Entomopathogenic Fungi: Nature’s own pest control

My first encounter with an entomopathogenic fungus wasn’t in a lab. It was in the field, staring at a beetle covered in a white coating. At first, I didn’t know what I was looking at. Then I realized: that white layer was Beauveria bassiana, and the beetle was already dead — parasitized from the inside out by a fungus that had been living in the soil all along.

That moment stuck with me. I went on to spend a significant part of my career evaluating the quality of products based on entomopathogenic fungi, and I became a great admirer of what these organisms can do. They’re not a miracle solution (nothing in agriculture is) but they are one of the most fascinating and underused tools in biological pest control.

What exactly are entomopathogenic fungi?

Let’s break down the name: “entomo” means insect, “pathogenic” means disease-causing. So these are fungi that cause disease in insects. They’re naturally present in soils around the world and have been parasitizing pest insects for millions of years, long before we started farming.

Their main advantage is their ability to infect, colonize, and kill pest insects that damage crops. In a world where farmers are battling increasing resistance to chemical insecticides and dealing with an ever-growing list of pest threats, that sounds like exactly what we need.

Currently, more than 170 strains with bioinsecticidal potential have been identified worldwide. The most recognized genera include Beauveria, Metarhizium, Lecanicillium, Isaria (now reclassified as Cordyceps fumosorosea), Paecilomyces, and Hirsutella. Each has its own host range, optimal conditions, and strengths.

Which species should you know about?

Beauveria bassiana — This is arguably the most widely used entomopathogenic fungus in agriculture. Named after the Italian scientist Agostino Bassi, who demonstrated back in the 1830s that a microorganism could cause disease in insects (a revolutionary idea at the time), Beauveria has an impressively broad host range. It can infect whiteflies, aphids, thrips, beetles, caterpillars, mosquitoes, and more. Its versatility is its biggest strength — a single Beauveria-based product can address multiple pest problems at once.

Metarhizium anisopliae — Known as the “green muscardine fungus” because of the distinctive green color of its spores, Metarhizium is particularly effective against soil-dwelling pests like grubs, root weevils, and termites. It’s been used extensively in locust and grasshopper control programs in Africa and Australia. Some strains have an interesting dual ability: they can colonize plant root zones, acting as both pest control agents and plant growth promoters. 

Isaria fumosorosea (now Cordyceps fumosorosea) — Particularly effective against whiteflies, one of the most economically damaging pests in greenhouse and tropical agriculture. Isaria thrives in humid environments, making it especially popular in protected cultivation like greenhouses and tunnels.

Among the pest insects affected by entomopathogenic fungi are aphids, mites, thrips, mosquitoes, whiteflies, rootworms, moths, and many others. The list keeps growing as more strains are identified and tested.

How do they work?

The mechanism of action of entomopathogenic fungi is fascinating due to its complexity — and it’s remarkably consistent across different species. It’s so precise and effective that it’s almost hard to believe it occurs naturally.

Here’s the step-by-step process:

1 Adhesion

The fungal spore attaches to the insect’s body. Research suggests that electrostatic and hydrophobic forces play a role in this initial contact. Certain proteins (like MAD1 and MAD2) help the fungus recognize the insect as a suitable host.

2 Germination

Once on the insect, the spore germinates when environmental conditions are right — particularly temperature and humidity. This produces a specialized structure called an appressorium (think of it as a tiny anchor-and-drill combination) that prepares to break through the insect’s outer shell.

3 Penetration

The appressorium exerts mechanical pressure on the insect’s cuticle while simultaneously secreting enzymes — proteases, chitinases, lipases — that chemically break down its layers. This is what makes entomopathogenic fungi unique among biocontrol agents: they don’t need to be ingested. They attack from the outside.

4 Colonization

Once inside the body cavity (the hemocoel), the fungal mycelium spreads throughout the insect, feeding on its tissues and fluids. In many cases, the fungus also produces toxic secondary metabolites — compounds like beauvericin or destruxins — that suppress the insect’s immune system and accelerate death.

5 Sporulation

After the insect dies, the mycelium emerges externally and enters a reproductive phase, producing new spores on the surface of the cadaver. These spores disperse — through wind, rain, or contact with other insects — and the cycle starts again. This horizontal transmission is what gives entomopathogenic fungi the potential for self-sustaining pest suppression in the field.

Think about what this means: a chemical insecticide kills on contact and it’s done. One shot. An entomopathogenic fungus kills one insect and then spreads to others naturally. That’s a fundamentally different — and powerful — mode of action.

Where are these species isolated from?

