Use Of Biocontrol Agents Research Articles

Effects of biocontrol Bacillus sp. strain D5 on the pathogenic Fusarium oxysporum R1 at the microscopic and molecular level in Crocus sativus L. (saffron) corm.

Corm rot of saffron caused by Fusarium oxysporum is a major threat to saffron cultivation the world over. To minimize the ill effects of chemical fungicides, attention has been shifted to the use of biocontrol agents for disease management in a sustainable way. In saffron, various biocontrol agents against corm rot disease have been reported and characterized but no study has been done so far to understand their interaction at the molecular level. The present study was conducted to unravel the mechanism of action of an already characterized native biocontrol agent i.e. Bacillus sp. strain D5 (Bar D5) against F. oxsporum R1 (Fox R1) in the saffron corm. The growth inhibition of Fox R1 was observed in vitro and in planta (saffron corm) by real time imaging. Bacillus sp. strain D5 reduced Fox R1 load in infected corms by 50% as quantified by q-PCR and the colony-forming unit method. Comparative transcriptome analysis revealed upregulation and downregulation of various Fox R1 genes in presence of Bar D5. The genes related to carbon metabolism, cell wall and membrane synthesis, and growth of Fox R1 were significantly downregulated in Bar D5-primed and Fox R1-inoculated corms as compared to only Fox R1-inoculated corms.

Laboratory Evaluation of the Efficiency of The Entomopathogenic Fungus Beauvaria bassiana as a Biological Control Factor Against the Cucurbit Fly, Dacus ciliates

Al-Shweily, B.M., J.B. El-Zidawi and M.J. Hinnawi. 2024. Laboratory Evaluation of the Efficiency of The Entomopathogenic Fungus Beauvaria bassiana as a Biological Control Factor Against the Cucurbit Fly, Dacus ciliates. Arab Journal of Plant Protection, 42(3): 335-339. https://doi.org/10.22268/AJPP-001260 The cucurbit fly, Dacus ciliatus is a major pest which attack a wide range of crops and causes significant losses in agricultural production. Due to the high toxicity of chemical pesticides on human health and the environment, scientists focused on developing alternative safe methods to control this insect, including the use of biocontrol agents. Beauveria bassiana is one of the common fungi used as a bio-control agent. This entomopathogenic fungus was cultivated on Petri dishes containing PDA. The spore suspension of this fungus was prepared using sterilized distilled water, and three concentrations were used: 20×106 , 10×106 and 5×106 spores/ml. The effectiveness of these three concentrations was tested on larvae and pupae of the studied insect. The larval mortality rate ranged from 73.33% at the highest concentration to 33.33% at the lowest concentration used. Pupal mortality reached 66.66% at the highest concentration and 16.66% at the lowest concentration of spore suspension. Mortality rate was directly proportional to the spore suspension concentration of the entomopathogenic fungus. Keywords: Cucurbit fly, agricultural pest, biological control, Dacus ciliates, Beauveria bassiana, entomopathogenic fungi.

Identification of Gonatophragmium mori Causing Mulberry Zonate Leaf Spot Disease and Characterization of Their Biological Enemies in Guangxi, China.

Mulberry zonate leaf spot disease (MZLSD) is an important fungal disease of mulberry trees, which seriously affects the productivity and quality of mulberry leaves. MZLSD has been widely reported in sericultural production areas in Guangxi, China, in recent years. In this study, the causal agent of MZLSD was isolated from symptomatic samples and identified as Gonatophragmium mori (Acrospermaceae) based on morphological characterization and molecular analyses using nucleotide sequences of the internal transcribed spacer (ITS) and large subunit ribosomal DNA (LSU rDNA). Pathogenicity tests confirmed that G. mori is the pathogen responsible for MZLSD. Furthermore, we isolated antagonistic endophytic bacteria (AEB) from healthy mulberry leaves. Plate confrontation experiments showed that the lipopeptide crude extracts (LPCE) of three endophytic bacteria can inhibit the growth of G. mori, and the diameter of the antibacterial circle reaches more than 60 mm when their concentration of LPCE is 200 mg/ml. Light microscopy and scanning electron microscopy revealed that LPCE caused drastic changes in mycelial morphology. Fluorescence microscopy and transmission electron microscopy showed that the LPCE-induced apoptosis-like cell death in G. mori hyphae. Finally, based on morphological and molecular features, we identified the three isolates as Bacillus subtilis DS07, B. subtilis DS32, and B. velezensis Q6, respectively. To our knowledge, this is the first time to identify G. mori by combining characterization and molecular analyses, and we provide timely information about the use of biocontrol agents for suppression of G. mori.

