One-year-old and 3-month-old black walnut (Juglans nigra L.) and yellowpoplar (Liriodendron tulipifera L.) seedlings were treated with ring-labeled 14C-simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] in nutrient culture. Simazine uptake was measured and the levels of simazine and its degradation products monitored at 3, 6, and 9 days following treatment for 1-year-old seedlings and at 3, 8, and 13 days for 3-month-old seedlings. Concentration of simazine and the phytotoxic degradation product monodealkylated simazine [2-chloro-4-amino-6-(ethylamino)-s-triazine] were significantly higher in yellowpoplar than in black walnut leaves. For 1-year-old seedlings, higher concentrations of phytotoxic compounds in yellowpoplar than in black walnut were attributed to greater simazine degradation by black walnut. For 3-month-old seedlings, higher concentrations in yellowpoplar were attributed to greater simazine uptake by yellowpoplar and greater degradation in black walnut. Simazine degradation proceeded rapidly in both species and N-dealkylation was a major pathway. Monodealkylated simazine and 2-chloro-4,6-diamino-s-triazine were isolated from various tissues of black walnut and yellowpoplar. Hydroxysimazine [2-hydroxy-4,6-bis(ethylamino)-s-triazine] was found in yellowpoplar roots but not in any black walnut extracts. Two other degradation products were isolated but not identified.

Spurred anoda is a major competitor with cotton in the southern United States. Physiological and antioxidant responses of two species of cotton (Gossypium barbadense L. cv. ‘Pima S-7’ and Gossypium hirsutum L., Delta and Pine Land Company cv. ‘Delta Pine 5415’) and two accessions of spurred anoda [New Mexico (NM) and Mississippi (MS)] were investigated under nitrogen (N) -sufficient and -deficient conditions in the greenhouse. Pima S-7 had the highest leaf N content of all the plants regardless of treatment. Biomass decreased in all species when N was withheld, with Pima S-7 exhibiting the least reduction and MS the greatest. Plant height decreased in cotton but not spurred anoda under N stress. Height:node ratio increased 9% in MS, but decreased 8% in DP 5415 when they were deprived of N. Withholding N reduced photosynthesis 45% regardless of species. Comparable decreases were found in stomatal conductance and transpiration, suggesting strong stomatal regulation of gas exchange under N stress. The quantum efficiency of photosystem II (dark-adapted F v/F m) decreased 4% under N deficiency. Alpha-carotene decreased for all species when N was withheld, except for the NM accession, in which the levels increased. Total chlorophyll and lutein decreased under N stress regardless of species, but alpha-tocopherol and the xanthophyll cycle conversion state increased. Pima S-7 had the most chlorophyll and lutein, and both cotton species had more alpha-tocopherol, anthocyanins, and free-radical scavenging capacity than spurred anoda. These enhanced pigment and antioxidant profiles of cotton, particularly Pima S-7, may contribute to cotton's ability to compete for N with spurred anoda.

When the topic of this talk was first discussed, it was suggested that I might deal with developments in weed science outside the USA, but one had only to pause for a moment to realise that this was a hopelessly vast topic which could not usefully be dealt with in one presentation. I had, therefore, to choose between discussing the advances occurring in the more developed territories such as Europe and Japan and the advances or lack of advance in the less developed countries. It was natural enough for me to narrow my discussion to the developing countries, not only because of my personal experience in this sphere, but also because I believe there is a great deal to consider in this context which is of relevance to the theme for today, namely “a positive concern for society”.

The response of close-spaced, pickling cucumbers (Cucumis sativus L.) to preplant incorporation treatments of O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide (bensulide), N-butyl-N-ethyl α,α,α-trifluoro-2,6-dinitro-p-toluidine (benefin), and dimethyl tetrachloroterephthalate (DCPA) and preemergence applications of 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) and the methyl ester of 3-amino-2,5-dichlorobenzoic acid (chloramben) has been evaluated over a 2-year period. DCPA and nitralin gave the best overall weed control, while benefin and the methyl ester of chloramben were less effective in controlling weeds. The poorest weed control performance was observed with bensulide. Nitralin, DCPA, benefin, and the methyl ester of chloramben caused crop injury if leaching rains followed application. Despite early herbicide injury, yields were usually not adversely affected.

