Grape hyacinth is a perennial bulbous species in the Liliaceae. It is commonly grown as an ornamental plant, but it can spread into agricultural fields and become weedy, potentially interfering with harvest and fall-planted crops. There has been limited research on controlling grape hyacinth in cropping systems. Fall and spring applied field-research studies were conducted to determine grape hyacinth control with herbicides labeled for use in wheat or winter fallow before planting soybean. Among fall-applied herbicides, paraquat resulted in the greatest initial grape hyacinth control (90% to 100%). Grape hyacinth control, 16 months after application (MAA), was variable, but the top-performing treatments were glyphosate and metsulfuron plus paraquat, resulting in 65% and 50% control, respectively. After spring applications, grape hyacinth control in November (7 MAA) was variable, but top-performing treatments were glyphosate and metsulfuron, which resulted in at least 26% control. Spring-applied paraquat, carfentrazone, metsulfuron, and sulfosulfuron resulted in 73%, 68%, 69%, and 60% reductions in grape hyacinth bulb counts, compared with the nontreated control 7 MAA, and were the top-performing treatments. Despite product-label prohibitions on rotation to soybeans, no soybean yield reductions were observed from any treatment in either study. Single applications of certain herbicides in the fall or spring can result in good control (>80%) of grape hyacinth initially, but long-term control is poor, and additional research is required.

Waterhemp control in Ontario has increased in complexity due to the evolution of biotypes that are resistant to five herbicide modes of action (Groups 2, 5, 9, 14, and 27 as categorized by the Weed Science Society of America). Four field trials were carried out over a 2-yr period in 2021 and 2022 to assess the control of multiple-herbicide-resistant (MHR) waterhemp biotypes in glyphosate/glufosinate/2,4-D-resistant (GG2R) soybean using one- and two-pass herbicide programs. S-metolachlor/metribuzin, pyroxasulfone/sulfentrazone, pyroxasulfone/flumioxazin, and pyroxasulfone + metribuzin applied preemergence (PRE) controlled MHR waterhemp similarly by 46%, 63%, 60%, and 69%, respectively, at 8 wk after postemergence (POST) application (WAA-B). A one-pass application of 2,4-D choline/glyphosate DMA POST provided greater control of MHR waterhemp than glufosinate. Two-pass herbicide programs of a PRE herbicide followed by (fb) a POST-applied herbicide resulted in greater MHR waterhemp control compared to a single PRE or POST herbicide application. PRE herbicides fb glufosinate or 2,4-D choline/glyphosate DMA POST controlled MHR waterhemp by 74% to 91% and by 84% to 96%, respectively, at 8 WAA-B. Two-pass herbicide applications of an effective PRE residual herbicide fb 2,4-D choline/glyphosate DMA POST in GG2R soybean can effectively manage waterhemp that is resistant to herbicides in Groups 2, 5, 9, 14, and 27.

Greenhouse, growth chamber, and field studies were conducted at Stoneville, MS, in 2000 to 2008, to determine the growth rate, reproductive and overwintering potential, and control of deeproot sedge. In growth chamber studies, deeproot sedge growth rate (ht) and plant dry wt were greatest at 25/35 C (night/day temperatures), when compared with regimes of 5/15, 15/25, and 20/30 C. Based on the average number of scales (fruiting sites per spikelet), spikelets per inflorescence, and culms per plant, deeproot sedge reproductive potential was 2.6-, 6.2-, and 17.4-fold greater than Surinam, green, and knob sedges, respectively. A single deeproot sedge plant produced an average of 85,500 achenes annually. Mowing at 15-cm ht weekly prevented achene production but did not kill deeproot sedge plants. The average number of inflorescences produced on mowed plants was 1.2 to 4 times greater in 2- and 1-yr-old deeproot sedge plants, respectively, when compared with unmowed plants. Mature deeproot sedge achenes were produced between monthly mowings. In a 3-yr field study, glyphosate, glufosinate, hexazinone, and MSMA provided more than 85% control of deeproot sedge, and above the soil, live deeproot sedge plant dry wt was reduced by 50, 64, 68, 72, 86, and 93% by dicamba, halosulfuron-methyl, MSMA, hexazinone, glufosinate, and glyphosate, respectively. All (100%) deeproot sedge plants 1 yr old or older overwintered at Stoneville, MS, at 33°N latitude.

