Sodium alginate was used to prepare pelletized formulations for each of five fungi. Aqueous mixtures of 1.0% (w/v) sodium alginate and homogenized mycelia of Alternaria cassiae Jurair & Khan, Alternaria macrospora Zimm., Fusarium lateritium Nees ex Fr., Colletotrichum malvarum (A. Braun & Casp.) Southworth, or a Phyllosticta sp. were pelletized by dropwise additions of each mycelial-alginate mixture into 0.25 M CaCl2. Abundant conidia were produced on the pellets 24 to 48 h after the pellets were spread into trays and exposed 10 min/12 h to 275-W sunlamps. These conidia germinated readily (90 to 100%) and readily infected the respective host plants. Each liter of mycelium plus growth medium from submerged liquid cultures produced 4 L of the mycelial-alginate mixture. Each liter of the mycelial-alginate mixture produced approximately 18 g of air-dried formulation. When 10% (w/v) clay was incorporated into the pellets, each liter of the mycelial-alginate mixture produced approximately 118 g of air-dried formulation. The pelletized fungi sporulated readily following storage at 4 or 25 C for 6 to 8 months. This method of pelletization is potentially useful for the formulation of inoculum of fungi used as mycoherbicides, for the mass production of pycnidium-forming fungi, and for the production of inoculum for host-plant resistance studies.

The critical period of weed interference in transplanted tomatoes (Lycopersicon esculentum Mill. 'Springset’) was from 28 to 35 days after transplanting. A single weeding during this period was sufficient to prevent yield reductions. A growth analysis revealed that significant differences in plant dry weight and fruit number between tomatoes from weed-free and weed-infested plots were not apparent until 56 to 70 days after transplanting. The shorter the initial weed-free period, or the longer weeds were allowed to remain in the plots before removal, the earlier reductions in tomato dry weight and fruit number appeared. Weed interference was due primarily to shading rather than water stress. Tomatoes from weed-infested plots had significantly lower stomatal conductances than those from weed-free plots, but did not differ in xylem-pressure potential or in canopy temperature. If tomatoes were kept weed-free for more than 28 days, or when weeds were present for less than 28 days after transplanting, stomatal conductances were not significantly reduced.

Terbacil (3 - tert - butyl - 5 - chloro - 6 - methyluracil) uptake by roots and translocation were evaluated as possible bases of tolerance in two species, strawberry (Fragaria × ananassa Duchesne 'Sunrise’ and ‘Guardian’) and goldenrod (Solidago fistulosa Miller). Tolerance of goldenrod to terbacil was at least five-fold that of strawberry. Strawberry was at least four - fold more tolerant than highly terbacil - sensitive cucumber (Cucumis sativus L. ‘Chipper’). Guardian, a reported susceptible strawberry cultivar, was as tolerant to terbacil as the tolerant cultivar, Sunrise. Distribution of 14C within the plant, but not uptake of label through roots, was found to be correlated to relative tolerance to terbacil when the roots of intact plants of all species were exposed for various time periods to a nutrient solution containing 2 -14C terbacil. The observed distribution patterns suggest that tolerance to terbacil in strawberry and goldenrod is at least partially attributable to the restricted translocation of root - absorbed herbicide. The greater tolerance of goldenrod than strawberry to terbacil was apparently unrelated to the restriction of herbicide to root tissue.

Early weed and crop interference was examined in a greenhouse pot experiment combining aspects of additive, substitutive, and diallel designs. Cotton (Gossypium hirsutum L. 'Stoneville 213′) and four weeds {purple nutsedge (Cyperus rotundus L.), large crabgrass [Digitaria sanguinalis (L.) Scop.], velvetleaf (Abutilon theophrasti Medic.) and prickly sida (Sida spinosa L.)} were grown singly and in all possible combinations of pairs including reciprocals for 5 weeks in 10-cm plastic pots. After 5 weeks large crabgrass was the tallest species in all combinations except when grown with purple nutsedge. Purple nutsedge, however, had more leaf area and greater dry weight than all other species. Height, leaf area, and dry weight were lowest in prickly sida. Mean relative yields in mixtures (a measure of competitive ability) were 1.90, 1.15, 1.13, 0.86, and 0.41 for purple nutsedge, large crabgrass, cotton, velvetleaf, and prickly sida, respectively, when grown with the other four species as associates. Conversely, purple nutsedge and cotton as associates depressed mean relative yields of competing species to 0.59 and 0.94. Large crabgrass, velvetleaf, and prickly sida as associates increased mean relative yields of competing species to 1.17, 1.18, and 1.55, respectively. Analysis of these data and replacement-series diagrams indicated that purple nutsedge was the most competitive, prickly sida the least, and the other species were intermediate and approximately equivalent in competitive ability.

Tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiozol-2-yl]-N,N′-dimethylurea} pellets (20% ai) applied at 0.6, 1.1, or 2.2 kg ai/ha in the spring at two locations and in the fall at a third location on the South Texas Plains did not significantly decrease buffelgrass (Cenchrus ciliaris L. # PESCI) standing crop or foliar cover compared to untreated areas. Buffelgrass standing crop was reduced for 8 months after application of 3.3 and 4.4 kg ai/ha of tebuthiuron to a sandy clay loam in the spring, but the same rates did not reduce standing crop after application to clay loam in the fall. However, buffelgrass foliar cover was reduced following application of 3.3 kg ai/ha or more of the herbicide, regardless of soil. Tebuthiuron applied at 2.2, 3.3, or 4.4 kg ai/ha to sandy clay loam soils killed buffelgrass plants in spots, but production by larger surviving plants compensated for reduction in plant density where 2.2 or 3.3 kg ai/ha were applied.

Leaves of greenhouse-grown honey mesquite [Prosopis juliflora (Swartz) DC var. glandulosa (Torr.) Cockerell # PRCJG] initially absorbed more triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} from application of the ester than the amine salt. After 24 h, however, honey mesquite had absorbed 66% of the applied ester formulation and 72% of the amine formulation. Triclopyr was rapidly transported from the treated leaf to other plant parts. Triclopyr concentrations recovered 4 h after treatment in the upper canopy, lower canopy, and roots averaged 0.12, 0.19, and 0.09 μg, respectively. Concentrations of triclopyr recovered after 24 h were not significantly different than after 4 h in the canopy. No ester from ester application was recovered in the canopy, other than that in the treated leaf. Triclopyr recovered from stems of honey mesquite in the field ranged from 0.16 to 0.72 μg/g in phloem and from 0.04 to 0.20 μg/g in xylem from a broadcast spray application of the butoxyethanol ester at 1.12 kg/ha. Concentrations of triclopyr were usually not significantly different in either the upper or lower stems whether sampled 3 or 30 days after treatment.

Excised roots of corn (Zea mays L. ‘B73 × Mo 17′) and oat (Avena sativa L. ‘Goodfield’) and potato (Solanum tuberosum L. ‘Kennebec’) tuber slices absorbed 14C-atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] in a similar manner during short (1 to 30 min) absorption periods. Within 30 min, atrazine concentrations in tissues and ambient solution were equal. After 24 h of absorption, corn roots contained the most 14C, followed in order by velvetleaf (Abutilon theophrasti Medic.) roots, oat roots, and potato tuber slices. Corn and velvetleaf accumulated 14C to concentrations above the ambient solution. Efflux of 14C was slower for corn than oat, potato, and velvetleaf. Metabolism of atrazine to hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine] accounted for accumulation and slow efflux of 14C in corn. These experiments show that initial, rapid absorption of atrazine is comparable, but long-term accumulation differs among these tissues.

