Disease Severity Percentage Research Articles

On-farm demonstrations on management of gray mold disease of castor

Gray mold of castor is one of the major destructive diseases causing huge yield loss. In on-farm demonstrationson fungicidal management of gray mold conducted during kharif 2017 and 2019 at different locations in Mahabubnagar Dist. and IIOR farm fields revealed that two sprays of propiconazole @0.1% recorded least percent disease severity and significantly increased the seed yield.

The Potential of Arbuscular Mycorrhizal Fungi (AMF) as Biocontrol Agent Against Stem Rot Diseases Caused Sclerotium rolfsii of peanut (Arachis hypogaea L)

This study was conducted to assess the biocontrol efficacy of arbuscular mycorrhizae fungi (AM Fungi) against stem rot disease caused by Sclerotium rolfsii Sacc. in peanut. The AM Fungi can be associated with almost all types of plants. The purpose of this study was to obtain isolates of arbuscular mycorrhiza fungi (AMF) as a potential biofungisida against Sclerotium rolfsii and can characterize the mechanism of the FMA in controlling S.rolfsii (salicylic acid) on peanut plants. The AM Fungi inoculant (40 spores g-1 in concentration) was introduced to peanut seedling (25 g plant-1 ) at planting time where as Sclerotium rolfsii inoculated 30 days after planting time. The experiment was arranged in the completely randomized design (CRD), which is 7 treatment sand repeated 10 times in the greenhouse experiment. The data were analyzed using analysis of variance (ANOVA) using STAT program 8 and the Tukey test at 5% significance level. The AM Fungi treatments showed significantly redused the percentage of disease severity in infected peanut plants around 34.28% - 57.15% and longer incubation period, respectively. They increased root colonization (20,00 - 46.67%) with a middle to high category. The AM Fungi C isolate (isolated from Solok county), and the A isolate (isolated from Payakumbuh city) were the best as a biocontrol against S rolfsii (57.15%), followed by isolate D (isolated from Padang Pariaman county) 54,30 %. They also increased Salicylic acid content 1,4 times (70.72 ppm) compared to control (49,59 ppm). It can be concluded that the application of AM Fungi as a biocontrol agent played an important role in plant resistance and exhibit greater potential to protect peanut plants against S. rolfsii.

The effective antagonistic potential of plant growth-promoting rhizobacteria against Alternaria solani-causing early blight disease in tomato plant

Tomato plants can be infected by several diseases, among them, the early blight disease, caused by the necrotrophic fungus Alternaria solani is very dangerous. Plant growth promoting rhizobacteria (PGPR) are enhanced the plant growth and suppress plant diseases. The current study was conducted in a pot experiment to investigate the bio-efficacy antagonistic bacterial isolates as either individual or combination against tomato early blight disease. Disease severity and protection percent, morphological indicators as well as yield characters were recorded. In vitro antagonistic activity assay of PGPR against A. solani was estimated. Metabolic indicators of resistance in plant as response to induction of systemic resistance (ISR) were recorded. Our results indicated that, PGPR isolates were reduced the percent disease severity by 13.0 % and recorded highly protection percent by 84.3 %. The beneficial effects of the used elicitors were extended to increase not only the morphological characters (shoot lengths, root lengths and leaflet number/plant) but also the yield characters. All tested elicitors caused the marked significant increases in the photosynthetic pigments. PGPR isolates were exhibited the most potent effect in terms of the contents of chlorophyll a, b and the total chlorophyll (a + b) followed by plants treated with A. xylosoxidans (A3), B. subtilis (B1) and L. fusiformis (L2) in the infected plants, compared to the non-treated infected control. PGPR isolates were increased total phenol (56.15 mg/100 g dry wt.), free proline (1.435 mg/g dry wt.), total protein (1.198 mg/g dry wt.) and the activities of peroxidase (0.705 μg/100 g fresh wt.) and polyphenol oxidase (1.281 μg/100 g fresh wt.). All the tested treatments resulted in increasing the contents of indole acetic acid (IAA), Abscisic Acid (ABA), Salicylic Acid (SA), and Jasmonic acid (JA) compared with those of the infected plants. PGPR isolates’ antifungal activity may be attributed to cell wall disruption of A. solani and the normal conidial development inhibition. Therefore, due to these outstanding properties of PGPR isolates as plant growth promoters and antifungal activity, this study could give insights for solving serious agricultural challenges and particularly in the treatment of A. solani invasion across the tomato plants.

