Fungicidal Effect Research Articles

Rational selection of morphological phenotypic traits to extract essential similarities in chemical perturbation in the ergosterol pathway

Terbinafine, fluconazole, and amorolfine inhibit fungal ergosterol synthesis by acting on their target enzymes at different steps in the synthetic pathway, causing the accumulation of various intermediates. We found that the effects of these three in- hibitors on yeast morphology were different. The number of morphological parameters commonly altered by these drugs was only approximately 6% of the total. Using a rational strategy to find commonly changed parameters,we focused on hidden essential similarities in the phenotypes possibly due to decreased ergosterol levels. This resulted in higher apparent morphological similarity. Improvements in morphological similarity were observed even when canonical correlation analysis was used to select biologically meaningful morphological parameters related to gene function. In addition to changes in cell morphology, we also observed differences in the synergistic effects among the three inhibitors and in their fungicidal effects against pathogenic fungi possibly due to the accumulation of different intermediates. This study provided a comprehensive understanding of the properties of inhibitors acting in the same biosynthetic pathway.

In vitro efficacy of various fungicides against fungi associated with leaf, stem, and soilborne diseases of Proteaceae in Hawai‘i, USA

Species in the Proteaceae have been important ornamental plants cultivated for both cut flowers and foliage in Hawaiian agriculture since the 1960’s. Symptoms ranging from spots on leaves and flowers, to branch lesions and cankers, as well as dieback have been reported on various Proteaceae in Hawai‘i and attributed to various fungi. Nurseries can experience significant economic losses if symptoms are not controlled. Few studies are available regarding the effectiveness of chemical treatments to reduce disease incidence and severity. The efficacy of six ornamental fungicides from various Fungicide Resistance Action Committee (FRAC) groups were evaluated in vitro for their ability to inhibit the mycelial growth of nine fungal isolates of six known or suspected protea pathogen genera (Diaporthe, Alternaria, Neofusicoccum, Neopestalotiopsis, Phompsis, and Calonectria). Isolates were recovered from symptomatic stems and leaves, as well as soil surrounding diseased Proteaceae grown at the Maui Agricultural Research Center (MARC), Kula, HI and from 10 commercial farms on Maui. All fungicides evaluated in the study inhibited the in vitro growth of some, if not all, of the nine isolates to some capacity. Tebuconazole was the most effective fungicide, reducing mycelial growth of all isolates by >85% or more compared to nonamended control plates. Rotation of these fungicides could potentially be used for disease management against a broad range of pathogens infecting Proteaceae in Hawaiʻi.

Enhancing bioactivity of Callistemon citrinus (Curtis) essential oil through novel nanoemulsion formulation

The main focus of this study was to create a stable and efficient nanoemulsion (NE) using Callistemon citrinus essential oil (EO). Various factors affecting the NE’s stability were optimized including oil %, Tween 80%, time of sonication, and its accelerated stability was examined. The research also considered the antibacterial, antifungal, and larvicidal effects of the optimized NE (B10). The optimum NE stood out for its stability, featuring a particle size of 33.15 ± 0.32 nm. Analysis via IR spectroscopy confirmed successful EO encapsulation in B10. The formulation remained stable for six months, with B10 showing significantly higher antibacterial and antifungal potency compared to the pure oil. When samples were subjected to tests against Fusarium oxysporum, B10 exhibited a MIC value of 62.5 mg/mL, whereas the pure oil showed a MIC value of 250 mg/mL. This indicates that the B10 formulation was 50 times more effective than the EO. In terms of antibacterial activity against Escherichia coli, the MIC value was 0.256 mg/mL for B10 and 4 mg/mL for the EO. Also, pure oil and B10 displayed larvicidal effects against Chilo suppressalis (Walker) larvae, with B10 eliminating 95.2% of larvae in 48 h. Overall, stable and optimum C. citrinus NE with its strong antimicrobial qualities, shows promise as an effective fungicide and insecticide.