Surface microrelief and agrichemical placement influence agrichemical movement through soil. This study determined if anhydrous ammonia shank placement influenced atrazine movement in a ridge tillage system. Atrazine and Br− were broadcast over the plot or banded on the ridge while N fertilizer was Injected into the ridge or valley. Rainfall (17 cm) was applied and leachate was collected incrementally from grid lysimeters placed 75 cm below the soil surface. Amounts of atrazine and Br− in leachate and postrainfall soil atrazine distribution were determined. The injection slot created by fertilizer application influenced chemical movement. When atrazine and the fertilizer injection slot overlapped, atrazine movement through the soil was enhanced. These data suggest that herbicide applications and fertilizer injection slots that are not covered should not overlap due to increased potential for movement.

The effect of 3,6-dichloro-o-anisic acid (dicamba) was studied on wild buckwheat (Polygonum convolvulus L.) and wheat (Triticum aestivum L.) at two growth stages. Wild buckwheat, treated when 5 to 8 cm tall, was very susceptible to dicamba which caused rapid dehydration of the leaves and growth of callus tissue at stem internodes. Wild buckwheat, treated when flowering, increased in growth 2 days after treatment and then decreased after 4 days. Wheat growth tended to increase in all plant parts after treatment with dicamba at both the 2 to 3-leaf and the boot stages. Dicamba increased the RNA and protein content in wild buckwheat at both growth stages and in wheat at the boot stage. Dicamba affected the transition temperature and precipitation of reconstituted nucleohistone but not the uncombined nucleic acid or histone in vitro, indicating that a DNA-histone-dicamba complex had occurred. The binding of dicamba to protein varied with different proteins and reduced the UV absorbance of the bound proteins.

Soil-applied herbicides were evaluated for control of blackjack oak (Quercus marilandica Muenchh.), huisache [Acacia farnesiana (L.) Willd.], honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell], live oak (Quercus virginiana Mill.), Macartney rose (Rosa bracteata Wendl.), winged elm (Ulmus alata Michx.), and yaupon (Ilex vomitoria Ait.) in Texas. Various spacing of spot treatments of pelleted tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} on huisache and live oak and picloram (4-amino-3,5,6-trichloropicolinic acid) on Macartney rose up to a 2.7-m square grid did not change herbicide effectiveness. Pelleted tebuthiuron at 2.2 kg/ha reduced the canopy of live oak and killed a significant percentage of plants; however, differences among herbicide formulations and distance of placement in a grid were small. On unburned plots, 2.2 kg/ha of tebuthiuron applied as pellets at 2.7-m centers and as a broadcast wettable-powder treatment killed fewer yaupon than pellets applied in most broadcast treatments. In individual-plant treatments, bromacil (5-bromo-3-sec-butyl-6-methyluracil) and picloram solutions at 2 g/plant killed 45% of the yaupon 1.5 to 2 m tall on a fine sandy loam, whereas 0.5 g/plant of either herbicide killed 70% or more of the yaupon plants 1 m tall on a loamy fine sand. Both bromacil and picloram at 1 g/plant killed all blackjack oak and winged elm sprouts 1 to 2 m tall. On a clay soil, 1 g of bromacil/plant killed 79% of the live oak and 88% of the winged elm plants, whereas picloram killed only 38 and 45%, respectively. Neither bromacil nor picloram was effective as soil treatments for killing honey mesquite.

