Cuphea is a new crop of temperate regions that produces seed oil that can substitute for imported coconut and palm kernel oils. Only four herbicides are known to be tolerated by cuphea to date. More herbicides, especially POST products, are needed for continued commercialization. In Minnesota and North Dakota, where cuphea currently is grown, greater control of Canada thistle and biennial wormwood is needed in cuphea. Because clopyralid is effective on both of these species, it was tested at rates ranging from about 25 to 850 g ae ha−1 in greenhouse and field trials. Visual assessment of injury, height, growth, and seed yield of cuphea were not reduced significantly in field-grown plants when clopyralid was applied at rates up to 400 g ae ha−1. Thus, at the rate commonly used in other crops, 200 g ae ha−1, clopyralid can be applied safely to cuphea.

Those preparing for a career in weed science extension are expected to take formal courses in weed science and related subject matter. They should gain experience in conducting and interpreting research. They also can benefit from formal courses and experience to develop communication skills for technology transfer. Such courses as psychology, journalism, photography, and public speaking should be considered. Along with research and teaching assistantships, educational institutions should establish extension assistantships to help those preparing for a career in weed science extension.

After 25 yr in research and teaching, I moved into administration about 2 yr ago. Thus I shall discuss with you the image of weed science as a recent outsider, which I consider myself. From this perspective, I want to point out both the positive and negative aspects of our weed science image. In other words, what are our strengths and weaknesses? Can we build on our strengths and overcome our weaknesses?

Cogongrass, a rhizomatous perennial, is among the world's most troublesome weeds. Research was conducted at the Southern Weed Science Research Unit, Stoneville, MS, to determine cogongrass rhizome mortality with increasing temperature and duration of exposure to heat and to determine if 2,3,5 triphenyl tetrazolium chloride (TTC) could be used to evaluate cogongrass rhizome mortality following heat treatment. Cogongrass rhizome mortality was 100% at 65, 79, 93, 107, 121, 149, 177, and 187 C at time periods greater than or equal to 25, 5, 2.5, 2.5, 2.5, 2, 2 and 1 min, respectively. The duration of heat required for cogongrass mortality decreases as temperature increased. The standard greenhouse bioassay was more effective than tetrazolium chloride in predicting viability of cogongrass rhizomes following heat treatments.

A laboratory study was conducted in 2003 at Louisiana State University in Baton Rouge, LA, to evaluate the interactive effects of bensulfuron or halosulfuron on clomazone in terms of rice foliar bleaching and chlorophyll content. Clomazone was applied alone at 0 and 1.227 μg/ml (672 g/ha) or in combination with bensulfuron at 0.0276 μg ai/ml (42 g ai/ha) or halosulfuron at 0.0345 μg ai/ml (53 g ai/ha) in a hydroponic solution. Bensulfuron and halosulfuron were also applied alone. Rice cultivars evaluated included short-grain ‘Pirogue’, medium-grain ‘Bengal’, and long-grain ‘Cocodrie’. Bensulfuron and halosulfuron, applied in a hydroponic solution, safened medium-grain Bengal, long-grain Cocodrie, and short-grain Pirogue at 21 d after treatment (DAT) from foliar bleaching caused by clomazone. Chlorophyll a and b and total chlorophyll content of all three rice cultivars decreased when treated with clomazone treatment. Only chlorophyll content of Cocodrie was increased by the addition of bensulfuron and halosulfuron compared with a single application of clomazone.

Field and laboratory experiments were conducted to evaluate the effect of postemergence johnsongrass control on incidence of maize chlorotic dwarf virus (MCDV) and maize dwarf mosaic virus (MDMV) in corn and to confirm the presence and movement of the blackfaced leafhopper, the insect vector of MCDV. Corn plants surrounded by MCDV- and MDMV-infected rhizomatous johnsongrass were either treated or not treated with nicosulfuron at 35 g ai/ha. Corn tissue samples were taken at the time of treatment and 4, 9, 14, and 21 d after treatment and the presence of MCDV and MDMV was determined by enzyme-linked immunosorbent assay (ELISA). Virus incidence in treated experimental units was higher at the later sampling dates relative to the nontreated. Earlier differences in incidence of MCDV and MDMV double infection in corn were detected where johnsongrass was controlled. Movement of the insect vector of MCDV was observed within the experimental area after johnsongrass was controlled, but was not significantly different from that in nontreated areas.

