Smallflower Morningglory Research Articles

Concurrent weed growth suppression with essential oils and species-specific response to fractionated coconut oil

Plant-derived oils are phytotoxic and thus are potential non-synthetic herbicides. The present study investigated the effectiveness of three essential oils (red thyme, clove bud, cinnamon bark) and a vegetable oil, fractionated coconut oil (FCO), used alone or in 2-way essential/FCO mixes for controlling some troublesome weeds at seedling stage. The tested weeds were mugwort (Artemisia vulgaris L.), crown daisy (Glebionis coronaria (L.) Spach), milk thistle (Sylibum marianum (L.) Gaertn.), dense-flowered mullein (Verbascum densiflorum Bertol.), goosegrass (Eleusine indica L. (Gaertn.)), entireleaf morningglory (Ipomoea hederacea (L.) Jacq.), small-flower morningglory (Jacquemontia tamnifolia (L.) Griseb), large crabgrass (Digitaria sanguinalis (L.) Scop.), hemp sesbania (Sesbania exaltata (Raf.) Rydb. ex A.W. Hill).Greenhouse trials included a negative control (non-treated) and a positive control (glyphosate) and were conducted in Sassari (IT) and Auburn (USA). In both locations, all the essential oils used severely injured weeds by 5 days after treatment (DAT), with least or no recovery by plants, with no harvestable plant biomass 20 DAT. FCO provoked more diverse species-specific responses, reducing biomass of crown daisy, large crabgrass, entireleaf morningglory and hemp sesbania compared to the non-treated control while it stimulated the growth of mugwort, dense-flowered mullein, goosegrass, and small-flower morningglory. Milk thistle was the only plant not influenced by FCO compared to the non-treated control. The essential oils mixed with FCO confirmed high phytotoxic effects with a significant improved action when red thyme oil + FCO was applied to goosegrass. Our research confirms the potential herbicidal effect of some phytotoxic essential oils and the potential beneficial growth effect of FCO to some species.

Seasonal Occurrence and Reproductive Suitability of Weed Hosts for Sweetpotato Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), in South Georgia

Abstract South Georgia represents an area of intensive agricultural production where cultivated crops serve as hosts of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), throughout the year. In addition to cultivated hosts, there are numerous weed species present in the agricultural landscape that are undoubtedly responsible for supporting B. tabaci population development. This study provided information on the most abundant weed hosts of B. tabaci from this region. We evaluated 31 different weed species, of which 16 weed species are reproductive hosts with varying degrees of preference. Suitable weed hosts included cypressvine morningglory (Ipomoea quamoclit L.), nodding spurge (Euphorbia nutans Lag.), prickly sida (Sida spinosa L.), sharppod morningglory (Ipomoea cordatotriloba Dennst.), smallflower morningglory (Jacquemontia tamnifolia L.), tall vervain (Verbena bonariensis L.), and wild poinsettia (Euphorbia heterophylla L.). These species are highly abundant and therefore likely influence B. tabaci populations in the landscape. Other species including bristly starbur (Acanthospermum hispidum DC) and redweed (Melochia corchorifolia L.) were highly preferred by B. tabaci but not nearly as abundant in the landscape. Furthermore, we identified 10 very common weed species that were poor reproductive hosts including wild radish (Raphanus raphanistrum L.), Palmer amaranth (Amaranthus palmeri S. Watson), common ragweed (Ambrosia artemisiifolia L.), Florida pusley (Richardia scabra L.), and henbit (Lamium amplexicaule L.).

Integrating cultivation using a tine weeder with herbicides in conventional peanut production

