To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
There are few data on the profile of those with serious mental illness (SMI) admitted to hospital for physical health reasons.
To compare outcomes for patients with and without an SMI admitted to hospital in England where the primary reason for admission was chronic obstructive pulmonary disease (COPD).
This was a retrospective, observational analysis of the English Hospital Episodes Statistics data-set for the period from 1 April 2018 to 31 March 2019, for patients aged 18–74 years with COPD as the dominant reason for admission. Patient with an SMI (psychosis spectrum disorder, bipolar disorder) were identified.
Data were available for 54 578 patients, of whom 2096 (3.8%) had an SMI. Patients with an SMI were younger, more likely to be female and more likely to live in deprived areas than those without an SMI. The burden of comorbidity was similar between the two groups. After adjusting for covariates, SMI was associated with significantly greater risk of length of stay than the median (odds ratio 1.24, 95% CI 1.12–1.37, P ≤ 0.001) and with 30-day emergency readmission (odds ratio 1.51, 95% confidence interval 1.34–1.69, P ≤ 0.001) but not with in-hospital mortality.
Clinicians should be aware of the potential for poorer outcomes in patients with an SMI even when the SMI is not the primary reason for admission. Collaborative working across mental and physical healthcare provision may facilitate improved outcomes for people with SMI.
In sub-Saharan Africa, there are no validated screening tools for delirium in older adults, despite the known vulnerability of older people to delirium and the associated adverse outcomes. This study aimed to assess the effectiveness of a brief smartphone-based assessment of arousal and attention (DelApp) in the identification of delirium amongst older adults admitted to the medical department of a tertiary referral hospital in Northern Tanzania.
Consecutive admissions were screened using the DelApp during a larger study of delirium prevalence and risk factors. All participants subsequently underwent detailed clinical assessment for delirium by a research doctor. Delirium and dementia were identified against DSM-5 criteria by consensus.
Complete data for 66 individuals were collected of whom 15 (22.7%) had delirium, 24.5% had dementia without delirium, and 10.6% had delirium superimposed on dementia. Sensitivity and specificity of the DelApp for delirium were 0.87 and 0.62, respectively (AUROC 0.77) and 0.88 and 0.73 (AUROC 0.85) for major cognitive impairment (dementia and delirium combined). Lower DelApp score was associated with age, significant visual impairment (<6/60 acuity), illness severity, reduced arousal and DSM-5 delirium on univariable analysis, but on multivariable logistic regression only arousal remained significant.
In this setting, the DelApp performed well in identifying delirium and major cognitive impairment but did not differentiate delirium and dementia. Performance is likely to have been affected by confounders including uncorrected visual impairment and reduced level of arousal without delirium. Negative predictive value was nevertheless high, indicating excellent ‘rule out’ value in this setting.
HIV-associated neurocognitive disorders (HANDs) are prevalent in older people living with HIV (PLWH) worldwide. HAND prevalence and incidence studies of the newly emergent population of combination antiretroviral therapy (cART)-treated older PLWH in sub-Saharan Africa are currently lacking. We aimed to estimate HAND prevalence and incidence using robust measures in stable, cART-treated older adults under long-term follow-up in Tanzania and report cognitive comorbidities.
A systematic sample of consenting HIV-positive adults aged ≥50 years attending routine clinical care at an HIV Care and Treatment Centre during March–May 2016 and followed up March–May 2017.
HAND by consensus panel Frascati criteria based on detailed locally normed low-literacy neuropsychological battery, structured neuropsychiatric clinical assessment, and collateral history. Demographic and etiological factors by self-report and clinical records.
In this cohort (n = 253, 72.3% female, median age 57), HAND prevalence was 47.0% (95% CI 40.9–53.2, n = 119) despite well-managed HIV disease (Mn CD4 516 (98-1719), 95.5% on cART). Of these, 64 (25.3%) were asymptomatic neurocognitive impairment, 46 (18.2%) mild neurocognitive disorder, and 9 (3.6%) HIV-associated dementia. One-year incidence was high (37.2%, 95% CI 25.9 to 51.8), but some reversibility (17.6%, 95% CI 10.0–28.6 n = 16) was observed.