They’re typically isolated from infected insects collected in the field. The process is straightforward but requires precision: you collect the parasitized insect, bring it to the laboratory, and isolate the fungus using selective culture media designed specifically for these microorganisms. From there, the strain is purified, characterized, and tested for virulence before it can be considered for product development.

This is one area where microbiology training really matters. The difference between a promising field isolate and a commercially viable strain depends on careful laboratory work — and a lot of patience.

Why aren’t they more widely used?

This is the honest question, and I think the answer has several layers.

First, there’s a lack of awareness and training. Many farmers simply don’t know these products exist, or if they do, they’re unfamiliar with how to use them properly. When you’ve been using chemical insecticides your entire career, the idea of spraying a living fungus onto your crops can feel counterintuitive.

Second, the speed issue. Entomopathogenic fungi are slower than chemicals. A chemical insecticide can knock down a pest population within hours. A fungus needs time to adhere, germinate, penetrate, and colonize — that process can take days. For a farmer watching a pest outbreak escalate in real time, that wait feels risky. Multiple applications may be necessary to achieve effective control, and that requires a shift in mindset from “kill now” to “manage over time.”

Third, specificity. Each fungus typically targets a specific pest or group of pests. If your crop is under pressure from multiple insect species simultaneously, you may need to combine several biological agents — which adds complexity and cost compared to a broad-spectrum chemical.

And finally, production and availability. Mass-producing entomopathogenic fungi requires specialized infrastructure — fermentation equipment, quality control protocols, cold chain logistics. This makes them more expensive to produce than synthetic molecules, and their availability in many markets is still limited.

None of these are reasons to dismiss the technology. They’re challenges to understand and work around.

What does success depend on?

This is critical, and honestly, it’s where I’ve seen the most mistakes in the field. Entomopathogenic fungi are living organisms, not synthetic chemicals, and they need the right conditions to work. Three factors matter above all:

Temperature. Each species has an optimal temperature range for growth, and high temperatures can significantly reduce spore viability. Applying them during the hottest part of the day — say, at noon under direct sun — is one of the most common mistakes. Late afternoon or early evening applications almost always perform better.

Humidity. This is arguably the most important factor. Fungal spores need high relative humidity to germinate and penetrate the insect cuticle. For example, Beauveria bassiana and Isaria fumosorosea spores require at least 70% relative humidity for the first 14 hours after application to successfully germinate. That’s a very narrow window, and if conditions are too dry during that period, infection simply won’t happen. This is why these products tend to perform best in irrigated fields, humid climates, or greenhouse environments.

Interaction with other chemicals. Mixing entomopathogenic fungi with certain agrochemicals can inhibit or reduce their effectiveness. This is mainly due to their sensitivity to fungicides (which, after all, are designed to kill fungi), but some insecticides and herbicides can also interfere. Always check compatibility before tank-mixing, and as a general rule, leave at least 5–7 days between a chemical fungicide application and a biological one.

When I was evaluating products based on entomopathogenic fungi, the cases where results were disappointing almost always traced back to one of these three factors. The fungus wasn’t the problem — the application conditions were.

A practical perspective

If you’re a farmer considering entomopathogenic fungi for the first time, my advice is simple: start small. Pick one crop, one target pest, and one product. Follow the label instructions carefully — especially regarding humidity, temperature, and application timing. Don’t expect chemical-speed results. Instead, measure over the course of the season: pest population trends, re-infestation rates, and the overall health of the treated area compared to untreated plots.

If you’re an entrepreneur or a company exploring biologicals production, entomopathogenic fungi are one of the most accessible product categories to start with. The basic process involves isolating a virulent strain, growing it on a solid or liquid medium (rice or grain substrates are common for solid-state fermentation), harvesting the spores, and formulating them into a stable product. We’ll get into the specifics of lab setup and production workflow in Article 4.

The bigger picture

Entomopathogenic fungi represent a viable and sustainable alternative to chemical insecticides. They’re not going to replace chemicals overnight — and they don’t need to. Their real power lies in integration: used alongside reduced chemical applications, cultural practices, and other biological agents as part of an IPM program, they can significantly reduce a farm’s dependence on synthetic products.

The challenges are real — speed, specificity, production costs, environmental sensitivity. But so is the potential. Continued research into the biology, ecology, and application methods of these fungi is steadily closing the gap between what’s possible in the lab and what’s practical in the field.

That white-coated beetle I saw years ago in the field was my introduction to a world I didn’t know existed. Since then, I’ve watched this technology grow from a scientific curiosity into a genuine commercial opportunity. The question isn’t whether entomopathogenic fungi work — the evidence is clear. The question is whether the industry is ready to invest in understanding them properly and applying them correctly.