Six cropping/weed control systems were evaluated from 1978 to 1980 for the control of yellow nutsedge (Cyperus esculentus L.). Supplementing cultivation of cotton (Gossypium hirsutum L. ‘Acala SJ-2′) with either preplant applications of fluridone {1 - methyl - 3 - phenyl - 5 - [3 - (trifluoromethyl)phenyl] -4(1H-pyridinone} or two hoeings for 2 yr preceding cotton treated with DSMA (disodium methanearsonate) and MSMA (monosodium methanearsonate) reduced populations of viable yellow nutsedge tubers 98 to 99% within 3 yr. Dry- or wet - fallowing plus tillage after barley (Hordeum vulgare L. ‘Kombyne’), and double cropping potatoes (Solanum tuberosum L. ‘White Rose’) treated with EPTC (S-ethyl dipropylthiocarbamate) with soybeans [Glycine max (L.) Merr. ‘Williams’] treated with alachlor [2-chloro - 2′, 6’ - diethyl - N - (methoxymethyl)acetanilide] for 2 yr preceding cotton, reduced populations of tubers 98 to 99% within 3 yr. A similar reduction of tubers (97%) was obtained by double cropping potatoes with milo [Sorghum bicolor (L.) Moench. ‘NK- 265′] for 2 yr preceding cotton.

Live oak (Quercus virginiana Mill. # QUEVM) on the Texas Coastal Prairie was treated with herbicides using ground and aerial application methods. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} and pellets of buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone} at 2.2 kg ai/ha were the most effective herbicides, killing 60 to 95% of the live oak. Tebuthiuron pellets 3.2 mm in diam were more effective than the wettable powder at 1.1 kg/ha. Bay Met 1486 {N-[5-(ethylsulfonyl)-1,3,4-thiadiazole-2-yl]-N,N′-dimethylurea}, Dowco 290 (3,6-dichloropicolinic acid), hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H, 3H)-dione], and picloram (4-amino-3,5,6-trichloropicolinic acid) reduced the live oak canopy at 2.2 kg/ha whereas 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} were ineffective. Foliage-active herbicides generally were most effective in reducing the live oak canopy during the year of application. The soil-active herbicides generally were most active 1 or 2 yr after herbicide application. All herbicides reduced the live oak cover sufficiently to allow an increase in grass cover 2 to 4 months after treatment. Tebuthiuron at 2.2 kg/ha maintained a high degree of grass cover at least 2 or 3 yr after treatment.

A compact incorporator-planter, which incorporates herbicides into moist soil simultaneously with planting of cotton (Gossypium hirsutum L.), was constructed and evaluated over 3 yr using six herbicides. Weed control was consistent with that reported for large, cumbersome units utilizing standard planters and incorporating units from ground-driven rotary tillers and was enhanced in seasons in which rain fell during the first 3 weeks after planting. Among the dinitroaniline herbicides, dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) controlled barnyardgrass [Echinochloa crus-galli (L.) Beauv.], and redroot pigweed (Amaranthus retroflexus L.) most effectively. Cotton stands and yields were equivalent to those obtained using standard cotton-planting methods.

The bleaching effects of norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3 (2H)-pyridazinone] and of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] were compared using the intact microalga Scenedesmus acutus and the fungus Phycomyces blakesleeanus. Under the influence of oxyfluorfen, but not of norflurazon, pigments and membranes were degraded. This activity is typical for oxyfluorfen. Norflurazon prevented carotene synthesis, but did not cause degradation of carotenoids, chlorophylls, or 35S-sulfolipid, a marker of photosynthetic membranes. Furthermore, light-induced ethane evolution by Scenedesmus is substantial with oxyfluorfen, but not with norflurazon present. Oxyfluorfen apparently causes radical-initiated peroxidation of polyunsaturated fatty acids.

Experiments were conducted from 1979 to 1982 to determine whether selected herbicide treatments applied before or after harvest would provide adequate weed control without the use of tillage between crops in continuous winter wheat (Triticum aestivum L.) production systems. of the herbicide treatments evaluated, only oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) at 2.2 kg ai/ha applied prior to wheat maturity adequately controlled summer annual weeds each year. Populations of yellow nutsedge (Cyperus esculentus L. # CYPES) and/or clammy groundcherry (Physalis heterophylla Nees) increased from continued preharvest use of oryzalin in no-till treatments and were greater than those resulting from conventional tillage or various postharvest no-till treatments containing glyphosate [N-(phosphonomethyl)glycine]. After 4 yr, populations of winter annual Cruciferae spp. at one location were lower in treatments that had poorer control of summer annual weeds or volunteer wheat. At a second location, winter annual broadleaf species were more numerous in conventionally tilled than in no-till treatments. Wheat yields obtained with no-till treatments were lower than yields obtained with conventional tillage in seasons favorable for high yields.

