Mg Of Active Ingredient Research Articles

Effect of quercetin administration on electron microscopic changes in testicular interstitial endocrinocytes during long-term central blockade of luteinising hormone in rats

Quercetin is a flavonoid with potential health benefits and it may help prevent cardiovascular diseases, reduce the risk of degenerative brain processes and cancer, and has antioxidant properties that neutralise free radicals. Substances in this group also have antioxidant properties, which help the body protect itself from the harmful effects of free radicals by neutralising these unstable molecules. Research indicates that the impact of free radicals on cell structure is associated with the development of chronic diseases such as diabetes, cancer, and cardiovascular pathologies. The aim of the study was to investigate the effect of quercetin administration on electron microscopic changes in the interstitial endocrinocytes of the testes under long-term central blockade of the synthesis of luteinising hormone by tryptorelin. The experiment involved 35 sexually mature male white rats. They were divided into two groups: the control group (I) received saline, while group II received subcutaneous injections of tryptorelin at a dose of 0.3 mg of active ingredient per kg of rat body weight to induce experimental central deprivation of luteinising hormone synthesis and additionally, quercetin was administered three times a day by gastric tube in terms of body weight. The study has demonstrated that the administration of tryptorelin results in structural and functional changes in the connective tissue components of rat testes. Specifically, there are quantitative and qualitative disorders in the population of interstitial endocrine cells, as well as electron microscopic changes at the subcellular level. Various pathological changes and abnormalities in the functional activity of the internal components of the cell were detected on days 270 and 365 of the experiment. The frequency, number, and size of Reinke crystals in relation to the cell volume correlated with changes in cells and increased at later stages of the study. A similar correlation with testosterone levels has not been found in the literature, which leads us to classify Reinke crystals as the result of degenerative processes in the cell. Thus, additional administration of quercetin reduces the adverse effect of tryptorelin and delays the onset of changes in the structure of interstitial endocrinocytes from day 180 to later observation periods.

Susceptibility of Bemisia tabaci (Hemiptera: Aleyrodidae) Adult Populations to Imidacloprid in Georgia, USA

Abstract Imidacloprid has been one of the most widely used insecticides for managing the sweetpotato whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in the United States since the U.S. Environmental Protection Agency first registered it in 1994. A major whitefly control failure occurred in the state of Georgia in 2017 when B. tabaci–induced economic losses in horticultural and field crops surpassed approximately US$160 million. Vegetable growers have historically used imidacloprid for whitefly management, which likely led to the insecticide control failures of whiteflies in spring vegetables. Despite this, only a single site documentation of imidacloprid resistance in adults from 2007 in Georgia exists, making the current status unknown. Thus, it is likely that Georgia has an ongoing risk of imidacloprid-resistant B. tabaci infestations. No multicounty, extensive survey for imidacloprid dose response in whitefly exists for the state of Georgia. Therefore, an adult mortality bioassay of a range of imidacloprid concentrations was used to evaluate B. tabaci populations from several counties in South Georgia, where most of these economic losses occurred. This included a maximum dose concentration representing the current highest labeled rate. Dose response to the insecticide was not uniform across locations, with whiteflies in several areas displaying unexpected susceptibility to imidacloprid. Median lethal concentrations (LC50s) ranging from 0.02 to 196.05 mg of active ingredient per liter in Georgia whitefly populations were substantially lower than the reference Florida whitefly population. This baseline information for the state is critical to future evaluations of this insecticide in resistance management programs.

Picarbutrazox Effectiveness Added to a Seed Treatment Mixture for Management of Oomycetes that Impact Soybean in Ohio.