Green and red fluorescent strains of Xenorhabdus griffiniae HGB2511, the bacterial symbiont of the nematode Steinernema hermaphroditum (India).

Steinernema entomopathogenic nematodes form specific, obligate symbiotic associations with gram-negative, gammaproteobacteria members of the Xenorhabdus genus. Together, the nematodes and symbiotic bacteria infect and kill insects, utilize the nutrient-rich cadaver for reproduction, and then reassociate, the bacteria colonizing the nematodes' anterior intestines before the nematodes leave the cadaver to search for new prey. In addition to their use in biocontrol of insect pests, these nematode-bacteria pairs are highly tractable experimental laboratory models for animal-microbe symbiosis and parasitism research. One advantageous feature of entomopathogenic nematode model systems is that the nematodes are optically transparent, which facilitates direct observation of nematode-associated bacteria throughout the lifecycle. In this work, green- and red-fluorescently labeled X. griffiniae HGB2511 bacteria were created and associated with their S . hermaphroditum symbiotic nematode partners and observed using fluorescence microscopy. As expected, the fluorescent bacteria were visible as a colonizing cluster in the lumen of the anterior intestinal caecum of the infective stage of the nematode. These tools allow detailed observations of X. griffiniae localization and interactions with its nematode and insect host tissues throughout their lifecycles.

Molecular genetic variability of Cryphonectria hypovirus 1 associated with Cryphonectria parasitica in South Tyrol (northern Italy).

Cryphonectria hypovirus 1 (CHV-1) has been widely studied and used as a biocontrol agent because of its ability to infect the chestnut blight fungus, Cryphonectria parasitica, and to reduce its virulence. Knowledge about the hypovirus, its presence, and diversity is completely lacking in South Tyrol (northern Italy), which may obstruct biocontrol measures for chestnut blight based on CHV-1. This work aimed to study the occurrence of CHV-1 infecting C. parasitica in South Tyrol and to perform a genetic characterization of the hypovirus. In South Tyrol, CHV-1 was found to occur in 29.2% of the fungal isolates investigated, varying in frequency between different regions and chestnut stands. Twenty-three haplotypes based on partial cDNA (complementary DNA) sequences of open reading frame (ORF)-A and 30 haplotypes based on partial cDNA sequences of ORF-B were identified among 47 and 56 hypovirulent fungal isolates, respectively. Phylogenetic analysis showed that all the haplotypes belonged to the Italian subtype of CHV-1 and that they were closely related to the populations of Italy, Switzerland, Croatia and Slovenia. Evidence of recombination was not found in the sequences and point mutations were the main source of diversity. Overall, this study indicated that the prevalence of CHV-1 in South Tyrol is low compared to many other central and western European populations and determined a need to actively impose biocontrol measures. Using sequence analysis, we identified some variants of interest of CHV-1 that should be studied in detail for their potential use in biocontrol.

