From Lab to Field: How Biopesticides Work in Practice

[Audio] Good morning, everyone — and welcome to Module 2 of our Biopesticide Training Series. My name is Angeliki, and I'll be your facilitator today. Before we get started, a quick orientation: this is Module 2 of 6. If you were with us for Module 1, you'll remember we covered the regulatory landscape — what biopesticides are, how they're classified, and why regulators treat them differently from conventional chemistry. Today we move from policy to practice. This session is called "From Lab to Field," and that title is intentional. There's often a gap between the science behind these products and what actually happens when someone opens a bag of WP formulation in a hot field at noon. My goal today is to close that gap for you. By the end of this 60-minute session, you will be able to explain how four distinct classes of biopesticides actually kill pests or suppress disease, describe the field protocols that make or break their performance, and understand how to slot them into a real IPM programme. One thing I want to say upfront: biopesticides are not magic, and they are not simply "safer" versions of chemicals you already know. They are biologically active organisms and compounds with very specific conditions for success. Understanding the mechanism is what drives smart decisions. That's the single most important idea to take from today. Let's get into it..

[Audio] Let's look at what you'll be able to do by the end of this session — these aren't just learning outcomes, they're practical competencies. Objective one: Identify the four main classes of biopesticides and their active agents. When you walk into an agrodealer or read a product label, you should immediately know which category you're dealing with — and what that implies. Objective two: Explain at least three distinct mechanisms of action against pests. This matters because the mechanism determines your application strategy. A product that kills by physical abrasion has completely different requirements than one that kills by infecting the gut. Objective three: Apply correct storage, timing, and mixing protocols. This is where most biopesticide failures happen — not because the product doesn't work, but because it was stored at the wrong temperature or applied at the wrong time of day. Objective four: Integrate biopesticides into an IPM programme for resistance management. Biopesticides are most powerful when they're part of a system, not used as a one-for-one swap for a synthetic. And objective five: Evaluate real-world efficacy data and limitations. We'll look at actual field trial numbers today. I want you to be able to read those data, understand what they mean, and know when a product is the right fit — and when it isn't. Keep these objectives in mind throughout the session. We'll return to them in the summary..

[Audio] Alright, let's start with the taxonomy — the four official classes of biopesticides as defined by the EPA and used across most regulatory frameworks globally. Class one is microbial biopesticides. These are living microorganisms — bacteria, fungi, viruses, protozoa — that are applied to suppress pests. The biggest names here are Bacillus thuringiensis, or Bt, which we'll spend significant time on today; Beauveria bassiana and Metarhizium anisopliae, which are entomopathogenic fungi; Trichoderma species, which target plant pathogens; and baculoviruses, which are highly host-specific insect viruses. Class two is biochemical pesticides. These are naturally occurring substances — not living organisms, but molecules derived from nature. Neem oil, or more precisely azadirachtin, is the classic example. Pyrethrin, spinosad, and insect sex pheromones also fall here. The key distinction from synthetics is that they occur naturally and have non-toxic modes of action on non-target organisms. Class three is plant-incorporated protectants, or PIPs. This is where genetics enters the picture. A PIP is pesticidal material that a plant produces from genetic material that has been introduced into it. Bt maize and Bt cotton are the most commercially significant examples — the plant itself produces the insecticidal Cry protein. Class four is semiochemicals and botanicals. This includes chemical signals that alter pest behaviour — sex pheromones for mating disruption are the headline application — as well as physical materials like kaolin clay and diatomaceous earth, which work through mechanical rather than biochemical means. Remember these four categories. Everything we discuss today fits somewhere in this framework..

[Audio] Before we go deeper into mechanisms, I want to give you the commercial and epidemiological context — because understanding why biopesticides are growing so fast explains why this training matters now. The global biopesticide market hit eight billion US dollars in 2024. That's a substantial industry. And projected compound annual growth of around eleven percent through 2033 means this sector is expected to nearly double in less than a decade. You will be working with more biopesticides in your career, not fewer. But here's the number that really drives the urgency: 783. That is the number of pest species that had documented resistance to at least one class of chemical insecticide as of 2024, according to IRAC. Seven hundred and eighty-three species. And that resistance costs agriculture more than fifteen billion US dollars in yield losses annually. That resistance crisis is the primary driver of biopesticide adoption. When a pyrethroid stops working on a whitefly population, or when diamondback moth no longer responds to organophosphates, growers need alternatives. Biopesticides — especially those with multiple or novel mechanisms of action — are those alternatives. Layered on top of this is regulatory pressure. The EU has progressively withdrawn approvals for synthetic active ingredients that fail re-registration under modern risk assessment standards. National governments are following suit. And consumer demand for low-residue, organic, and pesticide-free produce continues to grow in premium markets. The bottom line: biopesticides are not a niche anymore. They are becoming a structural part of how we manage crop protection globally..

