One approach to the control of rhizomatous perennial weeds is to alter plant growth form to predispose the difficult-to-reach tissue to herbicides. Yellow nutsedge (Cyperus esculentus L.) was the test plant used in this study. Gibberellic acid induced erect rhizome growth whereas triiodobenzoic or naphthylphthalamic acids induced tuft-type growth as a result of a promoted and accelerated transformation of rhizomes to shoots.

Two months after 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) application (2.7 kg/ha), 80 to 100% of the total residue (1.3 to 4.2 μg/g) was in the upper 5 cm of soil. Herbicide movement occurred in soils that contained 3.8% organic matter or less. Pyrazon did not move below 10 cm or accumulate in soil as a result of movement. Adsorption of pyrazon was related to soil organic matter content (r = 0.90) and accounted for differences in herbicide movement previously observed. Calculations of pyrazon movement, based on soil organic matter content, coincided with depths of movement observed under field conditions.

The effect of humidity on the rate and direction of translocation of stem-injected (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) in bean (Phaseolus vulgaris L., var. Stringless Green-pod) seedlings was determined. A total of 0.75 μg of 14C-labeled 2,4,5-T was injected into the stem with a 1-μl syringe pipette. Translocation was determined by assaying the nutrient solution and plant parts for 14C. High relative humidities enhanced downward translocation to roots and nutrient solutions. About 41% of the applied 2,4,5-T was found in the nutrient solution after 2 days' treatment at about 95% relative humidity while only 23% was found when treatment was conducted at 20% relative humidity. Low humidity during treatment caused much more 2,4,5-T to be translocated upward to the primary leaves and young shoots of the seedlings and this effect was more pronounced in plants which were grown in low humidity prior to treatment. The results confirm the conclusions of others and show that the increased basipetal phloem transport of herbicides in plants under high humidity is not due to an effect on penetration of herbicides in leaf tissue.

We developed two tractor-mounted spraying systems which utilize compressed air for dispensing the spray. The nursery sprayer consists of a spraying platform, two windshields, and two hand booms, and was developed to spray brush up to 6 ft tall. A field sprayer was developed to spray brush up to 15 ft tall. This sprayer has two 20-ft booms, mounted on a modified front end loader which could be rotated hydraulically to either side of the tractor.

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.

Based on bioassays of soil samples from field plots, the rate of disappearance of 5-amino-4-chloro-2-phenyl-3 (2H)-pyridazinone (pyrazon) was estimated with a multiple regression equation. Within a limited geographic region, pyrazon residues were directly related to the organic matter content of soil and inversely related to rainfall during the growing season. The bacteria population increased with the presence of pyrazon in soil at soil temperatures ranging from 4.5 to 29.5 C, indicating a wide capability of microbiological utilization of the herbicide in soil. There was no evidence that soil bacteria or actinomycetes were adversely affected by pyrazon. Thin layer chromatography of ethanol extracts of soil containing 3H-phenyl-labeled and 14C-pyridazinone-labeled pyrazon revealed that pyrazon is dephenylated to 5-amino-4-chloro-3-pyridazinone. In a sandy loam soil, less than 10% of the herbicide was degraded to 5-amino-4-chloro-3-pyridazinone after 10 weeks at 21 C.

Transformation of N-(1,1-dimethylpropynyl)-3,5-dichlorobenzamide (compound I) in soil occurs readily and two products are produced, initial cyclization giving 2-(3,5-dichlorophenyl)-4,4-dimethyl-5-methyleneoxazoline (compound II) followed by subsequent hydrolysis to N-(1,1-dimethylacetonyl)-3,5-dichlorobenzamide (compound III). These transformations can be brought about in vitro, the first step by means of acid or base, and the second by extended treatment with acid. The rate of cyclization and hydrolysis of compound I varies directly with soil temperature, being rapid at high temperature (37 C) and very slow at low temperature (5 C). The rate of chemical change of compound I in soil is influenced to a much greater degree by temperature than by soil moisture content. The effect of soil type on transformation of compound I was studied and compounds II and III were present in five of the six soils examined. The herbicidal activity of compounds II and III was negligible in comparison to compound I.

We constructed a foam applicator capable of creating 300 to 400 gal of foam from 1 gal of water. The equipment was successful for applying herbicides in cotton (Gossypium hirsutum L., var. Stoneville 213) and soybeans (Glycine max Merr., var. Lee) after emergence. Weed control was equal with applications in foam as compared to conventional applications in water sprays. Foam production was highly dependent on the type and concentration of surfactant used. Various additives increased foam persistence in laboratory studies. However, for maximum effectiveness under field conditions, additives are needed that are more effective in increasing foam persistence than the ones evaluated.

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.

An 1130 IBM computer was used to process data from experimental plots to evaluate performance of preemergence herbicides in Hawaiian sugarcane fields (planted with varieties of four Saccharum spp.). The evaluation technique compares performance of experimental herbicides with the performance of three standard herbicides [2-(ethyl-amino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron)] under a wide range of environmental conditions. Under most conditions the substituted triazine 2-(sec-butylamino)-4-(ethylamino)-6-methoxy-s-triazine (GS-14254) gave better total weed control without crop toxicity than any of the three standards, and was particularly well-suited to regions of high rainfall.