Southern Great Plains wheat growers typically apply either sulfosulfuron or propoxycarbazone-sodium for selective control of cheat. Although astute growers apply herbicides early in the growing season, herbicide application is often delayed until mid-winter or later. The effects of application timing of propoxycarbazone-sodium on cheat efficacy and on injury to the following grain sorghum crop have not been documented. Application of each herbicide at 17 intervals throughout the growing season indicated that cheat control with propoxycarbazone-sodium was greater than or equal to 90% even when application was delayed for several months after seeding. In contrast, cheat control with sulfosulfuron was variable when application was delayed more than 6 wk after wheat was seeded. Delaying sulfosulfuron application decreased wheat yield. Grain sorghum was not affected by propoxycarbazone-sodium residues regardless of application timing to wheat. Conversely, grain sorghum was severely injured by sulfosulfuron residues regardless of herbicide application timing.

Backcross-derived isolines of soybean [Glycine max (L.) Merr.] cultivars with and without the Rps1-k gene for resistance to Phytophthora rot (Pythopthora megasperma f. sp. glycinea) were grown in hydroponic culture with and without metribuzin [4-amino-6-(1,1-dimethylethyl)-3-3(methylthio)-1,2,4-triazin-5(4H)-one] added at 0.15 mg L−1. A marked tolerance to metribuzin was associated with Rps1-k possibly from an allele at the Hm/hm locus which is known to be linked closely with the Rps1 locus. This improved tolerance could reduce the occurrence of injury from metribuzin applications.

Suspected triazine resistant Pennsylvania smartweed plants were discovered near Holy Cross, Dubuque County, IA. Subsequent variable chlorophyll a fluorescence assays confirmed these selections to be triazine resistant. This is the first reported evidence of s-triazine resistance in Pennsylvania smartweed.

Grower response from a mail survey indicated that musk thistle is a common and spreading problem in Tennessee nurseries. Poor herbicide selection and timing were reasons for the lack of control in most nurseries. At 31 wk after treatment preemergence herbicides or herbicide mixtures that gave 80% or greater musk thistle control in evaluation studies were atrazine, simazine, simazine + metolachlor (1.1 + 4.4 kg ai ha-1), oryzalin + isoxaben, or dithiopyr. Oryzalin, metolachlor, napropamide, or simazine + metolachlor (0.5 + 2.2 kg ha-1) gave 65, 35, 0 and 78% control of musk thistle, respectively. Glyphosate or SC-0224 at 1.7 and 2.2 kg ha-1 gave 89% or greater control of emerged musk thistle. Lactofen or HOE-39866 at 0.8 kg ha-1 gave less than 66% control of emerged musk thistle at 8 wk after treatment.

The efficacy of the safeners naphthalic anhydride (NA), CGA-92194, and CGA-133205 as protectants of grain sorghum and of NA, R-29148, CGA-154281, and dichlormid as protectants of corn against injury from the chloroacetamide herbicide, SAN 582H, was evaluated under greenhouse conditions. SAN 582H applied alone reduced the shoot growth of ‘Funk G522DR’ and ‘Funk G623’ sorghum, but had no effect on the growth of the ‘GP-10’ genotype of sorghum. Corn (‘Northrup-King 9283’ hybrid) was considerably more tolerant than grain sorghum to SAN 582H. The rate of SAN 582H causing 50% reduction of corn shoot height (GR50) was 5.1 kg/ha as compared to 1.1 kg/ha for grain sorghum. NA applied as seed dressing at 5 or 10 g/kg seed, provided moderate protection to ‘G522DR’ and ‘G623’ sorghum and no protection to corn against SAN 582H injury. Dressing of sorghum seeds with CGA-133205 provided moderate protection to G522DR sorghum, whereas seed-applied CGA-92194 provided moderate protection to G623 sorghum against SAN 582H. The dichloroacetamide safeners R-29148, dichlormid, and CGA-154281 were all effective as protectants of corn against SAN 582H injury. These results demonstrate that, as with other chloroacetamide herbicides, the tolerance of corn and grain sorghum to SAN 582H can be enhanced with the use of safeners of the dichloroacetamide type and oxime ether type, respectively.