Endobacterial symbiont of Fusarium oxysporum f.sp. cubense and the pathogenicity of their symbiosis towards banana plantling

Fusarium oxysporum f.sp. cubense (Foc), a causal agent of panama disease was reported carrying bacterial endosymbionts. This research aimed to identify the endobacteria in 7 Foc strains and to study their symbiosis effect on the Foc pathogenicity towards Ambon Kuning and Tanduk banana cultivars. The pathogenicity of endobacteria-Foc symbiosis were tested in vitro on banana plantling. Crude filtrate and biomass suspension that were produced by culturing each Foc strains for 21 days in static condition either in PDB (Potato Dextrose Broth) (Foc − ) or in antibiotics supplemented PDB (Foc +) were used as effectors. The Foc pathogenicity was stated as disease severity percentage on leaves and on rhizome. The result showed that all Foc strains contained endobacteria. Enterobacter sp. was hosted by Foc IPBCC 19.1427 and Izhakiella australiensis was in the hyphae of Foc IPBCC 19.1430. Enterobacter sp. affected Foc IPBCC 19.1427 virulence towards banana cv. Tanduk through effectors in the filtrate, while that towards cv. Ambon Kuning was unclear. Izhakiella australiensis did not affect Foc IPBCC 19.1430 virulence towards the two banana cultivars. The pathogenicity of Foc should further be verified, as the antibiotics given could not completely kill the endobacteria.

Mapping bacterial leaf blight disease of rice (Xanthomonas oryzae pv oryzae) in North Sumatra

Bacterial leaf blight is the most important rice disease in Indonesia and other rice producing countries in Asia. Bacterial leaf blight disease, caused by the bacterial pathogen Xanthomonas oryzae pv oryzae, has a wide distribution in the tropics and sub-tropics. This research was aimed to determine the distribution of the disease in North Sumatera. The research experiment was conducted using the survey method to calculate the incidence and severity of disease in rice crops in seven locations. The highest disease incidence was found in Sumber Tani Village, Batubara District, and in Talawi Siabal Abal Village, Sipahutar District of North Tapanuli with a disease incidence of 100%. The highest percentage of disease severity was found in Siabal Abal Village, Sipahutar District of North Tapanuli, with a percentage of 82% severity.

EVALUATION OF CERTAIN BIOCIDES AND CHEMICALS INDUCING RESISTANCE IN MANAGEMENT OF CUCUMBER DOWNY MILDEW UNDER PROTECTED CULTIVATION

Downy mildew of cucumber is caused by the fungus-like pathogen Pseudoperonospora cubensis (Berk and Curtis), which causes loss in the yield in Egypt especially under protected cultivation where low temperature and high humidity are prevalent. The efficiency of two Bio-control agents i.e. T34 (Trichoderma asperellum, 109 spore/cm3) and Bio-Cure-B (Pseudomonas fluorescens, 108 spore/cm3) as well as three resistance inducing chemicals (RICs), i.e. potassium dihydrogenphosphate (K2HPO4), salicylic acid (C7H6O3), and potassium nitrate (KNO3) were evaluated for controlling cucumber downy mildew under greenhouse and plastic house conditions. Greenhouse experiment data revealed that, spraying cucumber plants with either biocontrol agent or tested RICs two times i.e. 5 days before and/or nine days after artificially inoculated by the P. cubensis significantly reduced percentage of disease severity, meanwhile plant length and foliage fresh weight were increased in comparison with control treatments. The treatments increased the activity of peroxidase, β-1,3-glucanase, beside increase in total carbohydrates and total phenolic contents. Under plastic house, all tested biocides and/or RICs either alone or double combinations caused significant reduction in disease severity associated with significant increment in some growth parameter of cucumber plants (plant length and fruit yield) when compared with control treatments in both seasons. However, application of tested RICs mixture with tested biocides was more effective in this regard than the only application of them individually. In this respect, tested biocides were also more efficient than resistance inducing chemicals (RICs).

Genetic Diversity Studies and Identification of Molecular and Biochemical Markers Associated with Fusarium Wilt Resistance in Cultivated Faba Bean (Vicia faba).