In vitro characterization of a Bacillus velezensis isolate as an antagonist of grapevine trunk disease pathogens

AbstractOne of the major and yet unsolved threats for viticulture is the group of vascular fungal infections, the so-called grapevine trunk diseases. Besides their latent nature and the enormous number of associated pathogens, their control is also hampered by the lack of effective fungicides, directing growing attention toward the use of biocontrol agents. In the present study the isolation, identification, and characterization of a bacterial strain are presented, showing biocontrol potential against some main causal agents of grapevine trunk diseases. The strain was isolated from the wood of an asymptomatic grapevine and selected for the fungicidal activity against the pathogen Phaeomoniella chlamydospora. According to 16S rDNA, gyrA, and gyrB sequences, the isolate belongs to Bacillus velezensis species. Confrontation tests with the bacterium or with its fermentation broth further revealed growth inhibition and fungicide activity against Botryosphaeria dothidea, Eutypa lata and Diaporthe ampelina pathogens. Fractionation of the bacterial culture filtrate suggests that the antifungal agents secreted by the B. velezenzis isolate are mainly lipoproteins. Phytotoxicity tests were also carried out with the isolate, showing no harmful effects on grapevine foliar disks.

Understanding attitudes towards the biocontrol of African lovegrass: a segmentation approach

ABSTRACTAfrican lovegrass (Eragrostis curvula Schrad. Nees, Poaceae) is an introduced pasture species which provides little grazing or nutritional value for livestock under the prevailing conditions in Australia. Current management options, which include herbicides, strategic grazing of new growth, species replacement and fertiliser application have not been effective at providing sustained reductions in African lovegrass cover. Therefore, biological control (biocontrol) of African lovegrass is now being considered as a potential management tool in Australia. An important initial step in this exploration is to understand community views about African lovegrass and the use of biocontrol agents to manage it. Psychological characteristics including attitudes, knowledge, concern, and environmental values were investigated using an Australia-wide online survey, and respondents were separated into distinct segments using latent profile analysis. This study revealed that, within the sample of stakeholders surveyed, there were two groups that held slightly different views about African lovegrass and the environment, but they did not differ in terms of high levels of support for the potential use of biocontrol agents for African lovegrass. This information provides evidence of strong support for the management of African lovegrass using biocontrol.

Structure of the Lysinibacillus sphaericus Tpp49Aa1 pesticidal protein elucidated from natural crystals using MHz-SFX.

The Lysinibacillus sphaericus proteins Tpp49Aa1 and Cry48Aa1 can together act as a toxin toward the mosquito Culex quinquefasciatus and have potential use in biocontrol. Given that proteins with sequence homology to the individual proteins can have activity alone against other insect species, the structure of Tpp49Aa1 was solved in order to understand this protein more fully and inform the design of improved biopesticides. Tpp49Aa1 is naturally expressed as a crystalline inclusion within the host bacterium, and MHz serial femtosecond crystallography using the novel nanofocus option at an X-ray free electron laser allowed rapid and high-quality data collection to determine the structure of Tpp49Aa1 at 1.62 Å resolution. This revealed the packing of Tpp49Aa1 within these natural nanocrystals as a homodimer with a large intermolecular interface. Complementary experiments conducted at varied pH also enabled investigation of the early structural events leading up to the dissolution of natural Tpp49Aa1 crystals-a crucial step in its mechanism of action. To better understand the cooperation between the two proteins, assays were performed on a range of different mosquito cell lines using both individual proteins and mixtures of the two. Finally, bioassays demonstrated Tpp49Aa1/Cry48Aa1 susceptibility of Anopheles stephensi, Aedes albopictus, and Culex tarsalis larvae-substantially increasing the potential use of this binary toxin in mosquito control.

Effect of the use of biocontrol agents and resistance inducers against race 1 of Fusarium oxysporum f. sp. lactucae on lettuce in a simulated climate change scenario

Effect of the use of biocontrol agents and resistance inducers against race 1 of Fusarium oxysporum f. sp. lactucae on lettuce in a simulated climate change scenario

The biocontrol agent Lactiplantibacillus plantarum AMBP214 is dispersible to plants via bumblebees.

