The influence of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} on control of wild oat (Avena fatua L. ♯3 AVEFA) when mixed in the spray tank with three herbicides was tested in greenhouse and in field trials at Lacombe and Scott, Canada, during 1981 and 1982. In field experiments, chlorsulfuron mixed with diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid} caused a 4 to 35% reduction in control of wild oat. Mixtures of chlorsulfuron with difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) caused a 0 to 19% reduction and mixtures with flamprop {N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL-alanine} a 2 to 30% reduction in control of wild oat. Addition of chlorsulfuron to the wild oat herbicides under greenhouse conditions also resulted in losses in control of wild oat. Increasing the rate of the wild oat herbicide in the mixture tended to overcome these losses.

Chlorpropham (isopropyl m-chlorocarbanilate) at 6.7 kg ai/ha controlled a mixture of field dodder (Cuscuta campestris Yunck. ♯3 CVCCA) and largeseed dodder (Cuscuta indecora Choisy ♯ CVCIN) for 3.0 and 4.3 weeks in two greenhouse experiments. The insecticide carbaryl (1-naphthyl N-methylcarbamate) at 0.8 kg ai/ha applied with chlorpropham extended control by 0.7 and 1.8 weeks, and PCMC (p-chlorphenyl N-methylcarbamate) at 0.8 kg ai/ha extended it by 2.7 and 2.8 weeks. Both additives also improved dodder control by chlorpropham in the field, with carbaryl having less effect than PCMC.

Several field studies were conducted during 1981 and 1982 to determine whether early preplant (EPP) applications of residual herbicides would prevent the establishment of vegetation before planting no-till soybeans [Glycine max (L.) Merr. ‘Williams’]. Early preplant applications of either cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile} or cyanazine plus oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) were applied in the fall and 3, 2, and 1 month(s) before planting no-till soybeans. In all studies, the treatments prevented vegetation from becoming established before planting, and season-long weed control was achieved with several different treatments. Early preplant cyanazine plus oryzalin provided greater than 90% control for the entire season where grass densities were low. Where grass densities were high (greater than 90% ground cover), EPP cyanazine plus a preemergence application of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] plus metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] or a postemergence application of sethoxydim {2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} controlled 90% of the weeds, which was equal to or better than the standard preemergence treatments used (80 to 98% weed control).

Field and greenhouse studies conducted in North Carolina in 1981 and 1982 evaluated the effect of the dimethylamine salt of 2,4-DB [4-(2,4-dichlorophenoxy) butyric acid] on soybeans. In the field, 2,4-DB at and above 0.07 kg ae/ha reduced soybean shoot mass, leaf nitrogen levels, and nodule activity. Soybean seed yields were reduced by 2,4-DB at and above 0.07 kg/ha. In greenhouse studies, total nodule activity was reduced by 0.07 and 0.14 kg/ha of 2,4-DB. Soybeans treated with 2,4-DB at initiation of flowering (R1 stage) or when pods were 1.9 cm long (R4 stage) yielded progeny with visible injury symptoms. Seedling emergence was also reduced in progeny of soybeans.

The airless paint sprayer was investigated as an alternative to compressed-gas spray systems. The airless sprayer was adapted to a conventional agricultural spray nozzle system. In addition, modifications to the airless sprayer's on/off switch were made to achieve a more consistent delivery. The equipment was found satisfactory for applying either emulsifiable concentrates or wettable powder herbicides at typical concentrations in water. The addition of a conventional conveyer-belt system completed the steps necessary to make the commercially available airless sprayer a viable alternative to compressed-gas propulsion systems.

Three applications/yr of glyphosate [N-(phosphonomethyl)glycine] with a ropewick applicator (RWA), a roller applicator (RA), and a recirculating sprayer (RCS) were compared to hoeing and cultivation for the control of johnsongrass [Sorghum halepense (L.) Pers. ♯3 SORHA] in cotton (Gossypium hirsutum L. ‘Acala SJ-2′) in six field experiments from 1979 to 1981. Averaged over the 3 yr and dates of application, plots treated with glyphosate contained 78% fewer live johnsongrass shoots (15/m2) than cultivated-control plots (68/m2). Although applications of glyphosate with the RWA and RA improved or tended to improve yields of cotton, only plots treated with the RWA yielded significantly more seed cotton than cultivated control plots in all years. However, yields of plots treated with the RWA still averaged 38% less than hoed plots. Plots treated with the RA produced significantly more cotton than cultivated-control plots only in 1981.

Desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)] controlled wild mustard (Sinapsis arvensis L. ♯3 SINAR) and redroot pigweed (Amaranthus retroflexus L. ♯ AMARE) more effectively than phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate). A synergistic interaction occurred with all tank-mix combinations of the two herbicides for wild mustard control, except combinations containing 0.71 kg ai/ha of desmedipham. The magnitude of the synergism decreased as the rate of desmedipham was increased and increased as the rate of phenmedipham increased. Both herbicides caused injury symptoms of leaf necrosis and height reduction to sunflowers (Helianthus annuus L.). Crop injury and sunflower heights were affected more by desmedipham than by phenmedipham. Injury effects were temporary and had no influence on sunflower yields.

Multiherbicide granules were formulated containing 1.3% fluazifop {(±)-butyl 2-[4-[[5-trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoate} (w/w) in polymerized tung oil overlaid on a granular matrix of gum xanthan-loess containing 2.7% linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] or oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide). Under greenhouse conditions the granules were as effective in selective control of velvetleaf (Abutilon theophrasti Medic. ♯3 ABUTH), hemp sesbania [Sesbania exaltata (Raf.) Cory ♯ SEBEX], corn (Zea mays L. ♯ ZEAMX), and red rice (Oryza sativa L. ♯ ORYSA) in soybeans [Glycine max (L.) Merr. ‘Hill’] as when the herbicides were sprayed separately. When applied preemergence at 0.56 to 0.14 kg ai/ha, tung oil-encapsulated fluazifop on loess granules killed 100% of stolon bermudagrass [Cynodon dactylon (L.) Pers. ♯ CYNDA] and was as effective as sprayed fluazifop.

Stem flow is the water from precipitation that is intercepted by plant canopies and conveyed down the outside of stems to wet the soil at the base of the plant. For western juniper (Juniperus occidentalis Hook.) trees, stem flow was only a small fraction of the precipitation intercepted by the canopy. However, this moisture may be important in the nutrient flux of the trees. The first stem flow in the fall after the summer drought was enriched in nitrate-nitrogen although the quantity of nitrogen per unit area was small. The combination of favorable moisture and temperature conditions at the base of the tree leads to litter decay and nitrification. The root system of the trees had many fine roots in the area that received stem flow. Canopy interception and stem flow should be taken into consideration in application of soil active herbicides for control of western juniper.

Under irrigated field conditions at Prosser, WA, Russian thistle [Salsola kali (L.) var. tenuifolia Tausch. ♯3 SASKR] began to emerge by mid-March each year and usually had completed its emergence by May 1. Common lambsquarters (Chenopodium album L. ♯ CHEAL) was the next to appear, usually during the third or fourth week of March. Barnyardgrass [Echinochloa crus-galli (L.) Beauv. ♯ ECHCG], redroot pigweed (Amaranthus retroflexus L. ♯ AMARE), hairy nightshade (Solarium sarrachoides Sendt. ♯ SOLSA), black nightshade (5. nigrum L. ♯ SOLNI), eastern black nightshade (S. ptycanthum Dun.), and cutleaf nightshade (S. triflorum Nutt. ♯ SOLTR) generally began to emerge during the first 2 weeks of April and emergence generally peaked mid-April to mid-May. Russian thistle and cutleaf nightshade had the most restricted emergence patterns, whereas seedlings of common lambsquarters, redroot pigweed, hairy nightshade, and black nightshade emerged each month from April through September. Shallow tillage at monthly intervals increased the overall emergence of common lambsquarters, redroot pigweed, black nightshade, and eastern black nightshade; decreased the emergence of barnyardgrass; and had no effect on the emergence of Russian thistle, cutleaf nightshade, or hairy nightshade.

The interference between dry bean (Phaseolus vulgaris L. var. Red Kidney), black nightshade (Solanum nigrum ♯3 SOLNI), and barnyardgrass (Echinochloa crus-galli ♯ ECHCR) was examined in replacement series experiments. A modified replacement series experiment also was performed to examine the effects of no interference, and intraspecific and interspecific interference on the height, leaf area, and dry weight of bean, black nightshade, and barnyardgrass. In both types of competition experiments, bean germinated earlier than either weed species and caused significant reductions in weed height, leaf area, and dry weight. The impact of bean upon itself was always greater than the effect of either weed species. In laboratory studies, barnyardgrass and black nightshade seeds were subjected to eight concentrations of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). Black nightshade was 100 times more tolerant to trifluralin than barnyardgrass. Field studies, conducted at several locations in the Central Valley of California in which trifluralin-treated plots were compared with nontreated plots, demonstrated that trifluralin favors trifluralin-tolerant weeds (black nightshade), but trifluralin-sensitive weeds (barnyardgrass) have not been eliminated despite 20 yr of trifluralin use.