The effects of MSMA on the development of straighthead, yields of rice, and hormonal balance in rice plants were observed in a greenhouse study. MSMA was applied to soil at 0, 6, and 9 kg ai/ha. At 6 kg/ha some straighthead and a 45% yield reduction occurred. At 9 kg/ha straighthead was evident, and yield was reduced by 85%. Analyses were made for ethylene with gas chromatography and for indoleacetic acid (IAA) with high performance liquid chromatography. Concentrations of ethylene and total arsenic detected in the tissue from rice leaves grown in MSMA-treated soil were higher at every growth stage when compared to plants grown in untreated soil. Both treated and untreated plants showed marked increases of these compounds during the reproductive stage and a decrease prior to panicle emergence. Significant changes occurred in IAA levels with the growth stage of treated and untreated samples, but MSMA had no obvious effect on IAA levels at any of the stages examined in this study.

A sequential extraction procedure was developed to study the fate of pendimethalin [N- (1 -ethylpropyl) -3,4- dimethyl - 2,6 - dinitrobenzenamine], trifluralin (α,α,α -trifluoro - 2,6 - dinitro - N,N - dipropyl - p - toluidine), and oryzalin (3,5 -dinitro-N4,N4 -dipropylsulfanilamide) in soil over a 6 - month laboratory incubation period. The distinction of non - bound residues was based on an acidic - methanol extraction followed by an extraction with an acetone :H2O : HCl (95:4:1, v/v/v) solution and then extraction with 0.5 N NaOH with further fractionation of the NaOH extract by partial precipitation. After 6 months, soil - bound 14C-residues of pendimethalin, trifluralin, and oryzalin contained 15, 14, and 23%, respectively, of the radioactivity applied to non - sterilized soil. The proportion of bound radioactivity associated with each organic fraction was nearly identical for each herbicide; 46, 12, 12, and 30% was associated with the acetone:H2O:HCl-soluble, fulvic acid, humic acid, and humin organic fractions, respectively. Soil sterilization reduced herbicide degradation by 31% and radioactivity in the fulvic acid, humic acid, and humin organic fractions by approximately 50% during the 6-month period. Radioactivity in the acetone:H2O:HC1-soluble fraction was reduced less than 10% by soil sterilization.

Using nutrient culture techniques, it was determined that a 14-day exposure to metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] concentrations in the range of 10-6 M reduced lengths and weights of seedling sweet corn (Zea mays saccharata L. ‘NK-199′) shoots and roots by 30 to 50%. With the exception of root weight, intensity of inhibition was proportional to day length. Reductions in accumulation of Ca, Mg, K, and P accompanied decreases in sweet corn growth. A 4-day exposure of sweet corn to 2.8 and 5.6 × 10-6 M metolachlor had no significant effect on growth and nutrient accumulation when treatments were followed by a 9-day incubation in metolachlor-free nutrient solution.

All herbicide treatments controlled the initial stand of Canada thistle [Cirsium arvense (L.) Scop.] and musk thistle (Carduus nutans L.) on a subirrigated range site. Annual retreatment controlled seedlings and the few plants that emerged from surviving root remnants after the first application. Average perennial grass production on unfertilized, herbicide-treated plots increased 110, 314, and 212%/yr over unfertilized check plots during the 3-yr period of treatment, i.e., 960, 3450, and 4300 kg/ha, respectively. Grasses did not fully reoccupy the site at the end of 3 consecutive yr of excellent thistle and forb control. The increase in grass production varied considerably among several herbicide treatments that controlled thistles equally. Grass production in the third year was greater under the 3,6-dichloropicolinic acid and 2,4-D [(2,4-dichlorophenoxy)acetic acid] treatment series than all other treatments. Ammonium nitrate enhanced the recovery of grass damaged by certain herbicides, but favored the competitive ability of the thistle more than that of the grasses.