Faba bean (Vicia faba L.) is one of the most important legume crops in Egypt. However, production of faba bean is affected by several diseases including fungal diseases. Fusarium wilt incited by Fusarium oxysporum Schlecht. was shown to be the most common wilt disease of faba bean in Assiut Governorate. Evaluation of 16 faba bean genotypes for the resistance to Fusarium wilt was carried out under greenhouse conditions. Three molecular marker systems (inter-simple sequence repeat [ISSR], sequence related amplified polymorphism [SRAP], and simple sequence repeat [SSR]) and a biochemical marker (protein profiles) were used to study the genetic diversity and detect molecular and biochemical markers associated with Fusarium wilt resistance in the tested genotypes. The results showed that certain genotypes of faba bean were resistant to Fusarium wilt, while most of the genotypes were highly susceptible. The percentage of disease severity ranged from 32.83% in Assiut-215 to 64.17% in Misr-3. The genotypes Assiut-215, Roomy-3, Marut-2, and Giza-2 were the most resistant, and the genotypes Misr-3, Misr-1, Assiut-143, Giza-40, and Roomy-80 performed as highly susceptible. The genotypes Assiut-215 and Roomy-3 were considered as promising sources of the resistance to Fusarium wilt. SRAP markers showed higher polymorphism (82.53%) compared with SSR (76.85%), ISSR markers (62.24%), and protein profile (31.82%). Specific molecular and biochemical markers associated with Fusarium wilt resistance were identified. The dendrogram based on combined data of molecular and biochemical markers grouped the 16 faba bean genotypes into three clusters. Cluster I included resistant genotypes, cluster II comprised all moderate genotypes and cluster III contained highly susceptible genotypes.

GanoCare® Improves Oil Palm Growth and Resistance against Ganoderma Basal Stem Rot Disease in Nursery and Field Trials.

Basal stem rot (BSR) caused by Ganoderma boninense is a major threat to sustainable oil palm production especially in Southeast Asia and has brought economic losses to the oil palm industry around the world. With no definitive cure at present, this study introduces a new fertilizer technology called GanoCare®, as an effort to suppress BSR incidence in oil palm. Experiments were carried out to evaluate the effect of GanoCare® on growth, physiology, and BSR disease suppression using sitting technique in the oil palm nursery stage. A follow-up using similar treatments was carried out in the field to test on severity of Ganoderma using baiting technique under natural condition. Treatments tested were 10 g/month and 30 g/three months given as pretreatment only or continuous treatment. Results showed that GanoCare® increased the height, bulb diameter, leaf area, chlorophyll content, photosynthesis rate, and fresh and dry weight of the leaf, bole, and root of oil palm seedlings in the nursery trial. Seedlings treated with GanoCare® exhibited reduced percentage of disease severity, incidence, and dead seedlings, compared to the control. In nursery and field, lowest percentage of dead seedlings due to Ganoderma was found in seedlings given combination of pretreatment and continuous treatment of 30 g/three months (T4) with 5.56 and 6.67%, while control seedlings significantly marked the maximum percentage of 94.45 and 93.33%. The most successful treatment in both nursery and field was T4 with disease reductions of 77.78 and 82.36%, respectively, proving that nutrients contained in GanoCare® are essential in allowing better development of a strong defense system in the seedlings.

Evaluation of Fungicides for the Management of Garlic White Rot (Sclerotium cepivorum) at Debre Berhan, Central Ethiopia

Garlic is one of the most important crops widely cultivated throughout the world including Ethiopia. It is the second most widely cultivated Allium species next to onion. The production of the crop is majorly threatened by fungal diseases. White rot of garlic caused by Sclerotium cepivorum, is the most devastating constraint in Ethiopia. A field experiment was conducted to evaluate the effect of fungicide types on incidence and severity of garlic white rot, yield and yield components of garlic and to identify the effective method of fungicides application under rain fed supplemented with irrigation at Debre Berhan University Research site in 2017/18 .The experiment was consisted of three types of fungicides (Apron star, MORE 720 WP and Mancozeb) with three methods of application (clove, clove plus foliar and foliar). The experiment was laid out as RCBD in a factorial arrangement with three replications. Fungicide types and methods of application significantly affected disease incidence, percentage of disease severity, area under disease progress curve (AUDPC), yield and yield components. Clove and clove plus foliar applied Apron star was the most effective in reducing the disease epidemics and gave better yield advantage. Clove applied Apron star has reduced the initial severity, final severity and incidence by 64.7%, 70.9% and 80.6% respectively, as compared to the untreated plots. About 63.6% and 51.9% increment of average bulb weight and yield were recorded in clove applied Apron star respectively, as compared to the untreated plots. The highest net return (35,350 birr) was obtained from clove applied Apron star plots, while the lowest net return (2350 birr) was obtained from foliar applied Apron star plots. Hence, it could be concluded that clove applied with Apron star needs to use for the disease management in the study area

