The changes in the nucleic acid metabolism were studied in plants susceptible and resistant to 4-amino-3,5,6-trichloropicolinic acid (picloram). The total RNA and DNA content of the tissue correlated inversely with the herbicide resistance; the resistant plants were low in nucleic acids, whereas sensitive plants were high. The increase in the nucleic acids of the sensitive species 24 hr after picloram treatment appeared to be associated with lower levels of ribonuclease and deoxyribonuclease. The inability of the resistant species to make more RNA may be associated with high levels of nucleases in the tissue.

Five species of Nymphaeaceae, representing four genera, were collected from various sites in New Jersey and their tissues analyzed for 12 elements. Three species were separated into leaf blades and petioles before the mineral analyses were made. Variations in the concentrations of many elements were noted between these two structures. Except for the petioles of these three species, the N content of the plants appeared to be sufficiently high so that no extra N would be required to prepare composts from them.

Water samples were taken from Pickwick Reservoir from 1965 through 1968 and the nitrogen and phosphorus content determined. The nitrogen and phosphorus content over a period of 3 years was not related to the year-to-year plant growth. Physical and climatic data were obtained from 1961 through 1968, and it was found that available light was controlled by the amount of rainfall and ensuing reservoir elevation during the critical plant growth period in April and May. Available light was correlated with the 2 years of severe infestations.

The influence of six Arkansas soils on the leaching characteristics of derivatives of 3-amino-2,5-dichlorobenzoic acid (amiben) and 3-nitro-2,5-dichlorobenzoic acid (hereinafter referred to as dinoben) in slotted soil columns was determined using large crabgrass [Digitaria sanguinalis (L.) Scop.] bioassay. The ammonium and aluminum salts of amiben and the sodium salt of dinoben were easily leached and leaching was not noticeably affected by soil type. The ammonium salt of amiben was not adsorbed, while the methyl ester of amiben was adsorbed by these soils. Adsorption was related to the clay and organic matter content of the soil. Methyl and butoxyethyl ester derivatives of amiben and dinoben resisted leaching in these soils and the amide of amiben was intermediate in leaching. The adsorption and leaching behavior of the ester derivatives of these compounds were complicated by their rapid hydrolysis in these soils. The hydrolyzed product behaved identically to the salt derivatives of the compounds in leaching, adsorption, and chromatographic properties. Hydrolysis of the methyl ester was inhibited by soil sterilization, dry soil, and temperatures below 20 C. In non-sterile, warm, moist soil, the half-life of the methyl ester of amiben was 28 hr. Four species of Bacillus were capable of hydrolyzing the methyl ester of amiben in pure culture studies.

Preplanting application of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), reduced the number of monosodium methanearsonate (MSMA) applications needed for the control of johnsongrass (Sorghum halepense (L.) Pers.). The combined effect enabled weed control to be completed before cotton (Gossypium hirsutum L.) began to bloom, and hence without causing damage to the crop.

Field bindweed (Convolvulus arvensis L.) was sprayed with a mixture of (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram). A mixture of picloram and 2,4-D each at 0.01 lb and 0.001 lb/A killed tops of plants faster than 2,4-D alone or picloram alone at the same rates. Higher rates of 1 lb/A picloram plus 1 lb/A 2,4-D and 0.1 lb/A picloram plus 0.1 lb/A 2,4-D were not consistently synergistic or antagonistic. The percent of plants which produced new growth were 0 for picloram alone at 1 lb/A, 20 for a mixture of 2,4-D and picloram each at 1 lb/A, and 40 for 2,4-D alone at 1 lb/A. Other rates of 0.1 lb/A, 0.01 lb/A, and 0.001 lb/A did not control regrowth of field bindweed. Application of unlabeled picloram simultaneously with 14C-2,4-D increased translocation of 14C-2,4-D, but the reverse was not true.

Pretreatment of potato (Solanum tuberosum L., var. Russet) tuber discs in pH 5.5 buffer significantly reduced uptake of picloram (10−3M). Tissue pretreated in buffer at 7 C subsequently absorbed more picloram than tissue pretreated at 25 C. Inclusion of cetyl trimethyl ammonium bromide (hereinafter referred to as CTAB) (2 × 10−4M) in the treating solution caused a significant increase in picloram uptake in tissues that were not pretreated in buffer. The reduction in uptake caused by buffer pretreatment was effectively reversed when CTAB was included in the treating solution. The results suggest that picloram uptake by potato tissue is related to the availability of the quaternary ammonium binding sites provided by membrane phosphatides.

