Three field trials were conducted in south Georgia under irrigated conditions in 2002/2003 and 2003/2004 to evaluate the effects of imazapic residues on oat growth and yield. Imazapic at 70 g ai/ha was applied during the first weeks of May, June, July, August, and September to bare soil. No additional tillage was performed after the herbicide application. Oats (cv. Coker 227) were planted the first week of October. Oat plant populations were not reduced by any timing of imazapic. Generally, oat plant heights and forage yields were reduced when imazapic was applied in August and September (1–2 mo before planting). Grain yields were not reduced by any timing of imazapic. Results of these tests suggest that the current 18-mo rotational restriction for oats following an application of imazapic could be reduced to 4 mo.

Kalmia angustifolia is a problematic understory shrub in boreal forests of eastern Canada. In this article, we discuss the nature of its interference with conifer regeneration, and control measures using herbicides. Although laboratory studies suggest the leaching of water-soluble phenolic compounds from Kalmia, allelopathic interference cannot be invoked as a cause of conifer regeneration failure because of lack of field evidences. Because of severe inhibitory effects of Kalmia on conifer growth and its role in long-term habitat degradation, the development of strategies for Kalmia management is a priority research area. Neither prescribed burning, plowing, scarification, nor 2,4-D application was proven effective in Kalmia control. Two studies were carried out using transplanted Kalmia to determine the efficacy of several herbicides and a herbicide plus burning treatment to control Kalmia. In one experiment, eight treatments were applied. They were control, glyphosate (3.36 kg/ha), glyphosate (2.88 kg/ha) plus surfactant Tween 20 (0.2%), glyphosate (2.88 kg/ha) plus surfactant Triton XR (0.2%), fosamine ammonium (5.38 kg/ha), triclopyr (4 kg/ha), hexazinone (2.2 kg/ha), and hexazinone (5 kg/ha). Triclopyr (4 kg/ha) provided the best control with significant reduction in the number and dry weight of sprouts, rhizomes, and current-year foliage of Kalmia compared with control. In another experiment, triclopyr (4 kg/ha), hexazinone (5 kg/ha), and hexazinone (2.2 kg/ha) plus burning treatments were applied. To determine the response of black spruce seedlings to the herbicide treatments, black spruce seedlings were planted in all the Kalmia pots except the ones that received the hexazinone (2.2 kg/ha) plus burning treatment. Triclopyr (4 kg/ha) caused the maximum damage to Kalmia, affecting all the above- and below-ground components of the plant. We recommend that an experimental field trial be established using triclopyr to test its efficacy for Kalmia control under field conditions.

Diagnosis of herbicide injury can be complex because of the large number and interaction of factors leading to herbicide injury. Computer-based expert systems have great potential to assist users, particularly nonexperts, in accurate diagnosis of herbicide injury. Rule-based and case-based reasoning are the most widely used forms of expert systems, and each system has strengths and limitations. Approaches that integrate rule-based and case-based reasoning may augment the positive aspects of the two reasoning methods and simultaneously minimize their negative aspects. The Herbicide Injury Diagnostic Expert System (HIDES) integrates rule-based and case-based reasoning and uses field-specific information, injury symptoms, herbicide use history, and herbicide information to diagnose crop injury from herbicides. The HIDES program uses a set of rules to identify suspect herbicide(s) that is the candidate for causing the observed injury and possible sources of the suspect herbicide(s). Case-based reasoning is used to propose a probable cause of injury by making an analogy to previously solved cases. A four-step procedure is followed when using HIDES: information collection, suspect herbicide identification, suspect herbicide source determination, injury reason suggestion, and knowledge accumulation.

Mortality of potted huisache seedlings averaged 87 to 100% 18 weeks after picloram or clopyralid was applied with a model carpeted roller at concentrations as low as 7.5 g ae/L. A 1:1 mixture of picloram and clopyralid was equally effective. Triclopyr was effective only when applied to small seedlings in the spring, and an ester was more effective than an amine formulation. A 1:1 mixture of clopyralid and triclopyr ester was intermediate in effectiveness between the two herbicides applied alone. Adding surfactant increased canopy reduction and plant mortality (P = 0.1 to 0.01), especially at lower herbicide concentrations.