Effect of Varieties and Fungicide Application Frequencies on Late Blight (Phytophthora infestans) Disease Development and Fruit Yield of Tomato in North Western Tigray, Ethiopia

Diseases like late blight are among the major constraints that limit tomato production in most tomato growing regions. Field experiment was conducted in North Western Tigray in 2018 main season with objectives: to investigate the effect of varieties and fungicide application frequencies on late blight disease development and tomato fruit yield. The treatments consisted of four tomato varieties (Melkashola, Melkasalsa, Sirinka-1 and Gelilema) and five application frequencies of the fungicide Matco 72% WP including the control. The experiment was laid out in a split plot design with three replications. Results indicated that integration of varieties and fungicide spray frequencies significantly reduced late blight disease development and maximizes tomato fruit yield. Melkasalsa variety is found better with lowest disease incidence (36.87%), disease severity (26.83%), AUDPC (587.5% days), DPR (0.0604unit per days) and highest marketable (50.05 tha-1) and highest total fruit yield (54.63 t ha-1) when sprayed four times. The highest percent disease incidence (81.50%), disease severity (74.60%), AUDPC (1558.3% days) and Disease Progress Rate (DPR) (0.1074 units per day) were obtained from untreated Gelilema variety. The lowest fruit yield (35.02 tha- 1) was harvested from none sprayed Gelilema variety. Highest MRR of 3058% was obtained on Melkasalsa variety treated thrice. Thus it is recommended to use 3 sprayings of the fungicide Matco 72% WP at 10 days interval where the variety Melkasalsa is to be used in the study area. However, other management practices should be employed to this variety to confirm its resistance ability and to maximize its fruit yield in the presence of the disease in main season.

Evaluation of biological control agents for managing squash powdery mildew under greenhouse conditions

Squash (Cucurbita pepo L.), is one of the most important vegetable crops for human nutriment in Egypt and the world. One of the most serious diseases that infect squash and cause yield losses was powdery mildew, caused by Podosphaera xanthisii. The aim of this study was to investigate the role of Bacillus subtilis, Paenibacillus polymyxa (109 cell ml/1), Trichoderma harzianum, T. album, T. viride and T. hamatum (107 spore ml/l) for controlling disease under greenhouse conditions. Results indicated that all treatments significantly inhibited the conidial germination of P. xanthii than control in vitro and decreased the incidence and disease severity after spraying with the bio-agents on squash plants under greenhouse conditions. The fungicide, Topas-100 (10.0% penconazole “w/v” [(R,S-1-(2-(2,4-dichlorophenyl)-Q pentyl)-1H-1,2,4-triazole]), followed by B. subtilis was highly significant for decreasing disease incidence (2.8 and 5.3%, respectively) and disease severity percentage (3.5 and 4.8%, respectively) than the control. The activities of biochemical changes, i.e., peroxidase, polyphenol oxidase, and total phenols, were significantly upregulated as results of most treatments. Also, bio-agent treatments caused significant increase in yield characteristics of squash plants such as fruit number/plant and fruit weight/plant than control. B. subtilis recorded the highest increase (110.9% and 98.7%) in fruit number and fruit weight/plant than control.