Plant protection products are essential for ensuring food production, but their use poses a threat to human and environmental health, and their efficacy is decreasing due to the acquisition of resistance by pathogens. Stricter regulations and consumer demand for cleaner produce are driving the search for safer and more sustainable alternatives. Microbial biocontrol agents, such as microorganisms with antifungal activity, have emerged as a promising alternative management strategy, but their commercial use has been limited by poor establishment and spread on crops. This study presents a novel system to overcome these challenges. The biocontrol agent Lactiplantibacillus plantarum AMBP214 was spray-dried and successfully dispersed to strawberry flowers via bumblebees. This is the first report of combining spray-dried, non-spore-forming bacteria with pollinator-dispersal, which scored better than the state-of-the-art in terms of dispersal to the plant (CFU/flower), and resuscitation of the biocontrol agent. Therefore, this new entomovectoring system holds great promise for the use of biocontrol agents for disease management in agriculture.

Selectivity of acaricides to Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae)

AbstractNeoseiulus barkeri Hughes has been used to control several pests, including the red palm mite, Raoiella indica Hirst. However, in some situations, the exclusive use of biocontrol agents is not sufficient to prevent the damage caused by pests. In these scenarios, the integration of chemical and biological controls is desired. For that purpose, the determination of selective acaricides, avoiding or reducing deleterious effects on the biological control agent is desirable. This study evaluated the lethal and sublethal effects of acaricides (abamectin, azadirachtin, fenpyroximate and pyridaben) on the predatory mite N. barkeri. We investigated the toxicity and selectivity of the acaricides and the survival, fertility, egg viability and instantaneous growth rate (ri) of N. barkeri exposed to acaricides. Additionally, we classified the acaricides according to the scale proposed by the International Organization for Biological Control (IOBC). Among the acaricides evaluated, abamectin was selective for N. barkeri because the estimated lethal concentration (LC50) for N. barkeri was higher than that for R. indica. None of the acaricides affected predator survival curves. However, azadirachtin and fenpyroximate reduced the average predator survival time. Pyridaben was the only acaricide that reduced the fertility of N. barkeri females and, consequently, their instantaneous growth rate (ri). All the acaricides affected the viability of N. barkeri eggs. Pyridaben was classified as moderately harmful, whereas other acaricides were classified as harmless.

Pre-treatment with Dazomet enhances the biocontrol efficacy of purpureocillium lilacinum to Meloidogyne incognita

BackgroundMeloidogyne incognita greatly restricts the production of protected vegetables in China. Application of biocontrol agent Purpureocillium lilacinum is an important practice to control the nematode; however, instability usually occurs especially in heavily infested field. This study aimed to illustrate the high efficiency of P. lilacinum agent with fumigant Dazomet in vitro.ResultsP. lilacinum YES-2-14 showed strong parasitic and nematicidal activities to M. incognita. Pre-treatment with Dazomet significantly enhanced the biocontrol effects of the fungus. After fumigation with Dazomet at a dosage of 7.5 mg kg− 1 soil, parasitism of YES-2-14 on M. incognita eggs increased by more than 50%. Meanwhile, when P. lilacinum fermentation filtrate treated following Dazomet fumigation at 10 and 20 mg kg− 1 soil, the mortalities of second-stage juveniles (J2s) increased by 110.2% and 72.7%, respectively. Both Dazomet and P. lilacinum significantly reduced the penetration ability of J2s to tomato roots. When P. lilacinum filtrate used alone, the J2s penetrating into the young roots decreased by 48.8% at 4 dpi; while in the combined treatment, almost no J2 was detected within the roots at 4 dpi and the number of knots reduced by more than 99% at 45 dpi, indicating a synergistic effect of the biocontrol fungus and fumigant.ConclusionsPre-treatment with Dazomet greatly increased the biocontrol efficacy of P. lilacinum to M. incognita. This research provides insight into the efficient management of plant parasitic nematodes and effective use of biocontrol agents.