Inactivation of Fusarium verticilliordes by dielectric barrier discharge plasma and its mechanism

Fusarium is a kind plant pathogenic fungus, resulting in severe crops infection and food safety issues. The development of novel strategy to inactive Fusarium is in urgent need. In this study, the inactivation effect and mechanism of dielectric barrier discharge (DBD) plasma on Fusarium verticillioides was studied. The results showed that the fungicidal effect of DBD plasma was positively correlated with the voltage strength and treatment time, which could reach 100% sterilizing rate at 60–80 V. The scanning electron microscope (SEM) observation indicated the integrity of the cell wall and cell membrane of the treated F. verticilliordes was damaged, leading to leakage of the contents. The changes of mitochondrial membrane potential, adenosine 5′-triphosphate (ATP) content, cell viability and reactive substances (intracellular reactive oxygen species (ROS), intracellular hydrogen peroxide (H2O2), ozone (O3) and reactive nitrogen species (RNS) (NO2−, NO3−, etc.)) were also tested to better understand the fungicidal mechanism of cold plasma. These results demonstrated DBD plasma could be a promising technique for Fusarium inactivation in food.

Optical Nanomotion Detection to Rapidly Discriminate between Fungicidal and Fungistatic Effects of Antifungals on Single-Cell Candida albicans.

Candida albicans is an emerging pathogen that poses a significant challenge due to its multidrug-resistant nature. There are two types of antifungal agents, fungicidal and fungistatic, with distinct mechanisms of action against fungal pathogens. Fungicidal agents kill fungal pathogens, whereas fungistatic agents inhibit their growth. The growth can be restored once the agent is removed and favorable conditions are established. Recognizing this difference is crucial as it influences treatment selection and infection prognosis. We present a technique based on optical nanomotion detection (ONMD) (i.e., observing the movement of the cells using an optical microscope) to discriminate rapidly between fungicidal (caspofungin) and fungistatic (fluconazole) drugs. The technique is based on the change in a yeast cell's nanomotion as a function of time during a two-hour treatment with the antifungal of interest followed by a one-hour growth period. The cells are entrapped in microwells in a microfluidic chip, which allows a quick exchange of growth medium and antifungal agent, enabling ONMD measurements on the same individual cells before and after treatment. This procedure permits to discriminate between fungicidal and fungistatic antifungals in less than 3 h, with single-cell resolution by observing if the nanomotion recovers after removing the treatment and reintroducing growth medium (YPD), or continues to drop. The simplicity of the approach holds promise for further development into a user-friendly device for rapid antifungal susceptibility testing (AFST), potentially being implemented in hospitals and medical centers worldwide in developed and developing countries.

Toxic eburicol accumulation drives the antifungal activity of azoles against Aspergillus fumigatus

Azole antifungals inhibit the sterol C14-demethylase (CYP51/Erg11) of the ergosterol biosynthesis pathway. Here we show that the azole-induced synthesis of fungicidal cell wall carbohydrate patches in the pathogenic mold Aspergillus fumigatus strictly correlates with the accumulation of the CYP51 substrate eburicol. A lack of other essential ergosterol biosynthesis enzymes, such as sterol C24-methyltransferase (Erg6A), squalene synthase (Erg9) or squalene epoxidase (Erg1) does not trigger comparable cell wall alterations. Partial repression of Erg6A, which converts lanosterol into eburicol, increases azole resistance. The sterol C5-desaturase (ERG3)-dependent conversion of eburicol into 14-methylergosta-8,24(28)-dien-3β,6α-diol, the “toxic diol” responsible for the fungistatic activity against yeasts, is not required for the fungicidal effects in A. fumigatus. While ERG3-lacking yeasts are azole resistant, ERG3-lacking A. fumigatus becomes more susceptible. Mutants lacking mitochondrial complex III functionality, which are much less effectively killed, but strongly inhibited in growth by azoles, convert eburicol more efficiently into the supposedly “toxic diol”. We propose that the mode of action of azoles against A. fumigatus relies on accumulation of eburicol which exerts fungicidal effects by triggering cell wall carbohydrate patch formation.

