Control Of Leaf Spot Research Articles

Dodine as an alternative to chlorothalonil in the control of leaf spot diseases in peanut

AbstractPeanut (Arachis hypogaea L.) is susceptible to leaf spot diseases caused by the fungi Nothopassalora personata and Passalora arachidicola, which can decrease yield substantially. Chlorothalonil is one of the most widely used fungicides to control these diseases but was recently banned in the European Union due to toxicity to amphibians and fish. Dodine is an alternative fungicide with a similar range of activity. However, information about its impact on the peanut physiology is lacking. The objectives of this study were to assess the effect of dodine on leaf photosynthesis, yield, and pod quality of peanut and evaluate the potential of dodine as a replacement of chlorothalonil in the control of leaf spot diseases. A 3‐year field experiment was conducted using Georgia‐06G. Treatments consisted of chlorothalonil at 0.86 kg a.i. ha−1 (high rate), chlorothalonil at 0.43 kg a.i. ha−1 (low rate), dodine at 0.68 kg a.i. ha−1 (high rate), and dodine at 0.34 kg a.i. ha−1 (low rate). Photosynthetic efficiency was altered by fungicide in only a few instances, and a clear trend was not observed. The high rate of dodine resulted in the least defoliation caused by leaf spot of all fungicide treatments. Pod maturity, yield, and grading parameters were not affected by fungicide. Overall, dodine did not impact negatively the photosynthetic activity, pod quality, and yield of peanut. Moreover, this chemistry was efficient in controlling leaf spot diseases under heavy disease pressure; therefore, dodine is a potential replacement of chlorothalonil in the control of leaf spot diseases in peanut.

Enhancing Sesame Productivity and Profitability with Cluster Front Line Demonstrations in Andhra Pradesh's Nellore District, India

Sesame (Sesamum indicum L.) is one of the most important oil crops grown in the Nellore district of Andhra Pradesh along with groundnut. Sesame productivity in the district is low and efforts have been made to increase productivity and area by using high-yielding varieties along with integrated crop management (ICM) practices. In the farmer's field, ICM practices like sowing of improved variety (YLM 66), seed treatment, providing sticky traps to monitor sucking pest vectors, application of neem oil at flowering, spraying of monocrotophos at capsule development stage are used. Insect control and carbendazim spray for leaf spot control have been demonstrated. The results showed that in 2021-22 and 2022-23, seed yield improved by 9.9 and 11.2 percent compared to farmers' practices. Economically, demonstration practices have been found to produce higher net profit per hectare over the years compared to farmer practices. In 2021-2022 and 2022-2023, the B:C ratio was 2.76 and 3.08. To increase oilseed production, farmers in Nellore should adopt economically viable techniques based on the technology rate percentage, which ranges from 21.0% to 27.0%.

Luobuma Leaf Spot Disease Caused by Alternaria tenuissima in China.

Luobuma (Apocynum venetum and Poacynum hendersonni) is widely cultivated for environmental conservation, medicinal purposes and the textile industry. In 2018, a severe leaf spot disease that attacked the leaves of Luobuma was observed in plants cultivated in Yuzhong County, Gansu Province, China. Symptoms of the disease appeared as white or off-white spots surrounded by brown margins on the leaves of A. venetum. The spots expanded and covered a large area of the leaf, presenting as "cankers" with progression of the disease, leading to leaf death. The initial symptoms of the disease on P. hendersonni were similar to the symptoms of A. venetum, with a larger disease spot than A. venetum, and the spot was black and thicker. The aim of this study was to identify the fungal species and evaluate the effectiveness of fungicides (hymexazol and zhongshengmycin) against the pathogen in vitro. The fungi species that caused the new disease was identified as Alternaria tenuissima based on the morphological characteristics, pathogenicity tests, and phylogenetic analysis of the internal transcribed spacer (ITS) region, glyceraldehyde 3-phosphate dehydrogenase (gpd), translation elongation factor 1-alpha (TEF) and the histone 3 (H3) gene sequences. The findings showed that hymexazol fungicide can be used to control leaf spot disease. This is the first report on Luobuma leaf spot disease caused by A. tenuissima in China.

