoff from leaf surfaces, and an acceleration of herbicidal decomposition in the plant. Light interception decreased the rate of 2,4-DB breakdown in alfalfa (Medicago sativa L.) but was not considered to be of practical importance.

Leaching of seven s-triazines in Lakeland fine sandy soil under greenhouse and field conditions was demonstrated by use of oats (Avena sativa L., var Seminole) and cucumber (Cucumis sativis L., var. Palomar) for bioassay. Depth of leaching was determined by abnormalities of these species grown in soil samples from the surface of treated soil to a depth of 22 in in the field and to 36 in in columns. Symptoms of injury by the different materials were similar and included primarily leaf chlorosis of both species and bending and breaking of cucumber stems within 7 to 10 days after planting; plants that failed to survive usually died 12 to 14 days after planting. Leaching of 2-methoxy-4-ethylamino-6-isopropylamino-s-triazine (atratone) was greatest, followed in decreasing order by 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine), 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 2-chloro-4-diethylamino-6-isopropylamino-s-triazine (ipazine), 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine (ametryne), and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne). Oats did not significantly reduce the soil concentration of ametryne and prometryne during a growing period of 56 days.

Herbicides were applied postplant to field grown peanuts (Arachis hypogaea L.) and cotton (Gossypium hirsatum L.) in association with various cultivation devices. Rotary cultivations were compatible with single or multiple chemical treatments applied to soil. For eight preemergence herbicides commonly used on a nonincorporated basis, use of the multiple-application multiple-rotarycultivation technique, in comparison to the common method of use, increased the early-season weed control rating from 3.4 to 4.5 (scale 1.0 = no control, 5.0 = perfect), reduced weeds from 209 to 37 plants/50 sq ft, increased length of control from 36 to 50 days, and reduced the manual hoe time requirement from 24 to 10 hr/A. Incorporation of single or multiple chemical treatments decreased crop safety for some herbicides especially where cotton was the crop. The power driven rotary cultivator was superior to the standard sweep-equipped cultivator and the weeder for use in conjunction with multiple chemical applications. Herbicidal applications incorporated with the rotary cultivator at 0, 7, and 14; 7, 14, and 21; or 0, 14, and 28 days after planting provided equal weed control.

Foliar sprays of 4-amino-3,4,5-trichloropicolinic acid (picloram) controlled winged elm (Ulmus alata Michx.) more effectively than 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Picloram and 2,4,5-T in a mixture effectively controlled the elm. Sprays of 2,4,5-T with ammonium thiocyanate (NH4SCN) added, and a (1:1) combination of NH4SCN and 3-amino-1,2,4-triazole (amitrole) additive, controlled the elm. Foliar sprays of 2,4,5-T without additives have been relatively ineffective. Soil moisture shortage, followed by watering immediately after treatment of winged elm with 2,4,5-T-C14, increased the translocation of 2,4,5-T as compared to plants maintained in moist or dry soils.

Picloram controlled winged elm when applied with an injector or as a soil treatment. The 2,4,5-T diluted in diesel oil, applied as an injector treatment, effectively controlled winged elm.

Additions of montmorillonite clay and soil of high organic matter content to growth media consisting of sand and nutrient solution significantly decreased the phytotoxicity of 2-methylthio-4,6-bis(isopropylamino)-s-triazine (prometryne) to wheat [Triticum aestivum L. em. Thell. (aestivum group) “Wakeland”]. Phytotoxicity was decreased to a greater extent at pH 4.5 than at pH 6.5. The reduction in phytotoxicity was attributed to adsorption of the herbicide by the additives. A larger proportion of the prometryne was present in the protonated form at the lower pH and the increased adsorption probably resulted from the coulombic bonding of these cations to the soil additives. Adsorption mechanisms are postulated and discussed.