AbstractResearch from the 1980s reported sweep cultivation being a cost-effective component in an integrated system to manage weeds in peanut. Previous weed management research conducted on organic peanut indicated that repeated cultivation with a tine weeder was an effective component in that production system. Studies were conducted in Tifton, GA, from 2014 through 2017 to determine whether tine weeding can be integrated with herbicides in conventional peanut production to supplement herbicides. Experiments evaluated a factorial arrangement of eight herbicide combinations and two levels of cultivation using a tine weeder. Herbicides were labeled rates of ethalfluralin PRE, S-metolachlor PRE, imazapic POST, ethalfluralin PRE + S-metolachlor PRE, ethalfluralin PRE + imazapic POST, S-metolachlor PRE + imazapic POST, ethalfluralin PRE + S-metolachlor PRE + imazapic POST, and a nontreated control. The herbicides chosen were based on knowledge of the weed species composition at the research sites and their common use in peanut. Cultivation regimes were cultivation with a tine weeder (six times at weekly intervals) and a noncultivated control. Benefits of tine weeding supplementing control from herbicides varied according to herbicide and weed species. For example, annual grasses were effectively controlled (88% to 97%) by ethalfluralin or S-metolachlor and did not need cultivation to supplement control provided by the herbicides. However, imazapic alone did not effectively control (54% to 75%) annual grasses and needed supplemental control from cultivation with the tine weeder. Similarly, imazapic effectively controlled (84% to 93%) smallflower morningglory and did not require cultivation to supplement control from the herbicide. However, cultivation with the tine weeder improved smallflower morningglory control (76% to 95%) when supplementing ethalfluralin or S-metolachlor. Peanut yields did not respond to any of the herbicide combinations integrated with cultivation using the tine weeder. During the time period when peanut was cultivated, there was greater total rainfall and more days of rainfall events in 2014 and 2017 compared with the other years. Rainfall and wet soils reduced the performance and weed control benefits of the tine weeder. This highlights the risk of depending on cultivation for weed control.

Salvage Palmer Amaranth Programs Can Be Effective in Cotton Resistant to Glyphosate, 2,4-D, and Glufosinate

Glyphosate-resistant Palmer amaranth escaping residual herbicides is difficult to manage in cotton because of its rapid growth and a limited number of effective herbicide options to control emerged plants. An experiment was conducted at two dryland and two irrigated sites in Georgia during 2011 and 2012 to determine if cotton resistant to glyphosate, 2,4-D, and glufosinate could be used to salvage a crop infested with large Palmer amaranth. Three POST herbicide systems, including sequential applications of 2,4-D, sequential applications of 2,4-D plus glufosinate, or 2,4-D followed by (fb) glufosinate, were applied with intervals of 5, 10, or 15 d between POST applications. All three systems were followed by diuron plus MSMA directed at layby. At the dryland sites with high temperatures and drought conditions, no program provided greater than 90% control. However, the 2,4-D plus glufosinate system was at least twice as effective in controlling 20-cm-tall Palmer amaranth and produced at least three times more cotton than the other two systems, when pooled over POST application intervals. Intervals of 10 or 15 d between POST applications were 23 to 27% more effective than a 5-d interval in controlling Palmer amaranth when pooled over POST herbicide systems; yields were nearly twice as much with the 10-d interval compared to 5 d. At the irrigated site, overall weed control was greater with less treatment differences noted. Palmer amaranth that was 20 cm tall at application was controlled 98 to 99%, 92 to 93%, and 81 to 94% by glufosinate plus 2,4-D, 2,4-D fb glufosinate, and 2,4-D fb 2,4-D systems at harvest, respectively. Intervals between POST applications only influenced control by the POST 2,4-D system, and the 10-d interval was more effective than the 5-d interval. Carpetweed, Florida beggarweed, and smallflower morningglory were controlled 99% at harvest by all systems; however, it was noted that control of carpetweed and Florida beggarweed prior to layby was less effective with 2,4-D than systems including glufosinate. In the event of an at-plant residual herbicide failure in fields infested with glyphosate-resistant Palmer amaranth, our research demonstrates that glufosinate plus 2,4-D sequentially applied 10 to 15 d apart followed by a timely layby application controlled the target weeds in cotton with resistance to 2,4-D, glyphosate, and glufosinate.

Combinations of Corn Gluten Meal, Clove Oil, and Sweep Cultivation are Ineffective for Weed Control in Organic Peanut Production

Weed control in organic peanut is difficult and lack of residual weed control complicates weed management efforts. Weed management systems using corn gluten meal in combination with clove oil and sweep cultivation were evaluated in a series of irrigated field trials. Corn gluten meal applied in a 30 cm band over the row at PRE, sequentially at PRE+2 wk after emergence, and PRE+2wk+4wk did not adequately control annual grasses and smallflower morningglory. Similarly, a banded application of clove oil applied POST did not adequately control weeds. The only treatment that improved overall weed control was sweep cultivation. Peanut yields were not measured in 2006 due to heavy baseline weed densities and overall poor weed control. Peanut yields were measured in 2007 and were not affected by any weed control treatment due to poor efficacy. While sweep cultivation improved weed control, weeds were controlled only in the row middles and surviving weeds in-row reduced peanut yield. Even when used in combination with sweep cultivation, corn gluten meal and clove oil were ineffective and offer little potential in a weed management system for organic peanut production.

