Field studies were conducted in 1978 and 1979 on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] management in peanuts [Arachis hypogaea (L.) ‘Florigiant′]. In both years, preplant incorporated applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided better than 75% initial control of broadleaf signalgrass. Preemergence applications of alachlor and metolachlor provided 90% or better initial control. Vernolate (S-propyl dipropylthiocarbamate) and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) provided less than 45% initial control. An at-cracking application of dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid) plus either alachlor or metolachlor increased control over that provided by at-planting herbicides alone and maximum yields were obtained. No at-planting herbicide alone provided better than 60% control at harvest and consequently yields were lower. In three of four experiments, sequential applications of at-planting and at-cracking herbicides provided better than 75% control at harvest. In the fourth experiment, only benefin and metolachlor followed by at-cracking applications provided better than 70% control at harvest.

Concentrations of 2,2-dichloropropionic acid (dalapon), trichloroacetic acid (TCA), and (2,4-dichlorophenoxy) acetic acid (2,4-D) were determined in irrigation water following bank applications for weed control. Maximum concentrations of dalapon in the water varied from 23 to 365 ppb from application rates of 6.7 to 20 lb/A. The highest levels of TCA ranged from 31 to 128 ppb following applications of 3.8 to 5.9 lb/A. Applications of 1.9 to 3 lb/A of 2,4-D produced maximum concentrations of 25 to 61 ppb. Reduction of herbicide levels appeared to be due to dilution as the water flowed downstream. Rates of reduction in herbicide levels showed that negligible concentrations would remain after the water traveled a distance of 20 to 25 miles. The low concentrations of herbicides observed in the irrigation water likely would not be hazardous to crops or animals.

The type of growth chamber environmental regime used altered the response of sugarbeets (Beta vulgaris L. ‘USH-9′) to desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)]. No difference occurred in growth retardation following treatment at different times of day when standard growth chamber constant day/night temperature and light cycles were used. When temperatures were programmed and light intensity varied during the day/night cycles, approximating out-of-doors daily cyclic conditions, the herbicide caused greater injury following morning treatments and less injury following late afternoon treatments. Data obtained in the growth chamber under the typical constant day/night pattern did not agree with field derived information; data obtained using the programmed temperature and varying light regime agreed well with field data and with known action of desmedipham. Plants stressed for moisture after treatment were less retarded than plants turgid at treatment; but both showed relationships to time of day at treatment similar to those noted above. Moisture stress prior to treatment diminished growth retardation by desmedipham, and reversed the treatment time of day effect.

Texas panicum (Panicum texanum Buckl. # PANTE) is a native of the Southwest, now increasing as a weed throughout the southern United States, whereas wild proso millet (Panicum miliaceum L. # PANMI) is an introduced weed currently increasing in importance in the northern Midwest. In controlled-environment chambers, both species produced more tillers, greater leaf area, and more total dry weight at 30/24 C day/night (simulated growing season temperature in Georgia) than at 24/18 C (simulated growing season temperature in Minnesota). Texas panicum accumulated more dry matter at 30/24 C than did wild proso millet, while wild proso millet accumulated more dry matter at 24/18 C than did Texas panicum. When the two species were grown together, Texas panicum was the superior competitor at 30/24 C while wild proso millet was superior at 24/18 C. Exposure to short photoperiods at an intermediate temperature of 27/21 C accelerated flowering and limited vegetative growth in both species. In the range of photoperiods (10 to 16 h) examined, wild proso millet always flowered earlier and, consequently, produced less vegetative growth than Texas panicum. Its responses to temperature and photoperiod indicate that wild proso millet probably would be competitively inferior to Texas panicum and other adapted grass weeds in the southern United States.

Green kyllinga is a relatively new weed species in well-irrigated turfs in the southwest US. To understand the germination requirements of green kyllinga, the effects of planting depth, temperature, pH, and osmotic potential were determined. Green kyllinga emergence was sensitive to planting depth. At 21 days after planting (DAP), emergence of green kyllinga was 60% when planted at the soil surface but only 20% at 0.5 cm and less than 5% at 1 cm. Germination occurred at temperatures between 17 and 30 C but was notably better between 20 and 24 C. Germination was uniform from pH 5.5 to 9.5. Germination decreased between the water potentials −0.1 to −0.6 MPa, although germination was high at water potentials found in irrigated turf. The environmental conditions found in nonstressed turf areas in Arizona will likely support the establishment of green kyllinga. The efficacy of herbicides for the control of green kyllinga was also determined. Control of kyllinga (95% or greater) was obtained with preemergence applications of oxadiazon, dithiopyr, and metolachlor, and with postemergence applications of DSMA, halosulfuron-methyl, and imazaquin.