Cultivar and Fungicide Evaluations for Cercospora Leaf Spot Control in Organic and Conventional Table Beet Production

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most destructive foliar disease of table beet (Beta vulgaris ssp. vulgaris) in Wisconsin, USA, and globally. Under conducive conditions, symptomatic lesions on the leaf expand and coalesce forming large necrotic areas that can ultimately lead to complete defoliation. This damage reduces productivity and threatens the ability to mechanically harvest. CLS damage also detracts from the visual appeal of fresh market bunched beets to such an extent that growers risk buyer rejection if CLS severity is observed to be greater than 5%. Fungicide use for CLS control is threatened by the emergence of resistant C. beticola strains, and the application of host resistance is constrained by limited knowledge of cultivar reaction to CLS in table beet. This study aimed to address the knowledge gaps of fungicide efficacy and cultivar reaction by conducting replicated field trials in multiple table beet growing environments across Wisconsin. Broad variation for resistance to CLS was observed among the 10 included cultivars. The mean area under disease progress curve (AUDPC) across environments for the most susceptible cultivar was 267% greater than the most resistant cultivar. Spearman correlations between environments for mean cultivar AUDPC value ranged from 0.71 to 0.99, revealing consistent cultivar CLS reactions across environments. Although susceptible cultivars surpassed 5% severity in all environments, the resistant cultivars remained below this threshold in six of the 10 environments. By comparison with resistant sugar beet (Beta vulgaris ssp. vulgaris) cultivars, however, all tested table beets appeared susceptible to CLS, highlighting the potential for a CLS breeding effort in table beet. Neither of the evaluated Organic Materials Review Institute–listed treatments were effective at limiting CLS disease progress, whereas both tested conventional fungicides significantly reduced disease severity over the nontreated plots. These findings may provide helpful guidance to table beet growers affected by CLS in Wisconsin and beyond.

Bacillus velezensis and Paenibacillus peoriae Strains Effective as Biocontrol Agents against Xanthomonas Bacterial Spot

Gram-negative bacteria belonging to the Xanthomonas genus include plant pathogens representing a major challenge in the field of agriculture for a wide variety of economically important crops, such as tomato, pepper, and lettuce. Due to the massive usage of agrochemicals, Xanthomonas spp. are developing resistance to copper pesticides typically used to control microbial infections. An interesting alternative approach to control bacterial phytopathogens consists of using eco-friendly biocontrol agents, often beneficial microorganisms. Here, following the targeted, broad-spectrum screening of thousands of microorganisms isolated from different environmental locations, we isolated Bacillus velezensis strain 71 and Paenibacillus peoriae strain To99 displaying potent antagonistic activity against Xanthomonas spp. We found that oxydifficidin and polymyxin A secreted by B. velezensis 71 and P. peoriae To99, respectively, are mainly responsible for the anti-Xanthomonas activity. We further evaluated the performance of cell suspensions and cell-free supernatants of these isolates in controlling tomato bacterial spot disease in growth chamber and greenhouse conditions to validate the in vitro results. The overall results demonstrate the potential of treatments based on the secondary metabolites from both isolates and their cells as an alternative to copper-based chemicals to control leaf spot diseases caused by Xanthomonas spp. phytopathogens.

Chitosan Enhances Low-Dosage Difenoconazole to Efficiently Control Leaf Spot Disease in Pseudostellaria heterophylla (Miq.) Pax.