The effects of temperature and dew period on infectivity of Puccinia chondrillina Bubak and Syd. and the effect of light intensity on uredospore germination were studied under controlled environmental conditions. When rush skeletonweed (Chondrilla juncea L.) plants were inoculated with uredospores at 8, 16, and 24 C, larger pustules developed faster at 24 C than at the cooler temperatures. The greatest amount of infection occurred at 8 and 16 C (75% of the leaf area infected compared to 25% at 24 C). The greater number of infection sites at cooler temperatures was coincident with an increase in uredospore germination at 8 and 16 C compared to 24 C. Increasing the dew period from 0 to 6 h increased the amount of infection by the rust. Light intensities as low as 0.5 klux significantly reduced uredospore germination on water agar. Germ tube growth was restricted significantly by light intensities of 2.5 to 4.5 klux. Applications of uredospores to aid in biological control of this serious weed would be most successful if made at dusk under cool temperatures when an extended dew period is expected.

Author' note: This article is based on remarks made in February 1998 at the annual meeting of the Weed Science Society of America in Chicago. Those remarks were in turn based on an article, to be published in Spanish, titled “Es Antinatural la Manipulación Genética de los Animales?” The Spanish version will appear in the Proceedings of the Segundo Congreso Caribeno de Bioetica, University of Puerto Rico, Mayaguez, March 1998. It addresses the question of the engineering of animals; the focus here is the engineering of plants. Whether one considers flora or fauna, the unnaturalness objection raises the same cluster of concerns. Consequently, an assessment of those concerns need not vary significantly in turning from animals to plants.

The duration of imazaquin soil activity on corn, grain sorghum, rice, and cotton was studied from 1988 to 1990. Imazaquin applied at 0.035, 0.07, 0.14 (1× rate), and 0.28 kg ai ha−1 was incorporated into the soil, and rotational crops were planted at various times after application. Initial crop visual injury was directly related to imazaquin application rate. Cotton was most susceptible, followed by corn, grain sorghum, and rice. The carryover of imazaquin from soybeans to cotton, grain sorghum, and wheat was studied in separate experiments in Arkansas in 1987 to 1989. Wheat planted in the fall following soybean harvest was not affected by imazaquin residues. Grain sorghum planted the following spring was injured (16–35%), but there was no yield reduction. Cotton recovered from early injury (< 35%) in one year and did not recover from severe injury (> 50%) in the other, resulting in yield reduction.

Metsulfuron sorption, dissipation, and leaching were studied in six Colorado soils. Sorption was studied in the laboratory by batch equilibration of soil horizons from the surface to 1 m deep found in each study area. Kd was correlated to several soil parameters with pH (-0.773) and percent organic matter (OM) (0.666) the strongest, although low. Kd generally decreased with depth at each site and ranged from 0.10 to 0.83 among surface soils. The lowest Kd was in the soil with the highest pH. Leaching and dissipation were studied by high-performance liquid chromatography/ultraviolet analysis of field samples collected 1 m deep. Bromide ion as conservative tracer was applied concurrently with metsulfuron at the four dryland and two irrigated sites. In most cases, metsulfuron was found only in upper horizons, and the half-life ranged from 11.8 to 27.7 d, the shortest being in the soil with highest percent OM and lowest pH. Very little leaching below the surface horizon was detected in any soil.

Six multiple-cropping systems composed of: a) turnip (Brassica campestris spp. rapifera), corn (Zea mays L.), and snapbean (Phaseolus vulgaris L.); b) turnip, peanut (Arachis hypogaea L.), and snapbean; c) turnip, corn, and turnip; d) turnip, peanut, and turnip; e) snapbean, soybean [Glycine max (L.) Merr.], and cabbage (Brassica oleracea L.); and f) turnip, cucumber (Cucumis sativus L.), cowpea [Vigna unguiculata (L.) Walp.], and turnip were subjected to nematicide and weed control programs of cultivation or herbicides. Herbicide programs were superior to cultivation in control of weeds. Weeds remaining in the row following cultivation competed severely with crops. Weed species remaining were altered depending on the method of control and crop. Yellow nutsedge (Cyperus esculentus L. ♯3 CYPES) increased rapidly in all herbicide programs but not in cultivated plots. Pigweeds (Amaranthus spp.) were controlled by herbicides but increased in cultivated plots. Corn, peanut, soybean, and spring snapbean yields were higher in herbicide treatments than in cultivated treatments. Cucumber was the only crop that had increased yields for both main effects, herbicide and nematicide. Turnip was consistently injured in herbicide treatments, which was believed to be caused by residues from previous crops interacting with pathogens and possible allelopathic effects of decaying organic matter.