The fate of 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) in greenhouse-grown juvenile corn (Zea mays L., var. N. J. 9), soybean (Glycine max (L.) Merr., var. Kent), and crabgrass (Digitaria sanguinalis (L.) Scop.) was investigated. Linuron entered the plants from nutrient solution with the water absorbed. A small but measurable amount of the herbicide was found in the tissue as 3-(3,4-dichlorophenyl)-1-methoxyurea and as 3,4-dichloroaniline. A materials balance between linuron uptake and acetone extractable linuron plus metabolites found could not be achieved. Evidence is presented for the presence of “bound” linuron which accounted for from 15 to 25% of the herbicide absorbed.

Plant heights and seed yields of oats (Avena sativa L.), corn (Zea mays L.), and soybeans (Glycine max (L.) Merr.) were lower where these crops followed a heavy infestation of quackgrass (Agropyron repens (L.) Beauv.) than when they followed oats or fallow land. Application of ammonium nitrate (280 kg/ha) only partially corrected the adverse effect on yield of a previous quackgrass infestation. The effect of quackgrass persisted through the second growing season as measured by height and yield of wheat (Triticum aestivum L.) and compared with wheat after oats, corn, soybeans, or fallow, but the effect of nitrogen applied the first year only did not persist through the second year.

We compared foliage sprays of (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram) for control of Macartney rose (Rosa bracteata Wendl.) applied with ground equipment and airplane. Picloram at 0.5 lb/A was more effective than 2,4-D at 2 lb/A at all dates of application on mowed roses; however, time of application was important. Picloram was most effective in late April and early May, but 2,4-D was most effective in late May and early June. Combinations of picloram and 2,4-D were effective from late April to late June. If mowing is followed by foliage treatment of 2,4-D, the interval between mowing and spraying should be at least 1 year if mowing is done in the spring. The interval between mowing and spraying was not critical when picloram was applied not later than early May. Mowing in the summer reduced the effectiveness of subsequent 2,4-D and picloram treatments applied the following year. Aerial applications of 2,4-D and picloram on undisturbed Macartney rose plants in the fall were not as effective as spring applications; however, two successive fall applications of picloram at 1 lb/A resulted in control equivalent to that obtained with a single 2 lb/A application in spring.

Data were collected on 36 variables including application, environmental, edaphic, and plant conditions during a 3-year study of aerial brush control treatments at 79 sites. These then were correlated with defoliation responses of blackjack oak (Quercus marilandica Muenchh.) and post oak (Quercus stellata Wangenh.) to (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T). The stage of oak growth was of primary importance in obtaining maximum defoliation with 2,4,5-T; the oaks were most susceptible 6 to 8 weeks after the last killing frost. Air temperatures above 90 F, relative humidity below 60%, poor spray coverage and swath widths greater than 50 ft significantly reduced defoliation by 2,4,5-T. Total rainfall during the month before spray application was positively correlated with defoliation by 2,4,5-T, but correlations with rainfall for other time intervals before and after spraying were not significant. Wind above 6 mph at the time of treatment slightly reduced 2,4,5-T effectiveness, but wind direction and dew at spray time did not influence herbicide activity. Application rates of less than 1.75 lb/A were not as effective as higher rates. Aircraft design, spray-water carrier constituents, soil type, soil depth, soil temperature, and topography had no apparent influence on defoliation of oaks by 2,4,5-T.

Germination of tumble mustard (Sisymbrium altissimum L.), tansy mustard (Descurainia pinnata (Walt.) Britton), and yellowflower pepperweed (Lepidium perfoliatum L.) is partially dependent on total degree hours of incubation (temperature above 0 C times the duration of incubation). This relation was similar under constant or alternating temperatures. Alternating temperature regimes with −20 C inhibited germination, and greatly depressed subsequent germination at optimum temperatures. Tansy mustard and yellowflower pepperweed have temperature-dependent after-ripening requirements. Germination of all three species responded similarly to osmotic stress. The relation between tumble mustard germination under osmotic or soil moisture stress is dependent on the texture of the soil substrate. A mucilaginous coating greatly aids the germination of yellowflower pepperweed seeds on the surface of media under low (0.05 to 0.2 bars) moisture tension. Germination of seeds of the three species recovered in soil samples from the field is radically different from that of freshly harvested material. The seeds acquire a dormancy which is broken irregularly under ideal conditions for germination.