Seven herbicides and two herbicide combinations were applied once either preplant or postplant to control perennial grasses and forbs as planting-site preparation for 2-yr-old seedlings of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and Douglas fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] at locations in Washington and Oregon. Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H, 3H)-dione] applied at 2.2 kg/ha provided most effective and lasting herbaceous weed control in both states. A combination of dalapon (2,2-dichloropropionic acid) and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] applied at 9.0 + 4.5 kg/ha also proved similarly effective. In Washington, each conifer species responded with exponential growth increases over a 6-yr period. For ponderosa pine and Douglas fir, respectively, hexazinone treatment increased tree height by 58 and 70%, stem diameter by 70 and 69%, and stem-volume yield by 387 and 650% as compared to untreated checks. Corresponding gains for the two conifers associated with dalapon + atrazine were 73 and 54% in height, 63 and 46% in diameter, and 421 and 349% in yield.

Solar heating (SH) of the soil by mulching it with transparent polyethylene (PE) during the hot season elevated the soil temperature by 10 to 18 C above that of the non-mulched soil. SH for 4 to 5 weeks resulted in effective control of most summer and winter annual weeds, the effect lasting for more than 5 months after PE removal. Melilotus sulcatus Desf., Astragalus boeticus L. and bull mallow (Malva nicaeensis All. # MALNI) were not controlled by SH. Perennial weeds which propagate from vegetative parts were only partially controlled with short SH, but mulching for 8 to 10 weeks improved control. Mulching the soil with perforated or shaded transparent PE or black PE resulted in a smaller increase of soil temperature and thus less efficient weed control. A combination of SH with soil-incorporated EPTC (S-ethyl dipropylthiocarbamate) or vernolate (S-propyl dipropylthiocarbamate) did not improve the weed control over SH alone, but significantly enhanced the disappearance of the herbicides from the soil. SH inhibited the disappearance of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl) phenyl]-4(1H)-pyridinone} but did not change the residual phytotoxicity of bromacil (5-bromo-3-sec-butyl-6-methyluracil). SH treatment improved plant growth and increased the yield of wheat (Triticum aestivum L. ‘895′) and turnip (Brassica rapa L. ‘Purple top’), but not of parsley (Petroselinum sativum Hoffm.).

Common cocklebur (Xanthium pensylvanicum Wallr.) root tissue was used to investigate the mechanism of action of glyphosate [N - (phosphonomethyl)glycine]. Arrival of glyphosate in the root-tip was followed closely by a rise in ATP levels to 136% of control levels by 2 h after treatment. Incorporation, but not uptake, of 14C-leucine was significantly decreased within 2 h after treatment. Incorporation declined steadily over a 32 -h time course. Uptake of 33P by the roots was temporarily stimulated by glyphosate, and as a percent of the total 33P taken up, there was decreased incorporation into RNA and DNA fractions by 8 h. Our results indicate that glyphosate may cause the rapid rise in ATP level primarily by inhibiting protein synthesis.

Terbacil (3-tert-butyl-5-chloro-6-methyluracil) metabolism was evaluated as a possible basis of tolerance in two species, strawberry (Fragaria × ananassa Duchesne) and goldenrod (Solidago fistulosa Miller). Reported cultivar variation in strawberry tolerance to terbacil was examined by comparing herbicide metabolism patterns in an established tolerant cultivar, 'Sunrise’, with those of the reported susceptible cultivar, ‘Guardian’. A terbacil-sensitive plant, cucumber (Cucumis sativus L. ‘Chipper’), was also used as a basis for comparison. Using gradient elution high performance liquid chromatography (HPLC), two terbacil metabolites were separated and quantitated from methanol extracts of the three species treated with 14C-terbacil via roots in solution culture. The minor metabolite was identified as the non-phytotoxic derivative, 3-tert-butyl-5-chloro-6-hydroxymethyluracil, based on its co-migration with authentic 3-tert-butyl-5-chloro-6-hydroxymethyluracil in two chromatographic systems. The major metabolite was a glycoside, which yielded the hydroxylated derivative upon β-glucosidase hydrolysis. In all species, metabolites accumulated more rapidly and extensively in roots than in leaves. Metabolism was greater in the two tolerant species than in cucumber. However, the greater tolerance of goldenrod to terbacil compared to that of strawberry was apparently unrelated to differences in herbicide metabolism.