Weed Management and Cotton Yield under Two Row Spacings in Conventional and Conservation Tillage Systems Utilizing Conventional, Glufosinate-, and Glyphosate-based Weed Management Systems

A field experiment was conducted during three cropping seasons to compare weed control and cotton yield provided by conventional (CV), glufosinate-resistant (LL), and glyphosate-resistant (RR) weed management systems under standard (102 cm) and narrow (38 cm) row spacing grown in conventional and conservation tillage systems. The conventional tillage and/or CV cotton received a PRE application of pendimethalin. The CV, LL, and RR cotton varieties received two POST applications of pyrithiobac, glufosinate, and glyphosate, respectively, at two- and four-leaf cotton growth stages. A final (LAYBY) application of trifloxysulfuron was applied to 38-cm row cotton while a LAYBY POST-directed spray of prometryn plus MSMA was used in 102-cm row cotton. The LL and RR weed management systems controlled at least 97% of large crabgrass, Palmer amaranth, sicklepod, and smallflower morningglory, while the CV system controlled 89, 73, and 87 to 98% of large crabgrass, smallflower morningglory, and Palmer amaranth, respectively. Sicklepod control increased from 85% in 102-cm rows to 95% in 38-cm rows in the CV herbicide system. Yellow nutsedge and pitted morningglory control exceeded 98% and was not affected by tillage, row spacing, or weed management system. Cotton yield was not affected by row spacing any year, by tillage in 2005, or by weed management system in 2004 and 2005. In 2006, yield in the RR weed management system was 27 and 24% higher than LL and CV weed management systems, respectively. In 2004, yield of conventional tillage cotton was 18% higher than conservation tillage cotton, but in 2006 the yield in conservation tillage was 12% higher than conventional tillage.

Utility of Hyperspectral Reflectance for Differentiating Soybean (Glycine max) and Six Weed Species

Reflectance data were subjected to a variety of analysis methods to determine the utility of hyperspectral reflectance for differentiating soybean, soil, and six weed species commonly found in Mississippi agricultural fields. Weed species evaluated were hemp sesbania, palmleaf morningglory, pitted morningglory, prickly sida, sicklepod, and smallflower morningglory. Hyperspectral reflectance data were collected from mature plant leaves three times in 2002 and two times in 2003. Vegetation indices were calculated and subjected to principal component analysis (PCA) and linear discriminant analysis (LDA). The PCA, using vegetation indices, produced the poorest classification accuracies for the plant species studied, generally less than 50%, whereas LDA resulted in classification accuracies greater than those from PCA. Best spectral band combination (BSBC) provided the greatest classification accuracies, with all better than 80% for all data sets. The BSBC indicated three wavelength bands of interest for species discrimination in the short wavelength infrared portion of the electromagnetic spectrum, which are not commonly used in current vegetation indices for species differentiation. These areas of interest were located from 1,445 to 1,475 nm, 2,030 to 2,090 nm, and 2,115 to 2,135 nm. The top 10 wavelengths determined by BSBC were then added to the vegetation indices and reanalyzed using PCA and LDA. Classification accuracies increased for all species when these wavelengths were added rather than using vegetation indices alone, suggesting greater crop and weed species differentiation can be obtained when using sensors that include these wavelength regions of the short wavelength infrared portion of the electromagnetic spectrum.

