Electrophoretic analysis of storage protein accumulation in developing cowpea [Vigna unguiculata (L.) Walp. ‘Mississippi Purple’] seed indicated that a large increase in protein content per seed occurred between 10 and 11 days after flowering (DAF). Polypeptides with molecular weights of 54, 49, and 41 kilodaltons (kD) accumulated first, and one with a molecular weight of 59 kD appeared 2 days later at 13 DAF. Treatment of plants with glyphosate [N-(phosphonomethyl)glycine] when pods were 7 and 10 DAF prevented accumulation of the major storage protein polypeptides. The accumulation of these polypeptides was not inhibited as much when pods were 11, 12, or 13 DAF at the time of treatment with glyphosate. Pod length and seed fresh weight were inhibited by glyphosate treatment of plants bearing pods 7, 10, 11, and 12 DAF. Pod width, seed dry weight, and seed length were inhibited by glyphosate when plants bearing pods 7, 10, and 11 DAF were treated.

Absorption of 14C-chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonanide} by Canada thistle [Cirsium arvense (L.) Scop. # CIRAR] was 39% following foliar treatment and 16% when added to a nutrient solution in which the plants were growing. Translocation from the treated organ was limited regardless of treatment method; 10% of the applied 14C moved out of the treated leaf and 10% moved from the roots to other parts of the plant following absorption from the nutrient solution. When applied as a foliar treatment, 14C-chlorsulfuron had not been metabolized by Canada thistle 48 h later. However, when 14C-chlorsulfuron was added to the nutrient solution and absorbed by the roots, nearly 25% of the 14C in the plants was present as a polar product(s), 13% had an Rf value identical to benzenesulfonamide standards, and the remaining 62% was chlorsulfuron. Chlorsulfuron was not transformed similarly in a nutrient solution after 6 days in the absence of plants. Suppression of regrowth was the primary injury symptom observed following chlorsulfuron application. Chlorsulfuron also reduced whole plant weight and root bud number and weight.

Radiolabeled (14C) 2-[4-(3-chloro-5-trifluoromethyl-2-pyridinyloxy)phenoxy] propionic acid (Compound C); its methyl-,n-butyl-, and ethoxyethyl-esters; and fluazifop-butyl {(±)-butyl 2-[4-[(5-(trifluoromethyl)-2-pyridinyl)oxy] phenoxy] propionate} were applied to the primary shoots of young rhizomatous quackgrass [Agropyron repens (L.) Beauv. # AGRRE]. Plants were sampled from 0.5 to 24 days after treatment (DAT) and analyzed for radiochemical. All treatments caused phytotoxic symptoms in primary shoots, rhizomes, and tillers and significantly reduced growth of primary shoots and rhizomes. Treatment with compound C or its methyl and butyl esters eliminated regrowth from all rhizomes excised from treated plants. The ethoxyethyl-ester and fluazifop-butyl controlled regrowth from rhizomes from 50% of the plants and substantially reduced shoot regrowth from the remainder. Rhizomes that did produce shoots contained significantly less radiochemical than those from which no regrowth occurred. At 24 DAT, a maximum of only 1% of each radiochemical applied was translocated to the first tiller and rhizomes and had been sufficient to cause marked phytotoxic symptoms. Soon after application (1 DAT), the major metabolites in the treated leaves and remainder of the plant for all compounds were the free acid and substantial amounts of polar conjugates that were hydrolyzable to the free acids. Radiochromatography of extracts from rhizomes and first tillers from all treatments gave similar chemical profiles, with the free acids and their conjugates as the predominant components present. These results provide evidence that esters of the pyridinyloxyphenoxypropionic acids are rapidly hydrolyzed after absorption by quackgrass; the free acids are then translocated and are the active form of these herbicides.

Lipid metabolism and other biochemical responses to alachlor [2-chloro-2’,6’-dimethyl-N-(methoxymethyl) acetanilide] and the protectant flurazole [2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylic acid, (phenylmethyl ester)] in germinated grain sorghum [Sorghum bicolor (L.) Moench. ‘MFA GS 301’] were studied. Treatments included flurazole, applied to grain sorghum seed at 2.5 g ai/kg, alachlor at 8.2 × 10−6 M, and alachlor plus flurazole at these rates. Treatments did not alter total lipid synthesis or fatty acid composition. Seeds that germinated for 48 h in media containing alachlor or alachlor plus flurazole had a greater triglyceride:phospholipid ratio than those treated with flurazole or the control seeds, indicating that alachlor plus flurazole retarded catabolism of storage lipid. Oxygen consumption of seeds was reduced after the herbicide plus protectant treatment. Oxidation of 14C-pyruvate to CO2 was inhibited by alachlor and alachlor plus flurazole treatments, but not by flurazole alone.

