Weeks After Treatment Research Articles

Effect of turfgrass care products on soil biological health, disease suppression, and turfgrass quality

Despite the wide use of turfgrass care products such as wetting agents (WAs), plant growth regulators (PGRs), and biological products (BPs), little is known about their effect on soil biological health, turfgrass quality, and disease suppression. Studies were conducted to evaluate the effect of some commonly used turfgrass care products on soil biological health, dollar spot suppression, and turfgrass quality. The turfgrass care products were: nine WAs (Vivax, Fleet, Magnus, Cascade, Dispatch, Duplex, Pervade, Sixteen90, and Revolution); four PGRs (Anuew, Trimmit, Proxy, and Cutless) and; three BPs (Plant Helper, KaPreRemeD8-NSL, and KaPreRemeD8-NSP). Potted bentgrass (Agrotis stolonifera L.) were treated independently with the WAs, PGRs, and BPs, and deionized water was used as a control. Soil samples were collected from the pots at 7 and 14 weeks after treatment (WAT) and analyzed for soil biological health using soil respiration, urease, and phosphatase activities as indicators. Disease suppression was evaluated by inoculating potted bentgrass with an isolate of Clarireedia jacksonii, the causal agent of dollar spot of cool season grasses and the infection was visually assessed at intervals of 10 days. The WAs Dispatch, Fleet, Magnus, and Vivax stimulated rate of soil respiration at 7 WAT compared to the control. The PGRs Cutless, Trimmit, and Proxy had no effect on soil respiration whereas Anuew suppressed soil respiration. Turfgrass quality was improved by the WAs Revolution, Cascade, Pervade, Duplex, and Sixteen90 at 7 WAT, but none of the PGRs and BPs improved turf quality. Cascade stimulated phosphatase activity and was the only product to impact this indicator. None of the products had a significant effect on dollar spot suppression. These results could guide turfgrass growers and professionals in making decisions that enhance the quality of turfgrass without compromising the health of the soil that sustains it.

Response of Tahitian Bridal Veil (Gibasis pellucida) and Small-Leaf Spiderwort (Tradescantia fluminensis) to Postemergence Herbicides under Greenhouse Conditions.

Tahitian bridal veil (Gibasis pellucida) and small-leaf spiderwort (Tradescantia fluminensis) are both invasive species in natural areas throughout Florida. However, very little is known regarding herbicide control. To provide land managers with herbicidal control options for both species, postemergence herbicides were evaluated for efficacy in a greenhouse to identify herbicide options that control both species under similar settings. Four herbicides, including triclopyr acid, triclopyr amine + 2,4-D amine, triclopyr amine, and glufosinate were applied at standard label rates and compared to a non-treated control group for efficacy. Visual control ratings were taken at 2, 4, and 8 weeks after treatment (WAT), and shoot dry weights (WAT 8) and regrowth dry weights (WAT 12) were determined. Triclopyr (acid and amine) generally provided the most consistent control of both species as evidenced by the visual control ratings and shoot dry weight data which showed reductions of 76% to 89% in shoot biomass at trial conclusion. Triclopyr + 2,4-D reduced shoot dry weights by 52% to 54% and was the least effective when considering the control of both species.

Metabolome and Transcriptome Analysis Revealed the Pivotal Role of Exogenous Melatonin in Enhancing Salt Tolerance in Vitis vinifera L.

Vitis vinifera L. possesses high economic value, but its growth and yield are seriously affected by salt stress. Though melatonin (MT) has been widely reported to enhance tolerance towards abiotic stresses in plants, the regulatory role melatonin plays in resisting salt tolerance in grapevines has scarcely been studied. Here, we observed the phenotypes under the treatment of different melatonin concentrations, and then transcriptome and metabolome analyses were performed. A total of 457 metabolites were detected in CK- and MT-treated cell cultures at 1 WAT (week after treatment) and 4 WATs. Exogenous melatonin treatment significantly increased the endogenous melatonin content while down-regulating the flavonoid content. To be specific, the melatonin content was obviously up-regulated, while the contents of more than a dozen flavonoids were down-regulated. Auxin response genes and melatonin synthesis-related genes were regulated by the exogenous melatonin treatment. WGCNA (weighted gene coexpression network analysis) identified key salt-responsive genes; they were directly or indirectly involved in melatonin synthesis and auxin response. The synergistic effect of salt and melatonin treatment was investigated by transcriptome analysis, providing additional evidence for the stress-alleviating properties of melatonin through auxin-related pathways. The present study explored the impact of exogenous melatonin on grapevines' ability to adapt to salt stress and provided novel insights into enhancing their tolerance to salt stress.

