पर्यावरण अनुकूल कीट- पीड़क प्रबंधन के लिए सूक्ष्मजीवों का उपयोग

Microorganisms offer a vast resource for producing bioactive compounds, which are crucial in developing pharmaceuticals and biopesticides. Their diverse interactions within ecosystems make microbes a promising source for discovering new metabolite that could contribute to the creation of next-generation agricultural chemicals.

Eco-friendly pest management is one area that shows significant potential in the microbial revolution in agriculture as the globe struggles with climate change, environmental degradation, and food security. Long-term solutions are needed more than ever. Insect pests are recognized as significant obstacles, responsible for approximately 10.80% of global agricultural losses in the post-green revolution era.

Moreover, a recent report indicated an estimated 18–26% reduction in annual worldwide agricultural production, amounting to $470 billion. Chemical pesticides have been the standard solution for many years, farmers worldwide have relied heavily on synthetic chemical pesticides to control insect infestations due to their quick and effective results.

However, growing worries about the long-term and indiscriminate use of these synthetic chemicals have brought to light their detrimental effects. Chemical pesticides can infiltrate water and soil through runoff from applied areas, accidental spills, or improper disposal, leading to the contamination of groundwater, streams, lakes, and ponds. In addition to this, they can harm non-target organisms such as birds, fish, and beneficial microorganisms.

Pesticides may also cause both immediate and long-lasting severe health effects. This might develop month or years after exposure. Acute health effects include stinging eye, blindness, nausea and dizziness so there is a need to search a better and safer alternative for a bright and sustainable future. One such alternative is the advent of microorganisms in managing the pest populations.

Microorganisms are tiny living things that have the potential to make agriculture safer and more environmentally friendly. Microbes such as entomopathogenic fungi, bacteria, and viruses have been utilized for controlling insect pests across various ecosystems.

In order to harness the effectiveness of naturally occurring compounds, researchers have recently shifted their focus to natural bio-based alternatives, including microbes and their derivatives.This article explores the potential role of microbes in sustainable insect pest management, emphasizing minimal environmental impact and the preservation of non-target organisms.

1. Micro-organism and their application

A microorganism visible only under a microscope. Microorganism are extremely diverse, can be single celled or multicellular, including bacteria and fungi, as well as archaea, protists, algae, and certain amoebae. Viruses are not classified as living organisms, but they are often regarded as microorganisms because of their extremely small size (15 to 400 nm).

Micro-organisms thrive in diverse environments, from extreme conditions to forming microbiota in multicellular organisms. Evidence shows they existed 3.45 billion years ago, making them the earliest life forms. Microorganisms play a monumental role in sustaining life of earth. Microbes are essential in food fermentation, sewage treatment, fuel production, and as biological tools.

They support soil fertility and form human gut flora, but some are pathogenic, causing diseases and targeted by sanitation practices. These tiny life forms, encompassing bacteria, viruses, fungi, and protozoa, contribute significantly to various ecosystems, industries, and human well-being. Their important cannot be overstated, into the multifaceted roles microorganisms.

1. Food production: microorganisms ferment foods, producing yogurt, cheese, bread and beer.
2. Biotechnology: microbes produce biofuels, bioproduct and pharmaceuticals.
3. Waste management: microorganisms degrade pollutants, cleaning contaminated sites.
4. Pest control: microbes control pests and disease, reducing pesticide use.
5. Plant growth promotion: microbes produce growth-promoting substances.
6. Crop yield enhancement: microorganisms improve soil fertility, increasing crop yields
7. Soil remediation: microorganism’s clean pollutants from contaminated soil.
8. Entomopathogenic Micro-organisms in biological pest management

Globally, crops are affected by various pests, including weeds, insects, nematodes, and microbes like viruses, fungi and bacteria which lead huge yield reduction. With advancing research, the use of biopesticide products, including microbes and microbe-derived biochemicals, is on the rise.

Bacteria, fungi, and baculoviruses serve as key resources of biomolecules and secondary metabolites for the development of biopesticides. Biopesticides are very effective even in small quantities and break down quickly without leaving pollutants, which makes them vital for integrated pest management.

As environmentally friendly and sustainable alternatives to synthetic pesticides, they are specific to their targets and minimize environmental risks. Microbial pesticides represent a notable improvement over traditional agrochemicals, being both effective and biodegradable. Biopesticides have a shorter shelf life and do not leave residual effects on the environment, thus preventing bioaccumulation.

1.1 Entomopathogenic bacteria

Entomopathogenic bacteria are among the most commonly utilized microorganisms for managing insect pests. The predominant facultative bacteria in this category are those that form spores and protein crystals. These bacteria enter the host insect's body through the mouth during feeding, where they produce protein crystals and endospores.

The toxins and pathogenic agents contained within these crystals ultimately lead to the mortality of the insect by wrapping around its body and inducing toxicity. The family Bacillaceae has received significant attention in this context. Bacillus popilliae causes milky disease in scarabaeid beetles, while Bacillus sphaericus is known for its effects on mosquitoes.

Bacillus thuringiensis (Bt) is one of the most recognized and commonly utilized entomopathogenic bacteria. This bacterium produces two primary types of protein toxins: crystal and cytoplasmic, which are highly targeted and specific to various organisms, including Lepidoptera, Coleoptera, Diptera, and nematodes.