Development of a Novel Emulsion Formulation of Trichoderma asperelloides PSU-P1 Conidia against Stem Canker on Dragon Fruit Caused by Neoscytalidium dimidiatum

Stem canker on dragon fruit caused by Neoscytalidium dimidiatum causes severe losses in production of this fruit worldwide. Biological control by Trichoderma species is widely used to control several plant diseases. However, environmental conditions affect the use of biocontrol agents in the field. The development of a new formulation may offer an alternative way to address the problem of stem canker on dragon fruit caused by N. dimidiatum. In this study, we sought to develop a Trichoderma asperelloides PSU-P1 formulation that would be effective against N. dimidiatum. Three vegetable oils, two emulsifier-dispersing agents (Tween 20 and Tween 80), and one source of carbon (dextrose) were tested for carrier additives. We assessed the viability and antifungal ability of formulations incubated at ambient temperature and at 10 °C during a storage period of 1–6 months. The formulation composed of coconut oil, DW, and tween 20 in a ratio of 30:60:10 required a mixing time of 1.14 min; this was significantly faster than the mixing times of other formulations. Application of this formulation suppressed canker development; a canker area of 0.53 cm2 was recorded, compared with a control (pathogen only) area of 1.65 cm2. In terms of viability, this formulation stored at ambient temperature showed a surface area percentage of T. asperelloides PSU-P1 ranging from 64.43 to 75.7%; the corresponding range for the formulation stored at cool temperature was 70.59–75.6%. For both formulations, percentage inhibition gradually decreased from 1 to 6 months, with ranges of 59.21–77% and 60.65–76.19% for formulations incubated at ambient and cool temperatures, respectively. Our findings suggest that the formulation developed in this study prolongs the viability of T. asperelloides PSU-P1 conidia by up to 6 months, effectively inhibits N. dimidiatum in vitro, and reduces stem canker in vivo.

Assessing the Effectiveness of Eco-Friendly Management Approaches for Controlling Wheat Yellow Rust and Their Impact on Antioxidant Enzymes.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease that causes significant yield losses in wheat production worldwide, including in Egypt. The use of biocontrol agents is among the best eco-friendly management strategies to control this disease, as they are more sustainable and environmentally friendly than traditional chemical control methods. In a comparative analysis, antioxidant enzyme activity and various management approaches were compared with two bacterial biocontrol agents, Bacillus subtilis and Pseudomonas putida. This study showed the remarkable efficacy of endophytic bacteria, B. subtilis and P. putida, in mitigating wheat stripe rust infection across three wheat varieties, namely Misr1, Gimmeiza11, and Sids12. B. subtilis exhibited superior performance compared to P. putida, resulting in infection types of 1 and 2.66, respectively, following inoculation. The highest reduction rate was observed with Tilit fungicide (500 ppm), followed by B. subtilis and Salicylic acid (1000 ppm), respectively. Variations in wheat varieties' response to Pst infection were observed, with Misr1 exhibiting the lowest infection and Sids12 showing high susceptibility. Among the tested inducers, Salicylic acid demonstrated the greatest reduction in disease infection, followed by Indole acetic acid, while Oxalic acid exhibited the lowest decrease. Additionally, the study evaluated the activities of five antioxidant enzymes, including Catalase, Ascorbate peroxidase (APX), glutathione reductase (GR), Superoxide dismutase (SOD), and peroxidase (POX), in the wheat-stripe rust interaction under different integrated management approaches. The wheat variety Misr1 treated with Tilit (500 ppm), B. subtilis, Salicylic acid, Montoro (500 ppm), and P. putida exhibited the highest increase in all enzymatic activities. These findings provide valuable insights into the effectiveness of B. subtilis and P. putida as biocontrol agents for wheat stripe rust control in Egypt, emphasizing their potential role in sustainable, integrated, and environmentally friendly management practices.

