The effects of five herbicide and three in-the-row cultivation treatments on weed control and sugarbeet (Beta vulgaris L.) yield were studied at Mitchell and North Platte, Nebraska, during 1966 and 1967. Preplant soil incorporation treatments of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) + N,N,dimethyltri-decylamine salt of 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid (endothall), and S-ethyl N-ethylthiocyclohexanecarbamate (cycloate), and postemergence application of pyrazon + 2,2-dichloropropionic acid (dalapon) resulted in better weed control and more sucrose per acre than S-propyl butylethylthiocarbamate (pebulate) applied preplant and soil-incorporated, and the untreated check treatment. Herbicide-treated plots kept weed-free by handweeding did not differ from the handweed check in sucrose production. Rotary hoeing improved weed control and increased sucrose yields as compared to flextine harrowing and the no in-the-row cultivation treatment.

Long-term control of leafy spurge with glyphosate requires multiple applications because the plant reproduces vegetatively from abundant underground adventitious buds, referred to as crown and root buds. Determining the molecular mechanisms involved in controlling vegetative reproduction in leafy spurge following foliar glyphosate treatment could identify limiting factors or new targets for manipulation of plant growth and development in invasive perennial species. Thus, we treated leafy spurge plants with 0 or 2.24 kg ai ha−1 glyphosate to determine its impact on selected molecular processes in crown buds derived from intact plants and plants decapitated at the soil surface 7 d after glyphosate treatment. New shoot growth from crown buds of foliar glyphosate-treated plants was significantly reduced compared with controls after growth-inducing decapitation, and had a stunted or bushy phenotype. Quantification of a selected set of transcripts involved in hormone biosynthesis and signaling pathways indicated that glyphosate had the most significant impact on abundance of ENT-COPALYL DIPHOSPHATE SYNTHETASE 1, which is involved in a committed step for gibberellin biosynthesis, and auxin transporters including PINs, PIN-LIKES, and ABC TRANSPORTERS. Foliar glyphosate treatment also reduced the abundance of transcripts involved in cell cycle processes, which would be consistent with altered growth patterns observed in this study. Overall, these results suggest that interplay among phytohormones such as auxin, ethylene, and gibberellins affect vegetative growth patterns from crown buds of leafy spurge in response to foliar glyphosate treatment.

Several seed production fields of the Italian ryegrass cultivar ‘Tetrone’ were destroyed in 1988 by 280 to 350 g ai ha−1 racemic fenoxaprop applied for wild oat control. Because similar rates of fenoxaprop had possessed adequate safety when applied to ‘Oregon common’ Italian ryegrass, suspicion arose that the cultivars differed in tolerance. Seedlings of 21 commonly grown cultivars were screened in the greenhouse at the three-leaf growth stage to determine their fresh weight GR50 for fenoxaprop. The GR50 values for the two most tolerant cultivars, ‘Marshall’ and ‘Torero’, were more than threefold greater than the two most sensitive cultivars, ‘Futaharu’ and ‘Ace’. Cultivars could be separated into sensitive, intermediate, and tolerant groups, but the distribution of the GR50 values appeared to be continuous rather than discrete. Tolerance increased with growth stage, and the average GR50 for tillered plants was 80% higher than that for the two-leaf stage and 41% higher than that for the four-leaf stage seedlings. Cultivars differed slightly in the specific activity of acetyl–coenzyme A carboxylase (ACCase) (EC 6.4.1.2) and in the I50 values for the inhibition by fenoxaprop, but the only clear relationship between these biochemical factors and whole-plant tolerance was a threefold increase in ACCase activity at the tillered stage over that present in the younger seedlings.

Toxicological investigations were conducted on galenia [Galenia pubescens (Eckl. and Zeyh.) Druce], an introduced species of the family Aizoaceae. One lot of field-grown galenia assayed 2.5% nitrate (as KNO3) and 6.1% soluble oxalates. Three sheep were acutely poisoned after they were gavaged with this plant. Galenia grown in nutrient solution assayed 6% nitrate and 11.3% soluble oxalates. Chicks fed this material died of nitrate and oxalate poisoning. Galenia may accumulate toxic levels of both oxalates and nitrates and thus should be classed as a poisonous plant that would be considered hazardous to humans and livestock.