Utility of Multispectral Imagery for Soybean and Weed Species Differentiation

An experiment was conducted to determine the utility of multispectral imagery for identifying soybean, bare soil, and six weed species commonly found in Mississippi. Weed species evaluated were hemp sesbania, palmleaf morningglory, pitted morningglory, prickly sida, sicklepod, and smallflower morningglory. Multispectral imagery was analyzed using supervised classification techniques based upon 2-class, 3-class, and 8-class systems. The 2-class system was designed to differentiate bare soil and vegetation. The 3-class system was used to differentiate bare soil, soybean, and weed species. Finally, the 8-class system was designed to differentiate bare soil, soybean, and all weed species independently. Soybean classification accuracies classified as vegetation for the 2-class system were greater than 95%, and bare soil classification accuracies were greater than 90%. In the 3-class system, soybean classification accuracies were 70% or greater. Classification of soybean decreased slightly in the 3-class system when compared to the 2-class system because of the 3-class system separating soybean plots from the weed plots, which was not done in the 2-class system. Weed classification accuracies increased as weed density or weeks after emergence (WAE) increased. The greatest weed classification accuracies were obtained once weed species were allowed to grow for 10 wk. Palmleaf morningglory and pitted morningglory classification accuracies were greater than 90% for 10 WAE using the 3-class system. Palmleaf morningglory and pitted morningglory at the highest densities of 6 plants/m2produced the highest classification accuracies for the 8-class system once allowed to grow for 10 wk. All other weed species generally produced classification accuracies less than 50%, regardless of planting density. Thus, multispectral imagery has the potential for weed detection, especially when being used in a management system when individual weed species differentiation is not essential, as in the 2-class or 3-class system. However, weed detection was not obtained until 8 to 10 WAE, which is unacceptable in production agriculture. Therefore, more refined imagery acquisition with higher spatial and/or spectral resolution and more sophisticated analyses need to be further explored for this technology to be used early-season when it would be most valuable.

Morphological Comparison of Morningglory (IpomoeaandJacquemontiaspp.) Populations from the Southeastern United States

Morningglories are troublesome weeds in row crops and other agricultural areas throughout the United States. Plants of pitted morningglory, sharppod morningglory, and a fertile “hybrid” between pitted and sharppod morningglory (hybrid morningglory), were compared with cypressvine, ivyleaf, palmleaf, purple moonflower, red, and smallflower morningglories in greenhouse studies at Stoneville, MS. Plants from each of 76 accessions were studied for number of nodes to first internode elongation; stem color and pubescence; leaf area and dry weight of first four full expanded leaves; leaf blade pubescence on abaxial and adaxial surfaces and margins; leaf color, shape, and lobing; petiole length, color, and pubescence; sepal length, color, and pubescence; and corolla color, diameter, and length. Among these morningglories, the most diverse traits were pubescence and flower characteristics. Greatest morphological diversity was among hybrid morningglory accessions because characteristics were intermediate to pitted morningglory and sharppod morningglory accessions. Sharppod morningglory had five nodes to first internode elongation compared to three nodes in pitted and hybrid morningglory. Corolla color was white (90%) or white with faint pink veins (10%) in pitted morningglory, lavender (100%) in sharppod morningglory, and varied from pinkish lavender (45%), lavender (38%), white (12%), to white with pink veins (5%) in hybrid morningglory accessions. Pitted, red, and smallflower morningglory corolla diameters were not only smaller, but less variable in size than cypressvine, hybrid, ivyleaf, palmleaf, purple moonflower, and sharppod morningglories. Corolla diameter and lengths were most variable in sharppod morningglory accessions when compared to other morningglory accessions. The sepal tip shape was broader (broadly acute to obtuse) in palmleaf and sharppod than in hybrid, pitted, or other morningglories (acute to narrowly acute). In future studies, these morphological traits will be compared to determine if any are correlated with glyphosate sensitivity.

Comparisons Between X-ray Film- and Phosphorescence Imaging-Based Autoradiography for the Visualization of Herbicide Translocation

Autoradiography is a radioisotope-based technique that allows absorbed and translocated herbicide to be visualized. Autoradiographs are traditionally produced with X-ray film and exposure times of several weeks. Phosphorescence imaging (PI) was investigated as an alternative autoradiography procedure. Smallflower morningglory plants were root-exposed to a series of14C-atrazine concentrations, producing a series of increasing foliar radioactivity concentrations (i.e., dosage) that ranged from marginal to excessive with respect to autoradiography. Autoradiographs were subsequently produced from these14C-atrazine-dosed plants using both the X-ray film and the PI technique. Autoradiographs from both techniques were of excellent quality and nearly identical when the dosage was ∼20 to 70 Bq/mg. However, PI produces an acceptable image in dosages either above or below this optimum range. A 1-d exposure time was sufficient with PI, and longer exposure times were not detrimental to image quality. In contrast, a 3-wk exposure time was required with X-ray film. Autoradiographs of selected herbicides are presented to further demonstrate the utility of PI.

