Ivyleaf Morningglory Research Articles

Genetic architecture of heritable leaf microbes.

Host-associated microbiomes are shaped by both their environment and host genetics, and often impact host performance. The scale of host genetic variation important to microbes is largely unknown yet fundamental to the community assembly of host-associated microbiomes, with implications for the eco-evolutionary dynamics of microbes and hosts. Using Ipomoea hederacea, ivyleaf morning glory, we generated matrilines differing in quantitative genetic variation and leaf shape, which is controlled by a single Mendelian locus. We then investigated the relative roles of Mendelian and quantitative genetic variation in structuring the leaf microbiome and how these two sources of genetic variation contributed to microbe heritability. We found that despite large effects of the environment, both Mendelian and quantitative genetic host variation contribute to microbe heritability and that the cumulative small effect genomic differences due to matriline explained as much or more microbial variation than a single large effect Mendelian locus. Furthermore, our results are the first to suggest that leaf shape itself contributes to variation in the abundances of some phyllosphere microbes.IMPORTANCEWe investigated how host genetic variation affects the assembly of Ipomoea hederacea's natural microbiome. We found that the genetic architecture of leaf-associated microbiomes involves both quantitative genetic variation and Mendelian traits, with similar contributions to microbe heritability. The existence of Mendelian and quantitative genetic variation for host-associated microbes means that plant evolution at the leaf shape locus or other quantitative genetic loci has the potential to shape microbial abundance and community composition.

Effect of Black Soldier Fly Larvae and Food Substrates on Weed Seed Emergence

Black soldier fly larvae (Hermetia illucens; BSFL) composting is biotechnology used for organic waste management and an alternative to traditional composting. We designed a two-phase experiment to evaluate the effect of BSFL composting on the emergence of the following six weed species: barnyardgrass (Echinochloa crus-galli), common ragweed (Ambrosia artemisiifolia), giant foxtail (Setaria faberi), ivyleaf morningglory (Ipomoea hederacea), redroot pigweed (Amaranthus retroflexus), and velvetleaf (Abutilon theophrasti). The first experiment phase was in the laboratory (laboratory composting phase), which consisted of 100 seeds of each weed species subjected to five composting treatments [two controls (nontreated and standard Gainesville diet alone) and three types of substrates (standard Gainesville diet, vegetable waste, food waste) + BSFL]. Live pupa weighed 179 mg with the standard Gainesville diet + BSFL and 205 mg with the food waste diet + BSFL. Dry pupa weighed 68 mg and 70 mg, respectively. The BSFL in the vegetable waste + BSFL treatment did not pupate. During the second experiment phase, the composting treatments were placed in a greenhouse to evaluate weed emergence. Emergence in the nontreated control was 62% for barnyardgrass, 38% for common ragweed, 26% for giant foxtail, 66% for ivyleaf morningglory, 3% for redroot pigweed, and 69% for velvetleaf. Compared with the nontreated control, all treatments with BSFL reduced the emergence of each weed species to ≤1%, except for velvetleaf. This study suggests that BSFL composting may effectively reduce weed seed emergence of many weed species and could be a safe alternative to conventional composting processes to minimize weed pressure in compost. However, efficacy may vary by weed species and may be dependent on seed characteristics, such as an impermeable seedcoat.

Discrimination of morningglory species (Ipomoea spp.) using near-infrared spectroscopy and multivariate analysis

AbstractThe occurrence of weeds is one of the main factors limiting agricultural productivity. Studies on new techniques for the identification of these species can contribute to the development of proximal sensors, which in the future might be coupled to machines to optimize the performance of species-specific weed management. Thus, the objective of this study was to use near-infrared (NIR) spectroscopy and multivariate analysis to discriminate three morningglory species (Ipomoea spp.). The NIR spectra were collected from the leaves of the three weed species at the vegetative stage (up to five leaves), within the spectral band of 4,000 to 10,000 cm−1. The discrimination models were selected according to accuracy, sensitivity, specificity, and Youden’s index and were analyzed with a validation data set (n = 135). The best results occurred when the selection of spectral bands associated with the use of preprocessing was performed. It was possible to obtain an accuracy of 99.3%, 98.5%, and 98.7% for ivyleaf morningglory (Ipomoea hederifolia L.), Japanese morningglory [Ipomoea nil (L.) Roth], and hairy woodrose [Merremia aegyptia (L.) Urb.], respectively. NIR spectroscopy associated with principal component analysis and linear discriminant analysis (PC-LDA) or partial least-squares regression with discriminant analysis (PLS-DA) can be used to discriminate Ipomoea spp.