Pseudostellaria heterophylla (Miq.) Pax is a popular clinical herb and nutritious health food. However, leaf spot disease caused by fungal pathogens frequently occurs and seriously influences the growth, quality, and yield of P. heterophylla. In this work, the field control roles of difenoconazole, chitosan, and their combination in the leaf spot disease in P. heterophylla and their effects on the disease resistance, photosynthetic capacity, medicinal quality, and root yield of P. heterophylla are investigated. The results manifest that 37% difenoconazole water-dispersible granule (WDG) with 5000-time + chitosan 500-time dilution liquid had a superior control capacity on leaf spot disease with the control effects of 91.17%~88.19% at 15~30 days after the last spraying, which significantly (p < 0.05) exceeded that of 37% difenoconazole WDG 3000-time dilution liquid and was significantly (p < 0.01) higher than that of 37% difenoconazole WDG 5000-time dilution liquid, chitosan 500-time dilution liquid, or chitosan 1000-time dilution liquid. Simultaneously, this combination could more effectively enhance the disease resistance, photosynthetic capacity, medicinal quality, and tuberous root yield of P. heterophylla compared to when these elements were applied alone, as well as effectively reduce difenoconazole application. This study emphasizes that chitosan combined with a low dosage of difenoconazole can be proposed as a green, efficient, and alternative formula for controlling leaf spot disease in P. heterophylla and enhancing its resistance, photosynthesis, quality, and yield.

Control of sesame bacterial leaf spot with copper fungicides

In recent years, Mie Prefecture has been working to establish a domestic production area for sesame (Sesamum indicum L.), and the cultivation area has been increasing. Meanwhile, there is a wide incidence of sesame bacterial leaf spot (caused by Pseudomonas syringae pv. sesami Young, Dye & Wilkie, Acidovorax valerianellae Gardan, Stead, Dauga & Gillis, and Xanthomonas sp.), contributing to yield loss. No pesticides against the disease are currently registered in Japan, and no control measures have been established. We evaluated three copper fungicides (basic copper sulfate, sodium bicarbonate/anhydrous copper sulfate, and basic copper chloride/sulfur) in pot and field tests. Our results demonstrated that all fungicides could suppress the disease when applied before its onset or in its early stage.

Identification of a New Pathogenic fungi Causing Sorghum Leaf Spot Disease and Its Management Using Natural Product and Microorganisms.

Sorghum bicolor is cultivated worldwide. Leaf spot of sorghum, which leads to leaf lesions and yield reduction, is a prevalent and serious disease in Guizhou Province, southwest China. In August 2021, new leaf spot symptoms were observed on sorghum leaves. In this study, traditional methods and modern molecular biology techniques were used to isolate and identify the pathogen. Sorghum inoculated with the isolate GY1021 resulted in reddish brown lesion that similar to symptoms observed in the field: the original isolate inoculated was reisolated and Koch's postulates were fulfilled. Based on morphological features and phylogenetic analysis of the internal transcribed spacer (ITS) combined sequence with β-tubulin (TUB2) and translation elongation factor 1-α (TEF-1α) genes, the isolate was identified as Fusarium thapsinum (Strain accession: GY 1021; GenBank Accession: ITS (ON882046), TEF-1α (OP096445), and β-TUB (OP096446)). Then, we studied the bioactivity of various natural products and microorganisms against F. thapsinum using the dual culture experiment. Carvacrol, 2-allylphenol, honokiol, and cinnamaldehyde showed excellent antifungal activity, with EC50 values of 24.19, 7.18, 46.18, and 52.81 µg/mL, respectively. The bioactivity of six antagonistic bacteria was measured using a dual culture experiment and the mycelial growth rate method. Paenibacillus polymyxa, Bacillus amyloliquefaciens and Bacillus velezensis displayed significant antifungal effects against F. thapsinum. This study provides a theoretical basis for the green control of leaf spot of sorghum.

Comparative transcriptomics provides insights into the pathogenic immune response of brown leaf spots in weeping forsythia.