Corn (Zea mays L. ‘Funk's G-83’) seedling leaves exposed to flame-generated ultra-high temperatures produced in flame cultivation were fixed in glutaraldehyde, post fixed in osmium tetroxide, and embedded in Araldite. In the light microscope, bundle sheath cells of flamed tissue were more heavily stained with Azure II and less vacuolated than were nonflamed cells. Heated mesophyll cells contained swollen, disrupted, and granular chloroplasts. Examination of flamed tissue by electron microscopy revealed granular, dispersed cytaplasm and altered membrane systems. Chloroplast lamellar systems and envelopes, tonoplasts, and plasmalemmas were disintegrated in both bundle sheath and mesophyll cells.

The absorption and translocation patterns of foliar applied 14C- chlorsulfuron {2-chloro-N- [[(4-methoxy-6-methyl-1,3,5- triazin- 2 - yl)amino] carbonyl] benzenesulfon-amide} and 14C-metsulfuron {2- [[[[(4-methoxy-6-methyl-1,3,5- triazin- 2-yl)amino] carbonyl] amino] sulfonyl] benzoic acid} in wild garlic (Allium vineale L. # ALLVI) were similar. Both 14C-chlorsulfuron and l4C-metsulfuron were readily absorbed by wild garlic, with 62 and 58%, respectively, of the applied doses absorbed 144 h after application. After 144 h, 17% of the applied 14C-chlorsulfuron and 16% of the applied 14C-metsulfuron were translocated out of the treated leaf, with the greatest amounts concentrating in young shoot tissues. Chlorsulfuron and metsulfuron reduced wild garlic shoot dry weight, height, and the number of leaves, more when they were applied to the foliage, or to both the foliage and the soil, than when they were applied to the soil alone.

Survival of foxtail grass in undisturbed sites was tested in a 4-yr study of robust white foxtail (Setaria viridis var. robusta-alba Schreiber), robust purple foxtail (Setaria viridis var. robusta-purpurea Schreiber), giant green foxtail [Setaria viridis var. major (Gaud.) Posp.], yellow foxtail [Setaria lutescens (Weigel) Hubb.], and giant foxtail (Setaria faberi Herrm.). Regardless of taxa seeded, giant foxtail dominated the stand with small amounts of yellow foxtail in the fourth year. Although the foxtail taxa stands corresponded to the taxa seeded in the first year of growth, robust white foxtail, robust purple foxtail, and giant green foxtail completely or nearly disappeared within 4 yr of having been seeded alone or with other taxa, and generally sooner when mixed with giant foxtail. Because of the rapid dominance of giant foxtail, the robust white foxtail, robust purple foxtail, and giant green foxtails are not likely to become a source of seed for infestation from fencerows to production fields.

The uptake and transport of carboxyl-labeled and unlabeled butoxyethyl esters and ammonium salts of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) by honey mesquite (Prosopis juliflora (Swartz) DC, var. glandulosa (Torr.) Cockerell) leaves were compared as measured by liquid scintillation counting and gas chromatography. Absorption of 2,4,5-T was determined by assaying leaf-rinsing solutions and extracts of treated leaves. Transport of 2,4,5-T was measured by determining amounts of 2,4,5-T found in stem tissue. The methods of analysis gave comparable results when extraction, cleanup, and analytical procedures were identical. When cleanup and methylation procedures were eliminated for the radioisotopic analyses, radioisotopic analyses gave significantly higher values for extracts of treated leaves than did gas chromatographic analyses. Larger amounts of 2,4,5-T were recovered from leaves treated with the butoxyethyl esters of 2,4,5-T than with ammonium salts.