Control of pervasive row crop weeds with dicamba and glufosinate applied alone, mixed, or sequentially

AbstractDicamba and glufosinate are among the few effective postemergence herbicides to control multiple herbicide-resistant weeds in southeastern U.S. cotton and soybean production. Field studies were conducted to determine the effect of weed size and the application of dicamba and glufosinate individually, mixed, or sequentially on common ragweed, goosegrass, large crabgrass, ivyleaf morningglory, Palmer amaranth, and sicklepod control. Sequential herbicide treatments were applied 7 d after the initial treatment. The tested weeds sizes predominantly did not affect weed control. Control of broadleaf weed species with sequential herbicide applications never increased compared to the initial herbicide application. Two applications of glufosinate and/or dicamba + glufosinate controlled grasses better than one application. The order of the herbicides in the sequential applications did not affect broadleaf species control, whereas herbicide order was important for the control of grass weeds. Grass weed control was higher when glufosinate was applied before dicamba. Dicamba + glufosinate additively controlled the weeds, except for goosegrass, for which control was less for dicamba + glufosinate compared to glufosinate alone. The results of the experiment provide evidence that dicamba and glufosinate applied individually, mixed, and sequentially are effective on common row crop weeds found in the southeastern United States, but the species present may dictate how the herbicides are applied together.

Interference of morningglories (Ipomoea spp.) with ‘Fascination’ triploid watermelon

AbstractMorningglories (Ipomoea spp.) are among the most troublesome weeds in cucurbits in the United States; however, little is known about Ipomoea spp. interference with horticultural crops. Two additive design field studies were conducted in 2020 at two locations in Indiana to investigate the interference of ivyleaf morningglory (Ipomoea hederacea Jacq.), entireleaf morningglory (Ipomoea hederacea Jacq. var. integriuscula A. Gray.), and pitted morningglory (Ipomoea lacunosa L.) with triploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. Immediately after watermelon was transplanted, Ipomoea spp. seedlings were transplanted into the watermelon planting holes at densities of 0 (weed-free control), 3, 6, 12, 18, and 24 plants 27 m−2. Fruit was harvested once a week for 4 wk, and each fruit was classified as marketable (≥4 kg) or non-marketable (<4 kg). At 1 wk after the final harvest, aboveground biomass samples were collected from 1 m2 per plot and oven-dried to obtain watermelon and Ipomoea spp. dry weight. Seed capsules and the number of seeds in 15 capsules were counted from the biomass sample to estimate seed production. Ipomoea spp. densities increasing from 3 to 24 plants 27 m−2 increased marketable watermelon yield loss from 58% to 99%, reduced marketable watermelon fruit number 49% to 98%, reduced individual watermelon fruit weight 17% to 45%, and reduced watermelon aboveground biomass 83% to 94%. Ipomoea spp. seed production ranged from 549 to 7,746 seeds m−2, greatly increasing the weed seedbank. Ipomoea spp. hindered harvest due to their vines wrapping around watermelon fruits. The most likely reason for watermelon yield loss was interference with light and consequently less dry matter being partitioned into fruit development due to less photosynthesis. Yield loss was attributed to fewer fruits and the weight of each fruit.