Enhancing the Resistance of Quinoa to Alternaria Leaf Spot through the Application of Microalgae and Organic Manure

In order to assess the impact of an eco-friendly approach on plant development and yield of the quinoa crop, a Randomized Block Design (RBD) field experiment was carried out in Central Research Farm (CRF) at Department of Plant Pathology, SHUATS, Prayagraj, U.P. during the Rabi season of 2019-2020. Alternaria are extremely difficult to control, result in significant yield losses, and lower the economic value of the crop plants in traditional production systems. Chemical fungicides including antrocol, captan, difolaton, dithane M-45, and blitox-50 provided effective control but are harmful to the environment. Other potential management strategies for Alternaria diseases include the use of bio-control agents, therapeutic plants, other plant-based products, etc. Cow dung, goat manure, and microalgae were the organic amendments employed as treatment. The Alternaria spp. that cause Quinoa leaf spot were shown to be most susceptible to the treatment T6, which contained cow dung at a rate of 6 tons per hectare, microalgae at a rate of 2.5 kilograms per hectare, and goat manure at a rate of 3 tons per hectare. The maximum plant height (cm) at 40, 80, and 120 DAS is 62.29, 90.48, and 117.31, respectively. At 120 DAS, the same treatment produced a maximum yield of (23.45 q/ha). The same treatment yielded the highest gross return, net return, and cost- benefit ratio, which were, respectively, Rs. 70350/ha, 41326/ha, and 1:1.42. Based on the results, it was determined that cow dung at 6 tons per hectare, microalgae at 2.5 kg per hectare, and goat manure at 3 tons per hectare were the most effective pesticides against Alternaria spp. of Quinoa in Prayagraj.

Comparative transcriptome profiling provides insights into the growth promotion activity of Pseudomonas fluorescens strain SLU99 in tomato and potato plants.

The use of biocontrol agents with plant growth-promoting activity has emerged as an approach to support sustainable agriculture. During our field evaluation of potato plants treated with biocontrol rhizobacteria, four bacteria were associated with increased plant height. Using two important solanaceous crop plants, tomato and potato, we carried out a comparative analysis of the growth-promoting activity of the four bacterial strains: Pseudomonas fluorescens SLU99, Serratia plymuthica S412, S. rubidaea AV10, and S. rubidaea EV23. Greenhouse and in vitro experiments showed that P. fluorescens SLU99 promoted plant height, biomass accumulation, and yield of potato and tomato plants, while EV23 promoted growth in potato but not in tomato plants. SLU99 induced the expression of plant hormone-related genes in potato and tomato, especially those involved in maintaining homeostasis of auxin, cytokinin, gibberellic acid and ethylene. Our results reveal potential mechanisms underlying the growth promotion and biocontrol effects of these rhizobacteria and suggest which strains may be best deployed for sustainably improving crop yield.

Investigation of the Antifungal Activity of Bacillus megaterium Against Fusarium Species

Several Fusarium species are emerging as serious pathogens on small grain cereals worldwide. The use of fungicides is a short-term strategy in the fight against Fusarium diseases. The use of biocontrol agents is an attractive alternative strategy by reducing the chemical input to the environment as well as being economical. Bacillus species have received attention as biocontrol agents. In this study, the antagonistic activities of Bacillus megaterium CTBmeg1 and HMA5 strains on Fusarium culmorum UK99 and F. graminearum PH-1 isolates were investigated in vitro and at molecular level. On the 7th day of the dual culture assay, both of B. megaterium strains significantly reduced the mycelial growth of Fusarium isolates, with very high antifungal activity with the inhibition rate between 72.7% and 77.7%, respectively. Similarly, both strains caused high antifungal activity in the volatile organic compound (VOC) analysis between 52.1% and 62.4%, respectively. At the molecular level, in all tested groups, transcript levels of the tri5 gene, which is associated with trichothecene production, decreased, while the transcript levels of cat, an antioxidant gene, and mst20, a gene related to apoptosis, increased. Findings from this study showed that B. megaterium CTBmeg1 and HMA5 strains could be accepted as highly effective biocontrol agents against worldwide phytopathogens F. culmorum and F. graminearum.

