Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] significantly reduced the incidence of stem rot caused by the soil-borne pathogen Sclerotium rolfsii L. in field-grown peanuts (Arachis hypogaea L. ‘Florunner’). Dinoseb (2-sec-butyl-4,6-dinitrophenol) (1.7 kg/ha) used alone also reduced stem rot, but when combined with oxadiazon control was not significantly improved, although yields were significantly increased. Dinoseb was toxic to S. rolfsii in laboratory tests, suggesting that disease reductions and yield increases are attributable to this observation. Oxadiazon was non-toxic to the pathogen, indicating that disease control must be indirect, perhaps relating to the reduced plant spreading observed in treated plots. The reduction in ground contact is thought to reduce the probability of contacting pathogen inoculum. The potential value of oxadiazon in an integrated pest management system appears to be good because of simultaneous weed and disease control as well as frequent yield increases. This potential may be improved by use of dinoseb in the same program. Disease control is apparently an expression of the direct toxicity of dinoseb and the indirect effects of oxadiazon.

Enzymatically isolated leaf cells from cotton (Gossypium hirsutum L. ‘Stoneville’) and soybean (Glycine max (L) Merr. ‘Kino’) were used to study the effect of SAN 6706 [4-chloro-5-(dimethylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] on photosynthesis, protein, RNA, and lipid synthesis during the first 19 hr of herbicidal treatment. Cotton plants are tolerant to SAN 6706, whereas soybean plants are susceptible. SAN 6706 inhibited the incorporation of 14C-bi-carbonate, uridine, and acetate into cotton leaf cells but stimulated incorporation of leucine. Incorporation of all of these precursors into soybean cells was inhibited. Cotton and soybean cells each took up equivalent amounts of labeled SAN 6706. The incorporation activity of the cotton and soybean cells appeared to regulate the entrance of the precursors into the cells by depleting the intracellular precursor pools. It is suggested that the inhibition of RNA and lipid synthesis in cotton and soybean cells is an indirect result of inhibited photosynthesis. Isolated cotton cells were not tolerant of the herbicide.

Seven herbicides were tested for their effect on growth of Pyricularia oryzae Cavara, Hypochnus sasakii Shirai, and Xanthomonas oryzae Uyeda & Ishiyama Dowson on agar media and for subsequent influence on disease intensity on rice plants (Oryza sativa L.) in the greenhouse. The herbicides studied were: propanil 3′,4′-dichloro-propionanilide), NTN 5$006 [O-(2-nitro-4-methylphenyl)-O-ethyl-N-isopropyl-phosphor-amidothioate], simetryn [2,4-bis(ethylamino)-6-)methylthio)-s-triazine], terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine], nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether), molinate (S-ethyl hexahydro-1H-azepine-1-carbothioate), and aglypt (4-amino-3-methylthio-6-phenyl-1,2,4-triazine-5-on). The growth of P. oryzae, H. sasakii and X. oryzae on culture media containing 10 μg/ml commercial formulation of propanil was reduced to approximately 50% of the control. The other herbicides tested were less effective. Differences in disease severity produced on rice plants treated with the previously mentioned herbicides were in agreement with the results obtained by the culture method. The effect of simetryn and nitrofen on disease severity was stronger than expected from the small direct action on the pathogen in culture. It is suggested that the influence of these two compounds on the disease intensity is due to their effect on the host plant rather than the pathogen directly. Propanil was effective only if applied immediately or up to 1 day before inoculation, indicating that this herbicide is degraded on or within the rice leaves.

The influence of calcium arsenate (48% w/w tricalcium arsenate) rate, physical form, time of application, and phosphorus (P) rate on the growth of annual bluegrass (Poa annua L.) and Bray P1 extractable arsenic (As) were investigated. Both powder and granular formulations reduced clipping yields and enhanced extractable As levels. Higher initial soil As activity and significantly better control were obtained in one study when the powder formulation was used. Similar levels of control were achieved whether the As was applied prior to germination or to the mature turf. Soil P-levels did not influence the effectiveness of either As formulation.

