The soil comprises different types of organisms such as earthworms, nematodes, arthropods, fungi, and bacteria. These organisms play a significant role in the development of the soil structure, fertility, and the growth and development of plants. The study of nematodes is especially crucial given their role in regulating the ecosystem. Given the diversity of their species, nematodes are among the most researched organisms in the world. Through multiple studies, scientists keep discovering more information about the endless abilities of these organisms.
Of all the multicellular animals, nematodes are the most abundant on earth. A fistful of soil will have thousands of microscopic worms, most of them being plants, animals, or insects. Nematodes feed on fungi, bacteria, and other nematodes and constitute a part of the free-living species. Nematodes have a simple structure, and the Phylum Nemata has about twenty thousand species. Adult nematodes represent about 1000 somatic cells and potentially hundreds of cells related to the reproductive system. Nematodes have been categorized as a tube within a tube as they reside in the alimentary canal that extends from the mouth, an anterior end, to the anus at the tail. Nematodes have a reproductive, nervous, excretory, and digestive system. The size of nematodes is from 0.3 mm up to >8 meters.
Nematode Relationship with Soil Management Practices, Crop Production, and Microbial Communities
Nematodes play an essential role in the homeostasis of the ecosystem. For instance, scientists attribute the survival or death of the plant to the nematodes that are present in the soil. Through their feeding habits, nematodes contribute to Nitrogen mineralization which is the process through which they convert organic Nitrogen to an inorganic form, which is consumed by plants. Bacterial-feeding nematodes are most common in the agricultural soil, which increases the bacterial populations. A high population of bacteria grows when the soil is disturbed, increasing readily decomposed organic matter. Insect-parasitic nematodes act like biopesticides by infecting insects with bacteria that overwhelm the immune system of the insect, and it eventually dies. Such kind of nematodes is the subject of much research and the development of bio-pesticides. Plant-parasitic nematodes can be suppressed using natural enemies of nematodes that are found in the soil. These natural enemies include; as endoparasitic fungi, mites, protozoans, fungal egg-parasites, plant health promoting Rhizobacteria, predatory nematodes, obligate bacterial parasites, collembolan, tardigrades, and turbellarians.
Plant-parasitic nematodes cause damage to plants. They feed on plant roots, damaging the system and affecting the intake of water and nutrients. Symptoms of such injury are enlargement of the heart, distorted root structure, and reduced root mass. Through the damage caused by the nematodes to the source of the plant, other pathogens find their way into the system of the plant, making it weak. Collectively nematodes can feed on any plant cell. This has a significant effect on the production and yield of crops because the roots are attacked.
Any addition of fresh organic matter generally modifies soil aggregation and the soil biotic composition. When nematodes and microbes interact, they can stimulate either stimulate or inhibit microbial activities in the soil. A study was done to investigate the changes in nematodes and microbial communities among aggregate function. The results showed that total fractions affected the number of nematodes significantly. Also, these Aggregate functions affected microbial biomass. The research also showed that grazing on microbivores and microbes might decrease microbial activities. These microbial activities are necessary for providing a biological mechanism for organic fertilizer enhancing soil natural carbon storage in red soils.
Research Paper Description
The research paper chosen is about Entomopathogenic nematodes and their ability to kill insects using mutualistic bacteria. Entomopathogenic nematodes together with their endosymbiotic bacteria are useful as bioinsecticides that can control various types of economically important agricultural pests (Shapiro-Ilan & Gaugler, 2002). Because Entomopathogenic nematodes are sensitive to UV light, they can control the pests in protected environs or on the ground (Shapiro-Ilan & Gaugler, 2002). For high success levels, the scientists have to apply nematodes in large amounts. Entomopathogenic nematodes are being used to destroy plant-parasitic nematodes by using their symbiotic bacteria. Entomopathogenic nematodes are successful as biopesticides because it is possible to produce them in bulk. Three methods are used to create them which are reliable and liquid culture, in vivo and in vitro.