Peanut (Arachis hypogaea L.) response to low‐rate applications of selected herbicides at vegetative and reproductive growth stages

AbstractOff‐target drift of herbicides can seriously reduce peanut (Arachis hypogea L.) growth and yield and is of great concern to growers who will need to manage sensitive crops near new herbicide‐tolerant crops. Field experiments were conducted in 2021 and 2022 with 25% labeled rates of dicamba, glufosinate, glyphosate, lactofen, and paraquat to simulate drift on peanut. The objective was to evaluate the effects of low‐rate application of the herbicides on peanut injury and yield reductions and to determine if unmanned aerial vehicle (UAV) imagery‐based normalized difference vegetation index (NDVI) provides accurate estimation of peanut injury from the herbicides applied at vegetative (V3) and reproductive (R3) growth stages. Peanut suffered greater yield reduction (33%) when exposed to the herbicides at R3 than at V3 growth stage (19%) across all herbicides applied. The order of herbicides that induced yield reductions in peanut was glyphosate > glufosinate = dicamba > paraquat = lactofen. Regardless of exposure timing, NDVI values generated from UAV imagery could not differentiate paraquat or lactofen injury from the weed‐free check. However, NDVI values could differentiate between injured and weed‐free check plants up to 2 and 4 weeks after treatment (WAT) for dicamba at R3 and V3 exposure timing, respectively, up to 4 WAT for glufosinate, and 8 WAT for glyphosate. NDVI from aerial imagery may be helpful to accelerate the detection of injury in large hectarages with greater accuracy compared with visual injury rating, which can be influenced by individual estimation bias.

Impact of reduced rates of tiafenacil at vegetative growth stages on rice growth and yield

Abstract Tiafenacil is a new nonselective protoporphyrinogen IX oxidase–inhibiting herbicide with both grass and broadleaf activity labeled for preplant application to corn, cotton, soybean, and wheat. Early season rice emergence and growth often coincide in the mid-southern United States with applications of preplant herbicides to cotton and soybean, thereby increasing the opportunity for off-target herbicide movement from adjacent fields. Field studies were conducted to identify any deleterious effects of reduced rates of tiafenacil (12.5% to 0.4% of the lowest labeled application rate of 24.64 g ai ha−1) applied to 1- or 3-leaf rice. Visual injury 1 wk after treatment (WAT) for the 1- and 3-leaf growth stages ranged from 50% to 7% and 20% to 2%, respectively, whereas at 2 WAT these respective ranges were 13% to 2%, and no injury was observed. Tiafenacil applied at those rates had no negative season-long effect because observed early season injury was not manifested as a reduction in rice height 2 WAT or rough rice yield. Application of tiafenacil to crops directly adjacent to rice in its early vegetative stages of growth should be avoided because visual injury will occur. When off-target movement does occur, however, the affected rice should be expected to fully recover with no effect on growth or yield, assuming adequate growing conditions and agronomic/pest management are provided.

