The term “biopesticides” refers to biological agents that include the use of botanicals, pathogenic microbial species like fungi, bacteria, and viruses, as well as the natural competitors of pests, including parasitoids and predators, nematodes and semiochemicals, to control the pest level.
Since nicotine was employed to regulate plum beetles from the 17th century, plant extracts were likely the first agricultural biocontrols. Agostino Bassi first showed that the white-muscadine fungus (Beauveria bassiana) could be used to create an infectious sickness in silkworms in 1835, which led to the beginning of research incorporating biological agents for insect pests in agriculture. In the 19th century, experiments using petroleum-based oils as plant protectants had been documented.
An increasing number of studies and biocontrol suggestions were created during the early 20th century, causing institutional growth in research on agriculture. Biopesticides significantly influence the sustainability of the agricultural economy.
Biological resources that are crucial to agriculture should be considered ecosystem-beneficial, which justifies the use of biopesticides in integrated pest management programs. They are organic molecules derived from living things (biological enemies) or their byproducts (semi-chemicals, phytochemicals, or microbial products) capable of controlling pests through non-toxic processes. They are regarded as low-risk, secure items for both people and their surroundings.
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Classification of Biopesticides
The Environmental Protection Agency has divided biopesticides into three main categories in accordance with the type of component they use, i.e., Microbial, Biochemical, and Plant-Incorporated Protectants.
- The majority of broad-spectrum, pest-specific biopesticides fall into the microbial category. Microbial pesticides use microorganisms such as bacteria, viruses, fungi, and protozoans as biological components.
- These types of species are precisely delivered to the target species.
- Microbial biopesticides are environment-friendly, host-specific, and self-replicating. Bt (B. thuringiensis) is one of the most commonly employed bacteria to combat insect pests to control insect pests.
- Lepidopterans, coleopterans, and dipterans are just a few of the many problems that it is used to fight off.
- The most prevalent commercially available bacterial species as bio-pesticides are Bacillus popilliae, B. thuringiensis, Clostridium bifermentans, Pseudomonas alcaligenes, Pseudomonas aureofaciens, Saccharopolyspora spinosa, Serratiaentomophila, and Streptomyces avermitilis; as for fungi-based pesticides, Beauveria bassiana, Metarhizium anisopliae, Nomuraea rileyi, Trichoderma viride, Paecilomyces farinosus, and Verticillium lecanii. The use of baculoviruses (BV) as viral biopesticides is every day.
Mode of action of B thuringiensis
B.thuringiensis can be used as a source of poisonous genes that, when expressed in plants, provide toxic particles harmful to several insect pests.
The steps involved are:
- Insects ingest endotoxin produced by bacteria during spore formation in leaves (B. thuringiensis)
- The alkaline (pH 9–12) midgut environment in insects such as Lepidopterans causes the crystals to dissolve.
- The solubilization of protein crystals releases and activates proteins such as cry protein in the insect’s gut.
- The activated protein binds to the specific receptor present in the gut wall of insects, causing pore formation.
- The pore formation leads to an osmotic imbalance between intracellular and extracellular environments, and cell lysis occurs.
- As a result, the microvilli are destroyed, the insect ceases feeding, and it eventually dies.
- Biochemical pesticides are plant-derived compounds that use non-toxic ways to control pests.
- On the contrary, traditional insecticides often consist of synthetic substances that directly kill or inactivate the bug.
- For instance, this pesticide comprises insect sex pheromones, which prevent mating, and various other scented plant extracts, such as phytochemicals that attract insect pests and function as toxicants, insect growth regulators, repellents, and antifeedants.
- These pesticides affect an insect’s physiology, metabolic pathway, or neurological system through ingestion, inhalation, or absorption by the insect’s cuticle. Restricting spiracles inhibits insect breathing, which causes asphyxia.
- It will disrupt the insect membrane’s ion channel and ion pump, disrupting signal transduction at the cellular level.
- Monoterpenes is an essential oil that works as a neurotoxin by interfering with the acetylcholinesterase enzyme, vital in transmitting nerve impulses in insects, resulting in their paralysis and eventual demise.
- Additionally, it prevents the synthesis of DNA, RNA, and proteins.
- Plant-incorporated protectants, genetically modified plants, or manipulated plants have the toxin-producing genes to combat the pest. For instance, the Bt gene is transferred in the cotton plant.
- The target gene is transferred into transgenic plants using Agrobacterium-mediated transfer, gene guns, or ballistic techniques. The above methods were applied to rice, corn, wheat, and maize.
- Additionally, the plant-incorporated protections may pose some hazards, including those to non-target pests, human health, the environment, the spread of the PIP gene to other plants, and the appearance of herbicide- or insect-resistant organisms.
- Biopesticide formulations are similar to those of synthetic pesticides. Active ingredients and inert or inactive substances are combined in biopesticide formulations.
- The formulation intended to manage the target pest contains one or more active ingredients (such as ethylene or B.thuringiensis), as well as inert additives (such as kerosene, beeswax, and propane) serve to improve the application and efficacy of the active ingredients.
- Based on their formulations, biopesticides are divided into dry and liquid.
- Dry materials include dust powders, granules, seed dressings, wettable powders, and wettable-dispersible powders, whereas emulsions, suspensions, emulsifiable concentrates, and ultra-low volume liquids are all examples of liquids.
Adavanatges of Biopesticides
Biopesticide holds some pros over synthetic pesticides:
- Biopesticides are less harmful than synthetic pesticides since they are made from natural components, thereby being gentler for the environment.
- Compared to synthetic pesticides, biopesticides are frequently more targeted in their effects and are more unlikely to harm non-target species.
- Biopesticides can aid in reducing the emergence of resistance to pesticides in pests, increasing the durability of pest control measures.
- In contrast to synthetic pesticides, biopesticides frequently leave less residue, lowering the risk of food and water pollution.
- Biopesticides are compatible with organic farming and can protect crops without jeopardizing the organic certification.
Disadvantages of Biopesticides
Biopesticide has a few cons, which are as follows:
- Biopesticides are photodecomposed by ultraviolet light, radiation, and heat and must be used only in the morning.
- Only a specific species or group of insects are poisoned by microbial insecticides; the others may still exist and inflict damage.
- Some of the fungal pesticides are expensive.
- Possibly having a shorter life span than synthetic pesticides, biopesticides are less practical to store and utilize.
- Biopesticides may need specialized tools or application methods, making them more challenging to apply.
- Bharti, V., & Ibrahim, S. (2020). Biopesticides: Production, Formulation and Application Systems. International Journal of Current Microbiology and Applied Sciences, 9(10), 3931–3946. https://doi.org/10.20546/ijcmas.2020.910.453
- Rajamani, M., & Negi, A. (2021). Biopesticides for Pest Management. In V. Venkatramanan, S. Shah, & R. Prasad (Eds.), Sustainable Bioeconomy (pp. 239–266). Springer Singapore. https://doi.org/10.1007/978-981-15-7321-7_11
- Schünemann, R., Knaak, N., & Fiuza, L. M. (2014). Mode of Action and Specificity of Bacillus thuringiensis Toxins in the Control of Caterpillars and Stink Bugs in Soybean Culture. ISRN Microbiology, 2014, 1–12. https://doi.org/10.1155/2014/135675