A survey of the fungal and bacterial flora of waterhyacinth, [Eichornia crassipes (Mart.) Solms] infested with two arthropods, Neochetina eichhorniae Warner (weevil) and Orthogalumna terebrantis Wallwork (mite) was undertaken to determine the role of microorganisms in the decline of this host in Florida waters. Generally arthropod-infested plants were more diseased, had smaller laminae, lower numbers of live petioles and higher numbers of dead petioles per plant than noninfested plants. Several parasitic fungi, including some known pathogens of waterhyacinth, and soft-rot bacteria were isolated from arthropod-infested and noninfested plants. Higher numbers of microorganisms were present on arthropod-infested than on noninfested plants. The fungi and bacteria occurred randomly on arthropod-damaged waterhyacinth. No vector relationship was discovered between the arthropods and any fungus or bacterium. However, Acremonium zonatum (Saw.) Gams a virulent pathogen of waterhyacinth, and other necrotic leaf-spot diseases (‘disease B’) were predominant on arthropod-damaged plants. Disease B was independent of the arthropods, while A. zonatum incidence on waterhyacinth in sample sites was related especially to damage by adult mites. The origin of the observed association between A. zonatum symptoms and mite damage on laminae is unclear, even though field observations suggest a direct relationship between them. The weevil was also capable of aiding A. zonatum infections by creating points of entry for this pathogen into the host. In laboratory tests, waterhyacinths could be killed by the combined effects of the weevil and A. zonatum, although death did not ensue in the field under existing levels of this disease. The combined effects of arthropods and diseases led to reduction in the photosynthetic area of waterhyacinth and under severe stress, to root- and crown-rots. It is recommended that the process of biological control of waterhyacinth in Florida should include an integrated approach, using insects and pathogens.

Herbicides used in corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], and soybeans [Glycine max (L.) Merr.] were applied in the spring and their persistence into late summer was determined during 1974 to 1976. Composite soil samples from the top 5 cm of field plots were taken each August and bioassayed in the greenhouse. Bioassay species used were winter wheat [Triticum aestivum L.) and soybeans for herbicides used in corn and sorghum, and winter wheat and white mustard (Brassica hirta Moench) for herbicides used in soybeans. Soil persistence of triazine herbicides caused more injury to winter wheat, soybeans, and white mustard than any other class of herbicides tested. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] showed the most soil persistence of the five triazines evaluated. At normal field application rates, herbicides other than the triazines showed little injury to the bioassay plants. Soil persistence of herbicides was further reduced when combinations of reduced rates of each herbicide were utilized. Herbicides used for spring applications in corn showed more soil persistence in August than did the herbicides for sorghum, while herbicides for soybeans generally were least persistent. Postemergence herbicide applications resulted in more injury in bioassay species than preplant incorporated or preemergence applications. Persistence of some herbicides will restrict certain options to the grower such as changing crops in case of crop failure, fall planting of winter wheat, double cropping, or certain crop rotations.

Several herbicide antidotes were used with barban (4-chloro-2-butynyl m-chlorocarbanilate) in the field and greenhouse. The seed treatments of R-25788 (N,N-diallyl-2,2-dichloroacetanilide) and NA (1,8-naphthalic anhydride) at 0.12 or 0.5% by seed weight reduced wheat (Triticum aestivum L. ‘Waldron’) injury with barban in the field and greenhouse. R-25788 and R-28725 (2,2-dimethyl-3-dichloroacetyloxazolidine) applied at 0.14 kg/ha as a spray with barban or R-28725 applied as a seed treatment at 0.06 or 0.25% by seed weight were ineffective in reducing wheat injury. S-449 (4-chloro-2-hydroxyiminoacetanilide) at 0.06 or 0.25% by seed weight reduced wheat injury with barban in the greenhouse; however, in the field these treatments increased wheat injury and reduced wild oat (Avena fatua L.) control.

