Concentrations of DIBOA [2,4-dihydroxy-1,4-(2H)-benzoxazine-3-one] and BOA [2-(3H)-benzoxazolinone], described previously as major allelochemicals in Secale cereale (rye), were determined in eight field-grown cultivars, harvested at booting, using high-performance liquid chromatography (HPLC). Allelochemicals were also quantified in greenhouse-grown cultivar ‘Bates’ harvested 30, 45, 60, and 75 days after planting (DAP). The total production of DIBOA and BOA from field-grown S. cereale ranged from 137 to 1,469 μg g−1 dry tissue among the eight cultivars. ‘Bonel’ cultivar had the highest hydroxamic acid (HA) content and ‘Pastar’ the lowest. Bonel also showed the highest activity on Eleusine indica (goosegrass) and Pastar the least, in culture plate bioassays using aqueous extracts. HA content in shoot tissue varied with S. cereale maturity. The greatest level of HA in greenhouse-grown Bates was obtained 60 DAP compared to 30 DAP.

Use of glyphosate in controlling Orobanche aegyptiaca (broomrape), a parasitic weed on dicotyledonous crops, was examined by determining glyphosate dose response and 14C-labeled glyphosate absorption, translocation, and metabolism patterns in Vicia sativa (common vetch) that is tolerant of low levels of glyphosate and Brassica napus (oilseed rape) that has been genetically engineered to be glyphosate resistant. Glyphosate provided excellent suppression of O. aegyptiaca growth in both V. sativa and B. napus. Absorption and translocation of 14C-glyphosate was similar between parasitized and nonparasitized V. sativa plants. 14C-Glyphosate was metabolized up to 32% in V. sativa, which could account for some of the tolerance of V. sativa to glyphosate. Approximately 27% of translocated 14C-glyphosate accumulated in O. aegyptiaca attachments on V. sativa. Absorption and translocation patterns of 14C-glyphosate were similar between parasitized and nonparasitized B. napus plants. Nearly one-third (31%) of the translocated radioactivity was found in O. aegyptiaca attachments on B. napus. No metabolism of 14C-glyphosate was detected in B. napus.

The antidotes dichlormid, MON-4660, CGA-154281, R-29148, and MON-13900 were tested in the greenhouse to protect Zea mays L. (corn) against RPA 201772 injury. High rates of RPA 201772 injured four Z. mays hybrids > 30%. R-29148 and MON-13900 were the most effective of the five antidotes evaluated. R-29148 applied at rates ⩾ 45 g ha−1 provided excellent protection against RPA 201772 injury and also prevented injury to Z. mays from diketonitrile, the active metabolite of RPA 201772. In laboratory studies, R-29148 did not alter absorption of 14C-RPA 201772 from soil; however, R-29148 significantly enhanced the rate of RPA 201772 metabolism and inactivation in Z. mays. The mixed function oxidase inhibitor piperonyl butoxide (PBO) increased RPA 201772 injury on all hybrids. These results demonstrate that Z. mays tolerance to RPA 201772 can be enhanced with the use of antidotes such as R-29148 and MON-13900, that R-29148 protects Z. mays from RPA 201772 and diketonitrile by the enhancement of metabolism, and that oxidative reactions may be involved in the metabolism of RPA 201772 in Z. mays.

Competitive cereal cultivars are less susceptible than others to weed interference. Their characterization may provide selection criteria that can be used as guidelines to develop new, even more competitive cultivars. Root exudates are a potential means by which competitive cultivars reduce weed growth. The objectives of this study were to evaluate the effect of cereal root exudates on Brassica kaber (DC.) L. C. Wheeler growth, to isolate and characterize the allelochemical compounds released by spring cereal cultivars, and to determine if a relation exists between these allelochemicals and cultivar competitiveness. Highly competitive (HC) and lesser competitive (LC) cultivars of four crop kinds (Triticum aestivum L. [wheat], Avena sativa L. [wild oat], two- and six-rowed Hordeum vulgare L. [barley]) were selected based on previous work. Exudates from undisturbed root systems of B. kaber and cereals were collected and used in a bioassay test with B. kaber. Root exudates were analyzed for 16 common phenolic compounds using high-performance liquid chromatography (HPLC). Bioassays indicated that cereal exudates had no negative effect on B. kaber germination, but all concentrations of cereal root exudates inhibited B. kaber root and hypocotyl growth. As cereal root exudate concentration increased, B. kaber growth decreased. For each crop kind, B. kaber growth inhibition was greater with HC cultivars than with LC cultivars. The root exudates of all crop kinds and cultivars contained benzoic, caffeic, ferulic, o-coumaric, and vanillic acids as well as scopoletin. Para-hydroxybenzoic acid was found in exudates from T. aestivum, A. sativa, and two-rowed H. vulgare cultivars. Para-coumaric acid was not identified in root exudates from LC H. vulgare cultivars. Gentisic acid was produced by A. sativa and H. vulgare. Vanillic and o-coumaric acids along with scopoletin may be responsible for the allelopathic effects of H. vulgare, T. aestivum, and A. sativa cultivars. These three compounds may be useful as possible indicators of allelopathic potential of genotypes under development and thus considered for use in breeding programs.