Seedling Emergence of Smallflower Morningglory and Green Foxtail Subjected to a Pulsed Electric Field

ABSTRACT Non-chemical approaches to weed control as possible methyl bromide alternatives, or for organic production, are needed in vegetable production. Effects of pulsed electric fields generated by a DC breakdown event and from a Blunlein transmission line type generator were tested to ascertain their effects on seedling emergence of Smallflower Morningglory [Jacquemontia tamnifolia(L.) Briseb.] and Green Foxtail [Setaria viridis(L.) Beauv.]. Seeds were air-dried and exposed to single and repetitive pulsed electric fields. To determine the effect of these systems the parameters of the pulsed system such as duration, rise/ fall time, repetition rate, and field strength, were tested. The DC breakdown results indicated a decrease in percent seedling emergence for Green Foxtail and an increase in seedling emergence for Smallflower Morningglory. A replicated study was conducted with a 50 ns pulse generator with an average of 59 kV output. The pulsed electric field method caused a small increase in seedling emergence from air-dried seed of Smallflower Morningglory, possibly due to disruption of the hard seed coat of this species. A better understanding of the application of a pulsed electric field may lead to a method for non-chemical weed control.

Weed Control in Cotton (Gossypium hirsutum) with Postemergence Applications of Trifloxysulfuron-sodium

Experiments were conducted in Florida from 1998 through 2000 to evaluate trifloxysulfuron-sodium applied POST for weed control in cotton. The addition of 0.25% (v/v) nonionic surfactant (NIS) to trifloxysulfuron-sodium, regardless of rate, increased sicklepod control 10 to 50% 6 and 19 wk after planting (WAP). All trifloxysulfuron-sodium treatments controlled Florida beggarweed and redweed 70 to 100% 6 and 19 WAP. Pitted morningglory was controlled 68 to 100% by trifloxysulfuron-sodium treatments; however, control was higher for treatments that contained 0.25% v/v NIS. Trifloxysulfuron-sodium provided poor control of smallflower morningglory. A sequential application of fluometuron PRE followed by trifloxysulfuron-sodium POST provided better control of smallflower morningglory than trifloxysulfuron-sodium alone 19 WAP. Cotton treated with trifloxysulfuron-sodium yielded higher than the nontreated check and early POST treatments that included 0.25% v/v NIS yielded approximately 20% higher than non-NIS treatments. Trifloxysulfuron-sodium applied POST provided season-long control of Florida beggarweed, pitted morningglory, redweed, and sicklepod with the addition of 0.25% v/v NIS but did not control smallflower morningglory in cotton.

Residual Herbicide Weed Control Systems in Peanut

Field studies were conducted to evaluate residual herbicides applied alone and with a contact weed control program in peanut in Georgia and Alabama. Residual herbicide treatments included pendimethalin preemergence (PRE) at 924 g ai/ha, diclosulam PRE at 18 and 26 g ai/ha, flumioxazin PRE at 70 and 104 g ai/ha, sulfentrazone PRE at 168 and 280 g ai/ha, and imazapic postemergence (POST) at 71 g ai/ha. All herbicides were applied alone and in combination with an early postemergence (EPOST) application of paraquat plus bentazon. Peanut injury ranged from 0 to 7% for diclosulam, from 0 to 28% for flumioxazin, from 0 to 59% for sulfentrazone, from 0 to 15% for imazapic, and from 4 to 12% for paraquat plus bentazon. Across locations and years, Florida beggarweed control was 92% or greater with flumioxazin PRE at 104 g/ha, 77% or greater with diclosulam PRE at 26 g/ha, 80% or greater with sulfentrazone PRE at 280 g/ha, ranged from 54 to 86% for imazapic POST, and was 68% or less for paraquat plus bentazon EPOST. For diclosulam, sulfentrazone, and imazapic, including paraquat plus bentazon EPOST improved Florida beggarweed control vs. these treatments alone. However, flumioxazin alone provided consistent and season-long Florida beggarweed control without paraquat plus bentazon EPOST. Sicklepod control with imazapic was consistently greater than 90%, but it was 70% or less with diclosulam, flumioxazin, and sulfentrazone. Paraquat plus bentazon EPOST used with the residual herbicide treatments resulted in variable sicklepod control ranging from 40 to 99%. Yellow nutsedge control was 95% or greater with sulfentrazone, varied from 56 to 93% with diclosulam, and was 87% or greater with imazapic. Tall and smallflower morningglory, wild poinsettia, Palmer amaranth, and bristly starbur control varied by residual herbicide treatment. Yields were similar for diclosulam, flumioxazin, sulfentrazone, and imazapic treated peanut.

