Advances in sustainable pesticides gain momentum

Microbial pesticides are increasingly being used in agriculture. A study by researchers at Liaocheng University in China describes advances in this field. They analyzed the different types of microbial pesticides and their mechanisms of action, highlighting the potential of these agents to promote safer and more sustainable agriculture.

Microbial pesticides use bacteria, fungi and viruses to combat pests and diseases through direct infection, competition for nutrients or induction of resistance in plants. With natural biodegradability, low environmental impact and high specificity, these biopesticides are gaining ground in the market. In April 2024, FAO and WHO released a manual to standardize the use of these products, including quality, safety and efficiency criteria.

Genus Bacillus

Among the microorganisms analyzed, the genus stands out Bacillus. Species such as B. thuringiensis (Bt) produce toxins that pierce the intestines of lepidopteran, coleopteran and dipteran larvae. “Cry” toxins form protein crystals that, when ingested by pests, lead to death by cell lysis. Bt-based products already represent a significant part of the biological insecticide market.

Bt is also effective against several species of flies and beetles. Its mode of action involves interaction with specific receptors in the intestine of larvae, resulting in the formation of pores in the cell membranes. This action compromises the integrity of the intestinal epithelium, causing widespread infection and death of the insect. As far as is known, its use is highly safe, with minimal effects on humans, domestic animals and non-target organisms.

The study also explores the benefits of Bacillus subtilis, whose action includes competition for space and nutrients, production of antibacterial compounds and induction of plant resistance. This species shows efficacy against several pathogens, such as the tomato wilt fungus (Fusarium spp.), in addition to improving soil structure when applied with biochar.

B. subtilis It also produces lipopeptides such as surfactin, iturin and fengycin. These compounds are capable of inhibiting phytopathogens by affecting their cell membranes. The symbiotic interaction with plants also contributes to the increase of phytohormones and improvement of the root system, benefiting nutrition and growth.

Another promising species is Bacillus amyloliquefaciens, a producer of lipopeptides and phytohormonal compounds. This bacterium acts both in the control of anthracnose and in stimulating the growth of tomatoes and peppers. Studies demonstrate its effectiveness against fungi such as Colletotrichum spp. And erwinia spp.. It also positively modifies the soil microbiota, favoring other beneficial bacteria.

Bacillus licheniformis is another example. This species is capable of synthesizing compounds such as gramicidin and subtilin, which suppress soil pathogens. It also strengthens root cell walls, making it difficult for invading organisms to enter. Experiments have shown its effectiveness against diseases of rice, cotton, and corn.

Genus Pseudomonas

The study also highlights the relevance of genus Pseudomonas, especially the species P. fluorescens e P. chlororaphis. These bacteria are common in soils and have broad antibacterial and antifungal activity. They produce compounds such as phenazines and siderophores, in addition to inducing systemic resistance in plants.

P. fluorescens It is used to control root rot and wilt. Its production of organic acids and enzymes degrades the cell walls of phytopathogenic fungi. Field studies have shown its ability to reduce the incidence of diseases such as sunflower blight by up to 87%.

P. chlororaphis It produces antibiotics such as HCN and volatile compounds that affect nematodes and insects. In addition, it promotes plant growth through the synthesis of auxins. Its joint application with beneficial fungi increases protection against pathogens.

Another species that stands out is Pseudomonas putida, notable for the production of biofilms and metabolites with antifungal properties. Its actions include the degradation of toxic organic compounds and the improvement of soil quality. It can also compete directly with pathogens for colonization of the rhizosphere.

Fungi

Fungi also play an important role. Metarhikum anisopliae e beauveria bassiana They infect pests by direct contact, penetrating the cuticle. Once inside the insect, they release toxins that cause its death. These fungi are highly effective against grasshoppers, aphids and other insects.

Other relevant fungi are Trichoderma spp., widely used in the control of phytopathogenic fungi. They act through mycoparasitism, producing enzymes such as chitinase and glucanase that degrade the cell wall of pathogens. In addition, they stimulate germination and plant growth.

Formulations and applications

The study also analyzes advances in formulations and applications. One of the innovations is the use of nanoparticles, such as silver and chitosan, synthesized by Streptomyces. These particles improve the adhesion and penetration of pesticides, increasing their efficiency. Tests have demonstrated effective action against bacteria that cause soft rot in potatoes.

Biopesticides challenges

Even with so many benefits, biopesticides face challenges.

The action is usually slower than that of traditional products. They also depend on ideal environmental conditions, such as temperature and humidity.

Furthermore, there is a lack of standardized regulations in many countries, which makes widespread adoption difficult.

More information at doi.org/10.1016/j.pestbp.2025.106512