Detailed knowledge about the environmental conditions required for weed seed germination and establishment in soil is an important prerequisite for the development of integrated and biological weed control strategies. Germination and establishment of Amaranthus retroflexus were studied at different temperatures, planting depths, soil types, nitrogen supply, and water potentials. The minimum temperature for seed germination was > 5 C; maximum germination occurred between 35 and 40 C. At temperatures between 25 and 35 C, an additive effect on germination rate was observed when temperature and water availability were increased. For all soils tested, the percentage emergence of seeds placed on the soil surface and 4 cm deep was significantly lower than seeds placed between 0.5 and 3 cm. Emergence in the four sandy soils was generally greater than in the two heavier soils included in the study. There was a highly significant interaction between seed depth and soil type. Plant growth was also greatest in the lighter soils. Plant height, number of leaves, leaf area, fresh and dry weight, and nitrogen and carbon percentage in plant tissues of A. retroflexus increased significantly with increasing soil nitrogen supply.

A field study was established in southern Iowa in 1994 to study seasonal and long-term weed population dynamics on land being brought back into production after 8 yr as part of the conservation reserve program (CRP). The study was a split-plot design with four replications; two tillage regimes, two crop rotations, and three herbicide application methods were used. Even though the tillage regime did not influence individual weed population density throughout the study, the no-till (NT) regime had more weeds compared to conventional tillage (CT). However, when weeds were grouped into categories, tillage influenced broadleaf weeds in 1994 and 1996 and total weeds in 1995. Plots under the NT regime had an average of 46 broadleaf weeds m−2 compared to 27 in CT in 1994, with Amaranthus rudis Sauer (common waterhemp) being the most prevalent. NT had a total of 186 weeds m−2 compared to 125 m−2 weeds in CT in 1995; however, in 1996, CT plots had 184 weeds m−2 compared to 121 m−2 in the NT regime. Except for broadleaf weeds in 1994, crop rotation did not influence the number of weeds, and herbicide application methods had the greatest effect on weed populations. Overall, weed populations were greater in 1997, 1996, and 1995 than in 1994 for all herbicide application methods. The no-herbicide treatment had the highest number of weeds throughout the study. The total number of weeds in band and broadcast treatments averaged 41 and 26 m−2 in 1994; 96 and 24 m−2 in 1995; 96 and 12 m−2 in 1996; and 109 and 95 m−2 in 1997. The use of broadcast herbicides in NT should be recommended for land coming out of CRP. Regardless of the herbicide application method or crop rotation, CT plots had better yields for both Zea mays L. (corn) and Glycine max L. (soybean). Glycine max had a better stand compared to Z. mays in the first year, indicating that a rotation starting with G. max might be preferred in the land coming out of CRP.

Weedy species of the genus Amaranthus, commonly referred to as pigweeds, have increased in frequency and severity over the past few years. Identification of these weeds is difficult because of similar morphological characteristics among species and variation within species. Studies were initiated to develop a molecular marker identification system utilizing restriction enzyme analysis of amplified ribosomal DNA (rDNA). A set of polymerase chain reaction (PCR) markers was developed to distinguish 10 weedy species of pigweeds. Restriction-site variation, utilizing five endonucleases, within the internal transcribed spacers (ITS) of the rDNA allowed for the positive identification of eight species and one pair of species. These markers will be useful for biological and ecological studies on the genus.