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Unveiling the ecotoxicological effects of azoxystrobin-based fungicides at realistic concentrations on the land snail, Theba pisana

The ecotoxicological consequences of azoxystrobin on land snails have not yet been addressed. Therefore, the present study aims to provide novel data on the threat of a commercial grade azoxystrobin (AMISTAR) at two environmentally relevant concentrations (0.3 µg/ml) and tenfold (3 µg/ml) on the model species, Theba pisana by physiological, biochemical, and histopathological markers for 28 days. Our results showed a reduction in animal food consumption and growth due to exposure to both azoxystrobin concentrations. It also induced oxidative stress and led to a significant decrease in lipid peroxidation (LPO) levels after 7 days of exposure, while the opposite effect occurred after 28 days. Except for the 7-day exposure, all treated snails had significantly reduced glutathione (GSH) content and increased catalase (CAT) activity at all-time intervals. Glutathione peroxidase (GPx), glutathione-S-transferase (GST) activities, and protein content (PC) were elevated in treated snails at all-time intervals. Moreover, alterations in acetylcholinesterase (AChE) activity between a decrease and an increase were noticed. Additionally, azoxystrobin exerted changes in T. pisana hepatopancreas architecture. Our study suggests that azoxystrobin may have negative ecological consequences for T. pisana and highlights its potential risks to the natural environment.

Screening of Castor Germplasm and Efficacy Studies of Bioagents and Fungicides Against Botryotinia ricini (Godfrey) Whetzel

Castor is an important non-edible oilseed crop having exceptional oil characteristics for the chemical industry. The crop hosts several diseases, among them gray mold is the most destructive one hindering its productivity. This article presents a study assessing the resistance of different germplasm lines screened against Botrytis ricini under artificial conditions. It also examines the effect of various fungicides on B. ricini isolates, which were obtained from infected Ricinus communis (castor oil plant) using standard tissue isolation techniques. The fungus was isolated from infected Castor raceme by standard tissue isolation technique and its pathogenicity was established by proving Koch’s postulates. Out of 47 germplasm lines screened, TSIL-19 showed resistance response to gray mold under both detached spike and capsule method. Under in vitro assessment, Trichoderma viride (86.11 %) and Pseudomonas fluorescens (71.48 %) bio agents exhibited maximum mycelial growth inhibition of the pathogen. Among the seven combination fungicides evaluated, Fenamidone 10% + Mancozeb 50% WG recorded highest mycelial growth inhibition (100%) of B. ricini.

Testing the efficacy of a newly released fungicide, Sphaerex, for control of Fusarium Head Blight in wheat

Fusarium head blight (FHB) is a destructive disease of wheat and other small-grain cereals. FHB causes reduction in crop yield due to pre-mature bleaching of spikes. Additionally, it deteriorates the crop quality due to the production of mycotoxins. An integrated management strategy is needed to effectively manage this disease. One of the most important strategies in the FHB management toolbox is chemical control. Fungicides start losing their efficacy over time due to the development of fungicide resistance in the pathogens. This necessitates the development and testing of new fungicides with multiple active ingredients or modes of action. In this 3-year study, we evaluated the effectiveness of a new fungicide with multiple active ingredients, Sphaerex (a proprietary mix of metconazole and prothioconazole) in an FHB-susceptible soft red winter wheat cultivar, Shirley in the eastern United States. Sphaerex provided significantly better control over untreated plots for FHB Incidence, FHB Severity, and DON content across all three years. The level of control of FHB and DON by Sphaerex was found to be similar to that provided by other standard FHB fungicides. The yield of the fungicide-treated plots was statistically similar to that of the untreated plots.

Accumulation and growth toxicity mechanisms of fluxapyroxad revealed by physiological, hepatopancreas transcriptome, and gut microbiome analysis in Pacific white shrimp (Litopenaeus vannamei)

Fluxapyroxad (FX), a typical succinate dehydrogenase inhibitor fungicide, is causing increased global concerns due to its fungicide effects. However, the accumulation and grow toxicity of FX to Litopenaeus vannamei (L. vannamei) is poorly understand. Therefore, the accumulation pattern of FX in L. vannamei was investigated for the first time in environmental concentrations. FX accumulated rapidly in shrimp muscle. Meanwhile, growth inhibition was observed and the mechanism derived by primarily accelerated glycolipid metabolism and reduced glycolipid content. Moreover, exposure to environmental concentrations of FX induced significant growth inhibition and oxidative stress and inhibited oxidative phosphorylation and TCA cycle in L. vannamei. The endocytosis signaling pathway genes were activated, thereby driving growth toxicity. Oxidative phosphorylation and cytosolic gene expression were further rescued in elimination experiments, demonstrating the mechanism of growth toxicity by FX exposure. The results revealed that FX persistently altered the gut microbiome of L. vannamei using gut microbiome sequencing, particularly with increased Garcinia Purple Pseudoalteromonas luteoviolacea for organic pollutant degradation. This study provided new insights into the potential toxicity of FX to marine organisms, emphasizing the need for further investigation and potential regulatory considerations.