Weeping forsythia is an important ornamental, ecological, and medicinal plant. Brown leaf spots reduce the large-scale production of weeping forsythia as a medicinal crop. Alternaria alternata is a pathogen causing brown leaf spots in weeping forsythia; however, its pathogenesis and the immune response mechanisms of weeping forsythia remain unclear. In this study, we identified the two mechanisms based on morphological anatomy, physiological indexes, and gene expression analyses. Our results showed that A. alternata induced leaf stomata to open, invaded the mesophyll, dissolved the cell wall, destroyed the cell membrane, and decreased the number of chloroplasts by up-regulating the expression of auxin-activated signaling pathway genes. A. alternata also down-regulated iron ion homeostasis and binding-related genes, which caused an increase in the levels of iron ions and reactive oxygen species in leaves. These processes eventually led to programmed cell death, destroying palisade and spongy tissues and causing the formation of iron rust spots. A. alternata also caused defense and hypersensitive responses in weeping forsythia through signaling pathways mediated by flg22-like and elf18-like polypeptides, ethylene, H2O2, and bacterial secretion systems. Our study provides a theoretical basis for the control of brown leaf spots in weeping forsythia.

First Report of Didymella sinensis Causing Leaf Blight on Italian Ryegrass in China.

Italian ryegrass (Lolium multiflorum Lam.) is a high-yield, high-quality forage grass and is cultivated widely in southern China. In April 2021, small black spots were observed on leaves of Italian ryegrass in the field of about 300 ha located in DuShan county, Guizhou province, China (25.62056°N, 107.53139°E). Approximately 1 to 3% of plants were affected. For isolation, eleven tissue pieces (about 0.5 × 1 cm) from four symptomatic leaves were surface-disinfested in 75% ethanol solution for 40s, rinsed thrice in sterilized distilled water and air dried; then these tissues were plated on potato dextrose agar (PDA), and incubated at 25°C for 4 days in the dark. Nine fungal isolates with similar colony characteristics were obtained, and three representative isolates (LMDS1, LMDS2 and LMDS3) were selected for further study. Colonies on PDA were 47 to 57 mm diam after 5 days, margin regular, dark gray in the center surrounded by white to gray, with floccose aerial mycelia on the upper side, and dark brown to black on the reverse side. There was no fungal sporulation when these isolates were incubated under continuous ultraviolet light on PDA, oatmeal agar (OA), malt extract agar (MEA) and potato carrot agar (PCA). ITS-rDNA, LSU-rDNA, and two other protein-coding genes (RPB2 and TUB2) were amplified with primers described by Chen et al. (2017). Sequences were deposited in GenBank (ON692740 to ON692742 for ITS, ON692775 to ON692777 for LSU, ON704660 to ON704662 for RPB2, and ON704657 to ON704659 for TUB2). BLAST analysis of all these four segments showed >99.7% identity with those sequences of ex-type isolate CGMCC 3.18348 of D. sinensis (Chen et al. 2017; Hou et al. 2020). Maximum likelihood (RAxML) phylogenetic tree based on the combined ITS, LSU, RPB2 and TUB2 alignments also showed these three isolates and the other two reported D. sinensis isolates formed a subclade with 100% bootstrap support. Referring to our previous method (Xue et al. 2020), five 8-week-old healthy plants of Italian ryegrass were spray-inoculated separately with a mycelial suspension of about 1.5 × 104 CFU/ml. In addition, five plants considered as non-inoculated controls were sprayed with sterilized distilled water. All plants were individually covered with transparent polyethylene bags for 5 days to maintain high relative humidity and placed in a greenhouse at 23 to 26°C. The small black spots similar to those observed on infected plants in the field developed on leaves fifteen days after inoculation. The symptoms consisted of brown to dark brown spots when leaves were severely infected; however, symptoms were not observed on non-inoculated plants (controls). Pathogenicity tests were carried out three times. The same fungus was re-isolated from the lesions, and confirmed by morphological characterization and molecular technique as described above, thus fulfilling Koch's postulates. To the best of our knowledge, this is the first report of D. sinensis causing leaf blight on Italian ryegrass in China. The accurate identification of this pathogen would be useful for the prevention and control of leaf spot on Italian ryegrass in the future.