Alternative Integrated Weed Management Options for Clopyralid-Resistant Common Ragweed

Common ragweed (Ambrosia artemisiifolia L.) is an extremely competitive broadleaved summer annual weed found in Christmas tree production systems within Michigan. Common ragweed has been reported to have resistance to glyphosate, PSII inhibitors, PPO inhibitors, and ALS herbicides. There have been reports from Michigan Christmas tree growers of common ragweed resistance to clopyralid, a synthetic auxin herbicide, in Montcalm County, Michigan. The objective of this study was to test alternative post-emergence herbicide combinations and organic mulch on clopyralid-resistant common ragweed for weed control efficacy. The following two stages of common ragweed were used: stage 1 (6–9 leaves) and stage 2 (12–14 leaves). For common ragweed in stage 1 in 2021 and 2022, as well as stage 2 in 2022, at all evaluation dates, mulch + clopyralid + oxyfluorfen provided the highest level of weed control. For stage 1 in 2022, this treatment combination provided 100% control from 2 weeks after treatment (WAT) and always showed better or equal weed control compared to all the other treatments. The combination of mulch + clopyralid + glyphosate provided 100% control by 2 WAT when plants were treated at stage 2 in 2022. For the plants treated at stage 1 in 2022, many of the treatments reached a fresh weight of 0 g, but in 2021, those same treatments resulted in a fresh weight of around 20 g. Based on fresh weight, the greatest plant growth occurred with glyphosate treatment in 2021 and clopyralid and mulch alone in 2022. This is likely due to common ragweed’s resistance to these herbicides.

Impact of metribuzin dose and water stress on chickpea plant health

Chickpea is an important rotational pulse crop for Saskatchewan field crops. Since 2019, Saskatchewan chickpea production has suffered from a plant health issue following rainfall events around flowering to early podding resulting in apical wilting and eventual branch death. Post-emergence broadleaf weed management in chickpea relies on metribuzin, which can result in variable injury in chickpea. The study objective was to evaluate the effect of metribuzin dose and water stress on chickpea health in the greenhouse. At two weeks after treatment (WAT), chickpea mortality reached 25% for 206 g ai ha−1 (label rate) metribuzin dose and 56% for 413 g ha−1 dose, respectively. Maximum chickpea vegetative chlorosis and necrosis was 81% for the 413 g ha−1 metribuzin treatment and 65% for the 206 g ha−1 treatment. Chickpea longest branch length was reduced from 34 to 26 cm at 8 WAT with the 206 g ha−1 metribuzin treatment. Three weeks of permitting the soil to reach the wilting point and induce symptoms reduced chickpea longest branch length from 38 to 24 cm by 8 WAT. Chickpea pod production was reduced by 75% with the 206 g ha−1 metribuzin treatment and 90% with the water stress regime. Metribuzin at labeled dosing in Saskatchewan induced plant death and considerable vegetative necrosis when evaluated in the greenhouse.

The Physicochemical Properties and Microbial Populations of Nicosulfuron Treated Soil in Yola, Adamawa State, Nigeria

The use of herbicides in the modern system of farming has really help in boosting crop production, this way meeting up with the ever increasing demand for food by the always increasing human population. However, these herbicides have different mode of actions and effect on soil components; and their continued usage has affected the soil microbial communities and other soil components most of which are the non-target. This study, therefore, was focused on evaluating the physicochemical properties and microbial population of nicosulfuron treated soils of Yola, Adamawa State, Nigeria. The study was carried out in both 2021 and 2022 in the Research Farm of the Department of Plant Science, Modibbo Adama University, Yola. The samples of the soil treated with the different concentrations of nicosulfuron were obtained at 0, 2, 4 and 6 Weeks after Treatment (WAT) at the depth between 0-12 cm. The physicochemical properties and the bacterial and fungal populations of the collected soil samples were determined using standard laboratory procedures. The results revealed that the soils treated with the 50, 100, 150 and 200 g/ha concentrations of nicosulfuron had a comparable values for physicochemical (except percentage moisture content, organic carbon and matter and total nitrogen) properties that include: pH, electrical conductivity, Calcium, magnesium and potassium ions, total exchangeable acidity, total exchangeable base, effective cation exchange capacity, percentage base saturation. On the basis of duration of application, however, the nicosulfuron had significant effect on the physicochemical properties with 6 WAT having the highest values for the physicochemical properties compared to other sampling durations. On the bacterial (except the fungal) population, the nicosulfuron also had a significant effect with the treated soils having the lowest populations of both bacteria and fungi. The study therefore, concluded that the duration of application of nicosulfuron have significant effect on physicochemical properties of soil in Yola. On the bacterial and fungal populations of the soil, nicosulfuron also had significant effect.