Tubers of purple nutsedge (Cyperus rotundus L.) were soaked in distilled water, 9.3 × 10−6M 6-benzylamino-9 (tetrahydropyran-2yl)-9 H-purine (SD8339), or 1.39 × 10−7M kinetin and sprouted in darkness. Excised plants from tubers sprouted in sand culture were grown in half-strength Hoagland solution in 50-ml erlenmeyer flasks enclosed with aluminum foil. The leaves and upper part of the stem of each plant were exposed to an illumination of 32 klux. Rhizomes as well as untreated and treated tubers were exposed to red (R), red followed by far-red (R-FR), or red followed by far-red and red (R-FR-R) monochromatic light. R, R-FR, and R-FR-R illuminations of rhizomes from untreated tubers and plants produced basal bulbs while dark controls did not. Pfr did not revert to Pr. Dark controls produced significantly fewer basal bulbs than did rhizomes of untreated tubers and plants exposed to R, R-FR, or R-FR-R illuminations. There was no significant difference between R, R-FR, and R-FR-R illuminations. Tubers treated with SD8339 or kinetin produced basal bulbs in darkness but untreated tubers did not. Rhizomes of tubers treated with SD8339 or kinetin and exposed to R illumination produced basal bulbs. There was a significant difference in the number of bulbs produced by SD8339 or kinetin treatments and R illumination in contrast with the water controls in darkness. The effect of R illumination was similar to that of SD8339 or kinetin.

A greenhouse experiment compared the vegetative growth in pure cultures and mixtures of winter Triticum aestivum cultivar ‘Mit’ and Lolium multiflorum cultivar ‘Marshall’ in continuously watered controls and drought treatments. Control L. multiflorum in pure culture 14 wk after planting produced more leaf area, tillers, and dry weights of stem and root than control T. aestivum in pure culture. The greater seed size, larger initial leaf area, and height allowed T. aestivum to produce greater final leaf area and dry stem weight in control mixtures than L. multiflorum. Watering following drought shifted the relative performance of the two species in pure cultures and mixtures compared to controls. The ability of T. aestivum to maintain a greater leaf expansion rate during drought and a greater leaf area afterward than L, multiflorum allowed T. aestivum to attain greater growth than L. multiflorum in pure cultures exposed to temporary drought followed by watering. Conversely, drought and its relief enhanced the relative competitiveness of L. multiflorum compared to controls in mixtures with T. aestivum. During 4 wk of watering following the drought, L. multiflorum in mixtures grew vigorously and was similar to T. aestivum in all measures except in height and dry stem weight. Thus, L. multiflorum was similar in root growth with T. aestivum in control and drought mixtures and had its aboveground competitiveness amplified by the cycle of drought and watering in this study. There was no evidence of an allelopathic interaction between the two species.

Results from both growth chamber and field experiments indicate that root absorption of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) applied postemergence to small broadleaf weeds is not a requisite for their control. Though broadleaf weeds absorb toxic quantities of atrazine from wet soil, they can be killed by foliar absorption alone because all of their meristems are exposed to a foliar spray. They are particularly sensitive when foliar penetration is enhanced by high relative humidity and wet foliage.

A grass seed attachment to a grain drill was modified to apply granular herbicides using positive metering mechanism. Uniformity of granule output was adjusted within ± 4% maximum error. Speed of travel did not appreciably affect the amount of granules applied per acre.

Weeds are ubiquitous and economically damaging in southern U.S. rice systems. Barnyardgrass has consistently been one of the most prevalent and troublesome of these. Although most rice cultivars do not suppress weeds dramatically, certain Indica cultivars and commercial hybrids are known to suppress barnyardgrass aggressively in conventional, drill-seeded rice systems in the southern United States. A field study was conducted to determine the degree to which either reducing or increasing standard seeding rates would affect natural suppression of weeds by conventional inbred and weed-suppressive cultivars. Five cultivars were evaluated at three seeding rates (160 [low], 320 [medium; conventional recommendation for inbred cultivars], and 480 [high] seeds m−2) and two weed levels (weed-free and weedy). Cultivars included a conventional, non–weed suppressive long-grain, ‘Wells’; high-tillering weed-suppressive cultivars ‘PI312777,’ ‘Rondo,’ and ‘4612’ from Asia; and the commercial hybrid ‘XL723.’ Overall, PI 312777 produced the most tillers, whereas XL 723 exhibited the greatest midseason shoot biomass and the greatest weed suppression. Yields of PI 312777 and 4612, both of which are Indica cultivars considered to be good weed suppressors, changed minimally across all seeding rates when compared with the other cultivars and thus tolerated weeds at the low rate nearly as well as at the high rate. Such a tolerance to weeds might be useful in the maintenance of weed suppression at reduced rice-seeding rates and suggests that reduced seeding rates of PI 312777 and 4612 would be less risky for yield loss when compared with the other cultivars tested. Visual suppression ratings were positively correlated with rice yield within weed-infested plots, suggesting that yield performance under weed pressure might be a good indicator of weed-suppression ability of cultivars in these systems. In contrast with PI 312777 and 4612, yields of the conventional inbred cultivar and commercial hybrid appeared to benefit from the high seeding rate. Overall, moderate to high seeding rates are likely to be needed for consistent weed suppression for all of the cultivar types evaluated in this study.

