Sugarbeet tolerance to and Canada thistle control from tank mixtures of clopyralid plus other postemergence herbicides and/or petroleum oil adjuvant applied at various times were determined. Herbicides were applied to 5 to 20 or 20 to 70-cm tall Canada thistle. Clopyralid at 0.14 and 0.21 kg ai ha-1 alone or with petroleum oil adjuvant did not injure sugarbeet. Tank mixing clopyralid with desmedipham/phenmedipham plus endothall injured sugarbeet 7 d after application in 2 of 3 yr but not when observed 14 d after application. Herbicides applied early postemergence in 1987 and late postemergence in 1988 controlled Canada thistle poorly due to rainfall 1 h after application and drought conditions, respectively. The addition of petroleum oil adjuvant enhanced control of Canada thistle by clopyralid at 0.14 kg ha-1, and control equaled that of clopyralid at 0.21 kg ha-1 alone. Addition of desmedipham/phenmedipham plus endothall to clopyralid did not reduce Canada thistle control. Petroleum oil adjuvant added to clopyralid at 0.14 kg ha-1 increased Canada thistle control to that achieved by clopyralid at 0.21 kg ha-1 plus desmedipham/phenmedipham plus endothall.

Studies were conducted to determine the response of ‘Jewel’ sweetpotato in propagation beds to DCPA and napropamide. Napropamide at 2.2 and 4.4 kg ha–1 caused slight injury, and reduced plant number and weight when compared with the untreated control. Napropamide at 1.1 kg ha–1 combined with chloramben at 3.3 kg ha–1 was not injurious; plant production was equal to the untreated control, diphenamid at 4.4 kg ha–1, and chloramben at 3.3 kg ha–1. DCPA at 8.3 and 10.0 kg ha–1 caused unacceptable injury and reduced plant number and weight.

Studies from 1985 to 1989 showed that disking 3, 7, 10, 14, or 30 d after applying chlorsulfuron, clopyralid, dicamba, glyphosate, picloram, or 2,4-D did not improve Canada thistle control in uncropped, dryland fields. Disking after a fall or after a fall plus a spring herbicide application did not influence Canada thistle control for any herbicide regardless of the time of herbicide application or the time between application and disking.

Growers and certified crop advisors (CCAs) across Indiana were surveyed during the winter of 2003 to 2004 to assess their perceptions about soybean cyst nematode (SCN) and use of SCN management practices. Most farmers (57%) and CCAs (72%) surveyed reported a moderate to high level of concern regarding SCN and its potential impact on soybean yield. The majority of those surveyed were also aware that some winter annual weeds can serve as hosts for SCN. Crop management practices specifically aimed at managing the impact of SCN were employed by 55 and 78% of growers and CCAs, respectively. However, only 21% percent of growers said that they had sampled a field for nematodes within the last two years. Growers from eastern and southern Indiana were less likely to be concerned about SCN, to implement SCN management strategies, and to have the soil tested for SCN than growers throughout the rest of the state. In addition, smaller farmers appear to be less concerned and knowledgeable about SCN than those who operate larger farms. The results of this survey suggest that the majority of Indiana growers would likely adopt winter weed control to manage SCN. Also, with respect to winter weed control, future Extension efforts should be focused on southern Indiana where both the risk for SCN reproduction on winter annuals and the need for education on SCN appear to be highest.

Eclipta is a seed-borne summer annual that is problematic in the production of container-grown landscape plants. Halosulfuron at 70 g/ha is registered as a directed application to landscape areas but not to container-grown landscape plants. Halosulfuron was applied preemergence (PRE) to seeded eclipta and postemergence (POST) to progressively older eclipta seedlings at rates ranging from 0.18 to 100 g/ha. For halosulfuron PRE treatments, eclipta control was determined from the foliage weight of surviving seedlings. For halosulfuron POST treatments, control was determined from the weight of foliage regrowth following the removal of the treated foliage 2 wk after treatment. Nonlinear regression and log-logistic analysis indicated that the rate required for 90% control (I90) for halosulfuron PRE was 45 g/ha. For halosulfuron POST, the I90 was 60 g/ha for plants having five or fewer true leaves and 98 g/ha for plants that had lateral branching from the basal crown. Analysis estimated the I90 for flowering-sized eclipta exceeded 300 g/ha. Selective placement studies revealed that the phytotoxicity resulting from POST treatments occurs by foliar and root uptake, with foliar exposure having greater activity. For POST treatments that were limited to foliage-only contact, a split application increased control up to 25% compared with a single application of the same total dosage. However, control remained inadequate because the rate required for 75% control (I75) was 157 and 121 g/ha for single and split applications, respectively. Halosulfuron sorption by a pine bark–based rooting substrate, as used in container production, was 96% of the amount applied. The propensity for surface-applied halosulfuron to be leached in this substrate was evaluated by eclipta bioassay. After 2 wk, with 23 cm of cumulative irrigation and rainfall, halosulfuron was detected 12 cm below the substrate surface. The propensity for substrate-adsorbed halosulfuron to return to the water phase may also contribute to PRE activity for eclipta control.