Glyphosate [N-(phosphonomethyl)glycine] toxicity to bermudagrass [Cynodon dactylon (L.) Pers.] increased significantly with each rate increase from 0.14 to 1.12 kg/ha. Under greenhouse conditions approximately 50% bermudagrass control was obtained at 0.56 kg/ha glyphosate. Visible toxicity and fresh wt of treated plants and regrowth of plants clipped at the soil surface 24 h after treatment were used as indices for penetration and translocation of glyphosate. Visible injury to bermudagrass with 0.56 kg/ha glyphosate was greater at 100% than at 40% relative humidity (RH) at both 22 and 32 C. Fresh wt data indicated that 0.56 kg/ha glyphosate was more toxic at 32 C than at 22 C at 40% RH, but no difference was observed at 100% RH. Less than 10% of the applied 14C-glyphosate penetrated the treated bermudagrass leaf at 22 C and 40% RH; whereas, more than 70% penetrated the treated leaf at 32 C and 100% RH. Five to six times more 14C-label was translocated into the plant at 100% than at 40% RH. Significantly more 14C-label translocated out of the treated leaf and into the plant at 32 C than at 22 C at 40% RH but no significant increase was observed at 100% RH.

Purple moonflower's (Ipomoea turbinata Lagasca y Segura) vegetative growth and seed maturation were characterized in noncompetitive field studies. Seedling emergence of 50% or greater of mature scarified seed occurred to a soil depth of 12 cm. At vegetative maturity a typical plant produced 11 primary, 50 secondary, 94 tertiary, and 7 quaternary runners having a total length of 185 m. The average number of leaves per plant was 1,120. Maximum seed size, seed wet weight, occurrence of first mottled seed, and first capacity to germinate occurred 20 days after anthesis in immature seed that were removed from the seed pod. Maximum germination occurred at 26 days after anthesis. Seed moisture content (dry weight basis) reached 8.5%, seed had formed an impermeable seed coat, and physiological maturity (defined as maximum dry weight) occurred 34 days after anthesis. The total number of purple moonflower seed produced per plant averaged 9350. The major mechanism of seed dormancy was impermeability of seed coats.

Weed-free sugarbeets [Beta vulgaris (L.) Beauv.] growing at a spacing of 60 cm (1/2 stand) yielded the same weight of roots as those spaced 30 cm (full stand), and those spaced 90 cm (1/3 stand) yielded about 90% as much. Gross sucrose yield was reduced somewhat more, because the larger roots growing in partial stands contained a lower percentage of sucrose than the roots in full stands. Annual weeds that emerged after July 1 were suppressed and. killed by competition from sugarbeets of normal vigor in a full stand, but became competitive when the sugarbeets were spaced at 1/2 or 1/3 of a full stand. Competition from barnyardgrass [Echinochloa crus-galli (L.) Beauv.] and pigweed (mixture of Amaranthus retroflexus L. and A. powellii S. Wats.), which reached a height of 150 cm, reduced root yields 5 to 39% in 1/2 stands and 19 to 49% in 1/3 stands, as compared with weed-free sugarbeets in the same stands. Hairy nightshade (Solarium sarachoides Sendt.) was abundant but never became taller than the sugarbeets. Its competition had no measurable effect on the sugarbeets.

Field experiments were conducted to study the feasibility of using several dinitroaniline herbicides for the selective control of johnsongrass [Sorghum halepense (L.) Pers.] from seed and rhizomes in soybeans [Glycine max (L.) Merr. ‘Bragg’]. The herbicides were incorporated into the soil with two disk cultivations immediately after application. These were trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.6 to 2.2 kg/ha, nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] at 0.6 to 2.2 kg/ha, dinitramine (N4,N4-diethyl-α,α,α,-trifluoro-3,5-dinitrotoluene-2,4-diamine) at 0.4 to 1.5 kg/ha, fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline] at 0.6 to 2.2 kg/ha, profluralin [N-(cyclopropyl-methyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] at 0.8 to 3.4 kg/ha, butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] at 1.7 to 6.7 kg/ha, AC-92390 (N-sec-butyl-2,6-dinitro-3,4-xylidine) at 0.8 to 3.4 kg/ha, and AN-56477 [N,N-di(2-chloroethyl)-4-methyl-2,6-dinitroaniline] at 2.2 to 4.5 kg/ha. On Bosket sandy loam soil, the best average johnsongrass control over a 2-yr period was obtained following profluralin at 1.7 kg/ha and butralin at 3.4 kg/ha. These treatments also resulted in highest average soybean yields. On Sharkey clay soil, profluralin at 3.4 kg/ha and butralin at 6.7 kg/ha resulted in maximum johnsongrass control and soybean yields. Immediate incorporation of profluralin and butralin into both soils for 2 successive years effectively controlled johnsongrass from rhizomes without soybean injury and with greatly increased soybean yields. Trifluralin, nitralin, and fluchloralin also provided acceptable johnsongrass control within individual experiments, and greatly increased soybean yields.