To date, there have been no reports of Dalmatian toadflax serving as a host for cucumber mosaic virus (CMV). Infestations of Dalmatian toadflax may serve as a reservoir of CMV, thereby facilitating aphid transmission of CMV to both agricultural crops and native plants. The goal of this study was to determine whether Dalmatian toadflax is a host for CMV. Dalmatian toadflax seedlings were randomly assigned to two treatments (18 replicates/treatment): no inoculation (control) and inoculation with CMV (Fast New York strain). The Dalmatian toadflax seedlings were inoculated by standard mechanical methods and tested for the presence of CMV using enzyme-linked immunosorbent assay (ELISA). Ten of the 18 CMV-inoculated toadflax plants tested positive for the virus; 6 of the 18 displayed systemic mosaic chlorosis and leaf curling. All control plants tested negative. Transmission electron microscopy obtained from CMV-positive plants confirmed the presence of CMV based on physical properties. To verify CMV infestation, tobacco plants were assigned to the following treatments (six replicates/treatment): no inoculation (control), CMV-negative (control) inoculation, and a CMV-positive inoculation. Plants were inoculated by standard methods. Five of the 6 tobacco plants treated with the CMV-positive inoculum tested positive for CMV using ELISA. All control plants tested negative for the virus.

Adjuvants influence weed control and crop tolerance provided by postemergence (POST) herbicides. Adjuvant effects on weed control and corn and soybean tolerance with CGA-248757 and flumiclorac applied alone and soybean tolerance with CGA-248757 and flumiclorac applied in combination with imazethapyr or CGA-277476 were evaluated. Velvetleaf control in the greenhouse and common lambsquarters, redroot pigweed, and common ragweed control in the greenhouse and field with CGA-248757 and flumiclorac were increased by the addition of an adjuvant. However, corn and soybean tolerance to these herbicides was not affected by adding an adjuvant. Laboratory studies suggest enhanced weed control from the addition of an adjuvant resulted from an increase in CGA-248757 and flumiclorac foliar absorption. In greenhouse studies, velvetleaf, common lambsquarters, and redroot pigweed control with CGA-248757 plus imazethapyr; velvetleaf control with flumiclorac plus imazethapyr; redroot pigweed and common ragweed control with CGA-248757 plus CGA-277476; and velvetleaf, redroot pigweed, and common ragweed control with flumiclorac plus CGA-277476 increased by adding an organosilicone adjuvant when compared with adding a nonionic surfactant (NIS). However, in field evaluations of CGA-248757 or flumiclorac plus imazethapyr, the addition of NIS or an organosilicone adjuvant resulted in equivalent soybean injury, common lambsquarters and redroot pigweed control, and soybean yield. Yet in tank mixtures of CGA-248757 or flumiclorac plus CGA-277476, the addition of an organosilicone adjuvant increased redroot pigweed control and soybean yield compared to adding NIS.

Chlorsulfuron, metsulfuron, clopyralid, 2,4-D, picloram, and dicamba plus 2,4-D were spring-applied to musk thistle in rosette, bolting, bud, and early flower growth stages. All treatments reduced viable achene production at all musk thistle growth stages at Mcgrew, NE, and Longmont, CO. However, differences occurred at Evergreen, CO, among treatments and growth stages. No achenes developed at Evergreen when herbicides were applied during the rosette stage with dicamba plus 2,4-D, picloram, or metsulfuron at 21 g ai/ha or during bolting with chlorsulfuron or metsulfuron at 21 g/ha. Chlorsulfuron applied during early bloom reduced viable achene production over 99% compared to untreated plants and the picloram treatment.