After commercial production of entomopathogenic nematodes, the technologists prepare them for delivery and application. Formulation improves the shelf life, and the product can be transported for use and handled better. Production of entomopathogenic nematodes through the in vivo and in vitro technology has made the organisms’ essential biopesticides. The biggest challenge is the cost of production. Chemical insecticides are much cheaper, which has been an obstacle to the development of this technology. Innovations and the restriction on the use of chemical pesticides will enable the broad application of the biopesticide in agriculture. Development of newer strains of Entomopathogenic nematodes will also play a significant role in the advancement of technology.
Summary of Overall Story
Nematodes are the most populous multicellular animals on earth. One of the critical functions of nematodes is the mineralization of nitrogen from organic to inorganic form. Nematodes are also known to cause damage to crops by eating them and affecting the yield. Researcher strives to understand nematodes and the ways that they can benefit the agricultural sector. One dominant technology being developed using nematodes is biopesticides. By using the symbiotic element of nematodes, scientists are finding ways to target pests that are affecting the yields of farmers. Researchers and the agricultural system are facing challenges in various ways in the application of bio-pesticides. Some of the problems include the cost of production; more technology is required to understand the pests and competition from chemical pesticides. The two papers will discuss how the application of entomopathogenic Nematode can be improved through technology and so far what has been happening. It will give insights into what should be done shortly and why. The second paper will talk about microbes and their contribution as biopesticides and how they can be improved for better yields with reduced costs and management.
Each Paper’s Contribution
In the first study, the aim is to optimize the use of entomopathogenic nematodes which is affected by the sampling methodologies. Poor sampling methodology and cost of production have changed the optimum use of nematodes to eradicate the weevil. Citrus farmers in Florida were using entomopathogenic nematodes because the root weevil was the greatest threat to citriculture; the chemical pesticides did not suppress the weevil larvae in the soil; the use of nematodes was expensive, and entomopathogenic nematodes had short-term efficiency (Duncan, 1999). Findings showed that the complex nature of insects because of recruitment from the soil to the canopy affected the biopesticide application. Additional knowledge is required to break the recruitment cycle of the root weevil. Another challenge was the ineffective suppression of insects above and below the ground.
A survey was done on indigenous ESPN and isolated from the Korean habitat. These isolates were evaluated for their efficacy as compared to important local and introduced insect pest of vegetables, turfgrass, rice, and greenhouse crops. Among these isolates, it was found that Mraeck, wants, Gerdin and bedding, heterorhabditis bacteriophora and patella are produced commercially. The Korean strains were then tested against insect pests and endemics. One could notice success in the greenhouse crops for example watermelon which was treated with a pesticide at sowing. This resulted in a decrease in mortality of the seedlings to 0.2 to 1.9% as compared to 25.5 to 71.6% in other untreated plots. The growers of watermelon In Korea are therefore dependent on ESPN for pest management. The most significant penetration of ESPN usage is in leafy, greenhouse-grown vegetables because of Favorable environment for nematodes resulted in better crops as compared to those crops treated with chemical insecticide. From the above example, growers are likely to use EPNs for pest control just when its use is more profitable than other sources. The growers in Korea provide favorable greenhouse conditions for ESPN for pest control which is a plus to them.
Red Guava is grown in subtropical countries and tropical countries to even though it is native to the American tropics. Brazil still stands to be the leading producer of these guavas followed by Mexico. The guava weevil and fruit flies mainly attack these fruits, the fruits, however, are affected by psyllid. Guava weevil is a menace in the production of the fruit in Brazil as it affects the quality, thereby, causing considerable damage. These pests are controlled through the weekly application of insecticides mainly to discourage adults. These weevils are so resistant that without proper chemical control, then all the fruit in the orchard would be damaged 100%. Over the recent years, fruit attack has increased due to; the resistance of weevils to control, the tendency of adult weevils to hide in the litter around trees and poor timing while applying chemicals. About nine species of nematodes were surveyed for biocontrol of the guava weevils. They were accessed under normal and greenhouse conditions. ESPN used in their control worked but also, farmers were urged to remove any bad fruit from the orchard, and this helped so much in the power of pests. Recently, in Brazil, they are being encouraged to use organic methods of planting, therefore, eliminating all pesticides that contribute to the increase in numbers of guava weevils.