Owing to the lack of effective POST herbicide options, producers typically rely on nicosulfuron as the main POST grass herbicide in sweet corn production systems. In 2019, a Wisconsin sweet corn producer reported fall panicum control escapes after spraying nicosulfuron. Seeds from mature plants were collected to (1) measure fall panicum response to acetolactate synthase (ALS)-inhibiting herbicides, (2) elucidate the resistance mechanism, and (3) evaluate its response to alternative POST herbicides. Greenhouse and laboratory investigations were conducted to assess fall panicum response to ALS-inhibiting herbicides and elucidate the resistance mechanism. Dose–response results showed that fall panicum was highly resistant to nicosulfuron with a resistance ratio of >12.9-fold (survived rates >254 g ai ha−1, or 8× the field label rate). Molecular and genetic studies indicated that there are multiple ALS gene copies in fall panicum and that resistance was due to a mutation in one copy, resulting in an Asp-376-Glu amino acid substitution. Additional greenhouse experiments indicate that clethodim (105 g ai ha−1), quizalofop-p-ethyl (70 g ae ha−1), glyphosate (864 g ae ha−1), and glufosinate (650 g ai ha−1) are effective POST options to manage the ALS-resistant fall panicum (>90.0% control and 96.8% biomass reduction) in rotational years. The 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides isoxaflutole (105 g ai ha−1), mesotrione (105 g ai ha−1), tembotrione (92 g ai ha−1), and tolpyralate (39 g ai ha−1) did not provide effective POST fall panicum control. Because these herbicides are commonly used for POST weed control in sweet corn, more investigations are required to evaluate combinations of HPPD-inhibiting herbicides with herbicides from other sites of action for POST fall panicum control. Herein we confirm the first case of herbicide resistance in fall panicum in the United States.

Non-dicamba-resistant soybean yield loss resulting from dicamba off-target injury has become an increasing concern for soybean growers in recent years. After off-target dicamba movement occurs onto sensitive soybean, little information is available on tactics that could be used to mitigate the cosmetic or yield losses that may occur. Therefore, a field experiment was conducted in 2017, 2018, and 2019 to determine whether certain recovery treatments of fungicide, plant growth hormone, macro- and micronutrient fertilizer combinations, or weekly irrigation could reduce dicamba injury and/or result in similar yield to soybean that was not injured with dicamba. Simulated drift events of dicamba (5.6 g ae ha−1) were applied to non-dicamba-resistant soybean once they reached the V3 or R2 stages of growth. Recovery treatments were applied approximately 14 d after the simulated drift event. Weekly irrigation was the only recovery treatment that provided appreciable levels of injury reduction or increases in soybean height or yield compared to the dicamba-injured plants. Weekly irrigation following the R2 dicamba injury event resulted in an 1% to 14% increase in soybean yield compared with the dicamba-injured control. All other recovery treatments resulted in soybean yields that were similar to the dicamba-injured control, and similar to or lower than the nontreated control. Results from this study indicate that if soybean have become injured with dicamba, weekly irrigation will help soybean recover some of the yield loss and reduce injury symptoms that resulted from off-target dicamba movement, especially in a year with below average precipitation. However, yield loss will likely not be restored to that of noninjured soybean.

Dicamba is a synthetic auxin herbicide that is prone to off-target movement, including drift and volatilization. Due to the increased acreage of dicamba-resistant soybean to control glyphosate-resistant weeds, dicamba drift injury to neighboring vegetable crops is of concern. A method to quantify leaf deformation (often referred to as leaf cupping) caused by dicamba injury was developed and compared to visual rating techniques to determine its accuracy and suitability. A second objective was to determine the relative dicamba sensitivity of several economically important vegetable crops. Soybean, snap bean, tomato, and cucumber were grown in a greenhouse and exposed to dicamba at 0, 56, 112, 280, 560, 1,120, and 2,240 mg ae ha−1, which is, respectively, 0, 1/10,000, 1/5,000, 1/2,000, 1/1,000, 1/500, and 1/250 of the maximum recommended label rate for soybean application (560 g ae ha−1). Plants were evaluated visually and using an imaging analysis technique that measures the leaf deformation index (LDI) with a leaf area scanner. LDI is calculated by dividing the two-dimensional projection of the area of the leaf in its natural configuration by the area of the flattened leaf. Across all four crops, log-logistic regression analysis indicated the LDI method had lower I50 values with lower standard error, demonstrating that the LDI method gives more precise estimates of sensitivity. This novel method provides an objective, quantitative method for measuring dicamba drift injury and determining relative sensitivities of valuable specialty crops.