Bt protein expressing transgenic plants represents an important advancement in agricultural biotechnology, providing an effective tool for pest management while promoting sustainable farming practices. The entomopathogenic bacterium Serratia marcescens found effective in management of grasshopper.

1.2 Entomopathogenic fungi

The biological control of insect pests using entomopathogenic fungi (EPF) is an effective and eco-friendly alternative to chemical insecticides. Several EPF genera, such as Beauveria, Metarhizium, Isaria, Lecanicillium, and Hirsutella, are used as biopesticides against agriculture, greenhouses, forests, storage, and residential pests.

EPF can infect insects belonging to the order Lapidoptera, Coleoptera, Hemiptera, Diptera, Orthoptera, and Hymenoptera. These fungi induce lethal diseases in insects, effectively managing their populations with little risk to non-target organisms due to their host specificity. EPF spores adhere to the insect's outer cuticle, germinate, and infiltrate the insect’s body.

This infection process includes spore attachment, cuticle penetration, and fungal development within the insect, eventually leading to the invasion of the hemocoel. The spores are covered in a protein and glucan layer that helps them stick to the insect cuticle and form appressoria for attachment.

The cuticle is penetrated by a combination of mechanical force and enzymatic actions (lipases, proteases, and chitinases). Inside the insect, EPF grow vegetatively, causing death through either mechanical damage (mummification) or the release of toxins. Khashaveh (2011) observed 68-92% mortality of Sitophilus granarius and Tribolium castaneum adult by application of Beauvaria bassiana.

Fig 1. (a) Cabbage looper infected with Nuclear Polyhedrosis Virus, (b) Banana aphid infected and killed with Beauveria bassiana, (c) Bt (Bacillus thuringiensis) protein-expressing transgenic tobacco showed enhanced resistance against Spodoptera frugiperda. The results compared vector control plants with transgenic events (Bt-2 and Bt-5), showing dead larvae on transgenic leaves marked by red circles.

1.3 Entomopathogenic virus

Baculovirus (dsDNA) is frequently researched to identify the most effective virus for controlling pests in crops. It is categorized into two main types: Granulovirus (GVs) and Nucleopolyhedrovirus (NPVs). While baculoviruses primarily target Lepidoptera, their hosts also include a variety of Hymenoptera, Diptera, and some Crustacea. In the United States in 2002, the US Forest Service and USDA-ARS utilized NPVs as microbial agents to combat gypsy moths (Lymantria dispar). Granulovirüs (GVs) was employed as a biological agent by Nakai (2013) in Japan to combat tea leaf crimpers (Adoxophyes honmai and Homona magnanima), and no detrimental infections occurred throughout the four growing seasons. Insects infected with baculovirus exhibit a whitish appearance due to a severe infection of the fat body, which is indicated by a thinner, more translucent exoskeleton that eventually ruptures as the disease progresses. The viruses are contained within proteinaceous structures known as occlusion bodies (OBs). Once these OBs dissolve in the insect's midgut, they release viral particles that invade the midgut epithelium and other tissues, causing extensive damage and ultimately resulting in the insect's mortality.

Conclusions

In our own country and around the world, chemical treatment is the most often employed technique to eradicate pests from stored products. Commonly applied insecticides against dangerous organisms upset the natural equilibrium between species and lead to the development of pesticide and residue resistance in the organisms. Biological control measures, such as entomopathogens, are being advocated as a substitute for chemical pestisides in recent years. Entomopathogens offer eco-friendly alternatives for managing insect pests in agriculture, promoting agro-sustainability. They present new possibilities for biological control and open research opportunities in the development of microbial pesticides.

References

1. Khashaveh A., 2011. The Use of Entomopathogenic Fungus, Beauveria bassiana (Bals.) Vuill. in Assays with Storage Grain Beetles. Joumal of Agricultural Science and Technology, 13(1): 35-43.
2. Nakai M., 2013. Potential of slow-killing insect viruses to control leaf-rollers in tea fields, 4th International Participated Entomopathogens and Microbial Control Symposium, Artvin, Turkey, p.36.
3. Deka, B., Baruah, C. and Babu, A., 2021. Entomopathogenic microorganisms: their role in insect pest management. Egyptian Journal of Biological Pest Control, 31, pp.1-8.
4. Vermelho, A.B., Moreira, J.V., Akamine, I.T., Cardoso, V.S. and Mansoldo, F.R., 2024. Agricultural Pest Management: The Role of Microorganisms in Biopesticides and Soil Bioremediation. Plants, 13(19), p.2762.
5. United States Department of Agriculture. Rangeland Grasshopper and Mormon Cricket Suppression Program, Final Environmental Impact Statement—2002. U.S. Department of Agriculture; Washington, DC, USA: 2002.

Authors:

Khushboo Upadhayay ¹, Dr. Jyotsana Tilgam^1*

¹ICAR-National Bureau of Agriculturally Important Micro-organisms, Maunath Bhanjan, Uttar Pradesh 275103

*Corresponding author – This email address is being protected from spambots. You need JavaScript enabled to view it.