In another research paper by Shapiro called Entomopathogenic Nematode Production and Application Theory, he together with his colleagues seek to find out production and application of ESPN technologically. ESPN is in the family of steinernematide, and it is supposed to biocontrol insects and parasites. Entomopathogenic nematodes are at the moment produced by different methods. That is they are either produced in vitro or in vivo. Both ways have its merits and demerits that concern cost of production, economies of scale, technical know-how and the product quality. The paper provides an analysis of factors that affect the production of ESPN and its application. Also, it gives ways and insights of achieving success will be using biological control.
In the In vivo method, trays and shelves are used and therefore two dimensional. This approach is made up of injection, harvest, concentration, and decontamination if necessary. That is, insects are inoculated on a tray with a specific absorbent paper. After four days, the insects are transferred to white traps; if they are infected, they are allowed to go on to reproductive nematode stages. In this method, the yield is affected by the dosage of nematodes. High dosage results to failed infection because of competition and low dosage results to mortality of hosts. Therefore, just enough dosage is required while challenging to achieve.
In vivo production varies a great deal between nematode species and insect hosts. The most common insect host used in this method is G. mellonella due to its high susceptibility to nematodes, ease in rearing, its availability and its ability to produce yields. Entomopathogenic Nematode can be applied with almost all agronomics equipment including; electrostatics sprayers, mist blowers, aerial sprays, pressurized sprayers (Shapiro & Gaugler, 2002).
. The system sued will mainly depend on the cropping system applied in that farm. Adequate agitation is required while applying ESPN that means that small plots will only need handheld appliances while bigger plots will need more powerful tools like the aerial sprays. ESPN can be implemented in various forms such as clay, peat, activated charcoal, water dispersible granules, polyurethane sponges and alginate. Certain factors may affect application success. These factors are mainly biological and are related to nematodes. First of all, a pest must be matched accurately with its particular nematode. These nematodes must be chosen based on host finding, its environment tolerance, and its persistence. Higher rates of application may be required depending on what pests are being targeted. When nematodes are applied sufficiently, then they can last for up to 8 weeks or so. The main problematic biological factors to nematodes are pathogens and other predators such as bacteria, fungi, mites, protozoan, and predacious nematodes.
Other factors that affect the successful application of entomopathogenic nematode include environmental factors like protection from UV radiation, temperature, adequate soil moisture, and humidity. UV radiation frequently hinders the survival and efficacy of, therefore, ESPN biocontrol mostly work on cryptic habitats like greenhouses, also UV rays are detrimental to nematodes. Good soils moisture that does not deprive nematodes oxygen is required for ESPN to work well as desired. Also, irrigation is necessary to central the correct humidity in the soil. Different nematode species has a different level of tolerance towards temperature. Some prefer warmer temperatures to colder temperatures. Soil texture also affects the movements of nematodes and to some extent its survival. Clay soil restricts its movement while soils with more sand encourage movement (Shapiro & Gaugler, 2002).
After all, is said and done, improved formulation is the only way enhanced efficacy in the application of Entomopathogenic Nematode can achieve. So far substantial progress has been made for example in mixing ESPN with polymer and surfactant. However, improved efficacy and efficiency can be leveled up through relying on leaf flooding in conjunction with a surfactant to increase the leaf coverage. The sprayable gel can be used to reduce the incidence of fire where ESPN is involved. Also, the application process can also be improved through upgraded application equipment, for example, optimizing spray systems like pumps, nozzles for enhanced survival of pathogens. Finally, a superior ESPN for biocontrol can be improved through strain improvement where genetics are altered to come up with something superior.
The second paper provides an overview of the factors that are involved in the application of a strain from innovation to the farmers. A successful transition requires the production of the microbe on a global scale. Some bacteria show promise in the laboratory but lack the vital characteristics as are necessary for broader adoption in the agricultural system. The research concludes that the efficacy and quality of the microbial products have improved over the last ten years resulting in an apparent increase in the yield and health of crops (Parnell, 2016). Microbiome, the presence of pests, cropping system, environmental conditions, and soil type are the key elements that influence the microbe benefits (Parnell, 2016). Further research is required for a better understanding of critical crops, soil, and microbes.