Catalase and peroxidase activities were run at several ages on two lines of corn (Zea mays L.)—GT112 RfRf, resistant, and GT112, susceptible to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine). Atrazine significantly decreased catalase activity in GT112, while in treated GT112 RfRf catalase activity was usually significantly increased. Catalase activity was higher in GT112 RfRf than in GT112 for both treatments at all ages. GT112 RfRf had a higher peroxidase activity than GT112 when both were untreated, but when treated with atrazine there was no overall trend.

In 1950 an experiment was initiated at Mississippi State University to evaluate the comparative efficiency of certain promising herbicides in controlling weeds in cotton. The use of herbicides for weed control in cotton was beginning to be accepted as an agricultural practice. Results from a long-time experiment involving the use of herbicides for weed control in cotton were needed.

Increased osmotic potential from 0 to −14 bars decreased the moisture uptake and germination of mechanically scarified hemp sesbania [Sesbania exaltata (Raf.) Cory] seed. Germination percentage for osmotic potential of 0, −2, −4, −6, and −8 bars was 86%, 86%, 70%, 19%, and 1%, respectively. This response to moisture stress was modified by imbibition, or hydration-dehydration, of the seed prior to the moisture stress. Imbibing the seed for as little as 2 h significantly increased its subsequent germination against moisture stress. One hydration-dehydration cycle had little or no effect on germination, but as the number of cycles increased, the germination percentage decreased. Prolonged hydration of 3 and 7 days followed by dehydration greatly reduced subsequent seed germination.

N fertilizers suppress witchweed plant growth and development, thus reducing the severity of parasite attack and increasing host yield simultaneously. However, the underlying physiological mode of N action occurring within the parasite cells remains largely unknown. This study aims at screening for the effects of N forms and different growth conditions on some N assimilation enzymes in witchweed seedlings grown aseptically without host plant, and in pots with host plants. Results show that supply of N in NH4 + or urea forms resulted in 83 to 92% reduction in nitrate reductase activity (NRc), compared with control. Increasing NO3 − concentrations from 0 mM to 100 mM, led to a corresponding increase in NRc in giant witchweed. NRc of giant witchweed seedlings grown under light and dark cycles were about 270 times higher than seedlings grown in continuous darkness. A combination of NH4 + and NO3 −, resulted in increased giant witchweed NRc, compared with NH4 + or NO3 − supplied singly. Highest shoot development and NRc was at NH4 + and NO3 − ratio 1:1, followed by ratios 1:3, 3:1, 0:1, and 1:0, respectively. Addition of N in soils resulted in increased NRc, followed by rapid deterioration and death of giant witchweed plants. NRc, GSc, and GDHc in witchweed, maize, cowpea, and tobacco were affected by diurnal fluctuations with higher enzyme activities occurring during the day than at night. Higher GSc than GDHc suggests that NH4 + assimilation occurs mainly through the GS pathway in witchweed plants. NRc and GDHc were two and four times higher in giant witchweed grown in aseptic media without host plant, than that grown in potted soils with host plants. These findings provide insight into the physiological mode of N action and their implications on witchweed control.

The reproductive characteristics of natural populations of meadow salsify were monitored between May 1990 and October 1991. Plants in even-aged populations did not produce seeds prior to the second winter and plants in uneven-aged populations died after seed production suggesting that meadow salsify at this site is a monocarpic perennial and not a true biennial. Delayed seed production may enhance abundance of this species by increasing the size of its bud bank. Plants of uneven-aged populations flowered over a range of root crown diameters; the percentage of plants bearing flowers increased with increasing root crown diameters. The minimum root crown diameter at which plants flowered in 1990 and 1991 was 0.2 and 0.6 cm respectively demonstrating that factor(s) other than plant size regulate flowering in this species. Seed production ranged between 100 to 850 seeds per plant. Total number of flower heads per plant and florets per plant were positively correlated with each other and with the root crown diameter. Root crown diameter is, therefore, a good indicator of potential fecundity in meadow salsify. Greater seed production by larger plants may compensate, at least in part, for the high juvenile mortality and longer generation time in this species. The results suggest that prolific seed production and long vegetative survival are important strategies in the maintenance of meadow salsify populations.