None of the current oomycota fungicides are effective towards all species of Phytophthora, Phytopythium, Globisporangium, and Pythium that affect soybean seed and seedlings in Ohio. Picarbutrazox is a new oomyceticide with a novel mode of action towards oomycete pathogens. Our objectives were to evaluate picarbutrazox to determine (i) baseline sensitivity (EC50) to 189 isolates of 29 species, (ii) the efficacy with a base seed treatment with three cultivars with different levels of resistance in 14 field environments; and (iii) if the rhizosphere microbiome was affected by the addition of the seed treatment on a moderately susceptible cultivar. The mycelial growth of all isolates was inhibited beginning at 0.001 μg, and the EC50 ranged from 0.0013 to 0.0483 μg of active ingredient (a.i.)/ml. The effect of seed treatment was significantly different for plant population and yield in eight of 14 and six of 12 environments, respectively. The addition of picarbutrazox at 1 and 2.5 g of a.i./100 kg seed to the base seed treatment compared to the base alone was associated with higher plant populations and yield in three and one environments, respectively. There was limited impact of the seed treatment mefenoxam 7.5 g of a.i. plus picarbutrazox 1 g of a.i./100 kg seed on the oomycetes detected in the rhizosphere of soybean seedlings collected at the V1 growth stage. Picarbutrazox has efficacy towards a wider range of oomycetes that cause disease on soybean, and this will be another oomyceticide tool to combat early season damping-off in areas where environmental conditions highly favor disease development.

Effects of glyphosate herbicide Roundup® on antioxidant enzymes activity and detoxification-related gene expression in honey bees (Apis mellifera)

Glyphosate (GLY) is a type of broad-spectrum herbicide and has been widely used for weed control. In the past few decades, GLY was generally considered to be low toxic or non-toxic to animals. However, recent studies demonstrated that GLY has adverse effects on honey bees. How honey bees’ internal antioxidant and detoxification system responds to GLY exposure needs to be investigated. In this study, we calculated the median lethal dose (LD50) of GLY in honey bees and evaluate the effect of GLY on detoxification-related gene expression and antioxidant enzyme activities of honey bees. Our results showed that the LD50 of GLY to honey bees at 24 and 48 h were 1773.06 and 537.67 µg active ingredient (a.i.)/bee, respectively, which suggested the low toxicity of GLY to honey bees. Moreover, we found significantly downregulated enzyme activity of superoxide dismutase (SOD), upregulated activities of glutathione S-transferase (GST) and acetylcholinesterase (AChE), as well as upregulated gene expression of CYP9Q1 in the head, and CYP9Q2 in the head and abdomen, which indicated the important roles of GST, AChE, and cytochrome P450 monooxygenase (CYPs/P450s) in protecting bees against GLY stress. Our study will help to clarify the role of antioxidative enzymes and detoxifying enzymes in terms of preventing or limiting GLY stress injury.

Essential oil-in-water microemulsions for topical application: structural study, cytotoxic effect and insect repelling activity

Essential oils (EOs) extracted from aromatic plants have been well recognized for their insect repellent properties. Although EOs are effective when freshly applied, their protective effect usually dissipates quickly due to low chemical stability and rapid volatilization of their ingredients. To address this issue, encapsulation in protective carrier materials at the nanoscale is proposed. In this study, oil-in-water (O/W) microemulsions containing geraniol or Citrepel® 75 (citrepel) as the oil phase, a mixture of water and diethylene glycol monoethyl ether (DEGEE) as the aqueous phase and caprylocaproyl polyoxyl-8 glycerides as surfactant were formulated and structurally characterized. DLS analysis showed that the emulsified oil droplets had low polydispersity (PdI<0.3) and average hydrodynamic diameter ranging from 13.7 ± 0.7–35.2 ± 2.7 nm, depending on composition. Mean viscosity of all prepared microemulsions was from 15.7 ± 0.3 cP to 23.8 ± 0.2 cP indicating the suitability of all preparations for topical application. EPR spectroscopy using spin probes gave information about the rigidity of the surfactants’ monolayer. In all cases an outer compact configuration of the interfacial layer and a more flexible inner one was observed. SAXS measurements revealed significant changes in the low q values related to the impact of geraniol and citrepel in microemulsion formulations. Looking at the high q region of the spectra, the curves were affected by the presence of the compounds in a concentration depended manner. Cytotoxicity studies on normal human epidermal keratinocytes (NHKs) confirmed that the sub-toxic dosage for geraniol-in-water and citrepel-in-water microemulsions is 56.25 μg active ingredient per cm2 of cell monolayer. Finally, diluted geraniol-in-water microemulsions were evaluated for repellence action against the Asian tiger mosquito (Aedes albopictus) showing activity for 3 h at a dose of 190 μg/cm2 active ingredient. Gaining a comprehensive understanding from all the results, promising candidates for topical application of geraniol as insect repellent based on safe microemulsions were proposed.