A study was conducted to evaluate effects of application timing and sulfometuron rate on weed control and bermudagrass tolerance. Sulfometuron was applied at rates from 13 to 105 g ai/ha and compared to 1120 g ae/ha 2,4-D amine. Control of Italian ryegrass and common vetch was not affected by October, November, December, or March application dates and 39 to 105 g/ha sulfometuron provided equivalent control of both species 6 mo after the initial treatment. Percent green cover of bermudagrass at 6 mo after the initial treatment was 22% or less following March applications compared to 36% or greater when applied in October, November, or December. More bermudagrass injury occurred following March treatments of 52 g/ha or greater sulfometuron where green cover was 14% and less compared to 22 and 30% green cover following 13 g/ha sulfometuron or 1120 g/ha 2,4-D amine, respectively.

An experimental directed sprayer has been improved for use in conservation-tillage and no-tillage field conditions and variable row widths. The directed sprayer consists of a rear-mounted toolbar with individually flotational spraying units on lightweight runners which move over field surfaces without the collection of loose residues. Improvements allow convenient adjustments which combined lateral, vertical, angular, and fore-and-aft repositionings to correctly aim the hydraulic nozzles for desired pesticide targeting. Such new designs are needed to deliver pesticides to targets at minimum application rates and with minimum environmental impacts.

Absorption, translocation, and metabolism of 14C-triclopyr were compared in the rice cultivars ‘Lemont’ and ‘Tebonnet’ under flooded and non-flooded conditions. Radioactivity washed from 14C-triclopyr-treated leaves was 26% at 6 h and decreased to about 11% of that applied at 96 h after treatment. Triclopyr was immobile with 98% of the recovered 14C remaining in the treated rice leaf. An average of 19% of triclopyr was metabolized at 6 h and was similar among flooded and nonflooded rice cultivars. Absorption, translocation, and metabolism of triclopyr did not differ among rice cultivars or flooding treatments.

Dr. Raghavan Charudattan has worked in the area of biological control of weeds with plant pathogenic fungi for nearly four decades. He has maintained his research program in this line throughout his career. The scientific discoveries and contributions that he has made have been recognized by his peers and demonstrated through his election as fellow of both the Weed Science Society of America and the American Phytopathological Society. The basic knowledge that he has contributed to our understanding of the fundamental biology of weed/pathogen interactions and his contributions in the areas of mycology, etiology, and natural products will have long-lasting effects. Equally important to the basic and applied research that he has conducted is his role as a mentor and colleague. Dr. Charudattan has contributed to the scientific development of more than 60 students, postdocs, and scientists from more than 20 countries. Dr. Charudattan has contributed to the establishment of biological control of weeds with pathogens as a permanent and highly productive area of weed control research.

Diuron, fluorochloridone, hexazinone, metribuzin, norflurazon, oryzalin, prodiamine, simazine, and terbacil controlled seedling asparagus planted in sprinkler-irrigated plots similarly (>89%). In furrow-irrigated plots, cinmethylin, diuron, fluorochloridone, hexazinone, napropamide, oryzalin, and prodiamine provided similar control (>86%) of planted seedling asparagus. Herbicides with high water solubilities that depended upon root uptake for maximum activity tended to control seedling asparagus better in sprinkler-irrigated tests than in furrow-irrigated tests. Fluorochloridone, norflurazon, and prodiamine provided partial control of volunteer asparagus (48 to 84%) in an established stand of furrow-irrigated asparagus.

Standard operating procedures (SOPs) were developed for repetitive field research tasks to help ensure that instructions were complete and to provide consistency and continuity in the senior author's field research program. SOPs are explicit step-by-step instructions for carrying out experimental tasks that are components of experimental plans. SOPs are not the same as protocols for unique, new experimental plans. However, protocols may incorporate sequences of SOPs, if desired. SOPs are most useful for new workers and when research tasks need to be repeated infrequently in time (e.g., once every 6 mo or less per year). SOPs may help researchers enhance data accuracy, precision, and reproducibility as part of their own statistical quality control procedures. The authors' field-tested SOPs are available on diskette for critical review, modification, and use by interested weed scientists.