Ivyleaf morningglory (Ipomoea hederacea Jacq.) competition is not intensified by drought in silage corn in central New York State, USA

Ivyleaf morningglory (IMG, Ipomoea hederacea Jacq.) is a summer annual vine that is native to the Americas and invasive globally. This species decreases field crop yields through competition and interference with harvesting. Here, we explore the potential of IMG to compete with silage corn ( Zea mays L.) in New York State, USA. In a 2-year field study, we measured silage yield at five IMG planting densities (0–8 plants m−2) under no-drought conditions and a drought treatment established with rainout shelters. Volumetric water content was 26%–28% lower in the drought treatment than the no-drought treatment. Drought reduced fresh corn silage yield ( P = 0.003). Fresh silage yield was 21 600 ± 700 kg ha−1 in the no-drought treatment in 2016, 19 100 ± 900 kg ha−1 in the drought treatment in 2016, 30 500 ± 900 kg ha−1 in the no-drought treatment in 2017, and 28 200 ± 700 kg ha−1 in the drought treatment in 2017. Silage yield was not strongly responsive to IMG density, regardless of drought. These data suggest that the risk of corn silage yield losses due to IMG is relatively low in New York State and unlikely to be affected by drought. The risk posed by IMG may differ in other cropping systems or regions and under climate change.

Drought and Competition With Ivyleaf Morningglory (Ipomoea hederacea) Inhibit Corn and Soybean Growth

Agricultural impacts of climate change include direct effects on crop plants and indirect effects, such as changes to the distributions and competitiveness of weed species. In the northeastern United States, warming temperatures are likely to result in periods of soil moisture deficit and changes to weed communities. Ivyleaf morningglory (IMG, Ipomoea hederacea Jacq.) is a summer annual vine that competes with field crops and interferes with harvesting. Climate change may increase the competitive effects of IMG on northeastern U.S. field crops. We conducted a greenhouse study to evaluate the effects of IMG on corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] under drought and non-drought conditions. The drought treatment was crossed against an IMG competition treatment with five levels: one crop plant without IMG plants, one crop plant with one, two, or three IMG plants, and one IMG plant without crop plants. Both drought and IMG (presence or biomass) reduced the biomass of corn and soybean (P < 0.05). Drought and IMG (presence) reduced soybean pod production (P < 0.001). IMG biomass was reduced by drought and the presence of corn (P < 0.001). Across all competition treatments, drought reduced IMG biomass by 71% in the corn experiment and 79% in the soybean experiment, compared with a corn biomass reduction of 50% and a soybean biomass reduction of 58%. Well-designed management programs should mitigate the risks associated with stressors such as IMG and drought, which may threaten northeastern U.S. field crop production under climate change.

Spray Deposition on Weeds (Palmer Amaranth and Morningglory) from a Remotely Piloted Aerial Application System and Backpack Sprayer

This study was designed to determine whether a remotely piloted aerial application system (RPAAS) could be used in lieu of a backpack sprayer for post-emergence herbicide application. Consequent to this objective, a spray mixture of tap water and fluorescent dye was applied on Palmer amaranth and ivyleaf morningglory using an RPAAS at 18.7 and 37.4 L·ha−1 and a CO2-pressurized backpack sprayer at a 140 L·ha−1 spray application rate. Spray efficiency (the proportion of applied spray collected on an artificial sampler) for the RPAAS treatments was comparable to that for the backpack sprayer. Fluorescent spray droplet density was significantly higher on the adaxial surface for the backpack sprayer treatment than that for the RPAAS platforms. The percent of spray droplets on the abaxial surface for the RPAAS aircraft at 37.4 L·ha−1 was 4-fold greater than that for the backpack sprayer at 140 L·ha−1. The increased spray deposition on the abaxial leaf surfaces was likely caused by rotor downwash and wind turbulence generated by the RPAAS which caused leaf fluttering. This improved spray deposition may help increase the efficacy of contact herbicides. Test results indicated that RPAASs may be used for herbicide application in lieu of conventional backpack sprayers.