The short-run economic consequences of bans on herbicides commonly applied to corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.] on a typical Indiana farm were analyzed. A dinitroaniline ban reduced soybean yields and net farm income 17 and 32%, respectively. A triazine ban reduced corn and soybean yields 3 and 20%, respectively, and net farm income by 38%. A simultaneous ban on all dinitroaniline, triazine, and amide herbicides reduced corn and soybean yields 14 and 17%, respectively, and net farm income by 65%. Harvest delays attributable to less effective weed control resulted in a loss in efficiency, yields, and profits, and increased machinery and labor requirements. Hence, herbicide bans under typical Indiana conditions would inflict substantial, short-run economic losses on individual farmers. This study did not measure any potential public benefits or costs of herbicide bans, however.

The influence of sublethal levels of a number of herbicides and plant growth regulators on the germinability of the seeds and the growth and development of seedlings of mouseearcress [Arabidopsis thaliana (L.) Heynh. ♯ ARBTH] was determined. Only 7 of the 22 chemicals tested had a persistent effect on progeny. Amitrole (3-amino-s-triazole) was one of the most effective compounds. It caused a characteristic bleaching only in shoot tips and pods in parent plants and appeared to act directly on the progeny by accumulation in the seed. Two auxin transport inhibitors, TIBA (2,3,5-triiodobenzoic acid) and CPII (5-O-carboxyphenyl-3-phenylisoxazole), and four of the six photosynthetic electron transport inhibitors included in the study also affected progeny. They appeared to act indirectly by interfering with seed development.

The rate of herbicide required to reduce growth of grain sorghum (Sorghum vulgare, Per. ‘Pioneer 8417′) by 50% (GR50) and soil adsorption coefficients (Ka) were determined for the experimental herbicide, fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone}, in 14 soils. A linear correlation analysis was conducted between GR50 values and the chemical and physical properties and fluridone absorption coefficient (Ka) for 14 soils. The GR50 values were significantly correlated to soil organic matter and Ka. A stepwise regression analysis suggests that Ka or organic matter content can be used to predict the rate of fluridone application required for herbicidal activity.

Sporisorium cruentum teliospores and sporidia (cultured from teliospores with about 30-fold spore increase) caused about equal, although variable, levels of smut infection of individual Sorghum halepense plants when applied to the foliage. Teliospores were applied in a water–surfactant suspension (106 spores ml−1) at 935 L ha−1 and sporidia in a water-in-oil invert emulsion (about 107 spores ml−1) at 468 L ha−1. In crop interference studies, a single foliar application of teliospores to space-planted S. halepense plants in a first-year crop of Saccharum sp. hybrids caused about 55% infection (at least one smutted panicle per plant) but did not reduce the level of S. halepense infestation or substantially improve Saccharum yield compared to noninoculated plants. Smutted panicles usually appeared 30 to 60 d after the foliar treatment, but many culms on a plant produced only healthy panicles. Two applications of teliospores, either 7 d apart in one experiment or 1 yr apart in another, significantly increased (P = 0.05) smut infection over one application but generally did not improve Saccharum yield substantially over plots infested with noninoculated S. halepense. In contrast to foliar spray inoculation, S. halepense plants injected with teliospores in the seedling stage prior to transplanting to the field were 98% infected with smut and were much less competitive with the crop than noninoculated transplants. In host range studies using several S. bicolor genotypes injected with teliospores in the greenhouse, the ratios of resistant to susceptible were 17 to 2 for grain types and 16 to 5, with 2 intermediate, for forage types, showing that genotypes have a relatively high level of resistance to the disease. The result of these experiments indicate that loose kernel smut has potential as a biocontrol agent for S. halepense, but only if infection by foliar treatment can be improved to levels at least comparable to injection.

The absorption by bean (Phaseolus vulgaris L. ‘Black Valentine’) of 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) at 1 μM concentration was increased in the presence of 10, 1, or 0.1 μM O,O-diethyl S-(ethylthio) methyl phosphorodithioate (phorate). An increase in absorption of 10 μM prometryne with addition of 1 μM phorate was recorded after 72 hr, but no increase was seen after 96 hr of absorption. Both prometryne and phorate inhibited state 3 respiration of mitochondria isolated from 6-day-old bean hypocotyls. Inhibition increased with increasing pesticide concentrations. When the pesticides were applied simultaneously, no interactions affecting state 3 respiration were observed. Neither prometryne nor phorate alone significantly affected phosphate accumulation by bean shoot mitochondria.