The Impact of the Addition of Urea Ammonium Nitrate to 2,4-D on the Control of Multiple-Herbicide-Resistant Canada Fleabane

Limited information exists on the impact of the addition of 28% urea ammonium nitrate (UAN) to 2,4-D, applied preplant (PP) to soybean, on the control of multiple-herbicide-resistant (MHR) Canada fleabane. A total of five field experiments were conducted over a two-year period (2020, 2021) in southwestern Ontario to determine if MHR Canada fleabane control with 2,4-D ester applied PP can be improved by adding UAN to the spray solution. Glyphosate + 2,4-D ester applied PP with various rates of UAN caused no soybean injury. The control of MHR Canada fleabane decreased when UAN was added to the spray solution, especially at higher rates evaluated. At 4 weeks after treatment (WAT), the predicted percent UAN concentration in the spray solution that caused a 5, 10, 20, or 50% decrease in MHR Canada fleabane control was 12, 17, 25, and 52%, respectively. At 8 WAT, the predicted percent UAN concentration that caused a 5, 10, 20, or 50% decrease in MHR Canada fleabane control was 10, 13, 18, and 33%, respectively. At 8 WAT, the predicted percent UAN concentration that caused a 5 and 10% increase in MHR Canada fleabane density was 36 and 73%, respectively. At 8 WAT, the predicted percent UAN concentration that caused a 5, 10, 20, or 50% increase in MHR Canada fleabane biomass was 2, 4, 8, and 19%, respectively. The predicted percent UAN concentration that caused a 5, 10, and 20% decrease in soybean yield was 1, 3, and 12%, respectively. This study concludes that the addition of 28% UAN, especially at the higher concentration, to 2,4-D ester reduces control and increases the density and biomass of MHR Canada fleabane.

Evaluation of Amblyseius swirskii Athias-Henriot and Amblyseius andersoni (Chant) (Acari: Phytoseiidae) as biological control agents of Eutetranychus orientalis (Klein) (Acari: Tetranychidae) on citrus

Amblyseius andersoni and Amblyseius swirskii are used to control the citrus pest Eutetranychus orientalis. Field experiments were conducted in Marrakech region for two months (November and December) in 2018 to evaluate the control effect of these predator species releases. In the control of E. orientalis population, Amblyseius andersoni with100 mites/tree reduced the densities under 3 motiles/leaf, while rates of 25 and 50 mites/tree these were maintained between 8.93 and 4.76 motiles per leaves, and between 12.16 and 4.33 eggs per leaves 5 and 6 weeks after treatment (WAT). Nevertheless, Amblyseius swirskii showed moderate performance, especially with 100 mites/tree densities ranged between 3.45 and 3.52 motiles per leaves, and between 14.8 and 9.46 eggs per leaves 5 and 6 WAT. The combination of both predators showed no significant difference to the former results. In summary, the two predators showed the potential to control E. orientalis in Moroccan citrus.

Dichlorvos (2, 2-dichlorovinyl dimethyl phosphate DDVP (SNIPER)) Toxicity on Histological Organs of Wistar Rats Fed on Treated Cowpea Grains (Vigna unguiculata (L.) Walp)