Evaluation of thiencarbazone‐methyl for use in acetolactate synthase‐resistant soybean

AbstractTo combat herbicide‐resistant weeds, new options are needed to effectively rotate herbicide modes of action and slow the development of additional herbicide resistance. Thiencarbazone‐methyl (TCM), an acetolactate synthase (ALS)‐inhibiting herbicide, is currently being evaluated for preemergence (PRE) and postemergence (POST) activity on many troublesome summer annual and perennial weeds. Multiple experiments were conducted to assess the utility of this product in soybean (Glycine max) production systems. Field experiments were conducted across Arkansas in 2016 and 2017 to determine the tolerance of ALS‐resistant soybean varieties to PRE and POST applications of TCM at either 0.03 or 0.06 lb acre–1. For all locations, no significant interactions or main effects were observed for any parameters evaluated. Overall, soybean injury remained consistently low, with <3% injury at 21 days after treatment (DAT) on all ALS‐resistant varieties. However, the ALS‐susceptible variety showed high levels of injury for both PRE (75%) and POST (98%) applications at 21 DAT. Two additional experiments were conducted in 2016, 2017, and 2018 to evaluate the efficacy of PRE and POST applications of TCM in ALS/glufosinate‐resistant soybean. For PRE applications, residual activity of TCM, imazethapyr, chlorimuron, nicosulfuron, halosulfuron, and flumetsulam at labeled rates for soybean or corn were evaluated. TCM at 0.06 lb acre–1was effective in controlling ivyleaf morningglory (91 %) and broadleaf signalgrass (97%) at 21 DAT, but was not effective in controlling ALS‐resistant Palmer amaranth (58%). In the POST experiment, TCM at 0.03 or 0.06 lb acre–1was compared to imazethapyr, chlorimuron, nicosulfuron, and halosulfuron with and without glufosinate (0.5 lb acre–1). Alone, TCM produced higher control of ivyleaf morningglory (99 to 100%) and broadleaf signalgrass (94 to 99%) at 21 DAT compared to all other ALS‐inhibiting herbicides. However, TCM alone was not effective in controlling ALS‐resistant Palmer amaranth (55 to 61%) at 21 DAT, but when combined with glufosinate control increased to 95 to 99%. The results from this research suggest that TCM could have utility in soybean weed control systems due to the high level of resistance exhibited by ALS‐resistant soybean varieties and the efficacy of TCM on common soybean weed species at both the PRE and POST application timings.

Evaluation of weed control in acetyl coA carboxylase-resistant rice with mixtures of quizalofop and auxinic herbicides

AbstractRice with enhanced tolerance to herbicides that inhibit acetyl coA carboxylase (ACCase) allows POST application of quizalofop, an ACCase-inhibiting herbicide. Two concurrent field studies were conducted in 2017 and 2018 near Stoneville, MS, to evaluate control of grass (Grass Study) and broadleaf (Broadleaf Study) weeds with sequential applications of quizalofop alone and in mixtures with auxinic herbicides applied in the first or second application. Sequential treatments of quizalofop were applied at 119 g ai ha−1 alone and in mixtures with labeled rates of auxinic herbicides to rice at the two- to three-leaf (EPOST) or four-leaf to one-tiller (LPOST) growth stages. In the Grass Study, no differences in rice injury or control of volunteer rice (‘CL151’ and ‘Rex’) were detected 14 and 28 d after last application (DA-LPOST). Barnyardgrass control at 14 and 28 DA-LPOST with quizalofop applied alone or with auxinic herbicides EPOST was ≥93% for all auxinic herbicide treatments except penoxsulam plus triclopyr. Barnyardgrass control was ≥96% with quizalofop applied alone and with auxinic herbicides LPOST. In the Broadleaf Study, quizalofop plus florpyrauxifen-benzyl controlled more Palmer amaranth 14 DA-LPOST than other mixtures with auxinic herbicides, and control with this treatment was greater EPOST compared with LPOST. Hemp sesbania control 14 DA-LPOST was ≤90% with quizalofop plus quinclorac LPOST, orthosulfamuron plus quinclorac LPOST, and triclopyr EPOST or LPOST. All mixtures except quinclorac and orthosulfamuron plus quinclorac LPOST controlled ivyleaf morningglory ≥91% 14 DA-LPOST. Florpyrauxifen-benzyl or triclopyr were required for volunteer soybean control >63% 14 DA-LPOST. To optimize barnyardgrass control and rice yield, penoxsulam plus triclopyr and orthosulfamuron plus quinclorac should not be mixed with quizalofop. Quizalofop mixtures with auxinic herbicides are safe and effective for controlling barnyardgrass, volunteer rice, and broadleaf weeds in ACCase-resistant rice, and the choice of herbicide mixture could be adjusted based on weed spectrum in the treated field.