The sensitivities of chlorophyll fluorescence and fresh weight as bioassay techniques for the determination of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one], diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] concentrations in soil were compared. The ratio of the initial inflection point (I) to the variable fluorescence maximum (P) of intact oat (Avena sativa L. ‘Chilocco’) leaves was determined for plants seeded directly into herbicide-treated soil and for those transplanted into treated soil after 14 days of growth in nutrient solution. Using the chlorophyll fluorescence of transplanted oats bioassay, 0-, 0.13-, 0.25-, and 0.50-ppm concentrations could be distinguished from one another within 8 h for metribuzin, within 24 h for diuron, and within 48 h for atrazine. These distinctions between rates could not be made 17 days after seeding into treated soil when using fresh weight as the bioassay indicator. Chlorophyll fluorescence of oats seeded directly into treated soil was also a reliable technique, but required much more time to attain sufficient plant size for convenient chlorophyll fluorescence determinations.

A weed survey system methodology was developed and used annually for 4 yr in the province of Saskatchewan. Based on a stratified random sampling procedure, fields were selected in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena sativa L.), rye (Secale cereale L.), rape (Brassica napus L., Brassica campestris L.), and flax (Linum usitatissimum L.) crops. The boundaries of the 43 agricultural extension districts in the province formed the strata. The provincial agricultural extension service provided staff to conduct the survey. Computer processing of the data enabled reports, containing summary tables and distribution maps, to be distributed to extension, research, and industry personnel within 3 months after completion of the field survey. The field surveys were conducted late in the growing season before harvest commenced; hence, the weed populations consisted of species that had been present during the early part of the growing season and may have contributed to yield losses. During the 4 yr of the survey, weeds were counted in 4423 fields. Of the 164 species recorded, 97 species occurred in more than three fields. Only 29 species were encountered frequently in the fields. Green foxtail [Setaria viridis (L.) Beauv. # SETVI), wild buckwheat (Polygonum convolvulus L. # POLCO), and wild oat (Avena fatua L. # AVEFA) were the top three species based on a ranking system using a measure called relative abundance.

Canada thistle [Cirsium arvense (L.) Scop. # CIRAR] root samples were collected at monthly intervals over a 2-yr period from two locations to determine seasonal fluctuations in the presence and growth potential of root buds. Root bud growth was highest during late fall and winter months following death of the aerial shoots. Root fragments incubated at a constant 15 C for 2 weeks in continuous light consistently had more buds than nonincubated roots, which indicated active bud differentiation during the incubation period. Incubated roots produced 3 to 9 cm of new shoot length/cm root length. There were no obvious seasonal patterns in the presence of root buds or their ability to elongate at different times of the year. Carbohydrate reserves were stored preferentially in roots rather than in developing root buds or the bases of shoots. These reserves ranged from as low as 3% of root fresh weight during spring months to as high as 26% in late fall months, although the levels did not increase consistently during summer months over the locations and years of this study.

Field experiments conducted over a 2-yr period demonstrated that common bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA] inhibited growth of newly planted peach (Prunus persica L. ‘Norman’) trees. Common bermudagrass densities of 100, 75, 50, and 25% ground cover reduced tree fresh weight by 86, 64, 43, and 19%, respectively, the first year (1978) and 87, 62, 44, and 28%, respectively, the second year (1979) after planting. Tree trunk diameter relative growth rate (RGR) was reduced by 75 and 100% common bermudagrass ground cover densities at all measurement dates only in 1978. Tree leaf N and K were reduced in both years by common bermudagrass; however, only at the 100% common bermudagrass density in 1978 was N at a deficient level. Leaf chlorophyll was reduced in trees grown in all densities of common bermudagrass only in 1978. Reduced tree growth cannot be explained entirely by competition for essential nutrients; thus an allelopathic effect of the bermudagrass on young peach roots is suspected.

Plant response studies were conducted from 1980 to 1982 under pasture and field plot conditions to determine the sublethal effects of the thistle rosette weevil [Trichosirocalus (Ceuthorynchidius) horridus (Panzer)] on Carduus thistles. Response to weevil damage was dependent upon thistle size and growing conditions. Damage by T. horridus destroyed apical dominance, which altered the thistle growth pattern. Infested plants consistently produced more stems and a larger crown than uninfested thistles. Large thistles were stimulated by weevil damage, producing heavier stems and more heads. Small infested thistles developed more quickly than small uninfested thistles. Small and medium infested thistles were shorter and produced fewer seeds and heads than uninfested thistles. The extent of thistle reduction by this weevil will ultimately be determined by the conditions under which thistles grow.