EFFCIENCY OF SOME BIOLOGICAL AND CHEMICAL TREATMENTS AGAINST WHEAT ROOT AND CROWN ROT DISEASE

Fusarium culmorum(W.G. Smith) Sacc., Bipolaris sorokiniana (Sacc.) Shoemaker, Rhizoctonia oryzae Kuhn and Fusarium spp. were isolated from wheat plants exhibiting typical root and crown rot symptoms from different districts at Sharkia Governorate, Egypt during 2015/ 2016 growing season. Pathogenicity test revealed that B. sorokiniana was the most virulent one causing pre-emergence damping-off followed by Fusarium culmorum. In addition, F. culmorum was the most virulent one responsible for post-emergence damping-off incidence. Rhizoctonia oryzae showed the highest percentage of root rot, Moreover, F. culmorum and B. sorokiniana showed the highest percentage of disease incidence. In the same trend, F. culmorum induce the highest percentage of disease severity. In vitro, Trichoderma sp. bio-agent and its culture filtrate were the most effective treatment that reduced mycelial growth of the tested fungi. In vivo, it decreased pre and post-emergence damping off, root rot, disease incidence and disease severity compared with the control. In addition, the obtained results indicated a significant increase on healthy survival plants and significantly improved the plant growth parameters i.e. fresh and dry weights of shoots and roots, plant height, spike length and 1000 grain weight. In vitro,Score and Amistar-top fungicides were the most effective in inhibiting the mycelial growth of R. oryzae followed by Amistar-top on B. sorokinana and Score onF. culmorum.Score was the most effective treatment revealed the highest percentage of healthy survival plants followed by Amistar-top and gave the highest protection against root and crown rot disease as shown by disease incidence and severity percentages.

ANTAGONISTIC POTENTIAL OF RHIZOSPHERIC BIOCONTROL AGENTS AGAINST SOYBEAN ROOT ROT- WILT DISEASE COMPLEX SYNDROME

Biological control is an environmentally safe alternative technique for management of plant pathogenic fungi. This work aims to identify and characterize potential bioagents prevalent in soybean soil. A total of 27 fungal isolates were recovered from soybean plants exhibiting typical wilt and root rot symptoms. Pathogenicity of each isolate was examined on soybean seedlings, and the most pathogenic isolates, were selected. Those isolates were identified based on their microscopic features as Fusarium oxysporum Schlecht, F. solani Mart and Rhizoctonia solani Kuhn. The identity of each isolate was confirmed by molecular phylogeny based on internal transcribed spacer (ITS) sequence. Additional 31 microorganisms of the population within soybean rhizosphere were isolated and their potential antagonistic ability was characterized in vitro and in vivo. A collection of three fungi, four bacteria, one actinomycete and one yeast isolate showed significant reduction of mycelial growth of the tested fungal pathogens. The same potential bioagents allocate significant decrease in disease severity percentage of wilt-root rot complex disease under greenhouse and open field conditions compared with mycorrhizae and Rhizolex-T. Potential mechanisms by which the bioagents suppressed soybean wilt-root rot complex disease, were addressed. Application with bioagents induced expression of peroxidase, polyphenol oxidase, chitinase, β-1,3-gluctronase, total carbohydrates and total phenols in treated soybeans, which significantly contribute to plant disease resistance. Quality parameters of soybean seeds from bioagent-treated plants showed favorable elevation in total proteins and oils within the seeds.

Occurrence of algal leaf spot on longan (Dimocarpus longan ) caused by Cephaleuros virescens in India

Longan (Dimocarpus longan Lour. ) is an evergreen subtropical fruit tree species of Sapindaceae family with a long cultivation tradition in South East Asia. Between July to September of 2014 and 2015, leaves of longan trees were found infected by green algae at experimental farm of National Research Centre on Litchi, Muzaffarpur, Bihar (India). The symptoms of the disease appeared on the upper leaf surface as dark gray to reddish-rust coloured lesions, slightly raised with a velvet-like appearance. The disease incidence among leaves was 28. 4-57. 3% while percent disease severity index was 13. 3 to 20. 2. The algal thalli were isolated and cultured successfully on potato dextrose agar and Bold's basal medium but there was no development of sporangiophores and sporangia in culture. In pathogenicity test, inoculums either from naturally infected leaves or from pure culture of algal filaments could not reproduce typical symptom of the disease even up to three months of inoculation. Based on the leaf symptom and morphological characteristics, the pathogen was identified as Cephaleuros virescens Kunze. To our knowledge, this is the first report of leaf spots caused by Cephaleuros virescens on longan trees in India.