BIOCONTROL OF RUST AND LEAF SPOTS DISEASES OF PEANUT USING CULTURE FILTRATES OF AKANTHOMYCESLECANIIIN NATURALCONDITIONS IN BURKINA FASO

Leaf spots and rust are the most destructive diseases of peanut in Tropical Africa, but it has shown that Akanthomyceslecanii isknown ashyperparasiteof rustandleaf spots fungi. Previous studies have investigated on the use of conidia of A.lecaniiin biocontrol of these diseases. However, the conidia are influenced by temperature and relative humidity, which could result in low efficiency of biocontrol agents in natural conditions. The use of secondary metabolites could help to fight against the plant diseases in natural conditions. Thus, we sprayed peanut plants with culture filtrates from 21-day-old cultures of two strains of A. lecanii grown in potato dextrose broth, to assess their efficiency against leaf spots and rust diseases innatural conditions. A susceptible variety SH470P and a moderately susceptible varietyPC79-79 of peanut to rust and leaf spots diseases were used. Our findings revealed that A. lecanii culture filtrates have significantly reduced the severity of rust and leaf spots diseases in SH470P only. In SH470P, the lowest severity of leaf spots in 2020 (59.26%) and 2021 (48.10%) were recorded in plots sprayed with culture filtrates of A. lecanii. The lowestseverity of rust (29.60%) was recorded in the plots sprayed with the A. lecanii culture filtrates in 2021 in SH470P. From our findings, the use of A. lecanii culture filtrates is a promising alternative in the control of peanut rust and leaf spots. But, further studies are required to determine the effective doses and active secondary metabolites against these diseases.

Using Inpyrfluxam to Control Peanut (Arachis hypogaea L.) Foliar and Soil-Borne Diseases

Aims: To determine peanut disease control and yield response to inpyrfluxam applied at various timings during the growing season.&#x0D; Study Design: Randomized complete block design with 4 reps.&#x0D; Place and Duration of Study: Field studies were conducted from 2016 through 2020 in the south Texas peanut growing region near Yoakum (29.276o N, 97.123o W).&#x0D; Methodology: Fungicides were applied with a CO2-propellant sprayer. The spray boom was equipped with three D2-23 hollow-cone spray nozzles per row with the middle nozzle centered over each plant in the row and another nozzle located as such to spray on each side of the plant to provide thorough coverage with a spray volume was 187 L ha-1. Some studies included a non-treated control while other studies included chlorothalonil only at 1.26 kg ha-1 as the comparison treatment. Each plot consisted of four rows spaced 97 cm apart and 7.9 m long.&#x0D; Results: Inpyrfluxam applied twice in a 4 to 5 fungicide spray program in combination with chlorothalonil provided early leaf spot control as good as or better than the standards of chlorothalonil plus either azoxystrobin alone or azoxystrobin plus benzovindiflupyr applied 2 times. Control of Rhizoctonia pod rot, caused by Rhizoctonia solani Kuhn, with inpyrfluxam at 0.04, 0.05. 0.075, or 0.1 kg ai ha-1 applied 2 times during the growing season was comparable to two applications of azoxystrobin at 0.22 kg ai ha-1. Control of southern blight, caused by Sclerotium rolfsii Sacc., with one to two applications of inpyrfluxam at 0.05 to 0.1 kg ha-1 was comparable to azoxystrobin plus benzovindiflupyr. Peanut yield response was influenced by the level of soilborne and foliar disease control exhibited with each fungicide program, as those programs which provided the best control also produced the highest yield.&#x0D; Conclusion: These studies show the ability of inpyrfluxam to provide control of multiple diseases found in southwest peanut production.

Identification, characterization and chemical management of Alternaria alternata causing blackcurrant leaf spot inChina.