Apocynum cannabinum is a native creeping perennial distributed throughout the U.S., with increasing importance in reduced tillage systems throughout the Midwest. Apocynum cannabinum has been shown to be a difficult species to control in field crops. Effective weed management is often a function of the timing of control practice. Knowledge of weed emergence patterns may be useful in predicting the optimum time of weed management. The objectives of these studies were to describe how temperature and moisture affect A. cannabinum seed germination and to describe the relationship between growing degree units (GDU) and A. cannabinum vegetative shoot emergence. At constant temperatures, seed germination was described as a sigmoidal function of temperature (r 2 = 0.83), with maximum germination (32%) from 26 to 34 C. Under alternating temperatures, seed germination increased in a linear relationship between mean temperatures of 15 and 34 C (r 2 = 0.85). Maximum seed germination (88%) occurred at a mean temperature of 34 C under alternating temperatures. The relationship between seed germination and osmotic potential between −1.0 and 0 MPa was described by a gompertz function (r 2 = 0.98). Germination at −1.0 MPa was 4% and increased in a near linear manner to the nontreated control (0 MPa), which had 80% germination. Vegetative shoot emergence in 1997 and 1998 had a sigmoidal relationship to GDU using a base temperature of 6 C (r 2 = 0.96). However, initial shoot appearance was not consistent over years, with first emergence recorded on May 21, 1997 (132 GDU), and May 5, 1998 (73 GDU). Approximately 50% of the shoots emerged before June 7, 1997 (282 GDU), and May 21, 1998 (285 GDU); therefore, optimal weed management programs will need to be initiated following this GDU accumulation.

Crop yield loss–weed density relationships critically influence calculation of economic thresholds and the resulting management recommendations made by a bioeconomic model. To examine site-to-site and year-to-year variation in winter Triticum aestivum L. (winter wheat)–Aegilops cylindrica Host. (jointed goatgrass) interference relationships, the rectangular hyperbolic yield loss function was fit to data sets from multiyear field experiments conducted at Colorado, Idaho, Kansas, Montana, Nebraska, Utah, Washington, and Wyoming. The model was fit to three measures of A. cylindrica density: fall seedling, spring seedling, and reproductive tiller densities. Two parameters: i, the slope of the yield loss curve as A. cylindrica density approaches zero, and a, the maximum percentage yield loss as A. cylindrica density becomes very large, were estimated for each data set using nonlinear regression. Fit of the model to the data was better using spring seedling densities than fall seedling densities, but it was similar for spring seedling and reproductive tiller densities based on the residual mean square (RMS) values. Yield loss functions were less variable among years within a site than among sites for all measures of weed density. For the one site where year-to-year variation was observed (Archer, WY), parameter a varied significantly among years, but parameter i did not. Yield loss functions differed significantly among sites for 7 of 10 comparisons. Site-to-site statistical differences were generally due to variation in estimates of parameter i. Site-to-site and year-to-year variation in winter T. aestivum–A. cylindrica yield loss parameter estimates indicated that management recommendations made by a bioeconomic model cannot be based on a single yield loss function with the same parameter values for the winter T. aestivum-producing region. The predictive ability of a bioeconomic model is likely to be improved when yield loss functions incorporating time of emergence and crop density are built into the model's structure.

Herbicide resistance has been reported in several Amaranthus species throughout the U.S. Because evidence exists of interspecies hybridization in some species of this genus, this study was conducted to determine whether acetolactate synthase (ALS)-inhibiting herbicide resistance could be transferred from Amaranthus palmeri to Amaranthus rudis through interspecific crosses. Plants of each species were grown in a growth chamber, and controlled interspecies crosses were made between ALS-resistant and -susceptible plants. A total of 15 putative hybrid plants were produced from an estimated 10,000 cross-pollinated flowers. Analysis of restriction enzyme digests of the ALS gene in which a single base substitution confers resistance inferred that herbicide resistance had been transferred from a resistant male A. rudis to the hybrid plant. Offspring of hybrid plants, backcrossed to the susceptible parent, survived herbicide treatment, demonstrating that herbicide resistance was transferred between species. DNA analysis also was performed using the amplified fragment length polymorphism (AFLP) technique between parental and putative hybrid plants. Several unique bands were found only in the hybrid.