Antifungal and Allelopathic Effects of Essential Oil from Calyptranthes concinna DC. Dried Leaves and of Its Major Constituent Elemicin

Essential oils (EOs) are natural products widely used in sustainable agrochemistry, not only because they are biodegradable and safe but also because they are regarded as alternatives to chemical fungicides against fungal species that attack crops. Allelopathy, another field of study, falls within the most recent and sustainable strategies applied to weed suppression to replace synthetic herbicides. Therefore, this study reports the chemical composition and allelopathic and antifungal effects of the EOs extracted from Calyptranthes concinna dried leaves (Cc-EO) and its pure major constituent elemicin. Their antifungal activities were evaluated by the disk diffusion method (DDM) at doses between 0.05 mg/mL and 0.4 mg/mL of Cc-EO and elemicin. The allelopathic effect was evaluated by studying the inhibition of germination and the growth of Lactuca sativa seeds. The chemical composition of Cc-EO was determined by GC-MS and GC-FID analyses. The major constituents of Cc-EO were elemicin (60.5%), α-cadinol (9.0%) and caryophyllene oxide (8.3%). Cc-EO and elemicin were assayed in vitro against 17 fungi of agronomic interest (Aspergillus niger, A. flavus, A. nomius, Penicillium digitatum, P. expansum, Sclerotinia sclerotiorum, S. rolfsii, S. minor, Fusarium graminearum, Myrothecium verrucaria, Corynespora cassiicola, Erwinia psidii, Colletotrichum musae, Alternaria carthami, Rhizoctonia solani, Rhizopus stolonifer and Macrophomina phaseolina). The concentration of Cc-EO (0.4 mg/mL) inhibited 100% of the mycelium growth of seven strains, equal to the fungicide fluazinam, which was used as a positive control. Elemicin showed antifungal activity against all fungi at all concentrations under investigation (above 50%). A strong allelopathic effect was recorded for Cc-EO and elemicin at the dose of 0.28 mg/mL, with the almost total inhibition of germination. This study revealed, for the first time, the strong and remarkable fungicidal and allelopathic effects of Cc-EO and elemicin, an important finding for the agrochemical field.

Bakanae Disease Resistance in Rice: Current Status and Future Considerations

Bakanae disease is mainly caused by Fusarium fujikuroi and is a significant fungal disease with a number of disastrous consequences. It causes great losses in rice production. However, few studies have focused on the details of bakanae disease resistance in rice. Here, we summarize and discuss the progress of bakanae disease resistance in rice. Besides rice germplasm screening and resistance-related gene/quantitative trait locus (QTL) exploration, the route of pathogen invasion in rice plants was determined. We further discussed the regulation of phytohormone-related genes and changes in endogenous phytohormones in rice plants that are induced by the pathogen. To achieve better control of bakanae disease, the use of natural fungicides was assessed in this review. During rice—F. fujikuroi interactions, the infection processes and spatial distribution of F. fujikuroi in infected seedlings and adult plants exhibit different trends. Fungal growth normally occurs both in resistant and susceptible cultivars, with less abundance in the former. Generally, bakanae disease is seed-borne, and seed disinfection using effective fungicides should always be the first and main option to better control the disease. Besides the friendly and effective measure of using natural fungicides, breeding and utilization of resistant rice cultivars is also an effective control method. To some extent, rice cultivars with low grain quality, indica subspecies, and some dwarf or semi-dwarf rice germplasms are more resistant to bakanae disease. Although no highly resistant germplasms were obtained, 37 QTLs were located, with almost half of the QTLs being located on chromosome 1. Using omics methods, WRKYs and MAPKs were usually found to be regulated during rice—F. fujikuroi interactions. The regulation of certain phytohormone-related genes and changes in some endogenous phytohormones induced by the pathogen were clear, i.e., it downregulated gibberellin-related genes and repressed endogenous gibberellins in resistant genotypes, but the opposite results were noted in susceptible rice genotypes. Overall, exploring resistant germplasms or resistance-related genes/QTLs for the breeding of rice with bakanae disease resistance, expanding research on the complex mechanism of rice—F. fujikuroi interactions, and using cost-effective and eco-friendly innovative control methods against the disease are necessary for present and future bakanae disease management.