Research conducted over 3 yr showed that volunteer Jerusalem artichoke was controlled effectively with clopyralid plus 2,4-D, dicamba plus 2,4-D, or 2,4-D alone applied postemergence at rates which did not injure spring barley. Glyphosate and paraquat applied preemergence to the crop did not reduce the number of Jerusalem artichoke shoots. Jerusalem artichoke which survived or escaped treatment was highly competitive with barley, as 4 to 6 surviving shoots/m2 could reduce seed yield 20%.

A native fungus, Botryosphaeria ribis, was evaluated under field conditions to determine its potential to control melaleuca. Applications consisted of either wound inoculations of trees with B. ribis or fresh stump treatments with B. ribis alone or mixed with imazapyr herbicide. There was no mortality among nondefoliated trees inoculated with B. ribis. Mortality of B. ribis-inoculated trees was increased by three complete defoliation cycles. Defoliated trees inoculated with isolate BR-5 exhibited 100% mortality compared to 17% for defoliated but noninoculated trees. Wounds inoculated with B. ribis during winter produced longer cankers than did noninoculated wounds. Stump regrowth reduction by treatment with B. ribis alone was less effective than treatment with imazapyr alone. Mixtures of B. ribis with imazapyr or imazapyr alone at comparable concentrations did not differ in stump regrowth control.

A 2-yr study was conducted to evaluate the response of yellow starthistle density and grass biomass to combinations of newly seeded grass, picloram, and fertilizer. A combination of ‘Tualatin’ tall oatgrass or ‘Paiute’ orchardgrass with 0.14 or 0.28 kg ae/ha of picloram effectively controlled yellow starthistle and improved forage production. Grass seeded alone or combined with fertilizer neither controlled yellow starthistle nor improved forage production. Three-way combinations of grass, picloram, and fertilizer did not affect yellow starthistle density in either year but resulted in more ‘Tualatin’ tall oatgrass biomass in 1987.

Control of common lambsquarters with glyphosate in Michigan soybean fields has been inconsistent. Stem-boring insects and evidence of insect tunneling were found inside the stems of common lambsquarters plants not controlled with glyphosate. In 2004 and 2005, field surveys and studies were conducted to identify and evaluate the prevalence of stem-boring insects in common lambsquarters in Michigan and Indiana soybean fields to determine whether tunneling by insects occurred before or following POST glyphosate applications and to evaluate the effect of glyphosate rate, application timing, and insect tunneling on the control of common lambsquarters with glyphosate. Two insect species, the beet petiole borer (Cosmobaris americana) from the Curculionidae family and an unidentified leafminer fly larvae from the Agromyzidae family were found inside common lambsquarters stems. Leafminer larvae were present in Michigan soybean fields in mid- to late-June, when most POST glyphosate applications are made in Michigan and Indiana; however, beet petiole borer larvae were not found in common lambsquarters stems until mid-July and would only be present in common lambsquarters plants if glyphosate applications occurred at that time. Results from three field experiments in East Lansing, MI, demonstrated the variability in common lambsquarters control. Control ranged from 79 to 98%, 75 to 99%, and 49 to 97% from glyphosate applied at 0.84 kgae/ha to 10-, 25-, and 46-cm common lambsquarters, respectively. In general, applying glyphosate to common lambsquarters plants 10 cm or less, or increasing the glyphosate rate beyond 0.84 kgae/ha, improved common lambsquarters control. Insect tunneling by leafminer and beet petiole borer larvae did not contribute to reduced common lambsquarters control with glyphosate applied to 10- and 25-cm common lambsquarters.