A 7-yr study was conducted to investigate successional dynamics of herbaceous vegetation after control of western juniper (Juniperus occidentalis Hook.) trees with picloram (4-amino-3,5,6-trichloropicolinic acid) pellets. Downy brome (Bromus tectorum L. # BROTE) rapidly dominated areas under dead tree canopies with an accompanying yield increase from almost none to about 1400 kg/ha within 4 yr after treatment. In the interstitial zone between tree canopies, a dramatic shift in herbaceous species occurred with tree control. Annual broadleaf species decreased, downy brome increased, and medusahead [Taeniatherum asperum (Sim.) Nevski # ELYCM] gradually became dominant. Total yield of herbaceous vegetation in the interstitial zone increased dramatically after picloram treatment, especially where few shrubs occurred. Available soil moisture, litter accumulation and decay after picloram treatment, and N in the surface layer of the soil affected responses of herbaceous vegetation, especially under dead tree canopies. Responses of annual weedy species to western juniper control emphasize the need for comprehensive manipulation of all components of the vegetation when range improvement is attempted.

Mayweed (Anthemis cotula L. # ANTCO) achenes and seed were germinated in the laboratory at constant temperatures ranging from 5 to 30 C. Maximum percent germination occurred at 20 C for both achenes and seed. Under all conditions tested, achene germination was less than seed germination. Both acid scarification for 15 min and soaking in 14 mM gibberellic acid (GA3) more than doubled achene germination. Pericarp leachate inhibited achene and seed germination only at high concentrations, indicating that inhibitors in the pericarp are not a primary cause of low germination in achenes. Optimum germination of achenes and seed occurred at pH 4.5 and over a range from pH 3 to pH 6. Achene germination was inhibited to a greater degree by moisture stress than was seed germination. It appears that structural integrity of the pericarp is the predominant factor affecting mayweed germination.

The dispersion of ethylene in the soil after application from a backpack ethylene applicator (BPEA) was determined using a bioassay of witchweed [Striga asiatica (L.) Kuntze # STRLU] seed germination. Witchweed seed were buried in packets in ridged seedbeds under field conditions. Ethylene dispersion was better when injected into the furrow than into the ridge top. Injections 30 cm deep were more effective in causing seed germination than injections 15 cm deep. Seed germination induced by ethylene injection into the furrow 30 cm deep was 13% more than that obtained from the ridge top injection 15 cm deep. Seed germination as high as 90% was obtained at soil depths to 75 cm at a horizontal distance of 100 cm from the point of ethylene injection. Ethylene diffused up to 300 cm horizontally and to 75 cm vertically to cause at least 45% seed germination in a field of Lakeland soil (Typic Quartzisamment). The BPEA was found to be an effective application tool in witchweed control operations.

Experiments were conducted in the field and controlled-environment chambers to determine wild oat (Avena fatua L. # AVEFA) control with difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) as influenced by applications at 4-h intervals during the day. Difenzoquat phytotoxicity was significantly higher in four of the six field experiments when applied at 1300 and 1700 h than at other times and was increased in the other two experiments. Difenzoquat phytotoxicity increased with temperature at treatment in the field experiments. Wild oat control was not increased by 8 h of 28 C before or after difenzoquat application compared to a constant 18 C in controlled-environment chambers. In controlled-environment chambers, wild oat control with difenzoquat was not influenced by the time of application during the day when humidity and temperature were kept constant.

Twenty herbicides were applied to a rangeland pasture in the Post Oak Savannah Resource Area of Texas in April 1978 and May 1979. At time of treatment, total vegetation cover was 88 to 100%, with 36% grasses and 52 to 64% broadleaf cover. From May 31 through September, total, grass, and broadleaf covers were 89 to 100, 51 to 65, and 27 to 44%, respectively. One to 2 months after treatment, grass cover generally increased except where certain herbicides, particularly bromacil (5-bromo-3-sec-butyl-6-methyluracil), dalapon (2,2-dichloropropionic acid), glyphosate [N-(phosphonomethyl)glycine], or hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H, 3H)-dione] had been applied. By September or October in the year of application only dalapon consistently reduced grass cover. In the year following treatment, grass cover was still reduced on the dalapon-treated plots. Most herbicides reduced broadleaf cover in the year of treatment. Broadleaf cover returned most rapidly to those areas treated with dalapon. During the year following treatment, broadleaf cover remained low on plots treated with picloram (4-amino-3,5,6-trichloropicolinic acid), 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and picloram + 2,4,5-T. For plots treated in 1978, the grass and broadleaf standing-crop weights of untreated plots were 490 and 450 kg/ha, respectively, in October 1978, and 2707 and 1033 kg/ha in October 1979. In 1978, grass weight increased with several herbicide treatments whereas only dalapon increased the broadleaf weight. For plots treated in May 1979 and harvested in September 1979, grass and broadleaf standing-crop weights of untreated plots were 2629 and 607 kg/ha, respectively.