Crop production is primarily affected by plant disease and pest which mostly lead to crop losses. This situation can be controlled by the use of biological organisms to control these pests. These phenomena are called Biocontrol. Biocontrol microbes have been proposed for control but still there remains uncertainty regarding costs, efficacy and field performance. Biocontrol agents are preparations that are derived from microorganisms and can suppress pests. These agents include microbes, bioactive compounds, and plant extract. Pest damage through biocontrol involves competition for space, mycoparasitism, antibiosis and induced resistance (Oerke &Dehne, 2004).
Plants usually take up specific microbes according to their development and their stress on nutrients available.
The effectiveness of microbial species to be taken by a plant highly depends on biotic and abiotic factors. Also, the previous history of the crops affects take up. The future of microbial products, therefore, depends on an increased understanding of the impact that microorganisms play in the development and growth crops. Further studies into these microbes are required especially in the effects of consortia and bacterial community structure on crop development.
An analysis of the three papers illustrates that the use of nematodes in as a biopesticide provides benefits to the environment and the yield of the targeted crop. The cost of developing the biopesticides and the issue of commercial production remain unsolved. According to the findings, farmers prefer the use of chemical pesticides because of their low prices. Despite their adverse effects, the move to limit the use of chemicals can further lead to the spread of biopesticides. Therefore, researchers need to conduct more investigations in the field to identify the approach with the most benefits and negligible drawbacks. The technology to develop a pesticide for all crops is challenging, and further innovation is needed to deal with the issue of pests.
Moreover, the scholars should develop new strains to improve the efficacy. Finally, the provision of biopesticides for the agricultural system will be a significant win. However, scholars need to invest more resources in the project to realize this objective with the support of all stakeholders.
Although nematodes are known to have adverse effects of crop yield, both scholars and farmers have identified some advantages. They not only feed on the plants by also infect potential pests with bacteria and eventually kill them. Scientists have used the symbiotic nature of nematodes to create biopesticides. Nematodes research has come a long way in the provision of solutions to pests. The high cost of production, short-term efficacy, cheap chemical production, and technological limitations present challenges to the development of biopesticides. More research and advocacy are necessary for the area. The environment will benefit the most if biopesticides are available to the farmers. Global use of biopesticides is still a pipe dream to those concerned because developing formulations that can suppress the multiple crops in agriculture will require considerable time and knowledge.
Scientists are in a bid to come up with ways that can control pests using nematodes Through ESPN in the above discussions we have highlighted the plights that need to be looked into while developing Biocontrol if by any chance farmers want to improve their yield and maintain their soil structure. In ESPN development certain factors must be considered. First, the soil animals present are a huge point of reference. Then other abiotic factors can be found. We have also established that microbes help in fighting soil pest and pathogens. Nematodes play a considerable role in the control of soil pest and the improvement of crop production as shown in different case studies, for example, the watermelons in Korea.
Duncan, L. W., Shapiro, D. I., McCoy, C. W., & Graham, J. H. (1999, August). Entomopathogenic nematodes as a component of citrus root weevil IPM. In Proceedings of Workshop on Optimal Use of Insecticidal Nematodes in Pest Management, 28-30. Retrieved from crec.ifas.ufl.edu/extension/diaprepes/bibliography/PDF/entomopathnematodes.pdf
Parnell, J. J., Berka, R., Young, H. A., Sturino, J. M., Kang, Y., Barnhart, D. M., & DiLeo, M. V. (2016). From the lab to the farm: An industrial perspective of beneficial plant microorganisms. Frontiers in Plant Science, 7, 1110. doi:10.3389/fpls.2016.01110
Shapiro-Ilan, D. I., & Gaugler, R. (2002). Production technology for entomopathogenic nematodes and their bacterial symbionts. Journal of Industrial Microbiology and Biotechnology, 28(3), 137-146.
Oerke E., Dehne H. (2004). Safeguarding production – losses in major crops and the role of crop protection. Crop Prot. 23 275–285. 10.1016/j.cropro.2003.10.001