Germination of witchweed [Striga asiatica (L.) Kuntze] seeds was induced by treating air-dry seeds with kinetin (6-furfuryl-aminopurine) at 1.16 × 10−4 M and 2.32 × 10−4 M without subjecting the seeds to the conventional preconditioning procedures. Rudimentary shoot development of the seedlings also was promoted. Tissue culture techniques were used also to study growth regulator and nutritional requirements for witchweed seedling development. Seedlings with normal leaves and stems were obtained under aseptic conditions in synthetic media at pH 5.4 in the absence of a host plant when cultured in the presence of kinetin, indole-3-acetic acid (IAA), sucrose, casein hydrolysate and mineral salts. No shoot development occurred in the absence of kinetin or zeatin [6-(trans-4-hydroxy-3-methylbut-2-enylamino)purine]. Shoot development was more advanced if IAA or gibberellic acid (GA3) was used in combination with the cytokinins. Witchweed seedlings are dependent on a host plant not only for their nutrition, but also for plant hormones such as a cytokinin required for the promotion of shoot development.

In a 3-yr field study, seven dinitroaniline herbicides controlled all weeds adequately, except for two species. None of them controlled shepherdspurse [Capsella bursa-pastoris (L.) Medic.], and only nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] controlled common ragweed (Ambrosia artemisiifolia L.). EPTC (S-ethyl dipropylthiocarbamate) was included as a standard of comparison and provided satisfactory control of all weed species. Three-year averages of alfalfa (Medicago sativa L.) injury ratings at herbicide rates estimated to be equivalent in biological activity to 0.8 kg/ha and 1.7 kg/ha trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) respectively were: butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] 0% and 3%, benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) 2% and 9%, profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] 5% and 19%, AC92390 (N-sec-butyl-2,6-dinitro-3,4-xylidine) 6% and 17%, trifluralin 6% and 26%, fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline] 14% and 45%, and nitralin 18% and 49%. EPTC caused an average 4% injury at 3.4 kg/ha. At equivalent rates to 0.8 kg/ha trifluralin, most treatments caused an increase in first cutting alfalfa yields accompanied by a decrease in weed yields, except in 1974 when few treatments resulted in increased alfalfa yields. Alfalfa recovered from early season injury caused by higher rates of the herbicides, so that total alfalfa yields were usually not reduced compared to the control. Total herbage yields (alfalfa + weeds) were not increased by any treatment, and were sometimes decreased, especially by high rates of the herbicides.

Five thiocarbamate herbicides, butylate (S-ethyl diisobutylthiocarbamate), EPTC (S-ethyl dipropylthiocarbamate), molinate (S-ethyl-hexahydro-1H-azepine-1-carbothioate), pebulate (S-propyl butylethyl-thiocarbamate), and vernolate (S-propyl dipropylthiocarbamate) were used in the greenhouse at doses of 0.5 to 5 kg/ha incorporated 6 cm deep in a silt loam. Purple nutsedge (Cyperus rotundus L.) tubers were planted 5 cm deep. Three and 9 weeks after treatments were applied, nutsedge plants were harvested. EPTC also was used at doses of 0.25 to 10 kg/ha and plants were harvested every 2 days up to 20 days and every 3 weeks up to 24 weeks. The most effective reduction in the number of sprouts above ground was given by butylate, EPTC, and vernolate followed by pebulate and molinate. Persistence was directly related to level of initial activity. No effect was observed on the number of tubers which sprouted. However, all the thiocarbamates stimulated the number of sprouts produced per nondormant tuber. These sprouts were abnormal and did not reach the soil surface. Treated tubers produced approximately twice as many sprouts as controls. The number of rhizomes produced from the basal bulb was reduced with all the thiocarbamates used, even 24 weeks after treatment for the higher doses.