Greenhouse studies were initiated to identify potential interactions of the postemergence herbicide acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} with the postemergence grass herbicides sethoxydim {2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio) propyl)-3-hydroxy-2-cyclohexen-1-one}, diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid}, and RO-13-8895 [acetone 0-(D-(2-(p-[(α,α,α-trifluoro-p-tolyl)oxy) phenoxy)propionyl)oxime}. Greatest control of barnyardgrass [Echinochloa crus-galli (L.) Beauv. # ECHCG] was obtained with the combination of acifluorfen and sethoxydim plus a crop oil concentrate. This combination increased foliar absorption of 14C-acifluorfen by barnyardgrass but not by soybean [Glycine max (L.) Merr. ‘Corsoy’]. The combination of acifluorfen with diclofop appeared to reduce phytotoxicity to barnyardgrass and increase it to soybean. Little or no interaction was observed in combinations of acifluorfen and RO-13-8895.

Field research was conducted in Arkansas to determine the effect of selected rice pesticides on the microbial herbicide Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. aeschynomene (henceforth designated C.g.a.) and to integrate C.g.a. into control programs for northern jointvetch [Aeschynomene virginica (L.) B.S.P. # AESVI] in rice (Oryza sativa L.). Water suspensions of dry-formulated spores of C.g.a. at 1.9 × 1011 spores/ha were applied midseason in sequence with normal use rates of other pesticides. Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl-carbamate) at 0.56 kg ai/ha, propanil (3’4’-dichloropropio-anilide) at 2.2 kg ai/ha, acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} at 0.14 kg ai/ha, or fentin hydroxide (triphenyltin hydroxide) at 0.56 kg ai/ha did not reduce disease development of C.g.a. on northern jointvetch. Sequential applications of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate] at 0.56 kg ai/ha reduced activity of the fungus on northern jointvetch when fungicide applications began 1 week after C.g.a. application but had no effect on mycoherbicide activity when applications began 2 weeks after C.g.a.

On-farm field experiments were conducted in the Piedmont Plateau and Coastal Plain of North Carolina in 1981 and 1982 to investigate the integration of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} with other chemical and cultural weed control tactics into soybean [Glycine max (L.) Merr.] weed management systems. Sethoxydim at 0.2 kg ai/ha provided control of broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash. # BRAPP], large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA], and fall panicum [Panicum dichotomiflorum Michx. # PANDI) equal to control achieved with registered rates of the soil-applied herbicides alachlor [2-chloro-2’,6’-diethyl-N-(methoxymethyl)acetanilide] and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). Control of broadleaf weed species with the postemergence herbicides bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one 2,2-dioxide] and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} equaled or exceeded the control obtained with the soil-applied herbicides linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5-(4H)-one]. Applications of 0.22 kg/ha of sethoxydim 2, 3, 4, and 5 weeks after soybean planting provided season-long control of fall panicum and crabgrass in 1981. In 1982, crabgrass control was 88 to 99% up to 4 weeks after planting. Later applications provided inadequate control of the grass species. Variations in volume and pressure of application had no effect on control of 10-cm goosegrass [Eleusine indica (L.) Gaertn. # ELEIN] or broadleaf signalgrass with 0.2 kg/ha of sethoxydim. Increasing pressure increased control of 30-cm goosegrass and broadleaf signalgrass. Increasing volume increased only control of goosegrass. Bentazon and acifluorfen provided better control of broadleaf weeds when applied early than when applied late. In two of four experiments tank mixtures of sethoxydim and bentazon resulted in an initial decrease in grass control compared to corresponding sequential applications. Soybean yields were comparable, however.

The addition of chlorflurenol (methyl 2-chloro-9-hydroxyfluorene-9-carboxylate) at 0.6 kg ai/ha or mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl] acetamide} at 0.3 kg ai/ha to picloram (4-amino-3,5,6-tricloropicolinic acid) at 0.3 kg ae/ha increased leafy spurge (Euphorbia esula L. # EPHES) control compared to picloram alone. Application of 84 kg/ha nitrogen in the fall prior to a spring treatment of 0.3 kg/ha picloram decreased the original stand (75%) compared to no nitrogen (18%). In greenhouse experiments, chlorflurenol and mefluidide increased the amount of 14C-picloram absorbed approximately twofold when applied in combination but not when applied independently. Based on 14C-picloram absorbed, chlorflurenol and mefluidide each increased the amount of 14C translocated to the root system, whether applied independently or in combination with picloram. An increase in root bud numbers was observed following an application of 0.6 kg/ha chlorflurenol or nitrogen.