[Audio] Now we get to the heart of today's session — mechanisms of action. This is the most important conceptual slide in the module, so I want to spend a few minutes here. One of the key advantages biopesticides hold over many synthetic pesticides is that they don't rely on a single molecular site. Most synthetic insecticides work by blocking one receptor, one enzyme, one channel. Biopesticides typically employ multiple, complementary mechanisms — and that is their structural advantage for resistance management. Let me walk you through the six mechanisms shown here. The first is direct infection and parasitism. Entomopathogenic fungi like Beauveria and Metarhizium land on an insect, penetrate the cuticle physically and enzymatically, and colonise the body cavity. The insect dies within five to fourteen days. No ingestion required. The second is toxin production. This is Bt's mechanism. It produces crystal proteins — Cry and Cyt toxins — that form pores in the midgut epithelium of susceptible insects, causing osmotic shock and cell death. Highly specific to the target insect order — which we'll examine in detail on the next slide. The third is induced systemic resistance. Trichoderma and Bacillus subtilis don't just attack pathogens directly — they prime the plant's own immune system, activating salicylate and jasmonate defence pathways. The protection spreads through the plant even where the biocontrol agent isn't present. The fourth is competition and antibiosis. Beneficial microbes can simply outcompete pathogens for nutrients and physical space in the rhizosphere. Bacillus strains also produce antimicrobial metabolites — iturin A and fengycin are key examples — that disrupt fungal cell membranes. The fifth is physical and mechanical action. Kaolin clay creates a physical barrier on plant surfaces that confuses and deters insects. Diatomaceous earth works by abrading the insect cuticle, causing death by desiccation. These are not biological actions in the microbial sense, but they're still classified as biopesticides because they derive from natural mineral sources. And the sixth is mating disruption through semiochemicals. Synthetic sex pheromones flood the environment with signal molecules — males cannot locate females, mating fails, and the population declines over successive generations. Six different ways of achieving pest control, often without any direct toxicity in the conventional sense..

[Audio] Bacillus thuringiensis deserves its own slide — it's the most commercially significant microbial biopesticide in the world and the one you're most likely to encounter in the field. Let me walk you through the mode of action step by step, because understanding this sequence is what tells you why application timing and target stage matter so much. Step one is ingestion. A susceptible larva eats plant tissue containing Bt spores and the crystal proteins — the Cry and Cyt toxins. Note that word: susceptible. Not every insect is affected. The specificity comes later. Step two is activation. Inside the insect's midgut, the alkaline pH — which ranges from pH 8 to 10, much higher than in vertebrates — dissolves the protein crystals. Gut proteases then cleave the protoxin into its active form. This step does not happen in birds or mammals, whose digestive systems are far more acidic. That's why Bt has such a favourable safety profile for non-target organisms. Step three is receptor binding. The active Cry protein binds to specific receptors on the midgut epithelial cells. Specificity is determined here — if the insect doesn't have the right receptor, nothing happens. This is why Bt var. kurstaki kills caterpillars but not beetles. Step four is pore formation. Once bound, the toxin inserts into the cell membrane and opens ion channels. The cell's ability to regulate osmotic balance collapses. Step five is death. Gut permeability fails entirely. Larvae stop feeding within hours — which is ecologically significant even before death, since feeding damage stops. Death follows within 24 to 72 hours for small larvae, and up to several days for older, larger ones. Now look at the table on the right. This is critical for product selection. Bt var. kurstaki — Btk — is your Lepidoptera product: caterpillars on vegetables and in forestry. Bt var. israelensis — Bti — targets Diptera, meaning mosquitoes and midges. Bt var. tenebrionis — Btt — targets beetles, particularly Colorado potato beetle. And Bt var. aizawai — Bta — is a Lepidoptera product particularly valuable against strains that have developed resistance to Btk. If someone tells you "I'm using Bt," the first question should always be: which subspecies? The answer determines what it can and cannot do..