Cowpea is an important grain legume that provides half of the plant protein and is consumed worldwide. The crop is usually affected by pests on the field and in storage which always result in huge losses, hence being controlled by using synthetic pesticides. However, consumption of cowpea grains treated with synthetic pesticides had resulted in bioaccumulation and several health-related problems. Therefore, this study examined the toxic effects of Dichlorvos (DDVP) treated cowpea grains fed to Wistar rats for four weeks. Sixteen male rats weighing 125±20g were used for this experiment. They were randomly divided into four groups of four rats each including the control and acclimatised for one week fed with Standard Feed Ratio (SFR). The DDVP (98% purity) was applied at the rates of 0 (control), 0.23, 0.33, and 0.43mL/kg directly to 1kg cowpea grains of IT 89k-391, respectively. Treated cowpea grains were milled (with a 2 mm sieve) and mixed with SFR and fed to the animals daily for four weeks. Data were collected weeks after treatment (WAT) on feed intake, body weight gain/loss, hematology, and, serum chemistry and analysed using ANOVA at p<0.05, while histopathology was examined. Results showed significant differences (p < 0.05) in all the parameters. There was a reduction in feed intake and body weights progressively in DDVP cowpea treated animals, while the control animals increased. Hematological parameters showed 0.23 mL/kg DDVP recording the highest hemoglobin (g/dl) (17.00±1.16), while the lowest value in white blood cells (1100±5.78 x 103/µL), and 0.43 mL/kg recorded the lowest and highest red blood cells (103/µL) (5.34±0.78) and (8.83±0.23) all between 1 and 4 WAT. Serum parameters revealed Total protein having lowest values (5.22±0.01, 5.13±0.01, 5.18±0.01) from 0.23, 0.33, and 0.43 mL/kg DDVP treated animals. Alkaline phosphate, Aspartate aminotransferase, and Alanine transaminase recorded the highest values from 0.43 and 0.33 mL/kg treatments at 3 and 4 WAT, respectively. Histopathology at 1 to 4 WAT revealed capillary congestion with necrotic changes, severe cell infiltration of interstitial and parenchyma with inflammatory cells in the kidneys of 0.23, and 0.33 mL/kg DDVP cowpea fed animals. On liver organs, 0.23, 0.33, and 0.43 mL/kg treatments showed necrosis, vacuolar degeneration of hepatocytes, and congestion with distinct cysts and granular formation. The central portions of livers were pale and distinct patterns of arrangement in cords were absent. However, the control animals recorded the highest values in the aforementioned parameters with clear and normal liver and kidney organs in the experiment. In this study, varied changes observed on the hematological, serum biochemical, and histopathological parameters at 0.23, 0.33, and 0.43 mL/kg dichlorvos (DDVP) treated cowpea grains could result in impairment of vital organs, hence ill health issues. Continued use of dichlorvos for cowpea grains in preservation should be discouraged to prevent health problems and promote high-quality nutrition and safe food.

Will Certain Adjuvants Improve the Preemergence Activity of Pendimethalin or S-metolachlor?

Aims: To determine weed efficacy when using adjuvants such as Grounded or Spectrum in combination with pendimethalin or S-metolachlor.
 Study Design: Randomized complete-block with 3 replications. 
 Place and Duration of Study: Field studies were conducted during the 2021 growing season near Yoakum (29.2765o N, 97.1238o W) in south-central Texas and near Corpus Christi (27.7817o N, 97.5737o W) along the upper Texas Gulf Coast.
 Methodology: Herbicides were applied preemergence either alone or in combination with Grounded at 2.3 L ha-1 or Spectrum at 0.6 L ha-1 after corn (Zea mays L.) or peanut (Arachis hypogaea L.) were planted at Yoakum and under a non-crop situation at Corpus Christi.
 Results: In corn when evaluated 7 weeks after treatment (WAT), the addition of Grounded to pendimethalin at 1.06 kg ha-1 reduced Palmer amaranth control when compared with pendimethalin alone at the same rate or with the addition of Spectrum. Smellmelon control with pendimethalin at 0.53 kg ha-1 improved with the addition of Grounded over pendimethalin alone. When evaluated 15 WAT, only Texas millet was present in consistent enough populations to evaluate and no differences in control were noted with/without an adjuvant with either pendimethalin or S-metolachlor. In peanut when evaluated 26 and 54 days after treatment (DAT), Texas millet or smellmelon control was not influenced with the use of either Grounded or Spectrum. In the non-cropland study, when evaluated 14 DAT, both Texas millet and Palmer amaranth control was > 97% with all combinations of pendimethalin or S-metolachlor with/without an adjuvant. At the 42 DAT evaluation, again no differences in weed control were noted between the herbicides without an adjuvant and with the addition of Grounded or Spectrum.
 Conclusion: In none of the trials did the addition of either Grounded or Spectrum to either pendimethalin or S-metolachlor consistently improve weed efficacy. Also the length of herbicide persistence was not increased with these adjuvants.