Earlier studies on the source of signals controlling correlative inhibition of root buds (underground adventitious buds located on the lateral roots) in Euphorbia esula indicated that either growing meristems (apical or axillary buds) or fully expanded leaves could prevent root buds from breaking quiescence. An investigation of the production and transport requirements of the leaf-derived signal is described. As few as three leaves remaining on budless stems greatly reduced the growth of (but not the number of growing) root buds. Also, light and CO2 fixation were necessary for the leaf effects on root bud growth, but not necessary for correlative inhibition imposed by growing axillary buds. Treatment of plants with Ametryn induced root bud growth on budless plants but not on plants with intact axillary buds. The polar auxin transport inhibitor N-1-naphthylphthalamic acid prevented transmission or the signal from growing axillary buds, but it had only a minor effect on the transmission of the leaf-derived signal. Treatment of plants with gibberellic acid (GA) induced growth of root buds under otherwise noninducing conditions to some extent in all plants. However, the greatest effects of GA were on plants with intact leaves (meristemless/budless and meristemless). GA had no significant effect on root bud quiescence under conditions that induced root bud growth.

We studied the effect of tillage systems (no-till, chisel, and moldboard plow) and the presence or absence of Zea mays L. (corn) on soil temperature, moisture, and, subsequently, the emergence phenology and density of Chenopodium album L. (common lambsquarters) at two sites (Elora and Woodstock) from 1993 to 1995. The tillage system affected the phenology of C. album seedling emergence only in 1995. In that year, more days were required to reach 80% cumulative seedling emergence in no-till than in the chisel or moldboard plow treatments. The delay in obtaining 80% cumulative emergence was attributed to a dry period from days 159 to 177 at Elora and from days 155 and 176 at Woodstock. The presence or absence of Z. mays did not affect soil temperatures, soil moisture, or C. album seedling emergence phenologies. Chenopodium album seedling density was influenced by tillage and environmental conditions. Large variations in seedling density were attributed to environmental conditions. The presence or absence of Z. mays did not affect C. album seedling density.

Laboratory studies were conducted to describe germination and seedling elongation of Ambrosia artemisiifolia L. (common ragweed) seed. The germination process was tested for the interaction of temperature and water potential across eight thermo-periods (7.5, 12.5, 17.5, 22.5, 27.5, 32.5, 37.5, and 42.5 C) and 12 water potentials (0, −0.03, −0.06, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, −1.8, and −2.1 mPa). The rate of seedling shoot and radicle elongation was described as a function of temperature and tested for eight day: night temperature treatments (10: 5, 15 : 10, 20 : 15, 25 : 20, 30 : 25, 35 : 30, 40 : 35, and 45 : 40 C). The rate of germination was mathematically modeled by a Weibull function. Probit analysis was used to determine the cardinal temperatures (base, optimum, and maximum) and base water potential (αb ). The base temperature (T b), optimum temperature (T opt), maximum temperature (T max), and αb for A. artemisiifolia germination were estimated as 3.6, 30.9, and 40 C and −0.8 mPa, respectively. The rates of shoot and radicle elongation were described by regression models. The T b , T opt, and T max for shoot and radicle elongation were estimated as 7.7 and 5.1, 29.5 and 31.4, and 43.0 and 44.3 C, respectively. A mathematical model describing the process of A. artemisiifolia seed germination in terms of hydrothermal time (θHT) was derived. The θHT model described the phenology of A. artemisiifolia seed germination using a single curve generated from the relationship of temperature and water potential. This model can help in predicting germination and emergence of A. artemisiifolia under field conditions.