HAND appear highly prevalent in older PLWH in this setting, where demographic profile differs markedly to high-income cohorts, and comorbidities are frequent. Incidence and reversibility also appear high. Future studies should focus on etiologies and potentially reversible factors in this setting.
Application timing and environmental factors reportedly influence the efficacy of auxinic herbicides. In resistance-prone weed species such as Palmer amaranth (Amaranthus palmeri S. Watson), efficacy of auxinic herbicides recently adopted for use in resistant crops is of utmost importance to reduce selection pressure for herbicide-resistance traits. Growth chamber experiments were conducted comparing the interaction of different environmental effects with application time to determine the influence of these factors on visible phytotoxicity and hydrogen peroxide (H2O2) formation in A. palmeri. Temperature displayed a high degree of influence on 2,4-D and dicamba efficacy in general, with applications at the low-temperature treatment (31/20 C day/night) resulting in an increase in phytotoxicity compared with high-temperature treatments (41/30 C day/night). Application time across temperature treatments significantly affected 2,4-D–induced phytotoxicity, resulting in a ≥30% increase across rates with treatments at 4:00 PM compared with 8:00 AM. Temperature differential had a significant influence on dicamba efficacy based on visible phytotoxicity data, with a ≥46% increase with a high (37/20 C day/night) compared with a low differential (41/30 C day/night). Concentration of H2O2 in herbicide-treated plants was 34% higher under a high temperature differential compared with the low differential. Humidity treatments and application time interactions displayed undetected or inconsistent effects on visible phytotoxicity and H2O2 production. Overall, temperature-related influences seem to have the largest environmental effect on auxinic herbicides within conditions evaluated in this study. Leaf concentration of H2O2 appears to be generally correlated with phytotoxicity, providing a potentially useful tool in determining efficacy of auxinic herbicides in field settings.
Despite its long coastline, relatively little is known about mainland China’s intertidal communities compared to Europe and the United States, although more is known from Taiwan and Hong Kong. In general, northern areas are dominated by temperate species, with tropical species in the south and subtropical areas supporting a diversity of species from both regions. Studies of intertidal systems are in their infancy, developing since the 1930s and particularly after the 1960s with a primary focus on taxonomy and distribution patterns. While species lists and distributions have been available for mainland China since the 1930s, and more recently Taiwan and Hong Kong, many of these are outdated and recent approaches reveal many cryptic species complexes. Basic information of spatial and temporal patterns is available, but is focussed on few locations, while larger-scale or temporally replicated studies are rare, with Hong Kong being an exception. As a result, we know a lot about a few small areas, and have often used this to generalise much larger areas. This bias is even more true for studies investigating intertidal processes. Clearly, this is an under-studied region and, given the unprecedented anthropogenic pressures it faces, we may already be documenting a highly degraded intertidal system.
The number of people living with dementia in sub-Saharan Africa (SSA) is expected to increase rapidly in the coming decades. However, our understanding of how best to reduce dementia risk in the population is very limited. As a first step in developing intervention strategies to manage dementia risk in this setting, we investigated rates of cognitive decline in a rural population in Tanzania and attempted to identify associated factors.
The study was conducted in the rural Hai district of northern Tanzania. In 2014, community-dwelling people aged 65 years and over living in six villages were invited to take part in a cognitive screening program. All participants from four of the six villages were followed-up at two years and cognitive function re-tested. At baseline and follow-up, participants were assessed for functional disability, hypertension, and grip strength (as a measure of frailty). At follow-up, additional assessments of visual acuity, hearing impairment, tobacco and alcohol consumption, and clinical assessment for stroke were completed.
Baseline and follow-up data were available for 327 people. Fifty people had significant cognitive decline at two-year follow-up. Having no formal education, low grip strength at baseline, being female and having depression at follow-up were independently associated with cognitive decline.