Predasi Kumbang Penyelam Dewasa Cybister sp. (Coleoptera: Dytiscidae) terhadap Larva Nyamuk Aedes aegypti

The use of biocontrol agents in controlling Aedes aegypti mosquitoes can be an alternative to avoid the adverse effects of dependence on chemical insecticides. Exploration of potential local insects as biocontrol agents is important in maintaining the balance of the ecosystem. This study aims to determine the predation rate of the adult diving beetle Cybister sp. against Ae. mosquito larvae. aegypti. This experimental research was carried out at the Integrated MIPA Laboratory, Halmahera University. A total of 1 predator and 30 late instar larvae of Ae. aegypti was placed in an aquarium (20 cm x 14 cm x 14 cm, 2 L capacity) containing 1 liter of water. Observation of predation of Cybister sp. adults against Ae. aegypti was carried out for 72 hours at intervals of 6 hours. This predation experiment was carried out with three replicates. Analysis of the predation rate of Ae. aegypti refers to a mathematical model. The statistical test used was correlation to see the speed of larval predation and analysis of variance. The results showed that the adult diving beetle Cybister sp. able to reduce the number of Ae. aegypti with a predation rate in 12 hour intervals of 0.755; 0.294; 0.188; and 0.132 per hour respectively. This predation showed an accurate and significant relationship (R2 = 0.8608; P <0.05). The conclusions of this study indicate that the adult diving beetle Cybister sp. able to reduce the number of Ae. aegypti with a predation rate in 12 hour intervals of 0.755; 0.294; 0.188; and 0.132 per hour respectively, and statistically the predation shows an accurate and significant relationship.

Efficacy of biocontrol agents against Sclerospora graminicola causing downy mildew in fodder pearl millet

Downy mildew incited by Sclerospora graminicola is the main hurdle in the successful cultivation of pearl millet and is capable of causing more than 60% losses in terms of grain and fodder yields. The disease could be managed by fungicide applications but due to several associated environmental and health-related issues, there was a necessity to formulate some eco-friendly measures for downy mildew management. Thus attempts were made to find out the usefulness of three biocontrol agents (Bacillus subtilis, Pseudomonas fluorescens and Trichoderma viride) and two fungicides (mancozeb 64% + metalaxyl 4% and metalaxyl) under field conditions for three seasons (2017-2019) against downy mildew. The least downy mildew incidence (14.37%) was observed with seed treatment + foliar spray of B. subtilis as compared to untreated control (31.30%) with 54.10% disease reduction followed by seed treatment + foliar spray of P. fluorescens (17.58% disease incidence) with 43.82% disease control. The same treatments were significantly superior over others in increasing the green fodder yield by 56.59 and 40.79% respectively. Another treatment proven effective was seed treatment + two foliar sprays of T. viride which provided more than 43% reduction in downy mildew incidence as compared to chemical check which provided 30% disease control and increase in green fodder yield. These findings advocated the potential use of biocontrol agents against downy mildew of pearl millet in an eco-friendly manner.

Use of Entomopathogenic Nematodes for the Management of Banana Rhizome Weevil (Cosmopolites sordidus): A Review

Banana is an important fruit crop which is grown in tropical and subtropical parts of the world. Banana production is inhibited by various insect pests. Though chemical insecticides are recommended for control of these pests, use of biocontrol agents are alternative method .One of the biocontrol agents is the entomopathogenic nematodes (EPNs). This review finds the work of some of the successful EPN species or strains from different geographical locations that may affect practical bio control of banana rhizome weevil, a major pest of banana. Emphasis is made on roles of EPNs in reducing banana rhizome weevil (Cosmopolites sordidus) and directions of future research in biocontrol programme are presented.