Greenhouse experiments were conducted to determine ‘Len’ hard red spring wheat response to triallate and chlorsulfuron applied separately and together. Chlorsulfuron at 12 or 23 g/ha plus preplant incorporated (PPI) triallate at 1120 g/ha antagonized triallate toxicity to wheat. Chlorsulfuron reduced triallate injury to wheat less when applied preemergence (PRE) after PPI triallate compared to both herbicides applied PPI. Soaking wheat seeds in 21 and 31 ppbw chlorsulfuron solutions for 24 h before placing into triallate-treated soil did not reduce triallate injury to wheat. Applying chlorsulfuron to triallate did not reduce triallate toxicity to wild oats.

The herbicide 2,4-D has been in commerce and a subject for research since 1944. It is undoubtedly among the most thoroughly researched pesticides in the world. In our society, 2,4-D has played an indispensable role. It is most important in the production of our food and fiber; in the control of noxious weeds causing public health problems such as common ragweed (Ambrosia artemisiifolia L.) and poison-ivy [Toxicodendron radicans (L.) Ktze.] in the maintenance of our utility supply lines and highway and railroad systems; and as a useful tool for creating desirable wildlife habitats and beautifying our parks, golf courses, and the grounds about our homes.

Recently completed toxicological studies support the conclusions of earlier studies that 2,4-D may be used without undue risk to man, wildlife, or the environment. This does not mean, of course, that we should lessen our precautions to avoid exposure to applicators, prevent spray drift from getting on bystanders, or on pets such as dogs and cats, and following general good sanitation practices in its use.

There have been some reports of an association between the use of 2,4-D and NHL. However, in our opinion after considering all the toxicological and epidemiological evidence, it has not been established that the use of 2,4-D causes NHL or any other type of cancer including soft tissue sarcomas and Hodgkin's disease. As cited in this review, most scientific experts who have carefully examined all the data share this opinion.

Acifluorfen, chlorimuron, and thiameturon were compared in single and sequential treatments for cowpea control in soybean. Chlorimuron applied once at 8.8 g ai/ha at 14, 21, and 28 days after cowpea emergence controlled 80% or more of cowpea. Control was greater at 14 and 21 than at 28 days after emergence in one of three experiments. Cowpea control by chlorimuron was similar with single and sequential treatments. Soybean injury was lower, and soybean seed yields generally were higher with chlorimuron than with thiameturon or acifluorfen. Thiameturon and acifluorfen controlled less than 60% of cowpea. Three weedy cowpea cultivars responded the same to chlorimuron, but cowpea recovery was substantial in 1 of 3 yr.

Junglerice is becoming more prevalent in Tennessee, Arkansas, and Mississippi row crop fields. The evolution of glyphosate-resistant (GR) junglerice populations is one reason for the increase. Another possible explanation is that glyphosate and clethodim grass activity is being antagonized by dicamba. This question has led to research to examine whether sequential applications alleviate antagonism observed with dicamba plus glyphosate and/or clethodim mixtures and determine whether sequential treatments with those herbicides at 24 h, 72 h, or 168 h can improve junglerice control. Glyphosate + clethodim applications provided >90% junglerice control. The observed levels of antagonism varied by whether the location of the test was in the greenhouse or the field, and the timing of applications. In the greenhouse, clethodim + dicamba provided excellent control, whereas in the field, the same treatment showed a greater than 30% reduction in junglerice control compared with clethodim alone. However, control was restored by using a mixture of glyphosate + clethodim without dicamba. The environment at the time of application and relative GR level of the junglerice influenced the overall control of these sequential applications. When clethodim applied first followed by dicamba at 72 h or 168 h, better control was observed compared with applying dicamba followed by clethodim. Overall, mixing glyphosate + clethodim provided the most complete junglerice control regardless of timing. These data confirm that leaving dicamba out of the spray tank will mitigate herbicide antagonism on junglerice control. These data would also indicate that avoiding dicamba and glyphosate mixtures will also improve the consistency of control with glyphosate-susceptible junglerice.