The aims of this study were to identify the pathogen causing blackcurrant leaf spot, assess the pathogenicity of different isolates, the host range, and the sensitivity to common fungicides, and test the effectiveness of field control for controlling A. alternata in blackcurrants in China, and potentially elsewhere. In 2020 and 2021, an uncommon leaf spot on blackcurrants was observed in Harbin (125°42'-130°10'E, 44°04'-46°40'N), Heilongjiang Province, China. Based on morphological, molecular characteristics, and phylogenetic analyses, 10 fungal isolates, identified as Alternaria alternata, were obtained from infected blackcurrant leaves of 10 infected plants in this study. To our knowledge, this is the first description of A. alternata as a causal agent of leaf spot on blackcurrants in China. A. alternata has a wide host range and infects eight of the 10 crop and ornamental plants evaluated, namely Sorbus pohuashanensis, Malus pumila, Rosa davurica, Padus racemosa, Hippophae rhamnoides, Crataegus pinnatifida, Pyrus ussuriensis, and Sambucus williamsii, but not Viburnum trilobum and Prunus tomentosa. Moreover, ten blackcurrant cultivars were screened and found to have contrasting levels of resistance to A. alternata. One was moderately resistant, four were resistant, four were susceptible, and one was highly susceptible. The A. alternata isolate was most sensitive to propiconazole-azoxystrobin, with EC50 values of 0.0038 μg ml-1 and efficacy ranging between 83.34% and 84.13% at 317 μg ml-1 in the field. The work reported that A. alternata is the pathogen that causes blackcurrant leaf spot in northern China. It can infect a variety of crops and ornamental plants. Considering the control cost and effect, propiconazole-azoxystrobin is more suitable for controlling leaf spot in the field.

Evaluation and control of Alternaria alternata causing leaf spot in soybean in Northeast China.

The aims of this study were to characterize the causal agent of soybean leaf spot and determine the pathogenicity of the pathogen to the main crops in Northeast China and detect the sensitivity of pathogens to the main chemical fungicides and the potted control effect. In 2020 and 2021, an uncommon leaf spot was observed in Harbin, Heilongjiang Province (125°42'-130°10'E, 44°04'-46°40'N), China. The pathogen can infect soybean leaves and cause leaf spot. We collected diseased soybean leaves and isolated four pathogen organisms, all of which were identified as Alternaria alternata through morphological and molecular identification. Koch's postulates were used to confirm pathogenicity. To the best of our knowledge, this is the first report on soybean leaf spot disease caused by A. alternata in northeast China. Moreover, A. alternata had a broad host range and caused leaf spot in most legumes. However, it did not infect medicated lentil (Dolicho Lablab L.) or tobacco (Nicotiana tabacum L.). Assessment of A. alternaria susceptibility to fungicides by spore germination method, isolates of A. alternata were most sensitive to flusilazole, with EC50 values of 0.0040-0.0053 μg ml-1. Through two pot experiments, the average control efficacy of 0.1 mg ml-1 flusilazole on soybean leaf spot caused by A. alternata was 80.7%. The work reported that A. alternata is the pathogen organism that causes soybean leaf spot in northern China. The pathogen organism can infect a variety of leguminous plants. Considering the control cost and effect, flusilazole is more suitable for controlling leaf spot disease in the field, and benzoxystrobin can be used as an alternative fungicide.

Diagnosis and Control of Brown Leaf Spot of Kiwi (Actinidia deliciosa) Using Biochar-Zinc Oxide Nanocomposite (MB-ZnO) as a Non-Toxic Bio-Fungicides