Myrothecium verrucaria for Control of Annual Morningglories in Sugarcane1

Conidia of Myrothecium verrucaria, sprayed in an aqueous phase–paraffinic crop oil emulsion (1:1 v/v) at 470 L/ha, controlled red, ivyleaf, smallflower, and tall morningglory plants (three- to five-leaf stage) by causing severe necrotic injury to leaves and stems. Conidia were not efficacious if applied in an aqueous carrier without oil. When applied in the field as directed postemergence treatments to sugarcane, a concentration of 4 × 108 conidia/ml generally provided > 90% death of morningglory, comparable with the atrazine standard at 2.2 kg ai/ha, and did not cause significant crop injury. Conidia produced on potato dextrose agar or rice flour slurry were about equally effective. When killed by autoclaving, conidia continued to be efficacious, indicating that the symptoms produced by the fungus were not primarily caused by infection. A high performance liquid chromatography analysis of filtrates from the fungal growth media or of harvested conidia showed the presence of several macrocyclic trichothecenes (MT), some known to be phytotoxins. These included verrucarin A and H, roridin A and H, and isororidin E for filtrates and verrucarin A and roridin A for conidia. However, only trace amounts of MT were detected in leaves of treated morningglory plants at 24 h after treatment and none at 48 and 96 h even though the fungus was isolated from leaves up to 14 d after treatment. Further study is needed to identify the causal agents responsible for the phytotoxicity produced by M. verrucaria and to assess potential of this organism as a mycoherbicide.Nomenclature: Atrazine; Myrothecium verrucaria (Albertini & Schwein.) Ditmar:Fr.; ivyleaf morningglory, Ipomea hederacea (Jacq.) #3 IPOHE; red morningglory, Ipomea coccinea (L.) # IPOCC; smallflower morningglory, Jacquemontia tamnifolia (L.) Griseb. # IAQTA; tall morningglory, Ipomea purpurea (L.) Roth # PHBPU; sugarcane, Saccharum sp. hybrids ‘CP 72-370’.Additional index words: Biological weed control, macrocyclic, mycoherbicide, mycotoxins, trichothecenes.Abbreviations: DAT, days after treatment; HPLC, high performance liquid chromatography; IE, invert emulsion (water-in-oil); IPA, isopropyl alcohol; MT, macrocyclic trichothecenes; PDA, potato dextrose agar; POST, postemergence; RF, rice flour; SE, standard emulsion (oil-in-water); SIL, organosilicone surfactant; ST, sucrose–Tween 80 solution.

Residual Weed Control with Imazapic, Diclosulam, and Flumioxazin in Southeastern Peanut (Arachis hypogaea)

Abstract Imazapic, diclosulam, and flumioxazin have been registered for use in peanut since 1996. These herbicides provide substantial residual control of broadleaf weeds in peanut. A comprehensive review was conducted for these residual herbicides to determine their role in future weed control systems in peanuts. Weed control data for research from over 100 experiments conducted from 1990–2000 by Georgia, Florida, and Auburn Universities and USDA-ARS scientists were compiled. Residual herbicide systems evaluated were imazapic postemergence (POST) at 71 g ai/ha, flumioxazin preemergence (PRE) at 70, 87, and 104 g ai/ha, diclosulam preplant incorporated (PPI) and PRE at 18 and 26 g ai/ha, and paraquat plus bentazon early POST (EPOST). Other treatments included the residual herbicides used in combination with paraquat plus bentazon EPOST, for a total of 17 treatments. Regionally important weeds were selected and included: sicklepod, Florida beggarweed, purple and yellow nut-sedge, Ipomoea morningglory species, and smallflower morningglory. Sicklepod control with imazapic alone was 86% (50 tests), 73% (25 tests) with paraquat plus bentazon, and 63% or less with diclosulam and flumioxazin regardless of rate. Florida beggarweed control was 90% (29 tests) with flumioxazin (104 g/ha PRE); 78% (50 tests) with diclosulam 26 g/ha PPI; 72% (72 tests) with imazapic; and 70% (40 tests) with paraquat plus bentazon. Purple and yellow nutsedge control was 90% with imazapic. Yellow nutsedge control was 78% (18 tests) with diclosulam (26 g/ha PRE) and less than 69% with flumioxazin and paraquat plus bentazon. Paraquat plus bentazon increased weed control over residual herbicides alone.