The Effects of Phloem Girdling on Leaf Cell Physiology and Chlorophyll Biosynthesis in Peach Tree

Phloem girdling is used for many fruit trees to promote fruit set and quality. Although many studies showed the pomological and biochemical effects of girdling in fruit trees, there is very little information on how girdling affects cell physiology. The current study aimed to characterize the leaf xylem structure, cortex cell division, and expansion affected by trunk girdling during phloem healing in peach. The experiment was carried out on a two-year-old peach cv. Rich May grafted onto Garnem grown in 10 L pots in greenhouse. The girdling was performed on the trunk end of the May. The leaf samples were collected 1, 2, 3 and 4 weeks after treatment (WAT). The study showed that the girdling decreased tree growth, stomatal conductance and stomatal density. Girdling decreased chlorophyll biosynthesis in peach leaves. Furthermore, girdling treatment increased leaf cell expansion, xylem thickness, and xylem conduit number during two weeks. The results have demonstrated that leaf anatomy changed by girdling during phloem healing.

Sensitivity and Recovery of Tomato Cultivars Following Simulated Drift of Dicamba or 2,4-D

Tomato (Solanum lycopersicum L.) plants are commonly injured by the off-target movement of synthetic auxin herbicides. A greenhouse and a field trial were conducted to determine the relative tolerance of eight fresh market tomato cultivars to drift-simulating rates of dicamba or 2,4-D. Tomato cultivars included ‘BHN 589’, ‘Celebrity’, ‘Florida 91’, ‘Mountain Merit’, ‘Primo Red’, ‘Red Deuce’, ‘Red Morning’, and ‘Skyway’. Dicamba (3,6-dichloro-methoxybenzoic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) were applied at 2.8 g ae ha−1 and 5.3 g ae ha−1-D, respectively. By 14 weeks after treatment (WAT), herbicide-treated plants of each cultivar produced less total and marketable yield than their respective nontreated control in the greenhouse trial. For most cultivars, dicamba-treated plants had less marketable yield than 2,4-D-treated plants in the greenhouse. Herbicide treatments also reduced total and marketable yields of each cultivar when compared with their control in the field study at 14 WAT, except for ‘Mountain Merit’. The severity of yield loss from herbicide treatments was cultivar-dependent. Field-grown ‘Skyway’ plants treated with dicamba produced the lowest marketable yield. In contrast, herbicide-treated plants of ‘Florida 91’ produced high marketable yields in the field, but ‘Red Deuce’ plants receiving 2,4-D were also highly productive. Herbicide residue in fruit sampled the third week of the harvest was nondetectable. Because the type of auxin herbicide drift is often unanticipated, ‘Florida 91’ may be the preferred cultivar for cultivation among those tested to maximize tomato production in the field.

Effect of Biofertilizer Formulation with Addition of Consortium of Microbes and Biosurfactant DEA Palm Olein to Growth of Cacao (Theobroma cacao) Seedling

This study was to examine the response of biofertilizer formulation with the addition of consortium of microbes and biosurfactant DEA palm olein to the growth of cacao seedling. This research used randomized block design in factorial with two factors. The first factor was a biofertilizer formulation with addition of consortium of microbes consisting of seven levels: control; 2.5x107; 5x107; 7.5x107; 10x107; 12.5x107; and 15x107 CFU/mL. The second factor was the addition of biosurfactant DEA palm olein consisting of two levels, which are with and without the biosurfactant DEA palm olein. The result showed that the biofertilizer formulation with the addition of consortium of microbes was significantly affected the cacao height on 4 WAT (week after treatment), the leaf number on 6 and 12 WAT, and also in its root fresh weight parameters. The best level of the first factor was 5x107 CFU/mL. The respond of cacao height on 12 WAT and cacao root dry weight was significant to the addition of biosurfactant DEA palm olein. The best level of the second factor was with the addition of biosurfactant DEA palm olein.