Treatment of tobacco (Nicotiana tabacum L., var. NC-402) with 2,3,5-trichloro-4-pyridinol (pyriclor) leads to progressive disruption of chloroplast ultrastructure. Initial changes include the inception of a spherical form, swelling of the fret system, and commencement of loss of starch. More advanced changes include the complete disappearance of starch, further swelling and disorganization of the fret membrane system, followed by swelling and disruption of the membranes of the granal discs and rupture of the chloroplast envelope. The changes induced by pyriclor on chloroplast ultrastructure in tobacco are analagous to those caused by 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) on kidney bean (Phaseolus vulgaris L.) and barnyardgrass (Echinochloa crusgalli L. Beauv.). The shape and size of mitochondria were not altered by treatment with the chemical; however, there appeared to be a significant increase in the number of mitochondria present when alterations in chloroplast structure could be seen. The appearance of visual symptoms of phytotoxicity (chlorosis) correlated with the onset of disruptive changes in chloroplast ultrastructure.

Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triaazine] diffused at a rate of 15.2 × 10−8 sq cm/sec at 25 C which was faster than the diffusion rate of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) in the same soils. Diffusion rates were highly correlated with total surface area of the soil. Increasing soil moisture content, soil pH, and soil temperature resulted in greater diffusion rates. A relative indication of herbicide mobility may be obtained from some of the physical and chemical properties of the soils and herbicides involved; however, rate of diffusion appears to be governed by a combination of soil and herbicide properties.

Added surfactant (Atlox 210) at 1% (v/v) and high relative humidity enhanced the penetration of both 4-amino-3,5,6-trichloropicolinic acid (picloram) and (2,4-dichlorophenoxy)acetic acid (2,4-D) into detached leaves of aspen poplar (Populus tremuloides Michx.). The influence of added surfactant was greater for picloram and the dimethylamine of 2,4-D than for the ethyl or butoxyethanol ester of 2,4-D. Penetration of picloram and the dimethylamine of 2,4-D occurred more readily from the abaxial than from adaxial surfaces of leaves. The ethyl ester of 2,4-D penetrated equally readily from both leaf surfaces. Penetration of picloram and the dimethylamine of 2,4-D from the adaxial surface of leaves occurred readily in young leaves in early June. There was an increase in penetration in early July followed by a decrease in August and September to a level equal to or less than that in June. Penetration from the abaxial surface of leaves was nearly equal in June and July, but there was a gradual decrease in August and September. An increase in temperature from 10 to 25.5 or to 40.5 C resulted in a sharp increase in penetration of both picloram and 2,4-D under both low and high relative humidity. Autoradiographic evidence showed that movement of picloram within the leaf also was much more extensive at the higher temperatures. Partial removal of cuticular waxes from the adaxial surface of leaves with chloroform resulted in up to four-fold increases in penetration of picloram and 2,4-D. Differences in penetration rate of picloram between leaves of aspen poplar and balsam poplar (Populus balsamifera L.) did not account for reported differences in susceptibility between these two species.

Uptake and movement of various herbicides and auxins by bean (Phaseolus vulgaris L.) petiole sections were studied. Isopropyl m-chlorocarbanilate (chlorpropham) was the most mobile of the compunds studied, followed in order of decreasing mobility by: indole-3-acetic acid (IAA), 3-amino-s-triazole (amitrole), (2,4-dichlorophenoxy)acetic acid (2,4-D), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), and 3-amino-2,5-dichlorobenzoic acid (amiben). Amiben immobilization may have been due to glucoside formation in the tissues. IAA was rapidly transported through basipetally but not acropetally oriented tissue. Tissue orientation had little effect on the movement of the other compounds. Mobility of the compounds studied, in general, appears to be a function of the amount of uncomplexed parent chemical. Retention is likely the result of conjugation with products in the cells or of physical binding in the cells.