This is one of the first studies of cognitive decline conducted in SSA. Rates of decline at two years were relatively high. Future work should focus on identification of specific modifiable risk factors for cognitive decline with a view to developing culturally appropriate interventions.
Vegetable injury and yield loss has occurred when applying halosulfuron to low-density polyethylene mulch (LDPE) prior to transplanting. Research determined vegetable crop response to halosulfuron applied over LDPE mulch from 1 to 28 d prior to transplanting using (1) temperature effects in aqueous solution in laboratory experiments, (2) analytical evaluation of degradation from LDPE under field conditions, and (3) a field bioassay. Halosulfuron stability was evaluated on a thermal gradient table for temperatures at 10 to 42 C for 15 d. Half-life was inversely related to temperatures ranging from 38.5 d at 20 C to 3.2 d at 42 C, with little to no degradation at temperatures of 11 and 15 C. Analytical data indicated that the field half-life of halosulfuron at 26 or 52 g ha−1 applied to LDPE mulch under dry conditions was 2.6 and 2.8 d, respectively. Given the changes in the microclimate effects at the mulch surface by absorption of solar radiation, daily thermal energy quantified halosulfuron degradation (at the same rates) to be 51 and 55 MJ m−2, respectively. At 21 d after treatment (DAT), 90% of halosulfuron had dissipated from the mulch, with none detectable 35 DAT under dry conditions. When watermelon or yellow crookneck squash was transplanted into mulch previously treated with halosulfuron at 79 g ha−1, plant growth and development were equal to nontreated controls as long as there was a 14 d prior to transplant (DPT) interval accompanied by 13.5 cm of rain, or a 17 DPT interval accompanied by 6.2 cm of rain. However, at 79 g ha−1 applied at 9 or 1 DPT in 2013, and 1 DPT in 2014, halosulfuron injured yellow squash and reduced yield and fruit number. Halosulfuron at 79 g ha−1 applied 1 DPT significantly reduced watermelon yield in 2013, which was confirmed by vine length and plant biomass reductions in 2014. Halosulfuron POST controls Cyperus spp. in mulch vegetable production, but time and rainfall are required for dissipation to occur in order to prevent injury and yield loss.
The efficacy of WSSA Group 4 herbicides has been reported to vary with dependence on the time of day the application is made, which may affect the value of this mechanism of action as a control option and resistance management tool for Palmer amaranth. The objectives of this research were to evaluate the effect of time of day for application on 2,4-D and dicamba translocation and whether or not altering translocation affected any existing variation in phytotoxicity seen across application time of day. Maximum translocation (Tmax) of [14C]2,4-D and [14C]dicamba out of the treated leaf was significantly increased 52% and 29% to 34% in one of two repeated experiments for each herbicide, respectively, with application at 7:00 AM compared with applications at 2:00 PM and/or 12:00 AM. Applications at 7:00 AM increased [14C]2,4-D distribution to roots and increased [14C]dicamba distribution above the treated leaf compared with other application timings. In phytotoxicity experiments, dicamba application at 8 h after exposure to darkness (HAED) resulted in significantly lower dry root biomass than dicamba application at 8 h after exposure to light (HAEL). Contrasts indicated that injury resulting from dicamba application at 8 HAEL, corresponding to midday, was significantly reduced with a root treatment of 5-[N-(3,4-dimethoxyphenylethyl)methylamino]-2-(3,4-dimethoxyphenyl)-2-isopropylvaleronitrile hydrochloride (verapamil) compared with injury observed with dicamba application and a root treatment of verapamil at 8 HAED, which corresponded to dawn. Overall, time of application appears to potentially influence translocation of 2,4-D and dicamba. Furthermore, inhibition of translocation appears to somewhat influence variation in phytotoxicity across times of application. Therefore, translocation may be involved in the varying efficacy of WSSA Group 4 herbicides due to application time of day, which has implications for the use of this mechanism of action for effective control and resistance management of Palmer amaranth.