[Audio] Let's move from bacteria to fungi. Beauveria bassiana and Metarhizium anisopliae are entomopathogenic fungi — literally, fungi that cause disease in insects — and they have a completely different infection cycle from Bt. The most important thing to understand is this: entomopathogenic fungi do not need to be ingested. They infect through direct contact with the insect's exoskeleton. This is what makes them effective against sucking pests — aphids, whitefly, thrips — that Bt cannot reach because those pests don't consume enough leaf tissue to get a lethal Bt dose. Let me walk through the infection cycle. Stage one: a conidium — a fungal spore — lands on the insect exoskeleton. This is the point of entry. Stage two: the spore germinates within 6 to 24 hours. It forms a specialised structure called an appressorium, which uses a combination of mechanical pressure and enzymatic degradation — proteases, lipases, chitinases — to penetrate the cuticle. Stage three: hyphal bodies spread through the haemolymph — the insect's blood equivalent — evading the immune system partly through molecular mimicry and by producing immunosuppressive compounds called destruxins. Stage four: the host dies in 5 to 14 days. Crucially, the fungus then sporulates on the cadaver and releases new conidia, potentially establishing a secondary infection cycle in the pest population. Now for the critical field performance data. Used alone, Beauveria achieves up to 25% control of Colorado potato beetle larvae in 14 days. But combined with Bt, there is a synergistic effect — 6 to 35% greater reduction than the two products would predict if acting independently. This synergy has been confirmed across multiple field seasons. The biggest limitation in the field? UV radiation. Conidia lose viability rapidly in direct sunlight. The practical response: apply after 5 PM on sunny days to minimise UV exposure. This is a free intervention that can double efficacy. Modern oil-based formulations like BotaniGard ES and Met52 EC retain viability for 12 to 18 months, compared to less than 3 months for unformulated spores. Formulation has transformed what was once a logistically difficult product into something practically viable for commercial agriculture..

[Audio] Trichoderma species are the world's most widely deployed fungal biocontrol agents for plant disease management. If you're working with soil-borne pathogens — Botrytis, Fusarium, Rhizoctonia, Pythium, Sclerotinia — there is very likely a Trichoderma product that addresses your problem. What makes Trichoderma exceptional is the breadth of its mechanisms. Most biocontrol agents work through one or two pathways. Trichoderma works through five, and they're complementary. The first is mycoparasitism — the most dramatic mechanism. Trichoderma hyphae physically coil around the hyphae of pathogenic fungi like Botrytis cinerea, then produce cell-wall-degrading enzymes — chitinases and glucanases — that lyse the pathogen's cells from the outside. It's a direct physical attack. The second is antibiosis. Trichoderma produces volatile and non-volatile antifungal compounds that diffuse through the soil matrix. These compounds suppress pathogen spore germination before the pathogen ever reaches the root. Prevention, not just response. The third is competition. Trichoderma grows fast and is highly efficient at capturing carbon, nitrogen, and iron in the rhizosphere. Pathogens are simply outcompeted for the resources they need to establish. The fourth is induced systemic resistance. Root colonisation by Trichoderma triggers the plant's jasmonate and ethylene immune signalling pathways. This primes tissues above ground — tissues that the Trichoderma never actually contacts — against foliar pathogens. The agent is in the root; the protection extends to the leaf. This is a remarkable biological phenomenon. The fifth is rhizosphere engineering. Trichoderma modifies soil pH and microbiome composition over time, creating conditions that favour beneficial organisms and suppress pathogens at the community level. One practical note I want to flag: chitosan nanogels — an emerging delivery technology — have been shown to extend Trichoderma and Bacillus activity in field conditions from the typical 7 to 10 days to 3 to 4 weeks. That's a significant increase in residual efficacy, and it changes the economics and scheduling of applications considerably. Keep an eye on this space..

[Audio] We are now going to shift from biology to logistics — and this is where many biopesticide programmes fail in practice. Microbial biopesticides contain living or biologically active ingredients. That sounds obvious, but it has profound implications for how they must be handled. You cannot treat a bag of Beauveria the way you'd treat a bag of lambda-cyhalothrin. They are categorically different. Let me go through the risk factors. UV radiation is rated high risk — the most critical factor for foliar products. Sunlight destroys fungal spore DNA and Bt crystal proteins within hours. A product that was perfectly viable in the warehouse can be rendered ineffective by a midday application on a cloudless day. Heat is also high risk. Temperatures above 30 to 35 degrees Celsius reduce microbial viability significantly. Never store near engines, in vehicles in direct sun, or in unventilated sheds that heat up during the day. Moisture is medium risk. Excess moisture can cause premature germination in wettable powder and water-dispersible granule formulations, or introduce contamination. Keep products sealed. Freezing is medium risk. While some strains tolerate brief freezing, most do not. Unless your product label explicitly permits freezing, avoid it. Contamination is rated low risk in terms of frequency, but it's a common source of confusion. Chlorinated water — including the water many farmers use to clean spray equipment — can kill microbial products. Always rinse the sprayer with clean, unchlorinated water before loading a microbial product. For storage best practices: refrigerate between 4 and 8 degrees Celsius unless the label states otherwise. Oil-based formulations like BotaniGard ES and Met52 EC have a shelf life of 12 to 18 months when stored correctly. Wettable powder formulations are typically rated for 12 months. Keep products sealed until you're ready to mix. And if your operation uses Bt products from Valent BioSciences or similar quality manufacturers with encapsulated formulations, correctly stored product retains more than 80% of its activity for a full year. Log your storage temperatures. If something goes wrong with efficacy and you can prove storage was correct, you have evidence that the issue lies elsewhere. If you can't prove it, you don't know..