Rhizobium Inoculant and Seed-Applied Fungicide Effects Improve the Drought Tolerance of Soybean Plants as an Effective Agroecological Solution under Climate Change Conditions.

Rhizobial inoculation in combination with fungicidal seed treatment is an effective solution for improving soybean resistance to modern climate changes due to the maximum implementation of the plant's stress-protective antioxidant properties and their nitrogen-fixing potential, which will contribute to the preservation of the environment. Model ecosystems at different stages of legume-rhizobial symbiosis formation, created by treatment before sowing soybean seeds with a fungicide (fludioxonil, 25 g/L) and inoculation with an active strain of Bradyrhizobium japonicum (titer 109 cells per mL), were subjected to microbiological, biochemical, and physiological testing methods in controlled and field conditions. Seed treatment with fungicide and rhizobia showed different patterns in the dynamics of key antioxidant enzymes in soybean nodules under drought conditions. Superoxide dismutase activity increased by 32.7% under moderate stress, while catalase increased by 90.6% under long-term stress. An increase in the antioxidant enzyme activity induced the regulation of lipoperoxidation processes during drought and after the restoration of irrigation. Regeneration after stress was evident in soybean plants with a combination of fungicide seed treatment and rhizobial inoculant, where enzyme levels and lipoperoxidation processes returned to control plant levels. Applying seed treatment with fungicide and Rhizobium led to the preservation of the symbiotic apparatus functioning in drought conditions. As proof of this, molecular nitrogen fixation by nodules has a higher efficiency of 25.6% compared to soybeans without fungicide treatment. In the field, fungicidal treatment of seeds in a complex with rhizobia inoculant induced prolongation of the symbiotic apparatus functioning in the reproductive period of soybean ontogenesis. This positively affected the nitrogen-fixing activity of soybeans during the pod formation stage by more than 71.7%, as well as increasing soybean yield by 12.7% in the field. The application of Rhizobium inoculant and fungicide to seeds contributed to the development of antioxidant protection of soybean plants during droughts due to the activation of key enzymatic complexes and regulation of lipoperoxidation processes, which have a positive effect on nitrogen fixation and productivity of soybeans. This is a necessary element in soybean agrotechnologies to improve plant adaptation and resilience in the context of modern climate change.

Effects of a co-bacterial agent on the growth, disease control, and quality of ginseng based on rhizosphere microbial diversity

BackgroundThe ginseng endophyte Paenibacillus polymyxa Pp-7250 (Pp-7250) has multifaceted roles such as preventing ginseng diseases, promoting growth, increasing ginsenoside accumulation, and degrading pesticide residues, however, these effects still have room for improvements. Composite fungicides are an effective means to improve the biocontrol effect of fungicides, but the effect of Pp-7250 in combination with its symbiotic bacteria on ginseng needs to be further investigated, and its mechanism of action has not been elucidated. In this study, a series of experiments was conducted to elucidate the effect of Paenibacillus polymyxa and Bacillus cereus co-bacterial agent on the yield and quality of understory ginseng, and to investigate their mechanism of action.ResultsThe results indicated that P. polymyxa and B. cereus co-bacterial agent (PB) treatment improved ginseng yield, ginsenoside accumulation, disease prevention, and pesticide degradation. The mechanism is that PB treatment increased the abundance of beneficial microorganisms, including Rhodanobacter, Pseudolabrys, Gemmatimonas, Bacillus, Paenibacillus, Cortinarius, Russula, Paecilomyces, and Trechispora, and decreased the abundance of pathogenic microorganisms, including Ellin6067, Acidibacter, Fusarium, Tetracladium, Alternaria, and Ilyonectria in ginseng rhizosphere soil. PB co-bacterial agents enhanced the function of microbial metabolic pathways, biosynthesis of secondary metabolites, biosynthesis of antibiotics, biosynthesis of amino acids, carbon fixation pathways in prokaryotes, DNA replication, and terpenoid backbone biosynthesis, and decreased the function of microbial plant pathogens and animal pathogens.ConclusionThe combination of P. polymyxa and B. cereus may be a potential biocontrol agent to promote the resistance of ginseng to disease and improve the yield, quality, and pesticide degradation.