In the above article (Paddick, 2017) The corresponding author's details were previously listed incorrectly. The correct details are; contact number +44 191 293 2709 and email address William.email@example.com. The original article has been updated with the correct contact details. The publishers apologise for any inconvenience and confusion this error has caused.
The majority of older adults with dementia live in low- and middle-income countries (LMICs). Illiteracy and low educational background are common in older LMIC populations, particularly in rural areas, and cognitive screening tools developed for this setting must reflect this. This study aimed to review published validation studies of cognitive screening tools for dementia in low-literacy settings in order to determine the most appropriate tools for use.
A systematic search of major databases was conducted according to PRISMA guidelines. Validation studies of brief cognitive screening tests including illiterate participants or those with elementary education were eligible. Studies were quality assessed using the QUADAS-2 tool. Good or fair quality studies were included in a bivariate random-effects meta-analysis and a hierarchical summary receiver operating characteristic (HSROC) curve constructed.
Forty-five eligible studies were quality assessed. A significant proportion utilized a case–control design, resulting in spectrum bias. The area under the ROC (AUROC) curve was 0.937 for community/low prevalence studies, 0.881 for clinic based/higher prevalence studies, and 0.869 for illiterate populations. For the Mini-Mental State Examination (MMSE) (and adaptations), the AUROC curve was 0.853.
Numerous tools for assessment of cognitive impairment in low-literacy settings have been developed, and tools developed for use in high-income countries have also been validated in low-literacy settings. Most tools have been inadequately validated, with only MMSE, cognitive abilities screening instrument (CASI), Eurotest, and Fototest having more than one published good or fair quality study in an illiterate or low-literate setting. At present no screening test can be recommended.
Cognitive stimulation therapy (CST) is a psychosocial group-based intervention for dementia shown to improve cognition and quality of life with a similar efficacy to cholinesterase inhibitors. Since CST can be delivered by non-specialist healthcare workers, it has potential for use in low-resource environments, such as sub-Saharan Africa (SSA). We aimed to assess the feasibility and clinical effectiveness of CST in rural Tanzania using a stepped-wedge design.
Participants and their carers were recruited through a community dementia screening program. Inclusion criteria were DSM-IV diagnosis of dementia of mild/moderate severity following detailed assessment. No participant had a previous diagnosis of dementia and none were taking a cholinesterase inhibitor. Primary outcomes related to the feasibility of conducting CST in this setting. Key clinical outcomes were changes in quality of life and cognition. The assessing team was blind to treatment group membership.
Thirty four participants with mild/moderate dementia were allocated to four CST groups. Attendance rates were high (85%) and we were able to complete all 14 sessions for each group within the seven week timeframe. Substantial improvements in cognition, anxiety, and behavioral symptoms were noted following CST, with smaller improvements in quality of life measures. The number needed to treat was two for a four-point cognitive (adapted Alzheimer's Disease Assessment Scale-Cognitive) improvement.
This intervention has the potential to be low-cost, sustainable, and adaptable to other settings across SSA, particularly if it can be delivered by non-specialist health workers.
Field studies were conducted to examine the dissipation of three soil-applied residual herbicides for bare soil compared with soil under low-density polyethylene (LDPE) mulch in 2003 and 2004. Studies indicated that halosulfuron and S-metolachlor dissipation was more rapid for bare soil than soil under LDPE mulch. Sulfentrazone dissipation from bare soil was equal to soil under LDPE mulch in 2003. However, sulfentrazone dissipation in 2004 was more rapid for soil under LDPE mulch than for bare soil. The order for half-life, defined as time for 50% dissipation (DT50), varied by herbicide and soil exposure. Averaged across 2003 and 2004, metolachlor DT50 was 2 d, halosulfuron 7 d, and sulfentrazone 16 d for bare soil. S-metolachlor DT50 was 4 d, halosulfuron 10 d, and sulfentrazone 13 d for soil under LDPE mulch. Correlation between quantified herbicide dissipation and bioassay for bare soil compared with soil under LDPE mulch in 2004 indicated that assay species root dry weights were negatively correlated with herbicide concentration. Data indicated that S-metolachlor and sulfentrazone bioassays, with oat and cotton, respectively, could be used to assess the level of dissipation for each herbicide.