Soil samples representing a time series from forest before clearing to land in cultivation for 20 yr were taken near Delta Junction, AK, to determine the changes that occur in the soil seed bank following clearing and agricultural use. The total number of seed was initially low in the forested sites but increased after 3 to 5 yr in cultivation due to seed production by native colonizers and by introduced weeds such as common lambsquarters (Chenopodium album L. ♯3 CHEAL). Viability of seed of several mature forest species was low. There was a shift from a seed bank dominated by native species in the forest and newly cleared sites to a seed bank dominated by introduced colonizers in the older fields. Although seed of introduced species increased in importance over time, native species, especially native colonizers, continued to be an important component of the seed bank throughout the 20-yr period represented.

The forage selection and grazing behavior of sheep in leafy spurge (Euphorbia esula L. ♯3 EPHES)-infested pastures was examined in a 3-month grazing study conducted during the summer, 1981. No definite preference for or avoidance of leafy spurge was detected. An initial 1- to 3-week avoidance was observed, followed by a steady increase in leafy spurge consumption. A maximum intake of 40 to 50% of the diet per animal was observed. Weight gain by ewes in pastures infested with leafy spurge was not significantly different from weight gain by ewes in pastures free of leafy spurge. Results from these studies indicate that leafy spurge may be classified as a forage for sheep. Sheep will consume a significant amount of vegetation while suffering neither harmful internal effects nor a significant loss of body weight. Sheep can be considered an effective biological control agent for leafy spurge.

Wild oat (Avena fatua L. ♯3 AVEFA) and Avena sterilis L. ♯ AVEST accessions from the United States were screened for tolerance to diallate [S-(2,3-dichloroallyl) diisopropylthiocarbamate], triallate [S-(2,3,3-trichloroallyl) diisopropylthiocarbamate], barban (4-chloro-2-butynyl m-chlorocarbanilate), diclofop {2-[4-(2,4-dichlorophenoxy) phenoxy] propanoic acid}, difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium), flamprop [N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL-alanine], and MSMA (monosodium methanearsonate). Some accessions were tolerant to more than one herbicide but none were tolerant to all herbicides. Tolerance to a herbicide was not restricted to certain areas of origin of the accessions, and tolerant accessions occurred even in locations that had not been treated previously with the herbicide. In general, accessions from Southern California and Arizona were shorter, produced more tillers, and required the least number of days to panicle emergence. However, accessions from within individual areas were nearly as variable in these characteristics as the entire 1200 accessions. Tolerance of accessions to flamprop, difenzoquat, MSMA, and diclofop was not due to low leaf surface area, since the tolerant accessions usually had the most leaf surface area. All the accessions tolerant to difenzoquat, MSMA, and flamprop, and three of the four accessions tolerant to diclofop, tillered less than the susceptible accessions.

The potential of several common weed species to produce adventitious shoots when the plants were excised approximately 1.0 cm below the cotyledonary node at the cotyledon growth stage and at the four true-leaf stage is reported. Indian jointvetch (Aeschynomene indica L. ♯3 AESIN), northern jointvetch [Aeschynomene virginica (L.) B.S.P. ♯ AESVI], and wild poinsettia (Euphorbia heterophylla L. ♯ EPHHL) produced adventitious shoots at both growth stages after shoot excision. Adventitious and vegetative regeneration of wild poinsettia damaged by herbicides was similar to that from decapitation.

Detrimental effects on growth and yield of soybeans [Glycine max (L.) Merr. ‘Amsoy 77′] from density and duration of competition by ivyleaf morningglory [Ipomea hederacea (L.) Jacq. ♯3 IPOHE] was evaluated in 1981 and 1982 near West Lafayette, IN. Ivyleaf morningglory was planted at densities of 1 plant per 90, 60, 30, and 15 cm of row in 1981 and 1 plant per 60, 30, 15, and 7.5 cm of row in 1982. Each density of ivyleaf morningglory competed for 22 to 46 days after emergence and the full season in 1981, and for 29 to 60 days after emergence and the full season in 1982. The best indicators of competition effects were leaf area index, plant dry weight, and yield of soybeans. Ivyleaf morningglory was more competitive during the reproductive stage of soybean growth. Photosynthetic irradiance and soil moisture measurements indicated that ivyleaf morningglory does not effectively compete for light or soil moisture. All densities of ivyleaf morningglory could compete with soybeans for 46 and 60 days after emergence in 1981 and 1982, respectively, without reducing soybean yield. Full-season competition from densities of 1 ivyleaf morningglory plant per 15 cm of row significantly reduced soybean yield by 36% in 1981 and 13% in 1982. The magnitude of soybean growth and yield reduction caused by a given density of ivyleaf morningglory was greater when warm, early season temperatures favored rapid weed development.