Fate of weed seeds in spent mushroom compost following commercial mushroom production

AbstractCommercial mushroom producers grow several varieties of mushrooms on compost. Upon completion of the growing cycle, the spent mushroom compost is often sold as a soil amendment for both agricultural and homeowner use. Mushroom compost ingredients often come from fields infested with weeds, and in turn compost may spread unwanted weed seed. We conducted studies to assess the viability of weed seed following specific stages of the commercial mushroom production process. Weed seed was more likely to survive if the entire production process was not completed. However, no viable hairy vetch, Italian ryegrass, ivyleaf morningglory, Palmer amaranth, or velvetleaf remained at the end of the study. Although the seeds of most species were eliminated earlier in the composting process, ivyleaf morningglory required the complete process to eliminate 100% of the seed. These results indicate that spent mushroom compost is free of many weed species upon removal from mushroom houses and is unlikely to spread weed seed.

Fluridone and acetochlor cause unacceptable injury to pumpkin

AbstractResidual herbicides are routinely applied to control troublesome weeds in pumpkin production. Fluridone and acetochlor, Groups 12 and 15 herbicides, respectively, provide broad-spectrum PRE weed control. Field research was conducted in Virginia and New Jersey to evaluate pumpkin tolerance and weed control to PRE herbicides. Treatments consisted of fomesafen at two rates, ethalfluralin, clomazone, halosulfuron, fluridone,S-metolachlor, acetochlor emulsifiable concentrate (EC), acetochlor microencapsulated (ME), and no herbicide. At one site, fluridone, acetochlor EC, acetochlor ME, and halosulfuron injured pumpkin 81%, 39%, 34%, and 35%, respectively, at 14 d after planting (DAP); crop injury at the second site was 40%, 8%, 19%, and 33%, respectively. Differences in injury between the two sites may have been due to the amount and timing of rainfall after herbicides were applied. Fluridone provided 91% control of ivyleaf morningglory and 100% control of common ragweed at 28 DAP. Acetochlor EC controlled redroot pigweed 100%. Pumpkin treated withS-metolachlor produced the most yield (10,764 fruits ha–1) despite broadcasting over the planted row; labeling requires a directed application to row-middles. A separate study specifically evaluated fluridone applied PRE at 42, 84, 126, 168, 252, 336, and 672 g ai ha–1. Fluridone resulted in pumpkin injury ≥95% when applied at rates of ≥168 g ai ha–1; significant yield loss was noted when the herbicide was applied at rates >42 g ai ha–1. We concluded that fluridone and acetochlor formulations are unacceptable candidates for pumpkin production.