Weed management can be a significant challenge in cropping systems, partly because the effects of tillage systems on weed seedbank and seedling population dynamics are not well understood. Field research was conducted from 1994 to 1996 in established tillage plots consisting of moldboard plow (MP), chisel plow (CP), and no-tillage (NT). The objectives were to determine the effects of long-term tillage systems on the timing and duration of Setaria spp. emergence and percentage cumulative emergence from the soil seedbank and to investigate the effect of tillage on Setaria spp. density and seed production following glyphosate application at Setaria spp. heights of 5, 10, and 15 cm. NT contained a greater number of Setaria spp. seed in the 0- to 1-, 1- to 3-, and 3- to 6-cm depths than MP or CP systems. There was little difference between the three tillage systems at depths greater than 6 cm. Setaria spp. emergence was greater in NT than in MP or CP in 1994 and 1996 and greater than in MP in 1995. There was a substantial increase in Setaria spp. emergence in NT between 3 and 4 weeks after planting (WAP) in 1994 and between 5 and 6 WAP in 1995 and 1996. Significant emergence did not occur past 5 to 6 WAP in 1994 and 1995 but continued over a longer period of time in 1996. Setaria spp. plants consistently reached targeted herbicide application heights 4 to 9 d earlier in NT than in CP and MP. In 1994, final Setaria spp. density was greater in NT compared to CP and MP at the 5- and 10-cm herbicide application timings. When glyphosate was applied to 15-cm-tall Setaria, very few weeds were present following application across all tillage systems. In 1995, NT resulted in greater Setaria spp. density than MP or CP across all application timings. There was no difference in final Setaria spp. density between MP and CP across all glyphosate timings in 1994 and 1995. Seed production was negligible in MP and CP, regardless of glyphosate timing. In NT, however, significant seed production occurred, especially with early application. Results indicate that the effectiveness of nonresidual herbicides for Setaria faberi Herrm. control is influenced by tillage system and the timing of application.

Critical period experiments were conducted in 1997 near Milton, WI, and in 1998 near Edgerton, WI, in which Eriochloa villosa (Thunb.) Kunth emergence was characterized and related to Zea mays L. yield loss and weed seed production. At Milton, 2.7% of the spring seedbank emerged, and at Edgerton, 14.5% of the spring seedbank emerged. Peak time of E. villosa emergence occurred early in the season at both locations, accounting for 84% of the total season emergence at Milton by 37 d after planting and 90% of the total season emergence at Edgerton by 27 d after planting. A secondary peak in emergence occurred at each site, accounting for 14% of the total season emergence at Milton between 38 and 52 d after planting and 8% of the total season emergence at Edgerton between 28 and 43 d after planting. Following the secondary peak in emergence at each site, approximately 2% of the total season emergence occurred. Zea mays grain yield was reduced when E. villosa interfered with Z. mays past the V11 stage at Milton and the V3 stage at Edgerton. Zea mays yield reductions at Edgerton were greater, occurred under shorter periods of weed interference, and were associated with greater E. villosa biomass than yield reductions at Milton. Eriochloa villosa that emerged after the V2 Z. mays stage at Milton and the V3 stage at Edgerton did not cause crop yield loss; however, these plants produced seed at 143 and 63% of the initial spring seedbanks, respectively.

Emergence characteristics, including initial time of emergence, magnitude of emergence, and mean time of emergence, of Amaranthus rudis Sauer, Setaria faberi Herrm., Eriochloa villosa (Thunb.) Kunth, and Abutilon theophrasti Medik. were studied in central Iowa during the first 3 yr following burial of seed collected and buried in the fall of 1994 or 1995. Although the initial emergence date varied among years, the emergence sequence among species was consistent. Eriochloa villosa and A. theophrasti were the first species to emerge, with initial emergence occurring between April 28 and May 10. Initial emergence dates for these species were the same, except for 1995 when A. theophrasti emerged 4 d prior to E. villosa. Amaranthus rudis was the last species to emerge, with initial emergence ranging from 5 to 25 d after A. theophrasti. First-year emergence in 1995 was 8% for A. theophrasti, 7% for A. rudis, 41% for E. villosa, and 33% for S. faberi, based on the number of buried seed. Proportional emergence during the first year following burial in 1996 was similar to 1995 for A. theophrasti and S. faberi, but greater emergence was observed in 1996 for E. villosa and A. rudis. During the 3 yr of both studies, cumulative emergence of the two grass species (43 to 71%) was higher than for the broadleaf species (13 to 35%). A high percentage of the total annual emergence of E. villosa occurred within the first 2 wk of initial emergence, whereas a high percentage of A. rudis emergence occurred late in its emergence period. Emergence characteristics of the four species were consistent among years and seed sources.