Hydrilla [Hydrilla verticillata (L. f.) Royle ♯ HYLLI] was cultured in flowing water in outside aquaria on rooting media differing in fertility and texture. Nutrient content was determined for rooting media at the beginning of the experiment and for plant tissues at harvest. Growth, as measured by rates of stem elongation, areal coverage of aquaria by plants, and biomass accrual, was highly related to N-, P-, and K-fertility of rooting media. Rooting media were the most important source of phosphorous since water supplies were not adequate to support plant growth. There was evidence of P-deficiencies in plants grown on infertile rooting media. Both N and K were adequately supplied from either water, rooting media, or both. Production of plant biomass was most closely related to P-levels in tissues which were closely related to supplies in rooting media. Pretest soil N (comparable to preestablishment conditions) was best related to biomass production, indicating that growth and establishment of hydrilla may be predictable through assessment of hydrosoil fertility. The need for sampling and analytical procedures to assess fertility is emphasized.

Field experiments were established in 1978 and repeated in 1979 to monitor quackgrass [Agropyron repens (L.) Beauv. ♯3 AGRRE] rhizome growth through a growing season. Quackgrass shoots grew most vigorously when temperatures were moderate. They elongated and differentiated an inflorescence in June. Rhizome apical tips remained belowground in late spring, early summer, and early fall. Quackgrass rhizome tips grew vertically and emerged from the soil in midsummer and late fall. Experiments conducted in growth chambers revealed that photoperiod, temperature, and nitrogen level affected quackgrass shoot and rhizome growth. Shoots grew vigorously at 21C and elongated to differentiate an inflorescence when exposed to a photoperiod of 14 h or longer. Rhizome apical tips remained belowground when plants were grown at 21 C and received 16 or 12 h of light, but the tips curved upward and emerged from the soil when quackgrass was grown at 32 or 10 C, or when the plants received 14 or less than 10 h of light. The temperature and photoperiod responses coordinated to partition the growing season into primary rhizome and rhizome-tiller growth periods.

Growth chamber studies using one soil investigated the effects of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.0, 0.4, and 0.8 ppmw on the root development and the mineral status of wheat (Triticum aestivum L. ‘Neepawa’) seedlings. The 0.8-ppmw trifluralin rate increased the number of seminal roots, reduced lateral root production, decreased root extension, caused root tips to swell (club-like appearance), and reduced root dry weights. However, 0.4-ppmw trifluralin caused only slight damage to the seedlings. Towards the end of the two-week growth period, damaged seedlings showed signs of recovery, which included an increased number of seminal roots, development of normal root extensions from clubbed root tips, and development of normal lateral root patterns. Trifluralin increased percent calcium and magnesium and decreased percent nitrogen, phosphorus, and potassium in wheat plants. The nutrient concentrations were more affected in 21-day-old plants than in 35-day-old plants, indicating the wheat seedlings were able to recover from trifluralin injury.

The formulation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) encapsulated within a starch granule can reduce the loss in activity associated with the delayed incorporation of the emulsifiable concentrate formulation of trifluralin. Good weed control and high soybean [Glycine max (L.) Merr. ‘Wells II’] yields were obtained when a starch formulation of trifluralin was applied in the fall and incorporated at planting time the following spring. The cultural practices of shallow incorporation, delayed incorporation, and/or midseason cultivation intensified the weed control provided by a starch formulation of trifluralin. The adsorption of additional trifluralin onto the granule surface, cross-linking starch xanthate with a weak oxidant, and mixing granules with different release rates also increased initial control. Granules produced by the starch-calcium and starch-borate processes exhibited many of the same characteristics of granules produced by the older starch xanthate process, but are much less expensive to produce and do not require the use of the toxic carbon disulfide in the encapsulation process. The combination of an appropriate starch formulation of trifluralin with proper cultural practices provided good weed control from fall and spring applications of trifluralin.