Influence of Flumioxazin Rate and Herbicide Combinations on Weed Control in Peanut (Arachis hypogaea L.)

Abstract Field studies were conducted during 1997 and 1998 at three different locations in Georgia to determine peanut and weed response to pendimethalin at 1.1 kg ai/ha applied preplantincorporated (PPI) followed by flumioxazin at 71, 87, and 105 g ai/ha applied preemergence (PRE). Other residual treatments combinations with pendimethalin PPI included flumioxazin mixed with metolachlor or dimethenamid PRE, diclosulam PRE, norflurazon PRE, and imazapic applied postemergence (POST). Herbicide combinations that included flumioxazin controlled Florida beggarweed, tropic croton, and small flower morningglory at least 78% or greater. Late season Florida beggarweed control was 90% or greater with pendimethalin PPI plus flumioxazin at 87 to 105 g/ha applied PRE. Pendimethalin plus flumioxazin did not control sicklepod or yellow nutsedge. Smallflower morningglory control with all herbicide treatments was 90% or greater. Entireleaf morningglory control (when used in combination with pendimethalin PPI) increased from 80% with flumioxazin at 105 g/ha to 90% for flumioxazin in combination with metolachlor. Yields were similar for flumioxazin, norflurazon, imazapic, and diclosulam treated peanut.

Herbicide efficacy, leaf structure, and spray droplet contact angle amongIpomoeaspecies and smallflower morningglory

Abstract Greenhouse and laboratory studies were conducted to evaluate responses of ivyleaf morningglory, pitted morningglory, palmleaf morningglory, and smallflower morningglory to several herbicides in relation to leaf structure, epicuticular wax, and spray droplet behavior. Two- to four-leaf stage plants of each species were highly susceptible to acifluorfen, bentazon, bromoxynil, glufosinate, and glyphosate. However, at the five- to eight-leaf stage, these species were less susceptible, and control was herbicide specific. Spray droplets of these five herbicides had a higher contact angle on ivyleaf morningglory than the other three species with a few exceptions. Stomata and glands were present on both adaxial and abaxial leaf surfaces of all species, and palmleaf morningglory and smallflower morningglory had more of these than did the other two species. Trichomes were present on all species except palmleaf morningglory. Epicuticular wax mass was highest in ivyleaf morningglory (57 μg cm−2) and lowest i...

Effect of Pyridate Formulation and Adjuvants on Broadleaf Weed Control in Peanut (Arachis hypogaea)1