Weed Control in Soybean with Preemergence‐ and Postemergence‐applied Herbicides

Core Ideas Herbicide premixes provided good (>90%) broadleaf and grass weed control in Nebraska. Preemergence‐applied herbicide premixes with different sites of action will help manage resistance weeds. Preemergence‐applied herbicides should be a foundation for weed management in soybean. In the past 20 years, weed control in soybean (Glycine max) was mainly based on postemergence (POST) applications of glyphosate, which resulted in glyphosate‐resistant weeds. Herbicide‐resistant weeds warrants evaluation of new strategies for effective control. Therefore, the objective of this study was to evaluate the performance of herbicides applied preemergence (PRE) and POST on 11 agronomic weeds in eastern Nebraska. The study was conducted in 2014 and 2015 in Concord, NE. The best PRE‐applied treatments were metolachlor + imazethapyr, fomesafen + imazethapyr, flumioxazin + imazethapyr, and flumioxazin + metribuzin, which controlled broadleaf and grass weed species ≥90 and ≥80%, respectively. However, weed control with POST herbicides was more variable, ranging from 19 to 91%. The POST‐applied fomesafen and fomesafen + imazethapyr controlled ivyleaf morningglory (Ipomoea hederacea), common lambsquarters (Chenopodium album), common waterhemp (Amaranthus tuberculatus), and redroot pigweed (Amaranthus retroflexus) ≥85%. Greater soybean yields were achieved with most PRE‐applied herbicides and POST‐applied fomesafen + imazethapyr only. Metolachlor + imazethapyr, metolachlor, and fomesafen applied PRE protected soybean yields better than when applied POST. Results suggested that PRE‐applied herbicide mixtures of different sites of action are the base for controlling weeds and protecting soybean yields in eastern Nebraska.

Evaluation of Weed Management Programs and Response of FG72 Soybean to HPPD-Inhibiting Herbicides

Field experiments were conducted at two locations in Missouri in 2012 and 2013 to evaluate herbicide programs in 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitor-resistant soybean, referred to as FG72 soybean, and their tolerance to four HPPD-inhibiting herbicides. At the Columbia location, PRE followed by (fb) POST and two-pass POST treatments provided 97% or greater control of all weeds except ivyleaf morningglory. At Moberly in 2012, PRE fb POST treatments provided 95% or greater control and 100% biomass reduction (BR) of glyphosate-resistant (GR) waterhemp, with the exception of isoxaflutole at 0.04 kg ha−1plusS-metolachlor at 0.6 kg ha−1plus metribuzin at 0.2 kg ha−1. In 2013, PRE fb POST treatments provided greater than 89% control and 93% BR. Two-pass POST treatments of isoxaflutole plus glyphosate always provided greater control and BR of GR waterhemp compared with glyphosate fb glyphosate. However, at Columbia, where glyphosate-susceptible weeds were present, there were no differences in control or BR between two-pass POST treatments. In the soybean tolerance experiment, isoxaflutole provided the lowest levels of injury. Applications of tembotrione at the 1× rate resulted in the greatest injury in both years. Topramezone at the 1× rate always provided less injury than tembotrione, but was always similar in BR. The 2× rates increased soybean injury over the 1× rate for the third trifoliate (V3) application, but not for the PRE and first-flower (R1) applications. V3 and R1 applications of isoxaflutole and mesotrione resulted in similar injury, height reduction, and BR to soybean 28 d after application in 2012 and 2013. Overall these results indicate that FG72 soybean could allow the use of HPPD-inhibiting herbicides such as mesotrione PRE along with isoxaflutole PRE and POST to provide an additional herbicide mechanism of action that was not previously available in soybean.

Utilization of Saflufenacil in a Clearfield® Rice (Oryza sativa) System

Research was conducted in Mississippi in 2012 and 2013 to compare the efficacy of saflufenacil to other broadleaf herbicides applied in mixtures with imazethapyr in a Clearfield rice system. Saflufenacil at 50 g ai ha−1, carfentrazone at 35 g ai ha−1, a prepackaged mixture of halosulfuron plus thifensulfuron at 35 plus 4 g ai ha−1, and a prepackaged mixture of propanil plus thiobencarb at 2,240 plus 2,240 g ai ha−1 were applied in mixture with imazethapyr at 70 g ai ha−1 early-POST (EPOST) to rice in the one- to two-leaf stage or late-POST (LPOST) to rice in the four-leaf to one-tiller stage. No differences in injury among the broadleaf herbicides or between application timings were detected at any evaluation. Imazethapyr combined with propanil plus thiobencarb or saflufenacil provided the greatest control of barnyardgrass 7 and 14 d after treatment (DAT). Hemp sesbania, ivyleaf morningglory, and Palmer amaranth control was greatest and similar for imazethapyr combined with carfentrazone, propanil plus thiobencarb, and saflufenacil; however, rough rice yield was greatest for imazethapyr combined with propanil plus thiobencarb or saflufenacil. Propanil plus thiobencarb or saflufenacil can be used in a Clearfield rice system to achieve optimum weed control and highest rice yields.