The response of potted ‘Cleopatra’ mandarin citrus seedlings to metalaxyl applied as a mixture with metolachlor, simazine, or bromacil, or as a sequential application after the herbicides was investigated under screen house conditions. The soils were drenched with herbicides at 2.5 ppmw (mg kg−1 soil dry wt basis) in tank-mixes with metalaxyl or metalaxyl was applied as a soil drench at 5, 50, and 250 ppmw 1, 2, 3, and 4 wk after herbicide application. Citrus seedling response to treatment was dependent on the presence or absence of herbicide, metalaxyl concentration, and the time following application. Fresh weights of citrus treated with 5 ppmw metalaxyl after herbicide application were no different from those treated with the mixture. Metalaxyl at 5 and 50 ppmw alone or with metolachlor did not affect citrus seedling fresh weight. However, delaying metalaxyl application at 50 ppmw by 3 or 4 wk after simazine and bromacil increased citrus seedling fresh weight as compared with the tank-mix. Separate applications of metalaxyl at 250 ppm reduced citrus seedling fresh weight less than the mixture for all the herbicides.

A carpeted roller applicator and broadcast sprayer were compared for application of glyphosate, metsulfuron, and picloram to control duncecap and tall larkspur on mountain range sites in southern Idaho and central Utah, respectively. Glyphosate was the most effective herbicide, controlling 96% of both larkspur species when applied by the sprayer and 78% when applied by the roller. There was no difference in larkspur control between application methods using metsulfuron or picloram. Application of herbicides by the carpeted roller was less detrimental to forbs compared to the sprayer, and the roller application of glyphosate did not reduce grass cover. Grass cover doubled following treatments with picloram and metsulfuron.

Herbaceous weed control was studied on a loblolly pine planting site in central Louisiana. Pine growth was enhanced without eradicating weeds; reducing weed biomass about 50% increased the mean inside bark volume of loblolly pine saplings 53% on the weeded treatments compared to the untreated control after five growing seasons in the field. Pines receiving both preplant weed control with glyphosate or disking and postplant weed control with a series of yearly treatments (1982, atrazine plus simazine; 1983, atrazine plus oxyfluorfen; 1984, hexazinone; and 1985, hexazinone) had 62% greater volume than pines on the preplant-only treatments. So, the best gains in loblolly pine volume required postplant weed control.

Field studies were conducted near Oxnard, CA, to assess propagule survivability of two annual and two perennial weed species in 7.6 m3 static piles of fresh or aged yard waste mulch over a 56 d period. Mulch temperatures > 60 C generated at depths > 30 cm in fresh mulch caused all weed propagule mortality, whereas sublethal temperatures at shallower depths in fresh, and at all depths in aged piles allowed propagule survival. A controlled environment laboratory experiment suggested ≥ 1 d exposure provides 100% mortality of seed of little mallow at 72 C, California burclover seed (without burs) at 85 C, rhizomes of bermudagrass at 69 C, and nutlets of yellow nutsedge at 70 C. These studies indicate that reinfested, aged mulch does not produce sufficient heat to destroy weed propagules and, therefore, may become a weed-carrying substrate. Fresh mulch should be mixed to expose surviving weed propagules at shallow depths to lethal temperatures found at 30 cm or deeper in fresh mulch piles.

There are limited PRE herbicide options available to provide residual weed control in sweet corn grown on organic soils in the Everglades Agricultural Area (EAA). Field studies were established to determine the efficacy of PRE applied saflufenacil + dimethenamid-P at six rates ranging from 10 + 88 to 319 + 2802 g ai ha−1 on weed control and sweet corn tolerance on organic soils in the EAA in 2011 and 2012. Saflufenacil + dimethenamid-P is a premix recently labeled for PRE weed control in field corn at 50 + 438 to 90 + 788 g ha−1 depending on soil texture. There was no phytotoxic effect of PRE applied saflufenacil + dimethenamid-P on sweet corn. At 42 d after treatment, common lambsquarters, common purslane, and spiny amaranth were controlled 90% with saflufenacil + dimethenamid-P at 58 + 508, 71 + 622, and 58 + 512 g ha−1, respectively. Sweet corn yield at 95% of the weed-free yield was estimated to be obtained at 69 + 606 g ha−1 of saflufenacil + dimethenamid-P. Our results show that saflufenacil + dimethenamid-P at 69 + 606 to 71 + 622 g ha−1 controlled three common weeds and maintained acceptable sweet corn yield. Labeled rates of saflufenacil + dimethenamid-P for field corn on mineral soils were adequate for weed control in sweet corn on organic soils.