Indiana growers who purchase restricted-use pesticides are required to show the agrochemical dealer their private pesticide applicator license before the transaction can be completed. To keep the license current, growers may attend three private applicator recertification meetings or retake the exam every 5 yr. The meetings are county-based and must be a minimum of 2 h in length; they must include a topic mandated by the Office of the State Chemist. During the 2005/2006 private applicator recertification program (PARP) cycle, off-site movement of atrazine into surface water was the regulatory topic presented to 2,887 participants at 69 meetings. A team of individuals from different disciplines prepared educational materials to support the regulatory topic of the year. Surveys to assess grower awareness were conducted at the meetings and 1 yr later to monitor the long-term impact of the educational effort, and to evaluate which tactics were being adopted to reduce off-site movement of atrazine. Growers farming more than 800 ha had a higher degree of concern than small growers regarding the loss of atrazine as a weed management tool. Eighty-nine percent of the growers thought there would be a 314 to 1,255 kg/ha yield loss if atrazine was removed from the marketplace. Eighty-four percent of the growers estimated that weed control costs would increase $15 to $25/ha if no other products were available to replace atrazine. The three most acceptable management strategies to reduce atrazine movement were: more attention to label setback distances, establishment of grass filter strips around surface water, and reducing atrazine rates by tank mixing with other herbicides. The results of this project indicated that statewide programs such as this are effective in increasing awareness of an issue and documenting the impact of extension education programs.

The ability of the pesticide root zone model (PRZM) and the groundwater-loading effects of agricultural management systems (GLEAMS) model to predict movement of two herbicides in soil was evaluated using site-specific environmental data from sites in three states. Predictions of herbicide movement with site-specific data were compared to predictions using more generalized database soil and pesticide data within each model. Field experiments examined fluometuron and norflurazon movement in three soils representative of the cotton-growing regions of the southeastern United States. In comparing the use of site-specific vs. database values, the small increase in accuracy using site-specific inputs would not justify the large cost to obtain the data. The databases for each model gave predictions similar to those using the site-specific numbers. Both the PRZM and the GLEAMS model had similar accuracy levels in predicting the presence of fluometuron or norflurazon present in three surface soils, although each model tended to overpredict movement and total herbicide concentration, especially at lower herbicide concentrations. At higher herbicide concentrations, prediction accuracy was less than that probably needed to predict agronomically relevant herbicide concentrations in surface soils.

Various combinations of methods were evaluated for the control of ivyleaf morningglory growing in cotton. The combinations included chemicals incorporated to two depths or tanked-mixed as postemergence treatments and cultural methods that included in-row cultivation and hand weeding. The most effective combinations of methods included a herbicide such as cyanazine or prometryn in some treatments resulting in reduced ivyleaf morningglory population and improved cotton yields. Cultural methods without chemical assistance gave little or no control of ivyleaf morningglory based on weed populations and cotton yield. Statistically the best combinations had lint yields equal to the weed-free treatment, but the yields were reduced from 114 to 372 kg/ha. Also, most combination treatments had enough plant debris in the lint to reduce fiber grade.

Oxyfluorfen (0.28, 0.42, 0.56, and 0.84 kg ai ha−1) under clear polyethylene film was evaluated for weed control, crop injury, and effects on yields in transplanted muskmelon, cucumber, and summer squash. Numerous narrowleaf and broadleaf weeds were effectively suppressed by 0.42 ha−1 of oxyfluorfen. Crop injury, occurring soon after transplanting, was reported in New York and North Carolina. Injury was usually transient, and injured crops frequently grew more vigorously than those grown on untreated black polyethylene mulch. Muskmelons were consistently the most tolerant of the three crops. At high rates, yields of squash and cucumber in 1988 were reduced in New York and North Carolina, respectively. In greenhouse studies, positioning the cotyledons under the polyethylene film caused greater injury in all three crops than when cotyledons remained above the plastic.