Laboratory and greenhouse studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of the invasive weed Pueraria lobata (kudzu). Germination occurred over a range of alternating temperatures from 15/6 to 35/25 C. Seed germinated equally well in alternating light/darkness and continuous darkness. At all temperature regimes, percentage germination was much greater for hand-scarified seed (95 to 100%) than for nonscarified seed (7 to 17%), indicating that P. lobata seed possesses physical dormancy. Germination exceeded 51% in solutions with pH 5 to 9. Maximum germination (99%) was observed in distilled water at pH 5.4. Germination was greatly reduced in solutions with osmotic potentials below −0.4 MPa (28% at −0.6 MPa, and 13% at −0.9 MPa); no germination was observed at −1.3 MPa. Percentage emergence was greater than 45% at burial depths in soil of 0.5 to 10 cm, with maximal emergence (72 to 85%) at depths of 0.5 to 4 cm. Seed sown on the soil surface had low seedling emergence (< 13%). No seedlings emerged when seed was exposed to flooding for 7 d or more. Pueraria lobata seed is capable of germinating in a variety of climatic and edaphic conditions, but flooding may severely limit establishment of stands by seed.

Latent infections of Colletotrichum gloeosporioides f.sp. malvae (C. g. malvae) in plants and seed were determined in several crops under field conditions after application of C. g. malvae conidia at 12 times the recommended rate. Colletotrichum g. malvae was isolated in trace amounts from Brassica napus/campestris, Linum usitatissimum, Lens culinaris, Brassica juncea/hirta, Helianthus annuus, and Triticum spp. only at the 2-wk isolation. Colletotrichum g. malvae was never isolated from Beta vulgaris. After 5 wk, C. g. malvae was not detected in any of the crops, except for Carthamus tinctorius at harvest, and was not detected from wash water of plant tissue or seed after 72 h. Colletotrichum g. malvae recovery in the field, as in controlled environmental conditions, decreased with time, which indicates that buildup of inoculum did not occur. Fungi other than C. g. malvae and bacteria isolated from seed and from wash water of plant tissue increased with time throughout the growing season. Colletotrichum g. malvae was not recovered from seed or crowns of any of the crop cultivars at either location in either growing season, except for C. tinctorius. Only one seed of the C. tinctorius cultivar ‘S-208’ out of 17,280 C. tinctorius seed analyzed over three growing seasons tested positive for C. g. malvae. Colletotrichum g. malvae was found only on the seed coat; the germinated seedling was not infected. Colletotrichum g. malvae was not recovered from any of the wash water from seed. These results should alleviate any of the concerns regarding the fate of the millions of conidia applied during a normal spray operation on nontarget plants, the potential infectivity of nontarget plants, the potential buildup of C. g. malvae in the field, and the utilization of any of the C. g. malvae-treated crops for food or feed.

An experiment was conducted at two locations in Georgia and two locations in North Carolina during 1994 and 1995 to evaluate weed management in conventional-tillage bromoxynil-resistant Gossypium hirsutum L. (cotton). The weed management systems evaluated included different combinations of fluometuron preemergence (PRE), bromoxynil or bromoxynil plus MSMA early postemergence (EPOST), bromoxynil postemergence (POST), and cyanazine plus MSMA late post-directed (LAYBY). Fluometuron PRE improved control of Acanthospermum hisptdium DC. (bristly starbur), Cassia occidentalis L. (coffee senna), Chenopodium album L. (common lambsquarters), Desmodium tortuosum (Sw.) DC. (Florida beggarweed), Sida spinosa L. (prickly sida), Jacquemontia tamnifolia (L.) Griseb. (smallflower morningglory), and Anoda cristata (L.) Schlecht. (spurred anoda), compared to system that did not use fluometuron PRE. It also improved G. hirsutum yields at three four locations. Bromoxynil-containing systems provided better weed control and higher G. hirsutum yields than systems without bromoxynil. Bromoxynil EPOST controlled A. hispidium, C. occidentalis, C. album, D. tortuosum, S. spinosa, J. tamnifolia, and A. cristata. Control of these species was frequently improved by a second application of bromoxynil POST. Bromoxynil EPOST, POST, or EPOST plus POST did not control Senna obtusifolia (L.) Irwin and Barneby (sicklepod), but the addition of MSMA to bromoxynil EPOST improved S. obtusifolia control. Control of all dicotyledonous weeds was improved by a LAYBY treatment of cyanazine plus MSMA, and yields were improved at three of four locations with this treatment. Gossypium hirsutum was not injured by POST treatments of bromoxynil, and only temporary injury resulted from POST treatments of MSMA.