Sublethal exposure to pyriproxyfen does not impair the abilities of the backswimmer Buenoa amnigenus to prey upon Aedes aegypti larvae.

Pyriproxyfen is a juvenile hormone analogue that is commonly used to control the immature stages of mosquitoes in both artificial and natural water reservoirs. Recently, concerns have been raised regarding the community effectiveness of pyriproxyfen in preventing vector-transmitted diseases. Such concerns have been based on the unintended effects on non-target organisms and the selection of resistant mosquito populations. This investigation was, therefore, conducted to evaluate the toxicity of pyriproxyfen to Aedes aegypti (Diptera: Culicidae) larvae and the backswimmer Buenoa amnigenus (Hemiptera: Notonectidae), a naturally occurring mosquito larvae predator. We also assessed the abilities of backswimmers exposed to sublethal levels of pyriproxyfen to prey upon mosquito larvae (L2) under three larval densities (3, 6, or 9 larvae/100 mL of water) using artificial containers. Our results revealed that pyriproxyfen killed backswimmers only at concentrations higher than 100 μg active ingredient [a.i.]/L, which is 10 times higher than that recommended for larvicidal field application (i.e, 10 μg a.i./L). The abilities of backswimmers exposed to sublethal levels of pyriproxyfen (100 μg a.i./L) to prey upon mosquito larvae were not affected. Harmful effects on the backswimmer predatory abilities were detected only at concentrations of 150 μg a.i./L and when there was a higher prey availability (i.e., 9 larvae/100 mL of water). Together, our findings indicate that the reduced community effectiveness of this insecticide derives from factors other than its detrimental effects on non-target organisms such as backswimmers.

ВПЛИВ ЗАСТОСУВАННЯ МІКРОЕЛЕМЕНТІВ НА АЗОТНЕ ЖИВЛЕННЯ ПЕТРУШКИ, УРОЖАЙНІСТЬ I ЯКІСТЬ ЗЕЛЕНІ Й КОРЕНЕПЛОДІВ

The article presents the results of vegetation-field studies (for 2018-2020) to study the effect of trace elements on the yield and quality of greens and root crops of parsley on heavy loamy chernozems on loess-like loams. A soil mixture was poured into the vessel at the rate of 10 kg of heavy loamy chernozem. Microelements were introduced into the soil in an amount: boron – 1.0 mg; zinc – 2.5 mg; copper – 0.5 mg; manganese – 5.0 mg; molybdenum – 1.0 mg; cobalt – 1.0 mg; iodine – 2.0 mg of active ingredient per kilogram of soil. In the prepared soil, 100 parsley seeds were sown in vessels at the beginning of May. Trace elements were aplicated in the form of an aqueous solution of salts 20 days before chemical analyzes. Molybdenum in the form of ammonium molybdenum (0.05 % solution), manganese – in the form of manganese sulfate (0.6 %, solution) and boron – in the form of boric acid (0.15 % solution). The experiments were carried out in triplicate. Collecting greens was carried out when the plants reached a height of 20–25 cm, leaving petioles 2 cm high from the head of the root crop. The results of the research found that microelements: boron, copper, manganese, molybdenum and cobalt on chernozem on average over two years contributed to an increase in seed germination by 1.2–1.3 %, and the introduction of iodine into the soil slightly reduced seed germination. Parsley shoots appeared together, which was also influenced by the water–air properties of the soil. At the same time, the plants were well leafy and had a darker green color of the leaves, increased the productivity of greens and parsley root crops. In the variant where organic fertilizers were applied to the soil under the predecessor, the microelements increased the yield. This is due to the fact that organic fertilizers were introduced under the previous crop, when decomposed in the soil, they provide the plants with microelements. The increased yield of parsley root crops was obtained from the introduction of molybdenum and a double dose of copper. An increased yield of root crops compared to the control (without feeding) was obtained, respectively: cobalt – 151 g, double dose of copper – 135 g, copper – 108 g and zinc – 106 g. Thus, the use of trace elements for parsley in order to obtain high yield and quality marketable products are best used on poor soils of these elements.