Leaf discs of cotton (Gossypium hirsutum L.), broadleaf plantain (Plantago major L.), soybeans (Glycine max Merrill), and corn (Zea mays L.) were incubated 1 hr in aqueous solutions of methyl- or ring-labeled 3-(p-chlorophenyl)-l,l-dimethylurea-14C (monuron) or carbonyl-labeled 3-(3,4-dichlorophenyl)-l,l-dimethyl-urea-14C (diuron). The loss of herbicide and formation of metabolites were determined at approximately 1-hr intervals up to 7 hr. Cotton leaf discs actively metabolized monuron to l-(p-chlorophenyl)-3-methylurea (monomethylmonuron), l-(p-chlorophenyl)urea (p-chlorophenylurea), and p-chloroaniline. Plantain leaf discs strongly metabolized diuron to l-(3-,4-dichlorophenyl)-3-methylurea (monomethyldiuron) and l-(3,4-dichlorophenyl)urea (3,4-dichlorophenylurea). Plantain degraded monuron less actively than diuron and cotton degraded diuron less rapidly than monuron. In soybean leaf discs, metabolism did not progress beyond the first demethylation, and corn leaf discs were unable to metabolize the herbicides in short-term studies.

Persistence and movement of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) in a silty clay loam soil was studied. Single applications of 16 lb/A 2,3,6-TBA were made to field plots on 21 dates from 1955 to 1965. All treated plots were sampled to a depth of 8 ft in 1966, and a few were sampled to a depth of 11 ft. One-foot increments of soil were bioassayed to determine presence of the herbicide. Variation in amount and depth of penetration of 2,3,6-TBA was noted, but the herbicide had persisted in the soil 11 years. Persistence and movement could not be related to moisture before or after treatment, temperature after treatment, or, except for treatments applied in 1964 and 1965, time between treatments and sampling. Residues from fall applications appeared to be slightly greater than those from spring or summer applications.

Two field experiments were conducted to determine the soil persistence, crop toxicity, and effectiveness of four herbicides in controlling purple nutsedge (Cyperus rotundus L.). Excellent control of purple nutsedge was obtained with 2,6-dichlorobenzonitrile (dichlobenil) and good control was obtained with N-hydroxy-methyl-2,6-dichlorothiobenzamide. Both 3-iert-butyl-5-chloro-6-methyluracil (terbacil) and 5-bromo-3-teri-butyl-6-methyluracil were effective in controlling purple nutsedge, but maximum control was not obtained until 9 to 12 months after these chemicals were incorporated in the soil. Toxicity of all chemicals to beans (Phaseolus vulgaris, var. humilis L., Blue Lake), corn (Zea mays var. rugosa L., Golden Security), summer squash (Cucurbita moschata Duchesne, var. Yellow Crookneck), tomato (Lycopersicum esculentum Mill., var. Flora-del), and gladiolus (Gladiolus hortulanus Bailey, var. Friendship) increased as the rates were increased and decreased with time after treatment. Infestation of purple nutsedge from escaping tubers increased as the herbicidal persistence decreased.

Growth of Salmonella typhimurium LT-2 (Loeffler) Cast. and Chalm. was inhibited by 3-amino-l,2,4-triazole (amitrole), and 3-hydroxy-1,2,4-triazole, 3-chloro-l,2,4-triazole, and 5-amino-1,2,3,4-tetrazole (hereinafter referred to respectively as hydroxytriazole, chlorotriazole, and aminotetrazole). Toxicity of 2 × 10−2 M amitrole was partially overcome by 2 × 10−4 M histidine, and more effectively circumvented by combinations of histidine with 2 × 10−4 M adenine, 2 × 10−4 M riboflavin, or 2 × 10−4 M methionine. Serine reduced toxicity of 10−1 M amitrole when combined with both histidine and adenine but was less effective than methionine. Hydroxytriazole inhibition was partially overcome by adenine or less effectively by histidine but not by riboflavin, methionine, or serine. Chlorotriazole and aminotetrazole inhibitions were circumvented by 2 × 10−4 M methionine, 10−3 M serine, and 10−4 M cysteine but not by histidine, adenine, or riboflavin. The toxicity of high concentrations (10−3 M) of cysteine was reduced by chlorotriazole and aminotetrazole.