Winter annual weeds begin to germinate as zoysiagrass enters winter dormancy in autumn. These weeds can suppress zoysiagrass shoot development the following spring through competition for sunlight, moisture, and nutrients. Previous research involving winter annual weed control in dormant turfgrass has been conducted primarily on bermudagrass, but less is known about how various herbicides used for this purpose will influence zoysiagrass after dormancy transition. Two field studies were conducted over 7 site-years between 2016 and 2020 to evaluate 17 herbicide treatments that are typically marketed for broadleaf weed control in spring and 18 herbicide treatments that are typically marketed for annual bluegrass control during winter for their effects on a variety of weeds and semidormant ‘Meyer’ and dormant ‘Zeon’ zoysiagrass, respectively. Glufosinate, glyphosate + simazine, and indaziflam + simazine controlled Persian speedwell by more than 90% and control was significantly greater with auxin-type and other herbicide combinations. Dandelion and Persian speedwell were better controlled with a combination of simazine and glyphosate than when glyphosate was applied alone. Glufosinate controlled dandelion, hairy bittercress, and Persian speedwell more effectively than glyphosate. In Meyer zoysiagrass, glyphosate and glufosinate controlled annual bluegrass equivalently, whereas in Zeon zoysiagrass, glyphosate controlled annual bluegrass better than glufosinate did. Foramsulfuron or treatments that contained simazine resulted in >90% control of annual bluegrass. A flumioxazin admixture with diquat, glufosinate, or glyphosate improved annual bluegrass control. Herbicide treatments that contain diquat, glufosinate, glyphosate, and metsulfuron alone or in a tank-mix should not be applied to Meyer zoysiagrass with 5% visual green turf cover due to high injury potential. In both studies, glufosinate was more injurious to Meyer and Zeon zoysiagrass than glyphosate. Overall, several herbicides that control annual bluegrass or broadleaf weeds can be safely applied to Zeon zoysiagrass during dormancy or Meyer zoysiagrass during post-dormancy transition.

Tolpyralate is a 4-hydroxyphenylpyruvate dioxygenase–inhibiting herbicide that is applied postemergence for control of annual broadleaf and grass weeds in corn. Current Canadian label recommendations for tolpyralate specify the addition of a methylated seed oil (MSO) adjuvant (MSO Concentrate®) for improved weed control. The efficacy of tolpyralate applied with other proprietary adjuvants has not been widely reported in the peer-reviewed literature. Therefore, four field trials were conducted in corn over 2020 and 2021 in Ontario, Canada, to evaluate MSO Concentrate®, Agral® 90 (nonionic surfactant), Assist® Oil Concentrate (blended surfactant), Carrier® (blended surfactant), LI 700® (nonionic surfactant), and Merge® (blended surfactant) as adjuvants with tolpyralate for the control of annual broadleaf and grass weeds. At 8 wk after application (WAA), tolpyralate applied with MSO Concentrate®, Agral® 90, Assist® Oil Concentrate, Carrier®, or Merge® controlled velvetleaf, wild mustard, barnyardgrass, and foxtail species similarly. These adjuvants also enhanced the efficacy of tolpyralate similarly for the control of common ragweed at 8 WAA with the exception that Agral® 90 was inferior to Merge®. At 8 WAA, tolpyralate controlled common lambsquarters the greatest when applied with MSO Concentrate®, Agral® 90, Carrier®, or Merge®; these adjuvants with the exception of Agral® 90 were superior to Assist® Oil Concentrate. At 8 WAA, tolpyralate applied with LI 700® controlled common ragweed, barnyardgrass, and foxtail species less than when tolpyralate was applied with the other adjuvants tested; control of these weed species with tolpyralate was not improved with LI 700® when compared to tolpyralate applied without an adjuvant. Overall, tolpyralate applied with either MSO Concentrate®, Carrier®, or Merge® controlled all annual broadleaf and grass weed species similarly or greater than tolpyralate applied without an adjuvant or tolpyralate with Agral® 90, Assist® Oil Concentrate, or LI 700® at 8 WAA.