Occurrence of mycoparasitic fungi Sphaerellopsis paraphysata on pearl millet rust pathogen, Puccinia substriata in India

A mycoparasite was isolated on the rust infected pearl millet crop. It was isolated from an unusual pycnidia which was present along with the uredospores of rust. It reduced the uredial inoculum to a considerable extent. The morphology and molecular characters of the mycoparasite was studied. Its role as hyperparasite was established using Scanning Electron Micrographs, which clearly showed coiling and puncturing of uredospores of Puccinia substriata, by the mycelia of S. paraphysata. The confirmatory studies on the positive pathogenicity on rust fungi, showed a colourless septate mycelium, with an average conidial size of 9.27-12.92 ×2.55-5.87 µm and pycnidial size of 76.14-198.04×56.25-184.19 µm. The 540bp amplicon size of ITS sequence showed 96% similarity with S. paraphysata. The spore germination of Puccinia substriata on pearl millet leaves was reduced by 76%, 56%, 70% and the disease severity percentage was 13.3% on an average whereas in control it was 86.6%. The intimate association between S. paraphysata and Puccina substriata was proved by ultra microscopic structures in this investigation.

Characterization of the bioactive metabolite from a plant growth promoting rhizobacteria Pseudomonas aeruginosa VRKK1 and exploitation of antibacterial behaviour against Xanthomonas campestris a causative agent of bacterial blight disease in cowpea

A plant growth-promoting rhizobacterial strain B6 was isolated from a Cowpea rhizosphere soil in the Vellodu village of Dindugul district, Tamil Nadu, India. It could be identified as Pseudomonas aeruginosa VRKK1 through biochemical and 16S rDNA gene sequencing. The plant growth promoting behaviour already exhibited by this strain, further its bioactive metabolite extracted using chloroform. Crude extract and column purification study reveals that the idea of using this biometabolite against Xanthomonas campestris. F4 and F5 fractions showed 41 and 40 mm zone of inhibition which confirmed the broad spectrum antibacterial activity. Further this biometabolite analytically characterized and found to be as octadecanoic acid 2-oxo methyl ester. The identified biometabolite checked for the reduction of bacterial blight disease in cowpea with the disease severity percentage of 40.24% compared to control and induced plants.

Impact of fungal and plant metabolites application on early development stages of pea powdery mildew.

Pea powdery mildew incited by Erysiphe pisi represents a major constraint for pea crops worldwide. Crop protection is largely based on chemical control, although recently a renewed interest in the discovery of natural products as alternatives to synthetic fungicides application has emerged. Thus, 12 bioactive plant and fungal metabolites belonging to different class of natural compounds were evaluated, together with a commercial fungicide, at different concentrations on detached pea leaves for their potential to inhibit spore germination and subsequent stages of fungal growth. The most effective metabolites were tested at different concentrations in planta under controlled conditions to evaluate the level of control achieved by treatments before, concurrently and after pathogen inoculation. Pathogen development was macroscopically scored on whole plants as percentage of disease severity and area under the disease progress curve. Cavoxin, inuloxin C and sphaeropsidin A strongly inhibited E. pisi germination and haustoria formation and reduced colony size. This effect was dose dependent. These results were further confirmed in whole plants by spraying the metabolites on plant leaves for preventive or curative control, which reduced fungal developmental of E. pisi at levels comparable with those obtained by application of the fungicide. Cavoxin, inuloxin C and sphaeropsidin A have potential as alternatives to synthetic fungicides for the control of crop pathogens of economic importance such as powdery mildew. © 2019 Society of Chemical Industry.

Serangan Penyakit Rebah Kecambah Tanaman Cabai pada Tanah yang Berasal dari Persemaian Tanaman Petani di Lahan Rawa Lebak Kecamatan Pemulutan Kabupaten Ogan Ilir

Muslim et al, 2018. Damping-off of Chili Pepper Growing on Seedbed Soil from Farmers in Swamp Area of Pemulutan, Ogan Ilir. JLSO 7(1): Research on disease severity of damping-off on chili seedling from used seedbed nursery soil from swampy area land in Pemulutan, Ogan Ilir was conducted in order to know what kind of pathogen that attack chili seddling and how is severe it’s severity. This study was aimed to identify the damping-off pathogens of chili pepper and to measure inoculum potential of seedbed soil from farmers in swamp area of Pemulutan, Ogan Ilir. The experiment was conducted using survey method. The sample was taken by purposive sampling on chili seedbed nursery from six farmers all along swampy area in Pemulutan, Ogan Ilir. The result showed that observation based on the sympton and laboratory assay on damping-off disease infected chili seedling was caused by Rhizoctonia solani. The percentage of Pre-emergence damping-off incidence was ranged from 6.5˗35.5%. The highest Pre-emergence damping-off incidence was observed on soil from Mr. Mimin and lowest incidence was found from Mr. Nukman. The percentage of post-emergence damping-off incidence was ranged from 0.5˗56.5%, where the highest percentage was observed from Mr. Rahmat and the lowest was observed from Mr. Joni. The percentage of disease severity of damping-off was ranged from 0.55˗28.75%, where the highest disease severity was also observed from Mr. Rahmat and the lowest one was observed from Mr. Nukman. Based on disease severity of chili damping˗off observed in this study was high, chili damping˗off disease is important disease during providing seedling. This disease was potential to reduce the quality and quantity of chili production.