Stress caused by early weed competition is known to delay the rate of maize development which may result in a decrease in kernel number. Kernel number in maize is correlated negatively with the length of the anthesis-silking interval (ASI). A short ASI has been identified as an easily measured, visual trait which may identify enhanced drought tolerance in maize. Field studies were conducted to test whether: (1) delaying weed control would result in a lengthening of ASI in both a drought tolerant and non-drought tolerant maize hybrid and (2) the presence of drought tolerance genetics comes at a physiological cost, resulting in a greater yield reduction under weedy conditions. In this study, the response of a drought tolerant hybrid with its non-drought tolerant near-isoline was compared to seven different timings of weed control using wheat as a surrogate competitor. Results confirmed that there was no treatment by hybrid interaction at any site–yr for any of the parameters evaluated. Delaying weed control reduced plant height, leaf tip number, shifted and reduced biomass accumulation, kernel number and grain yield and lengthened ASI for both hybrids. Although yield losses occurred with the delay in weed control timing, no yield differences were observed between hybrids suggesting that there was no additional physiological cost associated with the drought tolerant traits. The drought tolerant hybrid, however, was found to have a shorter ASI, lower kernel number and higher kernel wt compared to the non-drought tolerant hybrid. This study confirmed that delaying weed control can influence the length of ASI, which is an important drought tolerant trait. The lengthening of ASI by early weed competition resulted in a rate of yield loss of 0.13 T ha−1 growing degree days (GDD)−1 when averaged across both hybrids and all treatments.

Goosegrass, a widely distributed annual weed, creates difficult problems in heavily used turf areas. The seriousness of this weed problem, especially on golf course greens and tees, has suggested studies for its control. Very little research has been conducted in regard to this grass. Germination studies by Toole and Toole3 showed that 0.2% potassium nitrate was superior to water when used to moisten the substratum. Their work also indicated exclusion of light had little effect on germination at alternating temperatures of 20°–30°. The present study includes more complete temperature and light comparisons, and attempts to demonstrate light and temperature effects on seed germination.

Work conducted in recent years with volatile herbicides has shown that many of these materials give extremely variable results when sprayed on the soil surface but are fairly consistent when incorporated in the soil. Methods of determining distribution and placement of these materials in soil are generally tedious and often complicated due to a number of factors, including volatilization and leaching. Substitution of a fluorescent material for the herbicide in the application equipment offers a useful method of studying placement and distribution of sprays in the soil.

Complete control of annual bluegrass (Poa annua L.) at all levels of P and at both planting dates was obtained with a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 2 lb/A. For both planting dates, high levels of P reduced the effectiveness of both calcium arsenate (CaAs) and to a small degree dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA). On a plant count basis, O-(2,4-dichlorophenyl)O-methyl isopropylphosphoramidothioate (DMPA) was more effective than N-(2-mercaptoethyl) benzenesulfonamide S-(O,O,-diisopropyl phosphorodithioate) (bensulide) for the control of annual bluegrass.

In the field, injury to bentgrasses (Agrostis palustris Huds.) from preemergence herbicides generally was specific to one or two varieties. Washington bentgrass was severely injured from a 12-lb/A application of 1-(2-methylcyclohexyl)-3-phenylurea (siduron).

Seeds of Striga asiatica (L.) Kuntze were induced to germinate with a stimulant from host exudates in the presence of a water-soluble germination inhibitor extracted from Striga seeds. Germination obtained was dependent upon the relative concentrations of stimulant and inhibitor present in the germination medium. The inhibitor had no effect on radical elongation of Striga seeds that germinated in its presence.

Broomrapes (Orobanche and Phelipanche species, Orobanchaceae) are obligate root parasites of dicotyledonous plants. This taxonomic group includes seven weedy parasites of agricultural crops that damage vegetables, sunflower (Helianthus annuus L.), and legumes. Processing-tomato (Solanum lycopersicum L.) fields in Israel have been recently found infested with a new broomrape, first identified as nodding broomrape (Orobanche cernua Loefl.) based on its host. However, its morphology resembled the closely related sunflower broomrape (Orobanche cumana Wallr.), an obligate parasite of sunflower. The new race (CUCE) parasitized sunflower, tomato, and tobacco (Nicotiana tabacum L.) in vitro, in a polyethylene bag system and in pots. Its seeds germinated in response to strigolactones (orobanchol, 5-deoxystrigol, 2′-epiorobanchol, and GR24) and dehydrocostus lactone (DCL), whereas O. cumana seeds responded only to DCL and GR24, and O. cernua only to strigolactones. Based on morphological similarities with O. cumana, shared molecular markers with O. cumana, ability to parasitize sunflower and respond to sunflower-germination stimulants, it was concluded that CUCE is a new race of O. cumana, with a host range expanding to Solanaceae crops. While being an important noxious weed of sunflower, this new O. cumana race is currently spreading and posing a threat to processing tomato in Israel. This finding is an alarming indication that broomrapes can shift host range and that similar new races of O. cumana could potentially appear in other countries.

If there was no heavy rainfall or surface irrigation before corn emergence, as ethyl-N,N-di-n-propylthiolcarbamate (EPTC) at 3 lb/A was incorporated deeper into the soil, more corn plants were injured, the height of plants was reduced, and a loss in weight or yield occurred, although the germination of the corn seed was not affected. Implements used to incorporate EPTC did not produce significantly different amounts of corn injury where used at the same depth.