Injections with 4-amino-3,5,6-trichloropicolinic acid (picloram), 2-methoxy-3,6-dichlorobenzoic acid (dicamba), and butoxyethanol ester of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) satisfactorily killed the tops of scarlet oak (Quercus coccinea L.) and white oak (Quercus alba L.) when applied in March or June. Triethylamine salt of 2,4,5-T adequately killed the tops of the oaks in June but not in March. Picloram was the most lethal herbicide used on red maple (Acer rubrum L.), and sprouting was controlled more effectively on all species with picloram than with the other herbicides.

The effects of 22 herbicides on oxidative phosphorylation in mitochondria from cabbage (Brassica oleracea var. capitata L.) have been studied. Carbamates, phenoxyacids, 3,5-dimethyltetrahydro-l,3,5,2H-thiadiazine-2-thione (DMTT), N-1-napthylphthalamic acid (NPA), 2,3,6-trichlorobenzoic acid (2,3,6-TBA), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), and 2-chloro-2-N,N-diallylacetamide (CDAA) inhibited phosphorylation to a greater extent than oxygen uptake in cabbage mitochondria. The compounds 1,2-dihydropyridazine-3,6-dione (MH), 2,2-dichloropropionic acid (dalapon), 2,2,3-trichloropropionic acid (hereinafter referred to as 2,2,3-TPA), sodium chlorate, and 3-amino-l,2,4-triazole (amitrole) at concentrations as high as 1 × 10–2 M did not have a large effect on oxidative phosphorylation in cabbage mitochondria. Respiration which was stimulated by 2,4-dinitrophenol (DNP) or adenosine diphosphate (ADP) was inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D). Although 2,4-D did not affect Mg++-stimulated adenosine triphosphatase (ATPase), it inhibited an oleate-stimulated ATPase activity and the ATP-32Pi exchange reaction in cabbage mitochondria. The results suggest that 2,4-D may inhibit respiration in cabbage mitochondria by an effect on a reaction involved in coupling phosphorylation with electron transport.

As determined by bioassay of segmented soil columns, a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), N-butyl-N-ethyl-a,a,a-trifluoro-2,6-dinitro-p-toluidine (benefin), and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) varied in their leachability in a clay loam soil, even though their water solubility is the same. Nitralin was by far the more easily leached, benefin was least leached, and trifluralin slightly more so than benefin. Four A-in or more of water readily leached nitralin deep enough into the soil in amounts great enough to adversely affect the root growth of sensitive crop plants. Trifluralin and benefin were leached into the soil in relatively minute amounts, and these amounts were not great enough to affect root growth of sensitive crop plants when at least 0.5-in of untreated soil separated the seed from the layer of soil in which the herbicides had been mixed. The apparent breakdown product of nitralin present in moist soil was leached as readily as nitralin.

The proteolytic activity of the cotyledons of squash (Cucurbita maxima Duchesne) increases several fold during germination. The different herbicides varied widely in their ability to inhibit this increase. An attempt was made to correlate this inhibition with inhibition of growth. A direct correlation was evident only when the inhibition of proteolytic activity was severe or very slight to nonexistent.

The phytotoxicity and the persistence of ethyl N,N-dipropylthiocarbamate (EPTC), S-propyl butylethylthiocarbamate (pebulate), ethyl N-ethyl-N-cyclohexylthiocarbamate (hereinafter referred to as R-2063), and S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate) were studied in nutrient solution and in five soil types. Both in nutrient solution and in soil, EPTC was the most toxic to barnyardgrass [Echinochloa crusgalli (L) Beauv.], followed in order by pebulate, R-2063, and diallate. Herbicidal injury, as reflected by the morphological aberrations that occurred in treated plants, was much more severe than the reduction in fresh weight. Thus, toxicity studies based on plant height had greater validity than those based on weight. The initial toxicity of each herbicide was high in those soils low in organic matter and low in soils high in organic matter. The persistence of the four thiocarbamates in the soil was associated primarily with adsorptive forces and microbial degradation. In a soil with extremely large or small adsorptive capacity, there was rapid inactivation of the herbicides because of strong adsorption to the colloids or lack of adsorption with consequent loss by volatilization. Under the latter conditions, the microbial breakdown played only a secondary role. The herbicides persisted longer in soils with more moderate adsorptive capacities but were subjected to more striking degradation by microorganisms. The patterns and rates of inactivation of the four herbicides in a given soil were quite similar. A particular concentration of each herbicide stimulated growth in barnyardgrass, as reflected both in the fresh weights and in the heights of the plants. The nature of this stimulation was not determined.