Field studies were conducted near Archer, FL, and Vienna, GA, in 1995 and 1996 to investigate the effects of pyridate formulation and adjuvants on broadleaf weed control in peanut (Arachis hypogaea). Pyridate formulations SAN 319H 450EC 361LZ, SAN 319H 450EC 216LZ, and SAN 319H 600EC 418LZ were evaluated at two rates, 1.07 and 2.14 kg/ha. Pyridate at 1.07 kg/ha plus 2,4-DB at 0.23 kg/ha were evaluated alone and with five adjuvants. The adjuvants included a crop oil concentrate, a nonionic surfactant, a nonionic surfactant with organosilicone blend, urea ammonium nitrate plus a nonionic surfactant, and chlorothalonil (a fungicide) plus a nonionic surfactant. No pyridate treatment injured peanut. Pyridate formulation did not affect broadleaf weed control. Increasing pyridate rate increased weed control and yield. Mixing 2,4-DB with pyridate generally enhanced sicklepod (Senna obtusifolia) and common cocklebur (Xanthium strumarium) control. Florida beggarweed (Desmodium tortuosum), smallflower morningglory (Jacquemontia tamnifolia), hairy indigo (Indigofera hirsuta), sicklepod, and common cocklebur control with pyridate was not enhanced by adjuvants. Adding chlorothalonil to pyridate plus 2,4-DB did not affect weed control or peanut injury.Nomenclature: 2,4-DB; chlorothalonil; tetrachloroisophthalonitrile; pyridate; common cocklebur, Xanthium strumarium #3 XANST; Florida beggarweed, Desmodium tortuosum # DEDTO; hairy indigo, Indigofera hirsuta # INDHI; peanut, Arachis hypogaea ‘Sunrunner’ and ‘GK-7’; sicklepod, Senna obtusifolia # CASOB; smallflower morningglory, Jacquemontia tamnifolia # IAQTA.Additional index words: SAN 319H 450EC 361LZ, SAN 319H 450EC 216LZ, SAN 319H 600EC 418LZ, crop oil concentrate, nonionic surfactant, organosilicone-nonionic surfactant blend, urea ammonium nitrate.Abbreviations: COC, crop oil concentrate; NIS, nonionic surfactant; NIS/OS, nonionic surfactant with organosilicone; POST, postemergence; WAT, weeks after treatment.

Weed management in bromoxynil-resistantGossypium hirsutum

An experiment was conducted at two locations in Georgia and two locations in North Carolina during 1994 and 1995 to evaluate weed management in conventional-tillage bromoxynil-resistantGossypium hirsutumL. (cotton). The weed management systems evaluated included different combinations of fluometuron preemergence (PRE), bromoxynil or bromoxynil plus MSMA early postemergence (EPOST), bromoxynil postemergence (POST), and cyanazine plus MSMA late post-directed (LAYBY). Fluometuron PRE improved control ofAcanthospermum hisptdiumDC. (bristly starbur),Cassia occidentalisL. (coffee senna),Chenopodium albumL. (common lambsquarters),Desmodium tortuosum(Sw.) DC. (Florida beggarweed),Sida spinosaL. (prickly sida),Jacquemontia tamnifolia(L.) Griseb. (smallflower morningglory), andAnoda cristata(L.) Schlecht. (spurred anoda), compared to system that did not use fluometuron PRE. It also improvedG. hirsutumyields at three four locations. Bromoxynil-containing systems provided better weed control and higherG. hirsutumyields than systems without bromoxynil. Bromoxynil EPOST controlledA. hispidium, C. occidentalis, C. album, D. tortuosum, S. spinosa, J. tamnifolia, andA. cristata.Control of these species was frequently improved by a second application of bromoxynil POST. Bromoxynil EPOST, POST, or EPOST plus POST did not controlSenna obtusifolia(L.) Irwin and Barneby (sicklepod), but the addition of MSMA to bromoxynil EPOST improvedS. obtusifoliacontrol. Control of all dicotyledonous weeds was improved by a LAYBY treatment of cyanazine plus MSMA, and yields were improved at three of four locations with this treatment.Gossypium hirsutumwas not injured by POST treatments of bromoxynil, and only temporary injury resulted from POST treatments of MSMA.

Polymeric microcapsules of alachlor and metolachlor: preparation and evaluation of controlled-release properties.

The microencapsulation of alachlor and metolachlor in the polymers cellulose acetate butyrate, ethyl cellulose, poly(methyl methacrylate), and poly(alpha-methylstyrene) with different emulsifiers is described. The controlled-release properties of these formulations were measured under greenhouse conditions on barnyardgrass, crowfootgrass, smallflower morningglory, and Palmer amaranth. The emulsifiers had little effect on the activity of the herbicides. The herbicidal activities of the poly(methyl methacrylate) and poly(alpha-methylstyrene) formulations were consistently lower on all weed species when compared to the activities of the cellulose acetate butyrate, ethyl cellulose, and commercial formulations. The ethyl cellulose formulation of alachlor exhibited controlled-release properties. The results with metolachlor were similar to those with alachlor except that none of the metolachlor formulations exhibited efficacy superior to that of the commercial formulation or controlled release properties.