Kiwi is one of the best natural sources of vitamin C and has wide applications. During October–November 2021, small brown spots were examined on the Kiwi leaves. The diseased leaf samples were collected and placed on potato dextrose agar nutrient media for diagnosis. Morphological, anatomical, and molecular studies revealed this disease-causing agent to be Rhizopus oryzae. Molecular characterizations of the isolated pathogen were performed by using actin translation elongation factor (EF-1α) and ribosomal deoxyribose nucleotide inter transcribed sequence (rDNA ITS ITS1/ITS4) and elongation factors (EFl-F/EFl-R) primers. A BLAST study of the resultant ITS1/ITS4 sequence showed &gt; 99% resemblance with R. oryzae (MT603964.1), while the EF-1α sequence revealed 100% similarity with translation elongation factor-1α gene of R. oryzae (MK510718.1). The obtained ITS1/ITS4 sequence was submitted to NCBI (MW603842.1). Koch’s postulates established the pathogenicity of isolated R. oryzae and proved it to be the brown spot pathogen of Kiwi. For the environmentally-friendly management of Kiwi leaf spot, maize biochar-Zinc Oxide (MB-ZnO) nanocomposite was used. The prepared nanocomposite was characterized by Fourier transform infrared (FTIR) spectroscopy, thermo gravitational analysis (TGA), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. After successful preparation, MB-ZnO was assessed for its possible antifungal potential against R. oryzae. MB-ZnO displayed substantial growth inhibition, and the highest growth inhibition (79%) was observed at a 19 mg/mL dose rate of nanoparticles. These excellent findings propose that Ball-milled synthesis is a fast, economical, and environmentally friendly method for nanocomposite in the near future. The nanocomposite is used as a nominal substitute for chemical fungicides.

Comparison of Elemental Sulfur Products as Tank Mix Partners with Azoxystrobin for Management of Late Leaf Spot (Nothopassalora personata) of Peanut

Management of fungicide resistance in Nothopassalora personata, the cause of late leaf spot of peanut ( Arachis hypogaea), is a challenge in peanut production areas of the southeastern United States. Field experiments were conducted in Tifton, Georgia, in 2020 and 2021 and in Plains, Georgia, in 2021 to determine the effects of mixtures of seven elemental sulfur fungicide products with the quinone outside inhibitor (QoI) fungicide azoxystrobin on late leaf spot in fields where QoI-resistant populations of N. personata are suspected. Application of azoxystrobin or sulfur alone resulted in little reduction of the standardized area under the disease progress curve (SAUDPC) or final disease intensity ratings compared with the nontreated control. However, mixtures of azoxystrobin with all micronized sulfur products evaluated had SAUDPC values and final disease intensity ratings less than those in the azoxystrobin-alone or Microthiol Disperss 80W sulfur-alone treatments. One nonmicronized sulfur formulation had SAUDPC values and final intensity ratings similar to those of azoxystrobin or Microthiol Disperss 80W sulfur alone. The results suggest that multiple micronized elemental sulfur products have potential for use as mixing partners with azoxystrobin leaf spot control in fields where the efficacy of azoxystrobin alone is not adequate.

Temperature and Humidity Regulate Sporulation of Corynespora cassiicola That Is Associated with Pathogenicity in Cucumber (Cucumis sativus L.).

Cucumber target leaf spot, caused by Corynespora cassiicola, is an emerging disease with a high incidence that causes severe damage to cucumbers on a global scale. Therefore, efforts need to be undertaken to limit the spread and infection of this pathogen, preferably by using environmentally friendly methods. In this study, the effects of temperature and moisture on the sporulation of C. cassiicola were investigated in vitro and in vivo. The novelty of our study refers to the observation of spore production and size as well as the revelation of a correlation between spore size and virulence. On potato dextrose agar (PDA) and cucumber-leaf extract agar (CEA), temperature played a critical role in spore production, which was strongly influenced by both temperature and moisture on detached leaves and cucumber seedlings. Maximum spore production was found at 30 °C on PDA and 25 °C on CEA, cucumber detached leaves and living plants. Lower spore productions were observed with a stepwise change of 5 °C. In addition, the largest spore production was found at 100% relative humidity (RH) in comparison to the other tested moisture. Moreover, moisture was found to be the most important factor affecting spore size, accounting for 83.09-84.86% of the total variance in length and 44.72-73.10% of the total variance in width. The longest-narrowest spores were formed at 100% RH, and the shortest-widest spores were formed at 75% RH. Furthermore, the result showed that larger spores of C. cassiicola were more virulent and small spores were avirulent. Our findings will contribute to the development of new strategies for the effective alleviation and control of cucumber target leaf spot.