The phytotoxicity of barban (4-chloro-2-butynyl m-chlorocarbanilate) applied 14 days after emergence to wheat (Triticum aestivum L. ‘Waldron’) and wild oat (Avena fatua L.), at constant, fluctuating or alternating day-night temperatures was determined in controlled environmental chambers. Wheat and wild oat susceptibility to barban increased as post-treatment temperature decreased. Maximum barban selectivity for wild oat in wheat occurred with a constant 18 C or an alternating 18 C day and 10 C night post-treatment temperature. At least three days of 10 C immediately following barban application were necessary to cause wheat injury. However, two days at 29 C immediately after barban application in an otherwise 10 C post-treatment regime reduced wheat injury. Further, a night temperature lower than the day temperature after barban application increased wild oat control but did not correspondingly increase wheat injury compared to the constant temperature treatments.

The addition of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] wettable powder to water solutions of glyphosate [N-(phosphonomethyl)glycine] in greenhouse studies reduced glyphosate activity on quackgrass [Agropyron repens (L.) Beavu.], corn (Zea mays L.), and beans (Phaseolus vulgaris L.). Atrazine [2-chloro-4-(ethylamino)-6-isopropylamino)-s-triazine] wettable powder reduced glyphosate activity on corn. This antagonism was more pronounced at threshold levels of glyphosate and was overcome by increasing the glyphosate rate. Simazine applied to corn through the soil did not reduce the activity of glyphosate applied to the foliage. Glyphosate activity on corn was reduced equally when glyphosate was mixed with 4.2 kg/ha of commercial simazine wettable powder or an equal amount of the inert ingredients used in the commercial product. When mixtures of glyphosate with either the commercial simazine product or the inert ingredients from the commercial product were centrifuged, the amount of phosphorus (used as a measure of glyphosate) in the supernatant was reduced by 10 to 20%. When the supernatants of the various mixtures were applied to bean plants, the reduced phytotoxicity from the mixtures was comparable to the antagonism noted in previous experiments. These data support the conclusion that the reduction in glyphosate phytotoxicity from mixing with atrazine or simazine wettable powders is due to a physical binding within the spray solution rather than from biological interactions within the plant.

Karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxypheny)-1, 1-dimethylurea], formulated as a ball 1.34 cm in diameter, was applied to brush-infested rangeland with fixed-wing aircraft and in a grid pattern by hand at an average density of four balls/12.4 m2 (1.83-m spacing). Control of woody plants with karbutilate applied by hand in an exact grid pattern was not different from aerial applications at the same rate. Based on evaluations at least 24 months after application, karbutilate at 0.56 or 1.12 kg/ha did not control honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] in the subhumid Post Oak Savannah or semiarid Rolling Plains of Texas. At 2.24 kg/ha, canopy reduction of honey mesquite averaged 70% with 20 to 25% of the population killed. Post oak (Quercus stellata Wangenh.), blackjack oak (Quercus marilandica Muenchh.), yaupon (Ilex vomitoria Ait.), or winged elm (Ulmus alata Michx.) in Post Oak Savannah were not killed by 2.24 kg/ha. Karbutilate eliminated all vegetation in a 25 to 45-cm diameter circle, depending on concentration of active ingredient in the ball, the year of treatment regardless of vegetation region. The bare areas were revegetated within 2 yr following application in the Post Oak Savannah. However, bare areas in sodgrasses, primarily tobosa [Hilaria mutica (Buckl.) Benth.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.], where 1.12 and 2.24 kg/ha were applied averaged 20 to 30 in diameter, respectively, 32 months after application to sandy clay loam in the Rolling Plains.

Field studies on the persistence of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] showed less persistence under no-tillage corn (Zea mays L. ‘Pioneer 3369A’) culture than conventionally tilled corn. Bioassay studies conducted in the greenhouse using oats (Avena sativa L. ‘Compact’) as indicator crop showed the lowest level of simazine remaining in soils of low pH (5.4 and lower). Persistence of simazine in the soil increased with increasing soil pH.

The occurrence of asymbiotic nitrogen fixing bacteria in the rhizosphere of twenty weed species has been investigated. Using the roll tube method root-rhizosphere soil samples were diluted and added to test tubes containing low N media. Tubes were flushed with nitrogen, stoppered, and rolled to form a thin film of media on the inner wall. After 7 days incubation the nitrogen fixation rates were estimated using the acetylene reduction technique. Rates ranged from 38 to 783 nmoles acetylene reduced per hour. Of twenty species tested, three showed high rhizosphere populations of asymbiotic nitrogen fixing bacteria.