The influence of 2,6-dichlorobenzonitrile (dichlobenil) on yield, size, and pigmentation of cranberries (Vaccinium macrocarpon Ait., var. Early Black) was studied. Data on the effect of fall and spring applications were collected over a 2-year test period and comparisons made. Yield increased and berry size decreased after 1 year from both fall and spring treatments. The slight increases in yield were attributed to good weed control and not to any direct effect of dichlobenil. Treatments of cranberries for 2 successive years (fall and spring) caused slight reductions in yield and berry size. Berries treated for 2 successive years with dichlobenil were analyzed for anthocyanin development. All applications considerably enhanced pigmentation, spring treatments having the greatest effect in this respect. Anthocyanin development increased with increase in the concentration of dichlobenil applied.

Rapid adoption of glyphosate-resistant (GR) corn hybrids has led to the reemergence of volunteer corn as a problematic weed in soybean and has made controlling the initial stand of corn in a replant situation more difficult. If volunteer corn in soybean or the initial corn stand in a replant situation is not controlled, yield loss can occur. Clethodim and glufosinate are often used to control GR corn in corn replant situations and in soybean. The objectives of this research were to evaluate the response of two hybrid corn varieties and their F2 progeny to clethodim and glufosinate and to evaluate the effect of plant nitrogen (N) concentration on clethodim and glufosinate efficacy. First, a dose-response study was conducted with clethodim and glufosinate on DeKalb 60-18 and 60-18F2, and DeKalb 63-42 and 63-42F2 to compare the response of the hybrids and their F2 progeny to the herbicides. DeKalb 63-42 was more tolerant to clethodim than 60-18 and 60-18F2. No differences were found between the hybrids and their respective F2 progeny in the response to clethodim or glufosinate. In a second dose-response study assessing the effect of N conditions on herbicide efficacy, both clethodim and glufosinate were less injurious to plants growing in low N than in high N availability.

A field experiment was conducted between 1988 and 1993 to determine the number of wild-proso millet seed that could be returned to the soil without increasing future soil seed bank populations. The first seed bank (1988) was 15,300 seed m−2 and ranged from 14,000 to 21,000 seed m−2, which represented a high seed population for the area. Seed rain treatments of 0, 3, 6, 12, 24, and 48% of the 1988 soil seed bank were returned each fall. By 1993, more than 90% of the original millet seed bank had been depleted for all treatments. It was estimated that 77% of the seed rain and 68% of the spring seed bank were lost each year. As a result, wild-proso millet must produce approximately three times the seed in the soil to maintain a constant seed bank population.

A field experiment was conducted in 2000, 2001, and 2002 at Stoneville, MS, to determine the effect of spurred anoda interference on yield loss of two cotton cultivars, ‘Delta Pine 5415’ and ‘Pima S-6’, grown under wide (1 m) (WR) and ultra narrow (0.25 m) row (UNR) spacings. The relationship between spurred anoda density and dry weight per plot was linear each year. At a spurred anoda density of 8 m−2, spurred anoda dry weight per plot was 507, 322, and 777 g m−2 in 2000, 2001, and 2002, respectively. However, spurred anoda did not interfere with seed cotton yield in 2001, which was probably attributable to the low branch development in that year. Yield losses exceeded 55% at a spurred anoda density of 8 m−2 compared with controls in both WR and UNR. The effect of spurred anoda density on boll numbers was nearly identical in 2000 and 2002, regardless of cotton cultivar and row spacing. Boll weights decreased in response to spurred anoda interference. Spurred anoda interference resulted in a decrease in cotton branch dry weight in WR but not in UNR. The yield decrease as a result of spurred anoda interference in WR was due to reduction in boll retention or fruiting sites (predicated on a decrease in branch weight). However, in UNR, the yield decrease was due to plant mortality; the plant density of both cotton cultivars decreased by one plant for each additional spurred anoda, but the yield per plant for surviving plants remained constant. Neither WR nor UNR cotton had significant advantage in response to spurred anoda interference. The decreased boll weight observed in UNR, and the failure to increase boll numbers m−2 to compensate for decreased boll weight in UNR compared with WR, may limit its appeal to cotton producers.