Glyphosate, alone and in combination with other herbicides or additives, was evaluated as a spot or shielded treatment for the control of silverleaf nightshade in cotton in three experiments over four years. Glyphosate used at 10.8 g ae/L in 1985 on dryland cotton controlled 81 to 98% of the silverleaf nightshade, but cotton lint yields were reduced by all treatments compared to the weed-free check. Glyphosate used at 7.2 g ae/L in 1986 on irrigated cotton controlled 6 to 83% of the silverleaf nightshade, and lint yields were reduced only when multiple spot applications were made. Spot applications of glyphosate were effective for silverleaf nightshade control when applied 7 wk after crop emergence in 1988. Weed control and cotton injury were lower with shielded applications than spot applications. In 1989, retreatments during a season or the next year resulted in 95% or greater silverleaf nightshade control. Cotton yield increases from herbicide treatment were not observed in 1988; however, yield increases were observed in 1989 when spot treatments were applied to the more successful 1988 plots.

Varying the type of nonionic surfactant greatly changed the biological activity of the ethyl ester of quizalofop-P on giant foxtail, barnyardgrass, and corn. These studies statistically evaluated 22 surfactants with widely different chemical, physical, and surface properties. Of the 14 surfactant properties analyzed, dynamic surface tension was the most important to enhance quizalofop-P activity. Alcohol ethoxylate surfactants like Genapol® 24-L-92 and Tergitol® 15-S-7 were among the most effective adjuvants. These surfactants performed significantly better than the commercial nonionic surfactant, Induce®, and equal to a high-quality petroleum crop oil concentrate, Agri-dex®. These surfactants offer a lower dose option to crop oil concentrates and a more effective surfactant alternative for mixtures that prohibit crop oil concentrates.

Field studies were conducted from 1998 through 2000 to compare weed population shifts in soybean and cotton using a total glyphosate system, preemergence (PRE) herbicides followed by glyphosate, and a conventional herbicide program. In the first year of the soybean study, populations of hemp sesbania were highest for treatments of PRE herbicides followed by either glyphosate or the conventional herbicide program because of better control from the total glyphosate system. Barnyardgrass populations in the first year of the study for the nontreated plots were 0 plants/m2 but increased in the third year to 61 plants/m2. Flumetsulam plus metolachlor followed by glyphosate at the lower rates and the nontreated check were the only treatments in which there was an increase in barnyardgrass over the 3-yr study. Broadleaf signalgrass populations increased in the third year with 0.1 kg ai/ha flumetsulam plus 2.1 kg ai/ha metolachlor followed by 0.84 kg ae/ha glyphosate, primarily because of reduced competition from lower populations of other weeds such as hemp sesbania. Pitted morningglory populations for all treatments decreased in the third year because of good control of this species and the high level of interference from other weed species in the first 2 yr. Johnsongrass populations decreased in the third year with 0.4 kg ai/ha flumetsulam plus 1.1 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Johnsongrass populations decreased with timely glyphosate sequential applications, with 5 plants/m2 in 1998 and 0 plants/m2 in 2000. Yields increased from the first year to the second year, corresponding to reduced weed pressure, and yields varied from 710 to 1,420 kg/ha. Because of weed pressure, soybean yields were not different in any of the treatments, including the nontreated, although treatments changed the species present. In the cotton study, weed populations over the 3 yr decreased, with the most significant reductions from the treatments of fluometuron plus prometryn plus metolachlor followed by either pyrithiobac or glyphosate. Weeds that showed the most significant decline were barnyardgrass and hemp sesbania, whereas johnsongrass increased, with 27 plants/m2 in treatments of 0.6 kg ai/ha fluometuron plus 0.3 kg ai/ha prometryn plus 0.7 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Lint cotton yields varied from 0 to 128 kg/ha. Because of the weed pressure, cotton yields were not different in any of the treatments, although treatments changed the species present. This research has shown that weed species can decrease over time with the continued use of any of these herbicide programs.