Six herbicides, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine], propham (isopropyl carbanilate), terbacil (3-tert-butyl-5-chloro-6-methyluracil), carbetamide [D-N-ethyllactamide carbanilate (ester)], pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide], and secbumeton [N-ethyl-6-methoxy-N′(1-methylpropyl)-1,3,5-triazine-2,4-diamine] were applied annually for four years to establish forage alfalfa (Medicago sativa L. ‘Washoe’). Downy brome (Bromus tectorum L.) control ranged from 80 to 100%. The average control of broadleaf weeds was 90 to 100% with simazine, terbacil, and secbumeton, compared to 30 to 40% with propham, carbetamide, and pronamide. Only simazine and terbacil were phytotoxic to the alfalfa. Based on weed control and crop tolerance, secbumeton performed best on the coarsetextured soil in this experiment.

Decomposition of 11 dinitroaniline herbicides was determined following 7 days exposure to unfiltered solar radiation in July and compared with that in the dark. Radiolabeled herbicides were applied at 1 kg/ha to dry soil thin layer plates. Decomposition of all dinitroanilines was higher when exposed to sunlight than if held in the dark under otherwise similar conditions. Thermal decomposition was noted for all dinitroanilines except profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] and dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine). Photodecomposition for each herbicide was: 7.8% AC 92390 [N-(1-ethylpropyl)-2,6-dinitro-3,4-dinitro-3,4-xylidine], 8.2% isopropalin (2,6-dinitro-N,N-dipropylcumidine), 9.0% butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine], 9.9% pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine], 17.1% benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), 18.4% trifluralin (α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine), 26.6% oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide), 30.4% fluchoralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], 40.6% nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], 47.6% profluralin, and 72.3% dinitramine.

EPTC (S-ethyl dipropylthiocarbamate) metabolism in corn (Zea mays L. ‘inbred B37’) was studied utilizing carbonyl-14C-EPTC and propyl-1-14C-EPTC. Two radioactive compounds were found in the organic-soluble fraction, namely, EPTC and EPTC-sulfoxide. Five metabolites were found in the water-soluble fraction. Amino acid analysis indicated that one water-soluble metabolite was a glutathione conjugate [S-(N,N-dipropylcarbamyl)glutathione] and that three other metabolites were probably degradation products of the glutathione conjugate. It was determined that EPTC-sulfoxide reacts chemically with reduced glutathione, yielding the conjugate. There was no detectable glutathione S-transferase enzyme activity associated with the sulfoxide cleavage.

Growth of sugarbeet (Beta vulgaris L. ‘Mono Hy A1’ and ‘Mono Hy D2′) and (B. patellaris Moq.) seedlings in cycloate (S-ethyl N-ethylthiocyclohexanecarbamate)-amended soil infested with the sugarbeet nematode (Heterodera schachtii Schmidt) was reduced (P = 0.05) at a concentration of 4 jug cycloate/g soil. Although the combination of cyloate with aldicarb [2-methyl-2-(methylthio) propionaldehyde-O-(methylcarbomyl) oxime] resulted in a significantly (P = 0.05) reduced growth of both sugarbeet cultivars and B. patellaris, it did not affect the nematicidal properties of aldicarb. Cycloate alone or in combination with aldicarb did not affect the growth of B. procumbens Chr. Sm. seedlings.