Topical and dietary toxicity of emamectin benzoate, chlorantraniliprole, cyantraniliprole and indoxacarb to larvae of the common armyworm Mythimna convecta (Lepidoptera: Noctuidae).

The common armyworm Mythimna convecta is an important pest of pastures and graminaceous crops in Australia, but materials currently registered for its control are limited to broad-spectrum compounds incompatible with integrated pest management (IPM) systems. In this study we assessed the response of M.convecta larvae to four alternative compounds using topical and dietary bioassays. Emamectin benzoate [LC50 (lethal concentration for 50% of insects tested) values 2.69 μg mL-1 topical, 0.017 μg active ingredient (AI)g-1 dietary] and chlorantraniliprole (LC50 values 4.87 μg mL-1 topical, 0.080 μg AI g-1 dietary) were significantly more active than either indoxacarb or cyantraniliprole. Our results showed strong parallels with data on the more extensively studied Australian strains of Helicoverpa armigera, with the most notable differences being the higher contact toxicity of emamectin benzoate to M.convecta and the lower acute dietary activity of formulated cyantraniliprole to this species, which was linked to feeding deterrence. Cyantraniliprole at dietary concentrations of ≥0.02 μg AI g-1 significantly reduced the weight of surviving larvae and frass production (an indirect measure of food consumption) over the seven-day exposure period. There was also some evidence of chlorantraniliprole deterring larval feeding, although to a much more limited extent. Both emamectin benzoate and chlorantraniliprole are suitable for use against M.convecta. The decision as to which of these compounds should be prioritized for further development should be based on their potential effects on beneficial species once their optimal field rates have been determined.

The use of biologically active supplements as an alternative for application of antibiotics in production of pork

The article presents materials of scientific research of possibility of using biologically active substances as an alternative for antibiotics in production of pork. The aim of this work is to study the effect of drug for veterinary use, that contain the main functional component – NONON, in comparison with biologically active additives «Lactusil» and «Sporothermin» in feeding young pigs on their growth and development. The studies were carried out on the basis of Lenin PZK of Surovikinsky district of Volgograd Oblast from January to June 2019. For this, 4 groups of large white piglets were formed, 30 heads each at the age of 2 months. In this case, the control group received a general economic diet (GED), animals of the I group received GED in common with VD in an amount of 0.5 g (5 mg of active ingredient) per day per 1.0 kg of feed for 14 days; II groups - GED + dietary supplement «Sporothermin» in amount of 1.0 kg per ton of compound feed; Group III - GED + dietary supplement «Lactusil» - at a dose of 0.2 ml / kg of live weight. The use of probiotics in the diets in comparison with VD has shown their high efficiency on growth, development and meat productivity of gilts. It was found that animals of groups II and III in biochemical, immuno-biological indicators and meat productivity were superior to analogs from control group and I group (treated with VD).

Comparative ecotoxicity of insecticides with different modes of action to Osmia excavata (Hymenoptera: Megachilidae)

Osmia excavata is an important pollinator in commercial fruit orchards. Little information has been published about ecotoxicity to O. excavata, especially the larvae. To clarify the risk of commonly used insecticides with different modes of action to the larvae of O. excavata, six insecticides (clothianidin, acetamiprid, sulfoxaflor, lambda-cyhalothrin, chlorfenapyr and abamectin) were selected for evaluation of their acute lethal toxicity and sublethal effects. Clothianidin and abamectin were the two most toxic insecticides to the larvae of O. excavata with LD50 values of 0.007 (0.006–0.008) and 0.0004 (0.0003–0.0006) μg active ingredient (a.i.) bee−1, respectively. And their ecological risks were high according to the hazard quotient values (HQ > 2500). Sulfoxaflor was identified as the only safe insecticide for O. excavata (HQ < 50) under field conditions. Sublethal toxicity tests showed that larval weight was significantly decreased by ingesting food treated with clothianidin, lambda-cyhalothrin and abamectin (less than the maximum field registered concentrations on fruit trees) due to interference with consumption per larva and reduction of the efficiency of conversion of ingested food. Additionally, above three insecticides significantly prolonged larval developmental duration before cocooning and decreased eclosion rate. Overall, there results suggested that clothianidin and abamectin should not be applied, especially during the flowering phase, the application frequency of lambda-cyhalothrin should be minimized for the purpose of conserving O. excavata. Our results provided important evidences for selecting appropriate insecticides for use in fruit orchards.