Pretreatment of bean (Phaseolus vulgaris L.) petiole sections with one of several metabolic inhibitors greatly stimulated the movement of 3-amino-2,5-dichlorobenzoic acid (amiben) and (2,4-dichlorophenoxy)acetic acid (2,4-D). However, the movement of 3-amino-s-triazole (amitrole), 3-(3,4-dichlorophenyl)-1-methylurea (linuron), and isopropyl m-chlorocarbanilate (chlorpropham) was stimulated only slightly or not at all. The basipetal movement of indole-3-acetic acid (IAA) was inhibited by concentrations of 2-sec-butyl-4,6-dinitrophenol (dinoseb) which stimulated respiration (5 × 10−7 M to 5 × 10−8M). Acropetal movement was stimulated by dinoseb concentrations greater than 10−5M. Translocation of root-applied amiben and 2,4-D to the stems and leaves of whole plants of bean, squash (Curcurbita pepo L.), and cucumber (Cucumis sativus L.) was stimulated by dinoseb root applications only at concentrations which were highly injurious to the plants. Amiben, 2,4-D, and their metabolites were extracted from dinosebtreated and untreated tissues. The stem exudate from cucumber plants fed amiben and 2,4-D via the roots contained primarily the parent compounds, which indicates that the parent compounds are the primary components translocated through the xylem.

An increasingly urgent need exists for men, broadly yet specifically, trained in the areas of crop protection. Crop protection includes weed control, insect control, plant disease control, and pesticide analysis. The need extends across teaching, research, development, sales, application, management, and other areas encompassed by crop protection. Administrative and financial advantages may result from the development of this type of program. Curricula for the BS, MS, and PhD degrees have been developed which offer a broad base of crop protection but allow pursuit of the degree from (or specialization in) any of the areas of crop protection. At the same time, however, chemistry and physiology form the disciplinary basis of all science curricula and the focal point is graduate training. Four courses relevant to all areas of crop protection and five additional courses in weed science have been developed.

Effects of the alkanolamine salt of (2,4-dichlorophenoxy) acetic acid (2,4-D) and sodium salt of 4-hydroxy-3,5-diiodobenzonitrile (ioxynil) upon seedlings of Chewings fescue (Festuca rubra var. commutata Gaud.), Park bluegrass (Poa pratensis L.), and Highland bentgrass (Agrostis tenuis Sibth.) were evaluated in growth room and field studies. In the former, injury to Park bluegrass from both 1 and 3 lb/A applications of 2,4-D was severe with pronounced but less marked effects on fescue and bentgrass. Results were similar from applications shortly after emergence and after clipping the grass. Negligible injury was caused by 1 lb/A of ioxynil. In the field, ioxynil gave better weed control than 2,4-D when applied at a seedling height of 1 inch. No injury was caused by ioxynil. Although 2,4-D reduced yields from early clippings, there was marked recovery, even at 3 lb/A. No treatments significantly affected plant stand.

After 3 days or more germination in 5-(2,3-dichloroallyl) diisopropylthiocarbamate (diallate) or S-(2,3,3-trichloroallyl)diisopropylthiocarbamate (triallate) vapor, shoots and roots of wild oat (Avena fatua L.) and spring wheat (Triticum aestivum L.) were measured, sectioned, stained, and squashed for comparison of growth and mitotic activity. Shoot tissue of wild oat was damaged more readily than root tissue by diallate vapor. The meristematic tissue at the base of the first leaf was apparently more vulnerable than stem apex tissue since it exhibited more divisions and a greater number of abnormalities. The effect of triallate was similar but less pronounced. Shoot tissue of wheat also was more sensitive to diallate than root tissue. This was indicated by reduced mitotic activity and by shoot inhibition. Few abnormalities were observed in wheat even at high concentrations. Results were similar with triallate. Root and shoot measurements indicated that wheat was more tolerant to triallate than to diallate. Shoot inhibition occurred in both wild oat and wheat at concentrations that did not affect mitosis. Mitotic damage from the use of either diallate or triallate thus appeared to be of secondary importance, the major effect being on some phase of cell elongation or expansion.