Purple nutsedge is among the most troublesome weeds of vegetables in the
Southeast US and a substantial impediment in the search for methyl bromide
alternatives. Greater understanding of the environmental cues that regulate
tuber sprouting may assist in improved nutsedge management. Experiments were
conducted to evaluate the effect of diurnal temperature variation on
sprouting of purple nutsedge tubers. Two temperature regimes were evaluated:
the first averaged 28 C, with daily fluctuations ranging from 0 to 19.5 C;
the second temperature regime averaged 16 C, with daily fluctuations ranging
from 0 to 18.5 C. When average temperature was 28 C, cumulative tuber
sprouting ranged from 88 to 92%, with no detectable differences among
diurnal fluctuations. The high average temperature in the first study may
have negated any type of enforced sprouting suppression. However, when
average temperature was lowered to 16 C (simulating early spring diurnal
fluctuations under polyethylene mulch), there was a positive linear
correlation between maximum tuber sprouting and temperature variation. With
an average temperature of 16 C, the absence of temperature variation
resulted in 52% purple nutsedge sprouting, while 87% sprouting occurred when
daily temperature varied 18.5 C at the same average temperature. The use of
various types of mulching material can affect average soil temperatures and
diurnal variations, potentially shifting nutsedge emergence. Further studies
are needed to determine if these data on tuber sprouting in response to
alternating temperatures can facilitate more efficient weed management.
A glyphosate-resistant Palmer amaranth biotype was confirmed in central Georgia. In the field, glyphosate applied to 5- to 13-cm-tall Palmer amaranth at three times the normal use rate of 0.84 kg ae ha−1 controlled this biotype only 17%. The biotype was controlled 82% by glyphosate at 12 times the normal use rate. In the greenhouse, I50 values (rate necessary for 50% inhibition) for visual control and shoot fresh weight, expressed as percentage of the nontreated, were 8 and 6.2 times greater, respectively, with the resistant biotype compared with a known glyphosate-susceptible biotype. Glyphosate absorption and translocation and the number of chromosomes did not differ between biotypes. Shikimate was detected in leaf tissue of the susceptible biotype treated with glyphosate but not in the resistant biotype.
A perennial species in its native range of Asia and Africa, Benghal
dayflower in North America establishes annually from seed. This species has
the unique ability to produce aerial and subterranean flowers and seeds.
Information on how various environmental factors affect Benghal dayflower
aerial and subterranean seed germination and emergence in the United States
is lacking. Studies were conducted to determine the effect of temperature,
planting depth, salt concentration, and pre-emergence herbicides on
germination or emergence of aerial and subterranean Benghal dayflower seed.
Maximum aerial seed germination occurred at 30 C, whereas maximum
subterranean seed germination occurred at 30 and 35 C. Germination at 40 C
was delayed relative to optimum temperatures. The seed coats in this study
were mechanically disrupted to evaluate the response of seeds to temperature
in the absence of physical dormancy. The physical dormancy imposed by the
seed coat could require additional study. Benghal dayflower was not tolerant
to ≥ 10 mM NaCl, indicating that this exotic species is not likely to become
problematic in brackish marshes and wetlands of coastal plain regions. There
was an inverse linear response of Benghal dayflower emergence and planting
depth, with no emergence occurring at a planting depth of 12 cm. A field
survey of Benghal dayflower emergence revealed that 42% of plants
established from a depth of 1 cm in the soil profile, with 7 cm being the
maximum depth from which seedlings plants could emerge. This suggests that
PRE herbicides must remain in the relatively shallow depths of the soil
profile to maximize control of germinating seedlings. Subterranean seeds
were less sensitive than aerial seeds to S-metolachlor, the
primary means of controlling this species in cotton. There were no
differences between the germination of aerial and subterranean seed in
response to treatment with diclosulam.