Heterodissemination: precision targeting container Aedes mosquitoes with a cohabiting midge species carrying insect growth regulator.

Management of Aedes albopictus and Ae. aegypti is challenging in large part due to the cryptic nature of their larval habitats. Autodissemination, using conspecific species to transfer pesticide, is unable to provide proactive control. Here we report results from a new hypothesis, heterodissemination, wherein females of the cohabiting non-biting midge, Chironomus decorus, reared in the laboratory, treated with pyriproxyfen, and released to transfer lethal concentrations to shared mosquito larval habitats. Pyriproxyfen-impregnated oil and powder formulations were developed. The average payload for each female midge treated with oil followed by powder formulations was 5.07 ± 0.92 μg of active ingredient or 1660 times the median lethal concentration (LC50 ) for Ae. albopictus or Ae. aegypti in 200 mL of water. Subsequent residue analysis showed pyriproxyfen transference from chironomids, treated with oil formulation only, into water-holding containers up to 2.06 ppb or 171.7 times the LC50 . Releasing 20 laboratory reared and contaminated Chironomus decorus into a small room resulted in 80.42 ± 0.67% and 75.67 ± 3.14% Ae. albopictus pupal mortality in open and cryptic sentinel ovicups, respectively. Container water volumes ranging up to 4 L did not affect efficacy. In a large field cage, 90.3 ± 2.5% Ae. albopictus mortality was resulted from releasing 100 treated female midges. Releasing 400 contaminated midges into a residential backyard resulted in 74.3% pupal mortality in sentinel ovicups. Room, large field cage and field release trials demonstrated that adult midges reared and treated in the laboratory transfer highly lethal concentrations of pyriproxyfen to Ae. albopictus container habitats. Heterodissemination provides a potential approach for precision, proactive mosquito control, which may draw attention for further studies. © 2020 Society of Chemical Industry.

“Modern agriculture” transfers many pesticides to watercourses: a case study of a representative rural catchment of southern Brazil

The total cultivated area in Brazil reached to 62 million ha in 2018, with the predominance of genetically modified soybean and corn (36 and 17 million ha, respectively) in no-tillage systems. In 2018, 5.3 × 105Mg of active ingredient of pesticides was applied in cropfields, representing about 7.3L of commercial product by habitant. However, the monitoring of water courses contamination by pesticides remains scarce and is based on traditional grab sampling systems. In this study, we used the grab (water) and passive sampling (Polar Organic Chemical Integrative Sampler-POCIS) to monitor pesticide contamination in the river network of a representative agricultural catchment of southern Brazil. We selected 18 sampling sites located in tributaries and in the main course of the Guaporé River, in Rio Grande do Sul State, with different land use predominance including forest, urban, and agricultural areas. Altogether, 79 and 23 pesticides were, respectively, analyzed in water and POCIS samples. The water of Guaporé River and its tributaries were highly contaminated by many pesticides, especially by four herbicides (2,4-D, atrazine, deethyl-atrazine, and simazine), three fungicides (carbendazim, tebuconazole, and epoxiconazole), and one insecticide (imidacloprid). The amount, type, and concentration of pesticides detected were completely different depending on the sampling technic used. POCIS was effective to discriminate the contamination according to the main land use of each sampling site. The monitored areas with the predominance of soybean cultivation under no-tillage tended to have higher concentrations of fungicide, while in the more diversified region, the herbicides showed higher values. The presence of five herbicides used in corn and grassland forage production was correlated with areas of integrated crop-livestock systems, in contrast to higher contamination by 2,4-D in areas of intensive production of soybean and winter cereals.

Evaluation of Antimicrobial Activity of Triphala Constituents and Nanoformulation.