Evaluation of Saflufenacil in Drill-Seeded Rice (Oryza sativa)

Palmer amaranth is the most common and troublesome broadleaf weed species of rice in Mississippi because of the effects of early-season interference and infestations on rice levees, and herbicides for residual or POST control of Palmer amaranth in rice are limited. Three studies were conducted in 2012 and 2013 to evaluate application rates and timings of saflufenacil in rice and to determine the influence of adjuvants when mixed with saflufenacil applied POST. In a PRE study, no injury occurred after saflufenacil PRE, and no control was observed from carfentrazone. Hemp sesbania and Palmer amaranth control increased with increasing saflufenacil rate when applied PRE. Hemp sesbania control with saflufenacil at any rate PRE was ≤ 25% at 35 d after treatment (DAT). Palmer amaranth and ivyleaf morningglory control with saflufenacil at 75 g ai ha−1PRE was ≥ 94% 35 DAT. In a POST study, rice injury was influenced by application timing and rate of saflufenacil; however, efficacy was not. Rice injury with saflufenacil at 25 g ha−1and carfentrazone early POST (EPOST) and late POST was similar 7 DAT. Saflufenacil at 50 and 75 g ha−1EPOST were the most injurious 7 DAT. Control of hemp sesbania and ivyleaf morningglory was similar for all rates of saflufenacil and carfentrazone; however, Palmer amaranth control with saflufenacil at any rate was greater than that of carfentrazone 14 and 28 DAT. In an adjuvant study, rice injury was influenced by adjuvant and saflufenacil rate. Saflufenacil applied alone or in mixture with crop oil concentrate (COC) was least injurious, and saflufenacil at 50 g ha−1was more injurious than saflufenacil at 25 g ha−1. Saflufenacil applied in combination with any adjuvant provided better control of hemp sesbania and Palmer amaranth than saflufenacil alone. On the basis of this research, saflufenacil should be applied PRE at 50 or 75 g ha−1, depending on weed spectrum, and POST applications should be made at 25 g ha−1in combination with COC after the two-leaf rice growth stage.

Thiencarbazone-Methyl Efficacy, Absorption, Translocation, and Metabolism in Vining Weed Species

The efficacy, absorption, translocation, and metabolism of thiencarbazone-methyl (TCM) in hedge bindweed, field bindweed, ivyleaf morningglory, tall morningglory, and wild buckwheat were evaluated in greenhouse experiments and field trials. Forty-eight hours after foliar microapplication,14C-TCM absorption was highest in ivyleaf morningglory (60%), followed by field bindweed (50%), wild buckwheat (35%), tall morningglory (17%), and hedge bindweed (9%). In all species,14C-TCM was translocated systemically. By 24 h after application,14C-TCM was detected in all parts of the plants. The translocation pattern is species-specific, with more translocation in tall morningglory and wild buckwheat. In all vining weeds14C-TCM was almost not metabolized whereas corn metabolized almost all14C-TCM 48 h after application. The efficacy of TCM was analyzed using dose–response curves. Wild buckwheat had the lowest value for the dose at which 50% of the activity occurs (2.1 g ai ha−1TCM), followed by hedge bindweed and ivyleaf morningglory. Field studies confirmed the high control of wild buckwheat with TCM. Even at the lowest tested concentration of TCM, wild buckwheat was controlled by over 90%. In contrast, efficacy of TCM in field trials against perennial vining weeds was very low, 25% for field bindweed and 65% against hedge bindweed. Control efficacy could be well explained by the translocation pattern of TCM in vining weeds.

Quantitative genetic variance and multivariate clines in the Ivyleaf morning glory, Ipomoea hederacea.