Palmer amaranth resistance to acetolactate synthase (ALS)–inhibiting herbicides was first identified in Georgia in 2000. Since then, complaints from peanut producers have increased concerning failure of ALS herbicides in controlling Palmer amaranth. Because efficacy of ALS herbicides can be compromised under adverse conditions, seeds from Palmer amaranth plants that escaped weed control were collected across the peanut-growing region in Georgia to investigate the cause of these reported failures. Greenhouse and growth-chamber studies were conducted using these seeds to evaluate whether weed escapes were a result of Palmer amaranth resistance to ALS herbicides. Each of the 61 accessions collected across Georgia exhibited varying levels of resistance to imazapic applied POST (< 55% control, relative to ALS-susceptible Palmer amaranth). Subsamples of the accessions were evaluated for their response to imazapic rates, which indicated variable levels of resistance across Palmer amaranth accessions. The rate of imazapic that provided 50% reduction in Palmer amaranth plant biomass (I50) for the known susceptible biotype was 0.9 g/ha of imazapic. Of the 10 accessions evaluated, 8 of them had I50 values that ranged from 3 to 297 g/ha of imazapic. The other two accessions could not be fit to the log-logistic dose–response curve and had undeterminable I50 values because of high levels of ALS resistance (> 1,400 g/ha of imazapic). Herbicide cross-resistance experiments indicated that 30 accessions were resistant to the ALS herbicides imazapic, chlorimuron, pyrithiobac, and diclosulam at the recommended field-use rates. However, each of these 30 accessions was susceptible to glyphosate. These data demonstrate that ALS-resistant Palmer amaranth occurs throughout the peanut-growing region of Georgia. Growers in Georgia will need to alter their weed-control programs in peanut to include herbicides with multiple modes of action that do not rely on ALS herbicides for effective Palmer amaranth control.
To date, there have been no reports of Dalmatian toadflax serving as a host for cucumber mosaic virus (CMV). Infestations of Dalmatian toadflax may serve as a reservoir of CMV, thereby facilitating aphid transmission of CMV to both agricultural crops and native plants. The goal of this study was to determine whether Dalmatian toadflax is a host for CMV. Dalmatian toadflax seedlings were randomly assigned to two treatments (18 replicates/treatment): no inoculation (control) and inoculation with CMV (Fast New York strain). The Dalmatian toadflax seedlings were inoculated by standard mechanical methods and tested for the presence of CMV using enzyme-linked immunosorbent assay (ELISA). Ten of the 18 CMV-inoculated toadflax plants tested positive for the virus; 6 of the 18 displayed systemic mosaic chlorosis and leaf curling. All control plants tested negative. Transmission electron microscopy obtained from CMV-positive plants confirmed the presence of CMV based on physical properties. To verify CMV infestation, tobacco plants were assigned to the following treatments (six replicates/treatment): no inoculation (control), CMV-negative (control) inoculation, and a CMV-positive inoculation. Plants were inoculated by standard methods. Five of the 6 tobacco plants treated with the CMV-positive inoculum tested positive for CMV using ELISA. All control plants tested negative for the virus.
Flumioxazin is a protoporphyrinogen oxidase inhibitor with potential for POST annual bluegrass control and PRE smooth crabgrass control in bermudagrass. However, flumioxazin applications are often less effective in winter, compared with fall, because of reduced efficacy on mature annual bluegrass. The objective of this research was to evaluate tank-mixtures of flumioxazin with six other herbicide mechanisms of action for POST annual bluegrass control in late winter and residual smooth crabgrass control. Flumioxazin at 0 or 0.42 kg ai ha−1 was evaluated in combination with flazasulfuron at 0.05 kg ai ha−1, glufosinate at 1.26 kg ai ha−1, glyphosate at 0.42 kg ae ha−1, mesotrione at 0.28 kg ai ha−1, pronamide at 1.68 kg ai ha−1, or simazine at 1.12 kg ai ha−1. Flumioxazin alone controlled annual bluegrass 61 to 70% at 8 wk after treatment (WAT) in three experiments from 2012 to 2014 in central Georgia. Flumioxazin tank-mixed with flazasulfuron, glyphosate, glufosinate, pronamide, and simazine provided good (80 to 89%) to excellent (> 90%) control of annual bluegrass at 8 WAT in 2 of 3 yr. These tank-mixtures were also more effective than flumioxazin alone in 2 of 3 yr, and control was greater or equal to the tank-mix partners applied alone. Treatments that included flumioxazin provided excellent (≥ 90%) control of smooth crabgrass at 6 mo after treatment in all 3 yr. Overall, tank-mixing flumioxazin with other herbicide chemistries may improve POST annual bluegrass control, compared with exclusive treatments, and effectively control smooth crabgrass in bermudagrass.