In field studies conducted over two years, soybean cultivars ‘Deltapine 415’, ‘Forrest’, ‘Asgrow 6785’, ‘Centennial’, 'Sharkey’, ‘Terra Vig 616’, ‘Hartz 6686’, and ‘Pioneer 9791’ responded similarly to POST application of AC 263,222. With supplemental overhead irrigation of 5.1 cm weekly for 4 wk initiated 21 d after herbicide applications, mature soybean height for the cultivars averaged 18% less than that of the untreated check for 27 g/ha AC 263,222, but only 8% less when not irrigated. Although nonirrigated soybean seed yield following AC 263,222 application the first year was not reduced compared with the untreated check, with irrigation seed yield reductions of 12 and 32% were noted for 13 and 27 g/ha AC 263,222, respectively. Seed yield the second year was not negatively affected with herbicide application whether soybean was irrigated or not irrigated. For individual years, seed yield for the untreated irrigated and nonirrigated checks was similar. In the first year soybean yield following AC 263,222 at 13 and 27 g/ha with irrigation was 16 and 30% lower, respectively, than when soybean was not irrigated. Decreases in soybean 100-seed weight accompanied the yield reductions.

Research was conducted to evaluate absorption, translocation, and metabolism of foliar-applied trifloxysulfuron in flue-cured tobacco. The majority of 14C-trifloxysulfuron was absorbed by 4 h, with an accumulation in the plant of 43% of the radioactivity after 72 h. Translocation of radioactivity did not significantly differ between harvest timings of 4 to 72 h after treatment. Not more than 4% of applied 14C-trifloxysulfuron moved out of the treated leaves of tobacco, whereas less than 1.9% accumulated in any one part. Tobacco metabolized 14C-trifloxysulfuron rapidly, with 60.9% of the absorbed herbicide remaining in the parent herbicide form 4 h after treatment, whereas only 12.1% remained after 72 h. These data suggest that limited absorption and translocation, as well as rapid metabolism, are the basis for tobacco tolerance to foliar-applied trifloxysulfuron and illustrate the potential safe and effective use of trifloxysulfuron in tobacco for POST weed control.

Renewed interest in studying auxin herbicides (WSSA Group 4) is increasing as a result of the release of genetically engineered crop varieties that are tolerant to preemergence and postemergence applications of specific formulations of dicamba. Auxin-resistant crops were developed in response to the development of weed species resistant to glyphosate and other herbicides. Research was conducted at multiple field locations in Georgia in 2018 and 2019 to examine weed control when postemergence herbicides were applied to dicamba- and glyphosate-resistant cotton at eight different points in time over a 24-h period. Applications were made at 1 h prior to sunrise all the way up to midnight during the same day to examine the effect of herbicide application timing on broadleaf weed control. Glyphosate, dicamba, and glyphosate plus dicamba were applied at each timing. Visual ratings of weed control were scored at 7, 14, 21, and 28 d after treatment (DAT). Weed control was affected by herbicide application timing. Midnight applications resulted in the lowest levels of control. Sicklepod, pitted morningglory, and prickly sida control was 49%, 38%, and 41%, respectively. Greatest control of all three species (up to 99%) occurred from the noon to 1 h prior to sunset application timings. Orthogonal contrasts of timing of application indicated that weed control was improved with day > night and pre-dawn > midnight.

A survey of 174 fields was conducted to investigate performance of herbicides applied after winter wheat harvest on weeds across western and southern Nebraska during August and September 1998. Glyphosate plus 2,4-D plus atrazine was applied on 32%, glyphosate plus 2,4-D or dicamba on 24%, paraquat plus atrazine on 23%, glyphosate on 8%, ICIA0224 plus 2,4-D or atrazine on 10%, and atrazine plus 2,4-D on 3% of the fields. These treatments controlled 85 to 100% of the weeds except atrazine plus 2,4-D, which controlled 30%. The frequency of occurrence of the most prevalent summer annual grasses was as follows: green foxtail, 65%; barnyardgrass, 46%; stinkgrass, 41%; witchgrass, 39%; and longspine sandbur, 36%. The most common broadleaf weeds and their frequency were redroot pigweed, 32%; tumble pigweed, 30%; tall waterhemp, 28%; and kochia, 25%. Virginia groundcherry, 22%; common milkweed, 11%; yellow woodsorrel, 9%; and field bindweed, 6% were the most common perennial weeds. The five most difficult weeds to control were yellow nutsedge, spotted spurge, Virginia groundcherry, common milkweed, and toothed spurge, with control ratings of 0, 3, 17, 26, and 33%, respectively. These weeds were not controlled with glyphosate or mixtures containing glyphosate. Only 35% of the fields were treated before summer annual grasses had headed. Late applications required higher herbicides rates for effective control.