The prevalence of nosocomial infections due to multidrug resistant (MDR) bacterial strains is associated with high morbidity and mortality. Folk medicine and ethnopharmacological data can provide a broad range of plants with promising antimicrobial activity. Triphala, an Ayurvedic formula composed of three different plants: Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb. (Combretaceae), and Phyllanthus emblica L. (Phyllanthaceae), is used widely for various microbial infections. Various extraction techniques were applied in the extraction of the biologically active constituents of Triphala in order to compare their efficiency. Microwave-assisted extraction (MAE) was shown to be the most efficient method based on yield, extraction time, and selectivity. The Triphala hydroalcoholic extract (TAE) has been chemically characterized with spectroscopic and chromatographic techniques. Triphala hydroalcoholic extract was evaluated alone or with carvacrol. Different drug formulations including cream and nanoemulsion hydrogel were prepared to assess the antimicrobial activity against selected microorganism strains including Gram-positive and Gram-negative bacteria and fungi. We used a lipophilic oil of carvacrol (5 mg/mL) and a hydrophilic TAE (5 mg/mL) ingredient in a dosage form. Two solutions were created: hydrogel containing nanoemulsion as a lipophilic vector dispersed in the gel as a hydrophilic vehicle and a cream formulation, an oil-in-water emulsion. In both cases, the concentration was 250 mg of active ingredient in 50 mL of final formulation. The formulas developed were stable from a physical and chemical perspective. In the nanoemulsion hydrogel, the oil droplet size ranged from 124 to 129 nm, with low polydispersity index (PdI) 0.132 ± 0.013 and negative zeta potential −46.4 ± 4.3 mV. For the cream, the consistency factor (cetyl alcohol and white wax) induced immobilization of the matrix structure and the stability. Triphala hydroalcoholic extract in drug nanoformulation illustrated might be an adjuvant antimicrobial agent for treating various microbial infections.

Excessive use of medically important antimicrobials in food animals in Pakistan: a five-year surveillance survey

ABSTRACT Demand for poultry meat is rising in low- and middle-countries, driving the expansion of large commercial farms where antimicrobials are used as surrogates for hygiene, good nutrition. This routine use of antimicrobials in animal production facilitates the emergence and spread of antibiotic-resistant pathogens. Despite potentially serious consequences for the animal industry, few studies have documented trends in antimicrobial use (AMU) at the farm-level in low- and middle-income countries. The objective of this study was to estimate AMU in a broiler chicken farm in Pakistan over a five-year period and to extrapolate national AMU in commercial broiler farming. Between 2013 and 2017, we monitored AMU in 30 flocks from a commercial broiler farm in Punjab, the most populous province of Pakistan. The amount of antimicrobials administered was calculated in milligram/population unit of the final flock weight (mg/fPU) and in used daily dose (UDD). The annual on-farm antimicrobial use was 250.84 mg of active ingredient per kilogram of the final flock weight. This consumption intensity exceeds the amount of antimicrobial used per kilogram of chicken of all countries in the world except China. Measured in mg per kg of final flock weight or population unit (fPU), medically important drugs such as colistin (31.39 mg/fPU), tylosin (41.71 mg/fPU), doxycycline (81.81 mg/fPU), and enrofloxacin (26.19 mg/fPU) were the most frequently used antimicrobials for prophylactic or therapeutic use. Lincomycin was the most frequently used antimicrobial used in-feed (29.09 mg/fPU). Our findings suggest that the annual consumption of antimicrobials in the broiler sector in Pakistan could be as high as 568 tons. This alarmingly high consumption estimate is the first baseline study on antimicrobial use in animals in Pakistan. Our findings call for immediate actions to reduce antimicrobial use in Pakistan, and countries with comparable farming practices.

Antimicrobial usage on 72 farrow-to-finish pig farms in Japan from 2015 to 2017

In Japan veterinary antimicrobials are used most in the pig production sector. However, there is a paucity of data on the quantity of antimicrobials used on pig farms in Japan. This study describes antimicrobial use on Japanese pig farms in 2015, 2016 and 2017 in terms of mg of active ingredient per kg of PCU (population correction unit). Data on antimicrobial use from a total of 72 farrow-to finish farms over these three years were used in the study. The results revealed that the average use of antimicrobials in 2015, 2016 and 2017 was 304.8 (SD = 226.3), 311.2 (SD = 241.0) and 342.9 (SD = 291.3) mg/kg PCU, respectively. Most (97%) of the antimicrobials were administered orally. The most commonly used antimicrobials were tetracyclines, followed by macrolides, penicillins and sulfonamides. Tohoku was the region in which the lowest quantities of antimicrobial were used whilst South Kanto was the region in which the largest amount was used. The use of antimicrobials was on the increase in the North Kanto, South Kanto and Kyushu regions.