Plant extracts, bioagents and new generation fungicides in the control of rice sheath blight in Guyana

Sheath blight disease has become a major constraint in cultivation of rice in Guyana inflicting significant yield losses. Eleven plant extracts, three biocontrol agents and five new generation fungicides were screened for their efficacy against sheath blight pathogen, Rhizoctonia solani under in vitro conditions. The extracts of lemon grass, thick leaf thyme, marigold and clove at 15% showed high inhibition to mycelial growth of R. solani. Among biocontrol agents, Bacillus cereus OG2L exhibited high inhibition against mycelial growth of R. solani. New generation fungicides viz., Antracol (Propineb), Nativo (Trifloxystrobin + Tebuconazole), Silvacur Combi (Tebuconazol + Triadimenol), Cyclops (Cinnamon Oil + Clove Oil) and a biofungicide (Serenade - Bacillus subtilis cepa QST 713) recorded complete inhibition of R. solani under in vitro conditions. The plant extracts, bioagent and new generation fungicides that showed high inhibition to R. solani under in vitro were evaluated for their efficacy against shealth blight disease under greenhouse and field experiments. The extracts of lemon grass (7.21; 8.04; 4.85%), thick leaf thyme (6.71; 7.28; 4.71%) at 15%; B. cereus OG2L at 2 g L−1 (7.86; 8.68; 5.09%) and new generation fungicides viz., Antracol 70WP (8.51; 7.79; 5.27%), Nativo (7.62; 7.21; 4.20%) and Serenade (7.78; 7.66; 4.79%) have recorded low percent disease severity compared to untreated control (26.25; 31.16; 20.43%) in greenhouse, field trials I and II, respectively. The plant extracts, bioagent and new generation fungicides recorded a greater reduction (73.63%) in sheath blight disease incidence with an average yield increased from 10.25 to 36.03% compared to the control. The current study has provided chemical and non-chemical options for an integrated management of sheath blight disease in rice plants.

Efficacy of Less Toxic Phytochemicals to Prevent the Insect Vector of <i>Mungbean Yellow Mosaic Virus</i> (<i>MYMV</i>)

Planting material BARI mungbean-5 and two phytochemicals viz. Imitaf, active ingredient imidacloprid and ACmix, active ingredient chloropyriphos (50%) + Cypermethrin (5%) were used in this experiment. In case of Imitaf, the lowest percent disease incidence (10.12% per plant and 3.51% per plot) and severity (7.21%) were recorded in four times spray (T4) at 70 DAS. The highest percent disease incidence (36.50% per plant and 11.37% per plot) and severity (23.33%) were recorded in no spray (T0) at 70 DAS. In case of ACmix, the lowest percent disease incidence (12.21% per plant and 4.21% per plot) and severity (7.53%) were recorded in four times spray (T4) at 70 DAS. The highest percent disease incidence (36.49% per plant and 11.37% per plot) and severity (36.67%) was recorded in T0 at 70 DAS. The highest number of flower, no of pod and yield was found in four times spray (T4) that was higher in Imitaf than ACmix. The highest chlorophyll content was recorded in four times spray (T4) for Imitaf (49.62 μmol·m-2·s-1) and ACmix (56.80 μmol·m-2·s-1), and the lowest chlorophyll content was recorded in T0 for Imitaf (42.01 μmol·m-2·s-1) and ACmix (48.34 μmol·m-2·s-1). However from the results of this experiment it was revealed that Imitaf gave the better performance to control the insect vector (Whitefly) of MYMV with four times spray.