Clinal variation is commonly interpreted as evidence of adaptive differentiation, although clines can also be produced by stochastic forces. Understanding whether clines are adaptive therefore requires comparing clinal variation to background patterns of genetic differentiation at presumably neutral markers. Although this approach has frequently been applied to single traits at a time, we have comparatively fewer examples of how multiple correlated traits vary clinally. Here, we characterize multivariate clines in the Ivyleaf morning glory, examining how suites of traits vary with latitude, with the goal of testing for divergence in trait means that would indicate past evolutionary responses. We couple this with analysis of genetic variance in clinally varying traits in 20 populations to test whether past evolutionary responses have depleted genetic variance, or whether genetic variance declines approaching the range margin. We find evidence of clinal differentiation in five quantitative traits, with little evidence of isolation by distance at neutral loci that would suggest non-adaptive or stochastic mechanisms. Within and across populations, the traits that contribute most to population differentiation and clinal trends in the multivariate phenotype are genetically variable as well, suggesting that a lack of genetic variance will not cause absolute evolutionary constraints. Our data are broadly consistent theoretical predictions of polygenic clines in response to shallow environmental gradients. Ecologically, our results are consistent with past findings of natural selection on flowering phenology, presumably due to season-length variation across the range.

Weed Control and Crop Safety with Premixed Pyrasulfotole and Bromoxynil in Grain Sorghum

Field experiments were conducted in grain sorghum at five locations in Kansas in 2009 and 2010, to evaluate the efficacy and crop safety of early- to mid-POST (EMPOST) and late-POST (LPOST) applications of premixed pyrasulfotole and bromoxynil (PYRA&BROM) in tank mix combinations with atrazine or atrazine plus 2,4-D ester or dicamba compared to bromoxynil plus atrazine. PYRA&BROM at 244 or 300 g ai ha−1 plus atrazine at 560 g ai ha−1 applied EMPOST controlled pigweed species (Palmer amaranth, tumble pigweed, and redroot pigweed), kochia, velvetleaf, common sunflower, ivyleaf morningglory, and common lambsquarters 93% or greater. Puncturevine control among three locations ranged from 85 to 99%. Control of most weed species was not improved by increasing PYRA&BROM rate from 244 to 300 g ha−1 or by tank mixing 2,4-D or dicamba with PYRA&BROM plus atrazine. However, ivyleaf morningglory control was improved at the LPOST timing by adding 2,4-D or dicamba at 140 g ae ha−1. In no instance did any PYRA&BROM treatment provide greater weed control than bromoxynil plus atrazine at 281 + 560 g ha−1 when applied EMPOST, but in most instances PYRA&BROM treatments were more effective than bromoxynil plus atrazine when applied LPOST. Generally, PYRA&BROM treatments were more effective when applied EMPOST than LPOST, especially when 2,4-D or dicamba was added. PYRA&BROM plus atrazine treatments caused foliar bleaching in sorghum within 7 ± 3 d after treatment, but recovery was complete within 3 to 4 wk and grain yields were not reduced. Tank mixing dicamba with PYRA&BROM and atrazine occasionally reduced visible crop response compared to PYRA&BROM plus atrazine. Our results indicate that PYRA&BROM plus atrazine with or without 2,4-D or dicamba selectively controls several troublesome broadleaf weeds in grain sorghum. Foliar bleaching of sorghum leaves can occur but the symptoms are transient, and grain yields are not likely to be reduced.

Epidemiology of Soybean vein necrosis-associated virus

Soybean vein necrosis-associated virus has been linked to an emerging soybean disease in the United States and Canada. Virus distribution and population structure in major growing areas were evaluated. Data were employed to design and develop sensitive detection protocols, able to detect all virus isolates available in databases. The host range for the virus was assessed and several species were found to sustain virus replication, including ivyleaf morning glory, a common weed species in soybean-growing areas in the United States. Koch's postulates were fulfilled using soybean thrips and transmission efficiency was determined. This article provides significant insight into the biology of the most widespread soybean virus in the United States.