Field and laboratory studies were conducted to examine herbicide dissipation when applied to low density polyethylene (LDPE) mulch for dry scenarios vs. irrigation. Analytical chemical analysis was used for quantification. In field studies, halosulfuron, paraquat, carfentrazone, glyphosate, and flumioxazin were surface applied to black 32-μm-thick (1.25 mil) LDPE mulch. LDPE mulch harvest began 1 h after treatment (HAT) then continued every 24 h for five consecutive rain-free days after treatment (DAT) to determine the level of herbicide dissipation from the LDPE mulch surface. In a related study, treated LDPE mulch was harvested 1 HAT, then sprinkler irrigation was applied, followed by a sampling five HAT, then the same irrigation and sampling procedure was repeated every 24 h for five consecutive DAT. The order for half-life, as defined as time for 50% dissipation (DT50), varied by herbicide and method of dissipation for dry and irrigated studies. Data indicated that glyphosate and paraquat dissipation was rapid following irrigation. Glyphosate and paraquat DT50 were both 1 h in the irrigated study, but 84 and 32 h for the dry scenario, respectively. This indicated that glyphosate and paraquat could be removed from LDPE mulch with rainfall or irrigation, primarily due to their high water solubility. Halosulfuron and flumioxazin DT50 were 3 and 6 h in the irrigated study, and 18 and 57 h for the dry study, respectively. Carfentrazone DT50 was similar at 28 and 30 h for the irrigated and dry studies, respectively. This indicated that carfentrazone was adsorbed to the LDPE mulch, and irrigation water did not remove it from the LDPE mulch. Results from 14C-herbicide laboratory studies were similar to those from field studies for halosulfuron, glyphosate, paraquat, and flumioxazin.
Field and greenhouse experiments were conducted to determine the effect of herbicides on napiergrass growth and control. In greenhouse experiments, hexazinone, glyphosate, and imazapic were applied POST, and carbon dioxide (CO2) assimilation was measured with the use of an open-flow gas-exchange system up to 22 d after treatment (DAT). Carbon dioxide assimilation was reduced to zero, indicating plant death, for hexazinone- and glyphosate-treated napiergrass by 2 and 12 DAT, respectively. Imazapic-treated napiergrass CO2 assimilation declined to a constant rate by 22 DAT, but never reached zero. Field studies at Chula and Ty Ty, Georgia, evaluated herbicides for napiergrass control. Herbicide treatments included autumn-only applications, autumn followed by spring applications, and spring-only applications. All autumn-applied treatments exhibited regrowth in the spring. Plants were not affected by cold winter temperatures. A spade tillage treatment was implemented in January 2010, but was not effective in controlling napiergrass. Spring treatments included split applications of autumn treatments and spring-only treatments of glyphosate, glyphosate plus sethoxydim, and imazapyr. Sequential autumn and spring treatments containing glyphosate at both locations failed to eradicate napiergrass. Imazapyr applied spring achieved 94% plant injury by 34 DAT, and indicated potential napiergrass control. Greenhouse results indicated multiple modes of action could be effective in reducing napiergrass growth, but were inconsistent with field results. Further field studies are needed to derive conclusive methods of napiergrass control.