EFFECTS OF BIOLOGICALS AND PLANT GROWTH REGULATORS ON THE SOWING QUALITY OF EGGPLANT SEEDS

Purpose. To investigate effects of biologicals with fungicidal and stimulating activities and natural and synthetic plant growth regulators on the sowing quality of seeds of various eggplant hybrids. Methods. Laboratory methods in compliance with DSTU 4138:2002. Results. Soaking of seeds of various eggplant hybrids in Phytocid, Mycosan-B, PhytoHelp, MycoHelp, Azotophyt, Vympel, Humisol, Ivin, and Emistim C solutions had positive effects on the sowing quality of seed: the germination energy increased on average by 1–34% and the laboratory germinability – by 2–28%. Regardless of the hybrid, soaking of seeds in Phytocid, PhytoHelp, and MycoHelp solutions significantly increased the germination energy by 34.2%, 32.5%, and 32.5%, respectively, compared to the control and the laboratory germinability of seeds by 27.6%, 27, 4% and 27.4%, respectively. When plant growth regulators Azotophyt, Ivin, and Emistim C were applied, the germination energy and laboratory germinability increased on average by 18–28% and 15–24%, respectively, compared to the control. With Mycosan-B, Vympel, and Humisol, the germinability and germination energy of seeds did not differ from the control levels. Soaking of eggplant seeds in solutions of the studied formulations positively affected the seedling length: there was on average a 1.24- to 1.94-fold elongation of seedlings. It was found that seeds of the investigated eggplant hybrids were contaminated with phytopathogenic micromycetes and, depending on damage degree, the hybrids were ranked in the following order: 'Sapfir'> 'Sharapova', 'Samurai' > 'Leire' > 'Night Lady', 'Fabina' > 'Destan'. Mycosan-B, Vympel, and Humisol were little effective (2.5–6.3%) against phytopathogens in comparison with the other formulations. Phytocid, PhytoHelp, and MycoHelp exerted potent fungicidal effects, which varied on different hybrids: 42.5–68.8%, 30.0–65.6%, and 32.5–65.6%, respectively. The fungicidal effectiveness of Ivin and Emistim C was 20.3% and 18.8%, respectively. Conclusions. Soaking of eggplant seeds in solutions of biologicals (Phytocid, PhytoHelp, and MycoHelp) and synthetic and natural plant growth regulators (Ivin and Emistim C, respectively) was shown to beneficially affect the sowing quality of seeds and suppress fungal phytopathogens. The greatest stimulatory effects of Phytocid, PhytoHelp, MycoHelp, Ivin, and Emistim C on the sowing quality of seeds were seen on hybs. 'Destan', 'Leire', and 'Fabina'. 51–58% suppression of phytopathogens was achieved when eggplant seeds were soaked in Phytocid, PhytoHelp, and MycoHelp; Ivin and Emistim C resulted in 19–20% suppression. The greatest suppression of phytopathogens on eggplant seeds was observed on hybs. 'Destan', 'Leire', 'Night Lady', and 'Fabina'.

Integrated Management of Stem and Root Rot of Cowpea Caused by Macrophomina phaseolina (Tassi.) Goid. using Fungicides, Bioagents and Organic Manures

Background: Cowpea crop is affected by various biotic and abiotic stresses which are responsible for its poor quality and low yield resulting in severe economic losses. Among the root diseases, stem and root rot caused by Macrophomina phaseolina is an important disease causing the yield losses ranging from 50-55 per cent. So, there is a need to formulate suitable management practices against root rot. Methods: Field experiment was laid-out in a randomized complete block design with three replications at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad during rabi 2021-22 and 2022-23 to determine the efficacy of economically viable and effective fungicides, bioagents and organic manures against stem and root rot of cowpea. The per cent disease incidence and yield per hectare were taken into consideration for statistical analysis. Result: In laboratory experiments, it was found that, the seed dressing fungicides mancozeb 50% + carbendazim 25% WP and carboxin 37.5% + thiram 37.5% DS were the most effective against M. phaseolina. Similarly, among the bioagents tested, T. harzianum was the most effective followed by T. Viride and P. fluorescens. A two-years evaluation of nine integrated treatment modules for rabi seasons revealed that, seed treatment with carboxin 37.5% + thiram 37.5 % WS resulted in the lowest disease incidence and the highest grain yield, 100 seed weight and B:C ratio. Cowpea stem and root rot incidence was increased with soil temperature and decreased with soil moisture.