Field studies were conducted to determine the effect of several herbicides on soybean thrips numbers in soybean. Adult soybean thrips numbers in the preplant-incorporated and preemergent herbicide treatments were observed to be either greater than or equal to, but never less than, numbers in the control plots. Larval soybean thrips numbers were not observed to be affected by the preplant-incorporated or preemergent treatments. The postemergence herbicide treatment of naptalam plus dinoseb consistently reduced both adult and larval soybean thrips numbers. The other postemergent treatments did not affect numbers consistently.

Only two spinach herbicides are currently available to producers, and with limited choices in herbicide mode of action (MOA), overuse of the current herbicides can result in dominance of uncontrolled weeds. Therefore, spinach producers need more herbicide options. Trials were conducted in processing spinach to evaluate the crop safety of dimethenamid-p (0.56 kg ai/ha), EPTC (2.94 to 3.40 kg ai/ha), or ethofumesate (0.84, 1.12 or 2.24 kg ai/ha) applied pre-emergent (PRE), and ethofumesate (0.09 or 0.18 kg ai/ha) applied early postemergent (EPOST) for potential use as alternatives to s-metolachlor (0.73 kg ai/ha) and cycloate (2.52 kg ai/ha). The control of London rocket was excellent with s-metolachlor, dimethenamid-p, and ethofumesate. Weed control with cycloate and EPTC was fair, and generally inferior to all others. Cycloate and s-metolachlor were safe to spinach, and only minor crop injury was observed with all other herbicides, except the high rate of ethofumesate PRE, which resulted in high levels of injury. Spinach outgrew all early herbicide injury with no significant yield losses. Ethofumesate applied EPOST caused no injury in year 1, although in year 2 injury was higher in all plots where it was applied twice, regardless of rate. In high-density plantings, dimethenamid-p caused significant crop injury to spinach, but only at one location on a sandy loam soil. In that trial, yields in dimethenamid-p plots were reduced an average 30% compared to the hand-weeded and s-metolachlor plots. As a result of this research, dimethenamid-p, EPTC, and ethofumesate should be considered candidates for expanded-use registrations in processing spinach production. More research is needed to determine additional rates and use patterns for improved crop safety, as well as an evaluation of soil types and spinach varieties.

Control of downy brome in cool-season perennial grasses grown for seed production must be done prior to seed harvest, because downy brome seeds cannot be separated from cool-season grass seeds. Field experiments were conducted near Powell, WY, and Bridger, MT, to evaluate several herbicides for control of downy brome from 1992 through 1994 in western wheatgrass, slender wheatgrass, beardless wild rye, thickspike wheatgrass, and meadow bromegrass. When fall-applied, only metribuzin at 0.4 kg/ha and oxyfluorfen plus metribuzin at 1.1 plus 0.3 kg/ha controlled 98 and 95% of the downy brome, respectively, without affecting grass seed viability or seed yield. Early spring applications of paraquat at 0.8 kg/ha controlled 100% of the downy brome, but suppressed perennial grasses. Glyphosate applied in early spring at 0.3 kg/ha controlled 48% of the downy brome, but suppressed perennial grasses. Seed yield reductions occurred when thickspike wheatgrass and meadow brome were treated with glyphosate at 0.3 kg/ha.

Fumitory (Fumaria officinalis L.) is a member of Fumariaceae, a family of annual and perennial herbs, whose best-known genera, in addition to Fumaria, are Corydalis and Dicentra (bleeding heart and Dutchman's breeches). Fumariaceae is mainly a temperate family that embraces 16 genera and 400 species. Economically, its use is limited to garden ornamentals (Heywood 1993). Brummitt (1992) and Hyam and Pankhurst (1995) place fumitory in Papaveraceae, but most authorities, including Mabberley (1989), put it in Fumariaceae.