The foliage and roots of Canada thistle (Cirsium arvense (L.) Scop.) readily absorbed 2-methoxy-3,6-dichlorobenzoic acid (dicamba) after which it was translocated by both phloem and xylem. The results are in harmony with a source-to-sink system of dicamba translocation in the phloem. Following foliar application, small amounts of dicamba were exuded by the roots into surrounding soil. Dicamba tended to accumulate in young, growing leaves following both foliar or root uptake. Leaves, but not roots, retained a substantial portion of the dicamba taken up. After 54 days, 63.1% of the recovered radioactivity in the treated leaf was still in the form of unaltered dicamba. The remaining 36.9% was in the form of an unidentified product. In other plant parts, much less change occurred. During a 54-day period, one-fifth of the dicamba applied was recovered as radioactive CO2.

In 1965 and 1966, alfalfa (Medicago sativa L., var. Cayuga) and birdsfoot trefoil (Lotus corniculatus L., var. Viking) were seeded in soil treated just before planting with ethyl N,N-dipropylthiocarbamate (EPTC). To determine herbicidal interaction on a field scale, 4,6-dinitro-o-Sec-butylphenol (DNBP) was applied as a postemergence treatment. No significant interaction of EPTC and DNBP was evident on legume or weedy grass stands on yield. Interaction of EPTC and DNBP on control of annual broadleaf weeds was noted 1 year but not the second. DNBP but not EPTC significantly reduced birdsfoot trefoil stands during both years and reduced alfalfa stands 1 year but not the other. EPTC controlled annual and perennial weed grasses and DNBP controlled annual broadleaf weeds successfully. The incorporation of EPTC in soil before planting alfalfa and birdsfoot trefoil followed by a postemergence DNBP treatment was considered to be a practical weed control method.

The effects of sublethal and lethal levels of 3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea (linuron) on the uptake of 32P and 45Ca were tested on tomato (Lycopersicum esculentum Mill., var. Kokomo) and parsnip (Pastinaca sativa L., var. Harris Model). Both levels of foliage-applied linuron stimulated the uptake of 32P from nutrient culture solution and its translocation to the leaves. The increased 32P in the leaves of the treated tomato plants was found in the inorganic phosphate fraction. Incorporation of the label in the phospholipid and nucleic acid fractions was decreased slightly. Linuron inhibited uptake and translocation of 45Ca in both plants.

An increase in Ca and SO4 uptake from nutrient solution in juvenile corn (Zea mays L. var. N. J. 9), soybean (Glycine max (L.) Merr., var. Kent) and large crabgrass (Digitaria sanguinalis (L.) Scop.) was obtained with 3-(3,4-dichloroyhenyl)-l-methoxy-l-methyl-urea (linuron) treatment. The uptake of K, Mg, NO3, and PO4 also was followed and varied with the ion and species.

Colonial bentgrass (Agrostis tenuis Sibth) and creeping bentgrass (Agrostis palustris Huds) exhibited the most tolerance to 1/2, 1, 1 1/2, and 3 lb/A of 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) when grown under cool temperatures, a long photoperiod, and a low pH medium. Injury from treatments was slight to moderate when applied from early to mid-spring, severe when made from late spring to early summer, and very severe when made from late summer to early fall. Silvex appeared to cause the most injury at the 1 and 1 1/2 lb/A rates. Injury was much less from the lower rate of 1/2 lb/A. Root fructosan concentrations decreased with increasing rates under cool temperatures and increased with increasing rates under high temperatures. Bentgrass appeared to tolerate silvex treatments better under low available moisture conditions than under high moisture levels.