[Audio] Storage gets products to the field alive. Application protocol determines whether they work once they're there. Let's talk about timing first, because it's the highest-impact zero-cost intervention available to you. Apply after 5 PM on sunny days — ideally between 5 and 7 PM. This is when UV-B intensity has dropped sufficiently that conidia tolerate the dose without losing viability. Research shows the acceptable threshold is a UV-B dose of less than 0.5 joules per square centimetre. After 5 PM, you're generally within that window. Target early instars — the youngest larvae. Young larvae are 10 to 100 times more susceptible to both Bt and entomopathogenic fungi than mature larvae. This has a compounding benefit: small larvae also cause less damage. Applying at the first sign of infestation, before populations establish, is always better than reactive application under high pressure. Avoid applications in strong wind above 5 metres per second — you lose coverage and the product goes where you don't want it. And never apply if rain is forecast within 4 hours; you'll simply wash the product off before it can work. Do not apply during midday heat above 30 degrees. Products degrade on contact with hot leaf surfaces, and spray droplets evaporate before coverage is achieved. Now for equipment and mixing — follow this sequence carefully. Step one: use large-orifice nozzles and coarse-mesh strainers. Wettable powder formulations will clog fine-spray nozzles. Step two: rinse the sprayer with clean, non-chlorinated water. A pH between 6 and 7 is ideal for most microbial products. Step three: pre-mix the product in a small volume of water and agitate before adding to the tank. This ensures even suspension. Step four: apply at the pressure specified on the label — typically 2 to 3 bar for foliar applications. Step five: ensure thorough canopy coverage, including the undersides of leaves. Larvae shelter and feed on the undersides. If your spray doesn't reach there, you're not targeting where the pest actually lives. Step six: use a calibrated sprayer. Volume per hectare is critical for microbial products in a way that is less critical for systemic chemicals. You need to deliver a sufficient number of viable spores or Bt units per unit of leaf area..

[Audio] A common question in training sessions is: can I mix my biopesticide with the synthetic I'm already using? The answer is often yes — but with important caveats, and compatibility must always be verified before you mix in the field. Let me walk through the compatibility table on this slide. Bt, Bacillus thuringiensis, is broadly compatible with most insecticides, adjuvants, and foliar nutrients. Use caution with broad-spectrum bactericides and alkaline pH solutions. Avoid chlorine-based disinfectants and strongly alkaline mixes — they destroy the crystal proteins. Beauveria bassiana and Metarhizium are compatible with most insecticides at label rate, and interestingly with neem oil, which has shown synergistic effects in some trials. Use caution with contact-type synthetic fungicides, which can damage fungal spores, and with high temperatures during mixing. Avoid copper fungicides, chlorothalonil, and chlorinated water entirely — these are fungicidal and will kill your biocontrol agent. Trichoderma is compatible with biofertilisers, growth promoters, and systemic insecticides. Use caution with low-rate synthetic fungicides. Avoid broad-spectrum fungicides like mancozeb and captan at full rates — they will suppress Trichoderma as effectively as they suppress the pathogens you're targeting. Neem oil is soft and broadly compatible with other biologicals and most non-ionic products. Use caution with highly alkaline solutions and certain emulsifiers that can destabilise the formulation. One positive note to close on: a recent greenhouse trial demonstrated that Bacillus subtilis — Batistar WP — and Beauveria bassiana — BotaniGard WP — could be co-applied without antagonism, simultaneously suppressing greenhouse whitefly and tomato powdery mildew. That's a single spray covering two separate pest problems with no negative interaction. These kinds of stacked biological programmes are where the field is heading. The practical rule: when in doubt, perform a small-jar compatibility test 24 hours before your application. Mix the products at label rates and observe for layering, flocculation, or phase separation. If the mix looks wrong, it probably is..