Leaves of a number of plant species were surveyed for their CO2 compensation concentration which is one of the distinguishing characteristics used to classify plants on the basis of their photosynthetic capacity. Monocot genera with low CO2 compensation values are mainly limited to tribes of Chlorideae, Paniceae, Andropogoneae, Tripsaceae, and a part of Festuceae in Gramineae. Major grain crops, except corn (Zea mays L.) and sorghum (Sorghum vulgare Pers.), are primarily in the tribes of Hordeae, Aveneae, and Oryzeae, and have high CO2 compensation concentrations. Seven genera of dicots with low CO2 compensation occur in the four families of Amaranthaceae, Chenopodiaceae, Portulacaceae, and Euphorbiaceae. Major dicot crops are in the families Leguminosae and Malvaceae and have high CO2 compensation points. Low CO2 compensation concentration also is correlated with low carbonic anhydrase activity. Conversely, high CO2 compensation concentration plants have a high carbonic anhydrase activity. Data on the influence of light intensity and temperature on the rate of photosynthetic CO2 fixation in leaves from plants with high and low CO2 compensation concentration indicate differential responses of photosynthesis to these environmental factors. The data are interpreted as supporting a hypothesis for competition by specific plants.

Seeds of several weed species, each with initially known responses to light and temperature, were buried in soil in an open field at 2.5, 7.6, and 15.2-cm depths during November. At 3-month intervals during the following year, the seeds were recovered in the dark and reexamined for their response to light and temperature, and their viability. Loss in viability occurred fastest with seeds having little initial dormancy and with shallow placement of seeds. Phytochrome was important in controlling germination of the recovered weed seeds, and manifested itself as an acquired type of dormancy, as well as an initial one. However, other factors in the soil environment appear to interact with the phytochrome system in the control of germination of weed seeds in soils.

The common purslane plant (Portulaca oleracea L.) flowered and produced seeds throughout the growing season. Seeds were mature about 15 days after flowering. Increased light intensity and temperature stimulated growth. In general greater yields were obtained under cool white light, followed by yields under green, blue, red, and yellow light, in that order. With high temperature during the light period and low temperature during the dark period, best growth occurred under green light.

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.

Carbon-14-labeled 2-chloro-4,6-bis(ethylamino)-s-trazine (simazine) was applied at a low concentration to the root media of rye (Secale cereale L.), soybean (Glycine max L.), and corn (Zea mays L.) plants growing in nutrient solution that contained nitrate or ammonium nitrogen. The shoots of the plants grown on nitrate nitrogen contained more radioactive simazine per unit fresh weight than the plants that were grown on ammonium nitrogen. Less herbicidal injury was observed on soybean plants grown in soil fertilized with ammonium sulfate than on soybean plants fertilized with calcium nitrate.

Studies were conducted to determine the tolerance of several crops to herbicide sprays containing three spray drift control adjuvants, a cross-linked polyacrylate (Norbak), a pseudo-plastic spray gel agent composed primarily of natural carbohydrates (Dacagin), and hydroxyethylcellulose (Vistik). Other studies were conducted to observe the effect of the adjuvants on the efficacy of 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat) when used with or without a surfactant, the effectiveness of the adjuvants in preventing 3-amino-s-triazole plus ammonium thiocyanate (amitrole-T) from being washed off plants, and the effect of the adjuvants in reducing vapor loss of the ethyl ester of (2,4-dichlorophenoxy) acetic acid (2,4-D) from leaves. Little increased injury was caused from the addition of the adjuvants to herbicides sprayed on several crops. The adjuvants added to paraquat were not effective substitutes for surfactant; however, Dacagin or Vistik added to paraquat combined with surfactant did not reduce the efficacy of paraquat. Norbak reduced the efficacy of paraquat, with or without the addition of surfactant. The adjuvants did not prevent amitrole-T from being washed off plants. Results of vapor studies suggested that Dacagin and Norbak reduced vapor loss of the ethyl ester of 2,4-D from plant surfaces.

Assimilate transport in purple nutsedge (Cyperus rotundus L.) was studied using autoradiographic technique. Results show the basic pattern of assimilate distribution was from areas of synthesis to areas of use or accumulation. The initial underground centers of high metabolic activity were replaced as these organs matured, by new centers of actively growing rhizomes, tubers, and roots. The planted tuber did not accumulate assimilates. Treatment of purple nutsedge plants with 2,6-dichlorobenzonitrile (dichlobenil) resulted in accumulation of assimilates in the tubers rather than in young underground tissues. Leaves of treated plants also accumulated labeled assimilate in excess of control plants. Assimilate accumulation in leaves of dichlobenil-treated plants resulted from the destruction of the phloem in the basal portions of the leaf-sheaths. An increase in tuber respiration accompanied an increase in accumulation of assimilates in dichlobenil treated tubers.