Field efficacy of novel fungicides against chickpea rust (Uromyces ciceris-arietini)

The host resistance in present-day chickpea cultivars against rust disease is lacking thus, the present study was carried out during the winter (rabi) seasons of 2019–20 and 2020–21 at Regional Research Station, ICAR-Indian Institute of Pulses Research, Dharwad, Karnataka to explore effective fungicides for the management of chickpea rust. All fungicides found to reduce chickpea rust severity, but differences in efficacy were observed throughout the study. Present studies revealed that two sprays of 0.1% azoxystrobin 18.2% + difenoconazole 11.4% sc fungicide at 15 days interval minimizes the rust severity to the tune of >77% and achieved a benefit cost (B:C) ratio of 2.32 i.e. in terms of monetary value farmers could get a net income of ₹35268/ha. Thus, timely spraying of identified modern fungicide combination can be taken advantage for better control of chickpea rust.

Evaluation of fungicides to manage rice false smut (Ustilaginoidea virens) in the hills of Nepal

Rice False Smut (RFS) caused by Ustilaginoidea virens is a major emerging disease of rice due to expanded area of hybrid rice cultivars, increasing use of nitrogenous fertilizers and change in climate. Due to the increasing incidences of this disease across the globe, there is a pressing need to develop techniques for false smut management. The application of fungicides with high efficiency, low toxicity, and low residue is currently the best option to control RFS. Therefore, current research was conducted to determine the effectiveness of fungicides to manage RFS. The experiments were conducted in a completely randomized block design with three replications of seven treatments at RFS-prone subtropical hills of Nepal in the main rice growing season, during 2020 and 2021. The fungicides include trifloxystrobin 25 % + tebuconazole 50 %, chlorothalonil 75 %, carbendazim 12 % + mancozeb 63 %, propiconazole 25 %, azoxystrobin 50 %, carbendazim 50 % and untreated control. Fungicides were applied as two foliar sprays, one at booting and the other at flowering. Fungicide spray significantly increased number of tillers per plant (P ≤ 0.01) and reduced the number of false smut-infected tillers per plant (P ≤ 0.05), false smut severity (P ≤ 0.05), and incidence (P ≤ 0.05). False smut incidence percentages were significantly reduced by all the fungicides except mancozeb + carbendazim compared to the non-treated control. The reduction in RFS incidence was 70 % in propiconazole, 71 % in trifloxystrobin + tebuconazole sprayed plots compared to the non-treated control plots. Thus, the application of suitable fungicide at the appropriate stage would give the satisfactory suppression of RFS in a farmers' field in Nepal.

Effects of Several Fungicides on the Spore Growth Period of Alternaria dauci, a Carrot Black Leaf Blight Fungus, Using a Rezasulin-based Spore Survival Assay

The effects of five fungicides on the spore growth phase of Alternaria dauci, which causes carrot leaf blight, were tested using the spore viability assay (SVA) and agar dilution method (ADM). The average EC50 values for chlorothalonil against seven isolates of A. dauci examined by SVA and ADM were 14.21 μg/ml and more than 100 μg/ml. Dithianon and folpet also had lower EC50 values in SVA than in ADM, while iminoctadine tris-albesilate had lower EC50 value in ADM. For fluazinam, the EC50 values of SVA and ADM were 1.63 and 2.40 μg/ml, respectively. As EC50 values of five fungicides according to the spore growth phase of A. dauci KACC 42997, the efficacy of each fungicide as chlorothalonil, dithianon, and folpet decreased when treated after spore germination rather than when treated with spores before germination. However, iminoctadine tris-albesilate was more effective when treated after spores germinated than when treated before treatment. The excellent effect of fluazinam on the pathogen was maintained until A. dauci KACC 42997 was cultured in potato dextrose broth for 6 hr and the germ tube grew beyond the size of the spore. However, when treated with iminoctadine tris-albesilate and fluazinam after culturing for 12 hr, as the EC50 values of the two fungicides increased to 8.87 and 20.65 μg/ml, their efficacies decreased. The results of this study show that the treatment time of the fungicide should be determined by considering the effect of the fungicide on the spore growth phase of pathogens.