Metabolic incorporation of adenine-2-14C by Saccharomyces cerevisiae was examined for alterations produced by 3-amino-1,2,4-triazole (amitrole) and histidine. The radioactivity recovered from cells after a 4-hour incubation was found predominantly in ethanol-insoluble components (nucleic acids and proteins) of untreated cultures. Amitrole inhibited incorporation of 14C into insoluble components. Carbon-labeled imidazoleglycerol phosphate, a precursor of histidine, and labeled imidazoleglycerol accumulated in the ethanol-soluble fraction of amitrole treated cells. Imidazoleglycerol accumulated in the external medium. Histidine prevented 14C incorporation into the hot trichloroacetic acid-insoluble residue (protein), prevented amitrole-induced imidazoleglycerol and imidazoleglycerol phosphate accumulation, and circumvented amitrole inhibition of 14C incorporation into the hot trichloroacetic acid-soluble (nucleic acids) fraction.

Common lambsquarters was treated with metamitron (M) and glyphosate (G) to investigate chlorophyll content as a single, biological parameter for indicating sub-lethal-treated weeds. In three different greenhouse experiments the herbicides were applied at dose rates of 1/8, 1/4 and 1/2 times the M-recommended dose rate (= 0.7 kg ai ha−1), and 1/16, 1/8, and 1/4 times the G-recommended dose rate (= 1.44 kg ai ha−1), respectively. Three weeks after herbicide application the chlorophyll content in leaves of plants treated with 1/2 M was lower than the control. At the same time the chlorophyll content in leaves of plants treated with 1/8 and 1/4 M was higher than the control. The chlorophyll content in the leaves of plants treated with 1/16 and 1/8 G was also higher than the control, but the chlorophyll content in the leaves of plants treated with 1/4 G was equal to the control. A dose of 1/2 M killed 30% of available plants within 29 d, but most of the plants were still alive after 29 d when 1/4 M, 1/8 M, 1/4 G, 1/8 G and 1/16 G had been used. The fresh weight of the biomass reflected the fitness of the plants observed with time and was related to chlorophyll content. The dry weight of the biomass, however, was probably related to the typical action of metamitron and glyphosate. Measurements with a remote sensing technique supported the measurement of chlorophyll with a spectrophotometer confirming a significant discrepancy with time between a herbicide's affect on chlorophyll content and on plant growth. Because differences in chlorophyll content may have caused differences in the progress of plant degradation in sub-lethal- and lethal-treated plants, it is concluded that the chlorophyll content can be used as a single, biological parameter for indicating sub-lethal dose rates of metamitron and glyphosate.

Intraspecific and interspecific interference effects on growth, gas exchange, and water potential of wild oat and spring barley were measured under greenhouse conditions using a 1:1.06 barley to wild oat replacement series. Intraspecific barley interference affected barley growth more than interspecific wild oat interference. Interspecific wild oat interference with barley reduced wild oat growth more than intraspecific interference. Wild oat plant height surpassed barley plant height near barley anthesis. Growth and gas exchange of barley and wild oat responded the same to short-term water stress.

Application time did not greatly influence control of velvetleaf (Abutilon theophrasti Medik. # ABUTH) or common lambsquarters (Chenopodium album L. # CHEAL) in no-till corn (Zea mays L. ‘Pioneer 3747’) with fluorochloridone {3-chloro-4-(chloromethyl)-1-[3-(trifluoromethyl) phenyl]-2-pyrrolidinone}. Giant foxtail (Setaria faberi Herrm. # SETFA) control was reduced as much as 25% by 90 days after planting when fluorochloridone was applied early preplant rather than preemergence. Fluorochloridone at 0.8 kg/ha applied preplant or preemergence gave 83% or greater control of common lambsquarters and giant foxtail for the entire growing season. However, velvetleaf control with the same treatments was 61% or less. Fluorochloridone caused minimal corn injury. Greenhouse bioassay indicated that fluorochloridone may carry over and injure soybean [Glycine max (L.) Merr.] the year after application. Imbibition of fluorochloridone by seed of corn and giant foxtail did not reduce germination at concentrations up to 10-3 M. Giant foxtail seedling fresh weight was reduced 80% following imbibition of 10-5 M fluorochloridone. Corn seedling fresh weight was not reduced by imbibition of up to 10-4 M fluorochloridone.