Emergence of Stemphylium Leaf Blight of Onion in New York Associated With Fungicide Resistance.

A complex of foliar diseases affects onion production in New York, including Botrytis leaf blight (Botrytis squamosa), purple blotch (Alternaria porri), Stemphylium leaf blight (SLB; Stemphylium vesicarium), and downy mildew (Peronospora destructor). Surveys were conducted in 2015 and 2016 to evaluate the cause of severe premature foliar dieback in New York onion fields. SLB was the most prevalent disease among fields with the greatest incidence, surpassing downy mildew, purple blotch, and Botrytis leaf blight. Sequencing of the internal transcribed spacer region of ribosomal DNA and the glyceraldedyhe-3-phosphate dehydrogenase and calmodulin genes identified S. vesicarium as the species most commonly associated with SLB. S. vesicarium was typically associated with a broad range of necrotic symptoms but, most commonly, dieback of leaf tips and asymmetric lesions that often extended over the entire leaf. Because of the intensive use of fungicides for foliar disease control in onion crops in New York, the sensitivity of S. vesicarium populations to various fungicides with site-specific modes of action was evaluated. Sensitivity of S. vesicarium isolates collected in 2016 to the quinone outside inhibitor (QoI) fungicide, azoxystrobin, was tested using a conidial germination assay. Isolates representing a broad range of QoI sensitivities were selected for sequencing of the cytochrome b gene to evaluate the presence of point mutations associated with insensitivity to azoxystrobin. The G143A mutation was detected in all 74 S. vesicarium isolates with an azoxystrobin-insensitive phenotype (effective concentrations reducing conidial germination by 50%, EC50 = 0.2 to 46.7 µg of active ingredient [a.i.]/ml) and was not detected in all 31 isolates with an azoxystrobin-sensitive phenotype (EC50 = 0.01 to 0.16 µg a.i./ml). The G143A mutation was also associated with insensitivity to another QoI fungicide, pyraclostrobin. Sensitivity to other selected fungicides commonly used in onion production in New York was evaluated using a mycelial growth assay and identified isolates with insensitivity to boscalid, cyprodinil, and pyrimethanil, but not difenoconazole. The frequency of isolates sensitive to iprodione, fluxapyroxad, and fluopyram was high (93.5 to 93.6%). This article discusses the emergence of SLB as dominant in the foliar disease complex affecting onion in New York and the complexities of management posed by resistance to fungicides with different modes of action.

Effects of Two Commonly Used Herbicides on Soil Microbes and Organic Matter of Soil from Maize and Cocoa Plantation

Herbicide application had been an effective method of weed control over the years, however, the effect of herbicides on the non-target soil microbes that play roles in degrading organic matter and nutrient recycling needs to be considered. The effects of two (2) most commonly used herbicides in Osun State on soil microbes of maize and cocoa plantation were assessed over a period of thirteen continuous days (exposure period). The herbicide treatments were the normal recommended field rate, (0.72 mg active ingredient per gram of soil for 2, 4-D amine and 0.24 mg for glyphosate, double the recommended field rate, (1.44 mg of active ingredient per gram of soil for 2,4-D amine and 0.48 mg for glyphosate). The bacteria and fungi populations were then determined at a three-day interval up to the 13th day after treatment. Result indicated that herbicides treatment had a pronounced toxic effect on microbes population at 4 days after treatment however the toxicity gradually reduced as the exposure time increases. Double recommended field rate has higher toxic effect than the normal field rate. Also, glyphosate has less inhibitory effect on bacterial population than 2,4-D amine. Thus, glyphosate is recommended at the normal recommended field rate for maize and cocoa plantation.

Influence of chlorothalonil and carbendazim fungicides on the transformation processes of urea nitrogen and related microbial populations in soil.