Growth, Fruit Yield and Proximate Composition Responses of Hot Pepper (Capsicum annuum L; Rodo Variety) to Potassium Fertilizer Application at Ado-Ekiti, Nigeria

Potassium (K) fertilizer application, as a component of the improved technologies necessary to maximize crop yield and quality, is often used to correct the plant, soil and environmental factors that limit K availability. The effects of 0, 30, 60 and 90 kg K2O ha-1 were studied on hot pepper (Capsicum annuum L; Atarodovariety) in 2014 and 2015 on the Teaching and Research Farm, Ekiti State University, Ado-Ekiti Nigeria in a Randomized Complete Block Design with four replicates. Each K rate was mixed with 75 kg N and 25 kg P2O5 ha-1 and applied 2 weeks after transplanting 5-week old seedlings spaced 60 cm × 40 cm apart. The data of growth parameters were collected at 2 weeks after treatment (WAT) and fortnightly till 10 WAT, number and weight of ripe fruits and fruit proximate composition. The plant height, number of leaves, leaf area and dry matter increased with age and K rates to highest values at 10 WAT and 90 kg K2O ha-1 in both years. The number of fruits, fruit and seed yield ha-1, fruit size, fruit length and breadth and pericarp thickness increased linearly from the control to the highest values at 90 kg K2O ha-1.The number of fruits and yield at 90 kg K2O ha-1 were 1.253×106, 14.24 t ha-1; and 3.73×106, 14.94 t ha-1 in 2014 and 2015, respectively but the 60 kg K2O ha-1 gave the highest agronomic efficiency. The slight increase in fruit moisture content would not predispose fruits to deterioration while the crude protein and fat, carbohydrate and ash contents, vitamin C and mineral nutrients increased significantly making K application necessary to balance the fertilizer protocol for optimum hot pepper production.

Co-application of thifensulfuron with glyphosate accentuates soybean injury

Three trials (two in 2019 and one in 2020) were completed at the University of Guelph, Huron Research Station near Exeter, ON, to determine if the co-application of thifensulfuron with glyphosate accentuates soybean injury in glyphosate-resistant (GR) soybean. At 1, 2, 4, and 8 weeks after treatment (WAT), thifensulfuron (6 and 12 g a.i.·ha−1 representing the 1× and 2× rate, respectively) applied POST with no adjuvants caused up to 5% soybean injury. The addition of a non-ionic surfactant + UAN to thifensulfuron increased soybean injury to up to 24%. There was no decrease in soybean density, dry biomass, height, and yield, except soybean dry biomass was reduced up to 22% with the addition of adjuvants to thifensulfuron at the 2× rate. Glyphosate (1800 and 3600 g·ha−1 representing the 1× and 2× rate, respectively) applied POST caused no adverse effect on soybean injury parameters evaluated. The co-application of glyphosate + thifensulfuron at the 1× and 2× rates, without additional adjuvants, caused a synergistic increase in soybean injury at 1, 2, 4, and 8 WAT, and a synergistic decrease in dry biomass and height. All other interactions were additive. The co-application of glyphosate + thifensulfuron at the 1× and 2× rates, with additional adjuvants, produced a synergistic increase in injury at 1 (1× and 2× rate), 4 (1× rate), and 8 (1× rate) WAT in soybean. All other interactions were additive.