Glyphosate [N-(phosphonomethyl)glycine] and EPTC (S-ethyl dipropylthiocarbamate) did not reduce significantly the percent germination of either ‘Saranac’ or ‘Vernal’ cultivars of alfalfa (Medicago sativa L.) grown in petri dishes. Glyphosate at 10−5 M significantly reduced shoot length of both cultivars. Vernal alfalfa appeared to be more susceptible to glyphosate than the Saranac cultivar. Soil applications of glyphosate also had no effect on percent emergence of either cultivar and reduced plant height only of Vernal when applied to the soil at 17.9 kg/ha. Applications of glyphosate at 2.2, 4.5, and 9.0 kg/ha to a Kentucky bluegrass (Poa pratensis L.) sod in a simulated sod seeding alfalfa establishment study in the greenhouse reduced dry weight of both alfalfa cultivars; Vernal was affected more adversely than Saranac. Application of 2.2 kg/ha glyphosate in four management systems showed that a 3-day planting delay after spraying reduced growth inhibition of alfalfa seeded in treated sod. These results were similar to those obtained with paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) in these management systems. Kentucky bluegrass clippings treated with paraquat 3 days or less before contact with alfalfa seedlings significantly reduced seedling dry weight. Clippings treated with glyphosate did not reduce alfalfa seedling dry weights significantly.

R-25788 (N,N-diallyl-2,2-dichloroacetamide) had no effect on 14CO2 evolution from carbonyl-14C-EPTC (S-ethyl dipropylthiocarbamate) treated corn (Zea mays L. ‘inbred Oh551’). Treatment with 1.0 ppmw R-25788 increased production of water-soluble and unextractable products from EPTC and increased the rate of disappearance of organic-soluble radioactivity. R-25788 increased levels of reduced and oxidized glutathione in corn roots. Pretreatment of corn in nutrient solution with R-25788 had no effect on glutathione synthetase activity in root tissue, but R-25788 at 5.0 and 500.0 nM showed an in vitro stimulation of the enzyme.

Rhizomes of johnsongrass [Sorghum halepense (L.) Pers.], cut into 2.5-cm or 15-cm lengths, were planted in the field within and below a 7.5-cm layer of soil mixed with trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0, 1.7, or 3.4 kg/ha. When planted 3.8- and 10-cm deep in nontreated soil, survival was 90% and 69%, respectively, for the longer rhizomes and only 39% and 10%, respectively, for the shorter ones. When planted within trifluralin-treated soil, 95% and 100% of the shorter rhizomes and 54% and 81% of the longer rhizomes were killed at 1.7 and 3.4 kg/ha, respectively. When planted below treated soil, only 11% or 19% of the longer rhizomes were killed. The shorter rhizomes planted below the treated soil survived at less than 10%.

Sainfoin (Onobrychis viciaefolia Scop. ‘Melrose’) seedlings tolerated at 15:1 commercial formulation of the sodium salts of MCPB {4-[(4-chloro-o-tolyl)oxy] butyric acid} and MCPA {[(4-chloro-o-tolyl)oxy] acetic acid} applied at rates up to 2.2 kg/ha in the greenhouse and 3.4 kg/ha in the field. Broadleaf weed control was only fair. Applications of 1.1 kg/ha, 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] ester caused moderate damage to sainfoin initially, but no reduction in yield. Weed control was fair to good. Higher rates of 2,4-DB caused excessive injury unless a heavy growth of weeds protected the sainfoin from contact with the spray. The use of 2,4-D [(2,4-dichlorophenoxy) acetic acid] amine damaged sainfoin severely, although weed control was fair. Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) at 3.4 kg/ha caused spotting on sainfoin leaves with no reduction in growth. Initial weed control was good, but sainfoin seedlings did not suppress new weed growth. Herbicide applications made when sainfoin had 1 to 3 leaves provided the best combination of crop tolerance and weed control.

Karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea] residues were monitored in Texas Post Oak Savannah soils immediately at the point of deposition of spheres containing approximately 0.765 g active ingredient (50%, w/w). Karbutilate residues (1.1 ppmw) were detected after 194 days in clay loam to 90 cm deep directly beneath the point of impact of the spheres. Although in one of two studies trace amounts (0.1 ppmw) of karbutilate residues were detected to 45 cm deep at 90 cm away from the point of impact after 111 days, vertical movement through the soil profile was much more evident than lateral displacement. After 191 days and at the point of sphere deposition, about twice as much residual karbutilate was detected in the surface 30 cm of a clay loam as in a loamy sand.