To improve crop yielding, a large amount of fungicides is continuously applied during the agricultural management, while the effects of fungicides residues on microbial processing of N in soil need further study. In the present study, two broad spectrum fungicides, chlorothalonil and carbendazim, were applied at the rates of 5, 10, and 50 mg of active ingredient (A.I.) per kg of dry soil combined with urea with 200 mg of N per kg of dry soil under laboratory conditions. The results showed that chlorothalonil obviously retarded the hydrolysis of urea, whereas carbendazim accelerated it in 4 days after the treatments (P < 0.05). Chlorothalonil reduced denitrification, nitrification, and N2O production (P < 0.05), but not for carbendazim. Further analysis on N-associated microbial communities showed chlorothalonil reduced nitrosomonas populations at the rates of 10 and 50 mg of A.I. per kg and autotrophic nitrifying bacterial populations at three application rates (P < 0.05), but Carbendazim decreased nitrosomonas populations only at the rate of 50 mg of A.I. per kg and also autotrophic nitrifying bacterial populations at three rates and heterotrophic nitrifying bacterial populations at the rates of 10 and 50 mg of A.I. per kg. The reasons for this difference were ascribed to arrest urea hydrolysis and impediment of denitrification and nitrification processes by chlorothalonil. In conclusion, to improve crop yielding, chlorothalonil might be more beneficial to conserve soil N by improving soil N fertility, compared with carbendazim.

Inhibitory Effects of Different Types and Doses of Herbicides on Soil Nitrification Potentials

To elucidate the inhibitory effects of different herbicides on soil nitrification, eight widely used herbicides, i.e., acetochlor, atrazine, dicamba, isoproturon, paraquat, puma, tribenuron-methyl, and 2,4-dichlorophenoxyacetic acid butyl ester (2,4-Dbe), which represent different chemical taxonomy were selected. Our results indicated that herbicide 2,4-Dbe displayed the best inhibitory effect on nitrification, followed by puma and tribenuron-methyl, whereas the remaining five herbicides exhibited less effect when 10 mg of active ingredient (A.I.) of every herbicide per kg of soil was applied in vegetable-planting soil. The inhibition appeared when 5–100 mg of A.I. 2,4-Dbe was employed, which was enhanced with an increment in its dose in both vegetable-planting and fluvo-aquic soils. However, the inhibitory effect of 10 mg of A. I. 2,4-Dbe exhibited obvious differences in these two types of soils, where the duration of inhibition was shorter as it only continued about a week in fluvo-aquic and calcic cambisols soils with strong nitrification activity but poorer effect as compared to 10 mg of dicyandiamide (DCD). In contrast, the duration of inhibition exceeded 2 months in dryland red and shajiang black soils with a weak nitrification activity which was equivalent to DCD. In addition, comparing with five nitrification inhibitors, 10 mg of 2,4-Dbe had better inhibition than the substituted pyrimidine (AM) and sulfocarbamide (SU), but was equivalent to DCD, nitrapirin, and 3,4-dimethylpyrazole phosphate (DMPP) at their recommended application rates in dryland red soil. These obtained data clearly indicated that 2,4-Dbe could play a stronger role as a nitrification inhibitor in soils.

Content of Photosynthetic Pigments and Leaf Gas Exchanges of Young Coffee Plants under Light Restriction and Treated with Paclobutrazol

The use of shading and paclobutrazol in coffee plants can be an important cultivation strategy to mitigate the negative effects of high solar radiation and atmospheric temperature. Therefore, the levels of photosynthetic pigments and foliar gas exchanges of young coffee plants submitted to doses of paclobutrazol were evaluated, in environments with artificial light restriction. Five experiments were performed: one in full sunlight and four in artificially shaded environments with black polyethylene meshes at 20%, 40%, 60% and 80% levels of light restriction. In each of these environments, an experiment was carried out, consisting of five treatments, defined by the application of paclobutrazol via substrate, at doses of 0, 10, 20, 30 and 40 mg of active ingredient per plant. Joint analysis of experiments and analysis of variance of the regression were made, for the study of levels of shading and doses of paclobutrazol. The light restriction optimized the photosynthetic apparatus of the plants, mainly at levels close to 60%, and considerably favored leaf gas exchanges of arabica coffee. The application of paclobutrazol in the studied dosages resulted in little or no effect on photosynthetic pigment contents and did not influence leaf gas exchanges of coffee plants.