Glyphosate-tolerant and glyphosate-resistant weeds are becoming increasingly problematic in cotton fields in Australia, necessitating a return from a glyphosate dominated system to a more integrated approach to weed management. The development of an integrated weed management system can be facilitated by identifying the critical period for weed control (CPWC), a model that enables cotton growers to optimize the timing of their weed control inputs. Using data from field studies conducted from 2003 to 2015, CPWC models using extended functions, including weed biomass in the relationships, were developed for the mimic weeds, common sunflower and Japanese millet, in high-yielding, fully irrigated cotton. A multispecies CPWC model was developed after combining these data sets with data for mungbean in irrigated cotton, using weed height and weed biomass as descriptors in the models. Comparison of observed and predicted relative cotton-lint yields from the multispecies CPWC model demonstrated that the model reasonably described the competition from these three very different mimic weeds, opening the possibility for cotton growers to use a multispecies CPWC model in their production systems.

Italian ryegrass is a major weed in winter cereals in the south-central United States. Harvest weed seed control (HWSC) tactics that aim to remove weed seed from crop fields are a potential avenue to reduce Italian ryegrass seedbank inputs. To this effect, a 4-yr, large-plot field study was conducted in College Station, Texas, and Newport, Arkansas, from 2016 to 2019. The treatments were arranged in a split-plot design. The main-plot treatments were (1) no narrow-windrow burning (a HWSC strategy) + disk tillage immediately after harvest, (2) HWSC + disk tillage immediately after harvest, and (3) HWSC + disk tillage 1 mo after harvest. The subplot treatments were (1) pendimethalin (1,065 g ai ha−1; Prowl H2O®) as a delayed preemergence application (herbicide program #1), and (2) a premix of flufenacet (305 g ai ha−1) + metribuzin (76 g ai ha−1; Axiom®) mixed with pyroxasulfone (89 g ai ha−1; Zidua® WG) as an early postemergence application followed by pinoxaden (59 g ai ha−1; Axial® XL) in spring (herbicide program #2). After 4 yr, HWSC alone was significantly better than no HWSC. Herbicide program #2 was superior to herbicide program #1. Herbicide program #2 combined with HWSC was the most effective treatment. The combination of herbicide program #1 and standard harvest practice (no HWSC; check) led to an increase in fall Italian ryegrass densities from 4 plants m−2 in 2017 to 58 plants m−2 in 2019 at College Station. At wheat harvest, Italian ryegrass densities were 58 and 59 shoots m−2 in check plots at College Station and Newport, respectively, whereas the densities were near zero in plots with herbicide program #2 and HWSC at both locations. These results will be useful for developing an improved Italian ryegrass management strategy in this region.

Oregon’s Willamette Valley is the major cool-season, grass-seed-production area in the world. Roughstalk bluegrass (RB) is a weed in waterlogged, grass-seed-crop fields. Growth chamber and greenhouse studies were conducted to determine the influence of waterlogging on the germination and establishment of RB and tall fescue (TF). Oxygen deficiency resulted in a germination delay in both species, but was greater for TF. Oxygen deficiency at 20 and 30 C was greater for TF compared to RB. Simulated waterlogging for 28 d reduced aboveground biomass more for RB (58%) than for TF (46%), but did not influence seedling survival. Compared to TF, the influence of waterlogging on RB was greater during early establishment. These responses may help RB maintain its germination rate while reducing the damage caused by the accumulation of toxic fermentation-metabolites during waterlogging which benefits RB in competition with TF, especially under high temperatures.