The investigation of potential herbicides for weed control in sweetpotato is critical due to the limited number of registered herbicides and the development of populations of herbicide- resistant weeds. Therefore, field studies were conducted at the Horticultural Crops Research Station, Clinton, NC and the Pontotoc Ridge–Flatwoods Branch Experiment Station, Pontotoc, MS to determine the effect of oryzalin application rate and timing on sweetpotato tolerance. Oryzalin at 0.6, 1.1, 2.2, 3.4, and 4.5 kg ai ha–1 was applied immediately after transplanting or 14 d after sweetpotato transplanting (DAP). At Clinton, oryzalin applied immediately after transplanting resulted in ≤1% leaf distortion 4 and 6 wk after transplanting (WAP) regardless of application rate. However, when oryzalin was applied 14 DAP, greater sweetpotato leaf distortion was observed from 2.2, 3.4, and 4.5 kg ha–1 (≤8%) than 0.6 and 1.1 kg ha–1 (≤4%). At Pontotoc, oryzalin applied immediately after transplanting resulted in ≤6% leaf distortion 4 WAP regardless of application rate. However, when oryzalin was applied at 14 DAP, greater leaf distortion was reported from 3.4 and 4.5 kg ha–1 (11 to 13%) than 0.6, 1.1, and 2.2 kg ha–1 (4 to 6%). Oryzalin application rate and timing did not affect yield of no.1, jumbo, or marketable sweetpotato. Based on these results, oryzalin herbicide has potential for registration in sweetpotato.

Putative glyphosate-resistant sourgrass was collected to determine its resistance level and to evaluate its metabolic profile after resistance. Although accumulation of shikimic acid is known to occur in glyphosate-susceptible populations, differences in the ability of resistant (R) and susceptible (S) biotypes to accumulate quinic acid, salicylic acid, and aminomethylphosphonic acid (AMPA) have been studied to a lesser extent. Our objective was to confirm glyphosate resistance in sourgrass and to understand the metabolic profile of these plants in response to the herbicide. Greenhouse experiments were carried out from January 2016 to June 2018. There were no significant differences in glyphosate translocation in the plants. No metabolism of glyphosate to AMPA was observed; therefore, metabolism of glyphosate to AMPA is not a mechanism in R biotypes. S biotypes showed higher concentrations of shikimic acid and quinic acid before glyphosate and accumulated less of both secondary acids in treated leaves 72 h after glyphosate application. Resistant biotypes showed higher concentrations of salicylic acid before glyphosate application.

Two field experiments were undertaken at Roseworthy, South Australia from 2006 to 2007 to evaluate the performance of herbicide application strategies for the control of herbicide-resistant rigid ryegrass in faba bean grown in wide rows (WR). The standard farmer practice of applying postsowing PRE (PSPE) simazine followed by POST clethodim to faba bean grown in WR provided consistent and high levels of rigid ryegrass control (≥ 96%) and caused a large reduction (P < 0.05) in spike production (≤ 20 spikes m−2) as compared with nontreated control (560 to 722 spikes m−2). Furthermore, this herbicide combination resulted in greatest yield benefits for WR faba bean (723 to 1,046 kg ha−1). Although PSPE propyzamide used in combination with shielded interrow applications of glyphosate or paraquat provided high levels of rigid ryegrass control (≥ 93%), these treatments were unable to reduce ryegrass spike density within the crop row (20 to 54 spikes m−2) to levels acceptable for continued cropping. Furthermore, a yield reduction (13 to 29%) was observed for faba bean in treatments with shielded application of nonselective herbicides and could be related to spray drift onto lower leaves. These findings highlight that shielded interrow spraying in WR faba bean could play an important role in the management of rigid ryegrass in southern Australia. However, timing of shielded interrow applications on weed control, crop safety, and issues concerning integration with more effective early-season control strategies require attention.

Common ragweed is a plant species causing allergic and asthmatic symptoms in humans. To control its propagation, an early identification system is needed. However, due to its similar appearance with mugwort, proper differentiation between these two weed species is important. Therefore, we propose a method to discriminate common ragweed and mugwort leaves based on digital images using bag of visual words (BoVW). BoVW is an object-based image classification that has gained acceptance in many areas of science. We compared speeded-up robust features (SURF) and grid sampling for keypoint selection. The image vocabulary was built using K-means clustering. The image classifier was trained using support vector machines. To check the robustness of the classifier, specific model runs were conducted with and without damaged leaves in the trainings dataset. The results showed that the BoVW model allows the discrimination between common ragweed and mugwort leaves with high accuracy. Based on SURF keypoints with 50% of 788 images in total as training data, we achieved a 100% correct recognition of the two plant species. The grid sampling resulted in slightly less recognition accuracy (98 to 99%). In addition, the classification based on SURF was up to 31 times faster.