Evaluation of Chemical Control Methods of Fountain Grass

Fountain grass (Pennisetum alopecuroides) is a common ornamental grass because of its glossy foliage and showy inflorescence. However, there have been reports of populations growing outside of cultivation and demonstrating invasive tendencies. There is limited research of the chemical control of fountain grass in natural areas. The objective of this experiment was to evaluate the impact of glyphosate, sethoxydim, and fluazifop on fountain grass. Treatments consisted of 2250 and 4500 g⋅ha–1 glyphosate, 262.5 and 525 g⋅ha–1 sethoxydim, and 200 and 400 g⋅ha–1 fluazifop; a nontreated control group was also included. The percent herbicide injury was determined visually 1, 3, 4, 6, and 10 weeks after treatment (WAT). Both rates of glyphosate resulted in 100% of the foliage injured by 3 WAT. The application of flauzifop and sethoxydim led to intermediate results ranging from 15% to 23% injury by 6 WAT, with no significant difference between active ingredients or rates. Nontreated control plants exhibited little to no injury throughout the study. Flauzifop, sethoxydim, and glyphosate all caused visible injury to fountain grass. For complete, fast-acting control, glyphosate is recommended. Herbicide control coupled with restorative plantings of native plants can help reduce invasive plant pressure and improve biodiversity of natural areas.

Antitranspirants Partially Mitigate Auxin Herbicide Injury on Tomato Plants

The use of dicamba and 2,4-D products on herbicide-tolerant crops has resulted in numerous cases of off-target movement and injury to sensitive plants, including tomato (Solanum lycopersicon L.). Two greenhouse studies were conducted to determine whether ‘Big Beef’ (‘BB’) or ‘Florida 91’ (‘FL’) tomato plants pretreated with an antitranspirant, including Moisture-Loc (ML) at 100 mL·L−1, TransFilm (TF) at 50 g·L−1, or Wilt-Pruf (WP) at 100 mL·L−1, mitigated injury from synthetic auxin herbicides. Dicamba or 2,4-D was applied at a rate corresponding to 1/200 of the manufacturer’s labeled rate of 0.56 kg ae/ha or 1.06 kg ae/ha, respectively. At 2 weeks after treatment (WAT), plants treated with ML or WP before either herbicide exhibited injury symptoms, but they were always less severe than those treated with the herbicide alone for both cultivars. However, shoot length measurements indicated that none of the antitranspirants consistently provided protection against herbicide injury at 2 WAT. By 12 WAT, ML or WP used before either herbicide increased the number of live reproductive organs compared with dicamba or 2,4-D alone for both cultivars. Floral abortion on tomato plants was also reduced when ML or WP was applied before an herbicide treatment by 12 WAT. Although WP and ML did not provide complete protection against synthetic auxin herbicide injury, the concept of using film-forming barriers may be useful in mitigating some of the short-term effects of drift on plants.

Using Machine Learning and Hyperspectral Images to Assess Damages to Corn Plant Caused by Glyphosate and to Evaluate Recoverability

Glyphosate is the most widely used herbicide in crop production due to the widespread adoption of glyphosate-resistant (GR) crops. However, the spray of glyphosate onto non-target crops from ground or aerial applications can cause severe injury to non-GR corn plants. To evaluate the crop damage of the non-GR corn plants from glyphosate and the recoverability of the damaged plants, we used the hyperspectral imaging (HSI) technique in field experiments with different glyphosate application rates. This study investigated the spectral characteristic of corn plants and assessed the corn plant damage from glyphosate. Based on HSI image analysis, a spectral variation pattern was observed at 1 week after treatment (WAT), 2 WAT, and 3 WAT from the glyphosate-treated non-GR corn plants. It was further found that the corn plants treated with glyphosate rates equal to or higher than 0.5X (X = 0.866 kilograms acid equivalents/hectare (kg ae/ha) represents the recommended spray rate for GR corn) would suffer unrecoverable damage. Using the Jeffries–Matusita distance as the spectral sensitivity criterion, three sensitive bands from the measured spectra were selected to create two spectral indices for crop recoverability differentiation in band ratio and normalization forms, respectively. With the two spectral indices, the corn plants recoverable and unrecoverable from damage were classified with an overall accuracy greater than 95%. Then, three machine learning algorithms (k-nearest neighbors, random forest, and support vector machine) were respectively combined with the successive projections algorithm to create models to relate selected feature spectral bands to glyphosate spray rates. The results indicated that the models achieved reasonable accuracy, especially in the group of recoverable plants. This study illustrated the potential of the hyperspectral imaging technique for evaluating crop damage from herbicides and recoverability of the injured plants using different data analysis and machine learning modeling approaches for practical weed management in crop fields.