Oxeye daisy (Chrysanthemum leucanthemum L.), a European perennial, was brought to North America as an ornamental. The plant is still grown in decorative gardens and it is one parent of ‘Shasta’ daisy (Holm et al. 1997). Tradition says that the oxeye daisy crept out of Massachusetts Governor Endicott's garden between Tuesdays, and claimed the whole nation in two centuries (Haughton 1978). It also arrived as a contaminant in imported hay and grain seeds (Haughton 1978). Oxeye daisy escaped cultivation and also spread quite readily from agricultural activities to become an aggressive competitor. It often forms thick patches, especially in cattle-grazed areas, reducing hay or forage production (Olson and Wallander 1999). Consequently, oxeye daisy has been declared a noxious weed in many areas (Holm et al. 1997). It is found throughout most of the United States and north into southern Canada from Labrador to British Columbia (USDA 1970).

Effects and interactions of two soil temperatures, 19 ± 1 and 27 ± 3 C, and seven soil-applied herbicide treatments on the morphological development and concentrations of eight essential nutrients in leaves, stems, and roots of pinto beans were determined. Soil temperature did not affect overall plant morphology but did affect some nutrient concentrations in the roots, stems, and leaves. Combinations of alachlor plus trifluralin at 2.2 plus 0.28 kg ai/ha and EPTC plus trifluralin at 2.2 plus 0.28 kg ai/ha caused greater negative effects than when the herbicides were applied separately. Oryzalin at 0.56 kg ai/ha and EPTC at 3.4 kg ai/ha induced the least number of morphological effects, while alachlor at 3.4 kg ai/ha, chloramben at 2.2 kg ai/ha, and trifluralin applied at 0.56 kg ai/ha produced an intermediate number. Alachlor, trifluralin, and combinations of alachlor plus trifluralin and EPTC plus trifluralin inhibited nodule growth. Each herbicide affected different nutrients. Alachlor plus trifluralin affected the level of each nutrient in at least one plant tissue. Many herbicide-soil temperature interactions occurred.

Herbicides were evaluated for control of field violet in strawberries in North Carolina and in Nova Scotia, Canada. DCPA at 11.0 kg ai ha−1 and terbacil at 0.5 kg ai ha−1 PRE controlled field violet 80 to 95%. Control with simazine PRE at 1.0 kg ai ha−1 was 70 to 75%. Oxyfluorfen at 0.6 to 1.1 kg ai ha−1 controlled 95 to 100% of the established field violet in dormant strawberries following a mid-winter application. Control with acifluorfen and lactofen applied during mid-winter was 75 to 90%. Oxyfluorfen applied to dormant plantings at rates in excess of 0.60 kg ai ha−1 caused foliar damage; however, yield was not reduced at rates up to 4.5 kg ha−1. Oxyfluorfen at 0.25 kg ha−1 caused severe injury to newly-transplanted strawberries.

Experiments were conducted to evaluate varietal susceptibility of azalea [Rhododendron obtusum (Lindl.) Planch] to fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid } and sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}. Injury observed on ‘Delaware Valley White’, ‘Hinocrimson’, and ‘Poukhanense’, following broadcast applications of fluazifop-P at 1.12 kg ai/ha, ranged from 5 to 53% foliar damage. Injury symptoms observed were leaf burn, spotting, and distortion, especially in younger leaves. Sethoxydim at 2.24 kg ai/ha caused either slight or no foliar injury to the cultivars tested. Both sethoxydim and fluazifop-P caused temporary growth reduction in ‘Hershey Red’. Foliar injury or growth reduction resulting from these herbicides was temporary, with no damage evident 6 weeks after application. Although adding either crop oil concentration or a nonionic surfactant increased phytotoxicity of fluazifop-P to Hinocrimson and Poukhanense, these adjuvants were not phytotoxic to azalea cultivars when applied alone.