The impact of annual preemergence herbicide usage on the rooting potential of seven commercially important woody ornamental species was studied. Granular formulations of dichlobenil (2,6-dichlorobenzonitrile), diphenamid (N,N-dimethyl-2,2-diphenylacetamide), simazine [2-chloro-4,6-bis(ethylamino)-s-triazine], and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine] employed as dormant season or spring applications had no inhibitory effects on the rooting of plants following transplantation. Season of transplanting influenced subsequent root growth of Japanese holly (Ilex crenata Thunb. var. convexa Makimo), Rosebud azalea (Rhododendron X ‘Rosebud’), and Hicks' yew (Taxus media Rehd. var. hicksii Rehd.) more than herbicide treatment. Hardwood cuttings taken from plants grown in herbicide-treated soil rooted as well as those from untreated controls. Plants grown in full sunlight or 55% shade exhibited similar root growth and insensitivity to preemergence herbicides.

Tubers from purple nutsedge (Cyperus rotundus L.) plants grown in the greenhouse for 2 to 10 weeks did not germinate after foliar applications of 4 kg/ha glyphosate (N-(phosphonomethyl)glycine). Some tubers from 12- and 24-week-old purple nutsedge plants survived glyphosate application. Translocation of 14C-glyphosate from treated purple nutsedge leaves to other plant parts increased from 5% of the amount applied at 1 day to 19% at 4 days after application. Specific activity of 14C in tubers was greater than in leaves of plants 2- to 6-week-old. With increasing plant age, specific activity decreased in both tubers and leaves. As purple nutsedge grew older, total 14C translocated increased in tubers, and decreased slightly in leaves. Thin layer chromatography showed no evidence of glyphosate metabolism in purple nutsedge.

Establishment and early growth characteristics were defined for sourgrass [Trichachne insularis (L.) Nees], one of the most serious pasture weeds in Hawaii. Optimum germination of sourgrass seeds was obtained in the light at 30 C or with alternating temperatures of 20 and 30 C or 25 and 35 C. Germination in complete darkness was poor except at alternating 25 and 35 C. Sourgrass germinated better than buffelgrass (Cenchrus ciliaris L.) and guineagrass (Panicum maximum Jacq.) at low moisture tension. Sourgrass was capable of emerging from a maximum depth of 5 cm but percent emergence was greatly reduced at planting depths greater than 3 cm. Sourgrass flowering response to photoperiod was day-neutral. Under conditions of adequate moisture, the growth of sourgrass was severely suppressed when grown with buffelgrass, or/or guineagrass. If grazing is restricted, either of these grasses would be useful for controlling sourgrass.

Specially designed growth boxes were used to simulate field subsurface injection of phenoxy herbicides. Sorghum (Sorghum vulgare Pers.) seedlings were grown in stainless steel containers (inserts) which were placed in plexiglass boxes containing a soil layer that had received 2,240 kg/ha of a 50:50 mixture of the n-butyl esters of 2,4-D [(2,4-dichlorophenoxy)-acetic acid] and 2,4,5-T [(2,4,5-trichlorophenoxy)-acetic acid]. Plant height data were collected periodically for all treatments. Subsurface herbicide application to both intact and cut root systems significantly altered root growth. Plants with treated, intact root systems showed retarded growth which became more pronounced with time. Plants whose root systems were treated, and cut on day 22, showed an initial acceleration of growth; a trend which eventually reversed itself and resulted in control plant height exceeding that of treated plants.

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.