Seed Bio-priming Mediated Control of Cercospora Leaf Spot and Bacterial Wilt Disease Resistance in Chilli (Capsicum annuum L.) under New Alluvial Zone

The potential bio-control agents Trichoderma harzianum, and Pseudomonas fluorescens in alone or combinationwere used as seed bio-priming for reviewing their efficacy in the reduction of the devastating diseases, theCercospora leaf spot (Cercosporacapsici) and Bacterial wilt (Ralstonia solanacearum) of chilli (Capsicum annuumL.). Considering two important seasons, the Rabi season was comparatively vital as its disease severity wasmore. In chilli, the disease index was significantly reduced in combining the Trichoderma harzianum +Pseudomonas fluorescens treated seeds, followed by the T. harzianum treatment compared to the control (hydroprimed)against cercospora leaf spot of chilli. In case of Bacterial wilt, it was found that T3 followedbyPseudomonas fluorescens treated seeds. Chilli seeds were primed with Trichoderma harzianum + Pseudomonasfluorescens revealed maximum disease protection that was displaying favour in pre-kharif and early stage(35DAS) in comparison to rabi and 60DAS of chilli production. The ability of genotype indicated variationwhere the distinct variation was noticeable in V2 (G-4) mentioning its high tolerance at 35DAS. Theapplication of combined bio-priming may be suitable to control both Cercospora leaf spot and Bacterial wiltof chilli.

Trichoderma asperellum behave as antagonist to control leaf spot and flower blight of Marigold

Alternaria zinniae (Pape, 1942) causes leaf spot and blossom blight in marigolds, resulting in yield losses of 50-60 % in tropical and subtropical climates. Chemical controls can have a negative influence on ecosystems and agronomic control approaches are difficult to execute change to Chemical control are highly toxic, enhance biodegradation and cause environmental pollution after repeated use. Potential adverse effects on the earth and prolonged use have prompted a complete exclusion or limited utilization of most chemicals and an urgent need for eco-friendly and efficient tools. In vitro evidence for the possible use of Trichoderma spp. for biocontrol of marigold leaf spot and flower blight has been reported in previous investiga-tions. In this study, we used a dual culture approach to investigate the antagonistic and myco-parasitic properties of 4 Trichoderma asperellum strains against Alternaria zinniae in vitro.

Control of leaf spot in yam with leaf extracts of bitter melon

The use of plant extracts to induce resistance against pathogens has shown to be a promising alternative in the management of plant diseases. The objective was to evaluate the potential of ethanolic extract of Mormodica charantia on management of the Curvularia eragrostidis and enzyme activation involved on defense responses in yam (Dioscorea alata). The isolate of C. eragrostidis was obtained from leaves of yam with symptoms. Mycelial growth and sporulation were evaluated. The treatments were: extract of Momordica charantia 10, 100, 500 and 1000 ppm, acibenzolar-S-methyl (200 mg.L-1), fungicide (200 g.ha-1) and control. The evaluations were done daily, until the 15th day of the application of the treatments. The severity of the disease was evaluated at the end of the experiment, by the size of lesions in each plant. For determination of β-1,3-glucanase and phenylalanine ammonia lyase, leaves were collected in periods of 192 h after treatments application. Fungitoxic action of the treatments in the control of C. eragrostidis in vitro was verified. The M. charantia extract conferred significative levels of protection in yam plants against C. eragrostidis reducing incidence and disease severity. Thus, it was promoted increase in enzymatic activity, preconditioning yam in induced defense mechanisms.