Combination treatments of 2,4-D [(2,4-dichlorophenoxy)acetic acid] + mecoprop {2-[(4-chloro-o-tolyl) oxy] propionic acid} + dicamba (3,6-dichloro-o-anisic acid) injured actively growing bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA] immediately after treatment. Treatments made at the normal (1.1 + 0.6 + 0.1 kg ai/ha) rate in August, September, or October, did not affect winter survival. A triple rate (3.3 + 1.8 + 0.3 kg/ha) delayed growth of ‘Tifgreen’ and ‘Tifdwarf’ more the following April than ‘Tifway’ and ‘Ormond’. Due to a reduction in turf stand from herbicide treatments, the cover of common chickweed [Stellaria media (L.) Cyrillo # STEME] was higher in plots to which herbicides were applied in August or September than in untreated plots. The cover of weeds was lower in Tifway and Ormond plots than in Tifgreen and Tifdwarf plots.

Four herbicides were applied at 6-month intervals, and incorporated by disking, to desert cropland soils at two locations. Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was applied at 0.9 kg/ha; and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were applied at 1.8 kg/ha. Following treatment the soils remained fallow without irrigation for 24, 18, 12, 6, or 0 months before planting eight crops. Sugarbeet (Beta vulgaris L.) growth was affected 24 months after applications of trifluralin. Growth of two or three crops at each location was affected 18 months after application of prometryne. Residues of atrazine and diuron usually caused greater injury to most crops than did prometryne or trifluralin. Six months after the first planting four additional crops were planted. In plots planted 30 months after treatment diuron reduced sorghum (Sorghum bicolor (L.) Moench) stands by 70% and reduced fresh weights of three crops at Mesa. Trifluralin reduced fresh weight of sorghum by 80% at Yuma. Crops responded differently to herbicide residues at the two locations. Injury to crops was most severe at Mesa despite higher rainfall during the fallow period at this location.

Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] at a concentration of 10−8M stimulated the elongation of the embryonic axis of red kidney beans (Phaseolus vulgaris L. ‘Charlevoix’). This stimulation of elongation was accompanied by a light-independent increase in protein synthesis as measured by radioactive amino acid incorporation.

Greenhouse studies were conducted to determine the influence of plant density and spray volume on the retention, spray deposition, efficacy, and translocation of the amine salt of triclopyr in purple loosestrife. More spray solution was retained on leaves at 935 Lha−1 than at 94 Lha−1 at populations of 0, 4, or 8 nontarget neighbors. Spray coverage decreased with decreasing height within the plant canopy when spray cards were placed in the top, middle, and soil surface adjacent to the central target plant. Within a population, spray card coverage generally increased as spray volume increased. Regrowth from the crown was affected by spray volume, and uniform spray coverage of the plant was required for adequate control of vegetative regrowth and was achieved with spray volumes of 374 and 935 L ha−1 spray volume. Regrowth of purple loosestrife was greater at 94 Lha−1 at all three plant populations indicating that less herbicide penetrated the canopy to reach the basal portion of the plant. A laboratory experiment was conducted to investigate the translocation of radiolabelled triclopyr to roots and crowns of purple loosestrife. Only 0.3 to 1.4% of absorbed 14C-labelled material was translocated to roots and crowns. Low spray volumes and dense stands of purple loosestrife would likely result in poor control because inadequate amounts of triclopyr reach the basal portion of the plant and translocate to vegetative propagules.