Understanding seed biology and onset of germination requirements is a key point for designing effective weed management programs. Gibberellins (GAs) are known to play a role in onset of germination of several species. Onset of germination often requires an increase in de novo GA content or an increase in sensitivity to GAs. Reduced germination of seeds incubated in solutions containing compounds that inhibit GA synthesis provide evidence that GAs are required to trigger germination. Trinexapac-ethyl (TE), a GA synthesis inhibitor, is frequently used as a plant growth regulator in crop production. However, to the best of our knowledge, TE has not been used to study the requirement of GAs in onset of germination. Germination studies were conducted using seeds of artichoke thistle and common teasel under a range of TE concentrations (0 to 500 μM TE), a combined solution of 125 μM TE + 100 μM GA3 for artichoke, and 250 μM TE + 100 μM GA3 for common teasel. Germination tests were conducted at 20/10 C (12-h thermoperiod) in darkness for artichoke and at constant 15 C with 12 h of light for common teasel. Germination of artichoke in 125 μM TE was reduced to 47% when compared with the check (95%), but the combined TE + GA3 solution maintained germination at 84%. Germination of common teasel in 250 μM TE was reduced to 10% when compared with the check (91%), and the combined TE + GA3 solution increased germination to 63%. These results demonstrate the utility of TE to study the role of GAs in onset of germination. This novel use of TE is a valuable option to study germination requirements of weed species, and therefore contributes to the design of weed management programs.

Sulfuryl fluoride (SF) is currently used as a fumigant for control of drywood termites and insects in building structures, vehicles, wood products, postharvest commodities, and food processing facilities. This research investigated the feasibility of using SF as a preplant soil fumigant for purple nutsedge control in plastic-mulched tomato production. SF treatments included SF injected through drip tapes or SF injected through drip tapes a few hours following shank injection of chloropicrin (Pic). Results revealed that SF alone at 224, 336, or 448 kg ha−1 was generally less effective compared with when it was applied in conjunction with Pic at 168 kg ha−1. SF alone provided inconsistent control of purple nutsedge. In contrast, SF + Pic was as efficacious or more efficacious on purple nutsedge than the industry standards, including 1,3-dichloropropene (1,3-D) plus Pic and metam potassium. None of the fumigant treatments visually injured tomato plants, stunted growth, or adversely affected tomato yield. In one of the four tomato seasons, tomato plants growing in plots fumigated with SF + Pic resulted in taller tomato plants and higher markable yields. Results indicate that soil fumigation with SF + Pic is safe on plastic-mulched tomato and effectively controls purple nutsedge.

Fall panicum is the most prevalent and problematic weed in rice in Florida. Outdoor studies were conducted in 2021 to determine the effect of flooding on fall panicum growth and its ability to produce and develop panicles. Fall panicum at the two- to four-leaf and four- to six-leaf stages of development were flooded in stock tanks maintained at flooding depths of 0, 10, 15, 20, and 30 cm for 56 d. Plant height, number of tillers and leaves, leaf area, shoot biomass, root biomass, and panicle branches for both fall panicum leaf stages of development decreased with increasing flooding depth. Fall panicum flooded at the two- to four-leaf stage survived flood depth of 15 cm, whereas plants flooded at the four- to six-leaf stage survived and emerged from a flood depth of up to 20 cm. The 10-cm flood depth resulted in the tallest plants with more leaves, tillers, and leaf area for both growth stages. The probability of fall panicum survival and ability to produce panicles decreased as flood depth increased. Flood depth required for 50% survival for four- to six-leaf-stage plants was estimated to occur at 14 cm, whereas that for plants at the two- to four-leaf stage occurred at 12 cm. The flood depth required to reduce panicle branch production by 50% was estimated to be 15 and 20 cm for two- to four-leaf, and four- to six-leaf-stage plants, respectively. These results show that flooding >10 cm is required to significantly reduce fall panicum survival and ability to produce panicles. Since flood level in rice is usually maintained at an average of 10 cm, chemical weed control will be important to supplement flooding for effective control of fall panicum in rice.