[Audio] Biopesticides don't replace IPM — they fit within it. And understanding where they fit determines how effectively you can use them. Look at the decision hierarchy on this slide. It's structured from least to most disruptive to the ecosystem. Prevention and cultural controls sit at the top — crop rotation, resistant varieties, sanitation, physical barriers. Then monitoring and economic threshold assessment. Then biological controls, which includes biopesticides. Then selective chemical pesticides. And only at the bottom, as a last resort, broad-spectrum chemistry. Biopesticides span three distinct roles within this hierarchy. The first is preventive use. Trichoderma applied as a seed treatment or soil drench before planting is a classic example. You're applying it before there's any measurable pest pressure, because you know the pathogen is in the soil and the cost of colonisation by Trichoderma now is far less than the cost of damping-off disease later. The second is curative use. Once monitoring confirms that a population is approaching the economic threshold — the point at which pest damage will cost more than the control measure — you apply Bt or Beauveria. This is timely, cost-effective intervention calibrated to actual need. The third is resistance rotation. This is arguably where biopesticides are most strategically valuable. Rotating between Bt Cry proteins, entomopathogenic fungi, and conventional chemistry applies selection pressure from multiple, unrelated mechanisms. No single mutation in a pest population can confer resistance to all of them simultaneously. Biopesticides with multiple mechanisms of action — like Trichoderma — are particularly valuable rotation partners. And the fourth role is conservation of beneficials. Selective biopesticides spare parasitoid wasps, predatory beetles, lacewings, and other natural enemies that provide biological control for free. When you replace a broad-spectrum spray with a selective biopesticide, you're not just protecting this crop — you're preserving the biological infrastructure of your whole farm..

[Audio] Let's look at what the field data actually shows. I want to be specific about numbers here, because biopesticide advocacy sometimes suffers from vague claims. The research is strong enough that we don't need to be vague. Bt alone achieves 50 to 85% control of Colorado potato beetle larvae within 14 days at label rate. That's from Wraight and Ramos, published in Biological Control in 2005 — one of the most cited papers in biopesticide science. That's a meaningful control level for a product with essentially zero re-entry interval and no MRL issues. When Bt is combined with Beauveria bassiana, the result is synergistic, not merely additive. Six to 35% greater reduction than the independent action of each product would predict. This synergy was confirmed across three field seasons. The interaction is real and repeatable. For Beauveria in cucumber production, a 2024 field trial in Nepal found 35.58 tonnes per hectare yield in plots treated with Beauveria, compared to 17.8 tonnes per hectare in untreated controls. That's roughly double the yield. The benefit-cost ratio was 4.19 — the highest of all treatments tested in that study. And for timing: research by Liang and colleagues in 2023 demonstrated that timing optimisation alone — simply shifting the application window to later in the day — can double field efficacy of fungal biopesticides. No additional product cost. No change in rate. Just timing. The message is clear: these products work. They work better when stacked. And they work dramatically better when applied correctly..

[Audio] I want to spend time on limitations. Not because biopesticides don't work — we just saw the data — but because honest assessment of limitations is what prevents misuse and protects your reputation as an advisor. Let me go through each limitation and the practical response to it. Speed of kill is rated medium concern. Bt acts within 24 to 72 hours for small larvae. Entomopathogenic fungi take 5 to 14 days. If you have a high-pressure infestation three days before harvest, biopesticides cannot carry that situation alone. The solution is proactive use — apply before threshold is exceeded — or combine with a fast-acting synthetic when urgency demands it. Environmental instability is rated high concern. UV, heat, and rain all degrade biopesticides faster than conventional chemistry. The foliar half-life of fungal conidia in full sun can be under 24 hours. The response: use encapsulated or oil-based formulations, and apply with correct timing. This is solvable with knowledge. Narrow host range is rated low to medium concern, and I want to reframe this one. Narrow host range is often presented as a weakness — and it does require accurate pest identification before purchase. But it's also the property that makes biopesticides safe for beneficial insects, safe for natural enemies, and ideal for resistance management. A product that only kills what it's supposed to kill is a feature, not a bug. Cold chain dependence is rated high concern — especially in regions where reliable refrigeration is not available at the distributor or retailer level. Modern oil-based and encapsulated formulations have improved this significantly, but cold chain remains an important infrastructure consideration for widespread adoption in lower-resource settings. Per-application cost is rated medium concern. Unit costs can exceed synthetic equivalents. However, when you factor in benefit-cost ratios of 2.9 to 4.19, savings on re-entry intervals, and MRL compliance in premium export markets, the economics often shift favourably. And finally: resistance to biopesticides is real. Bt resistance in diamondback moth — Plutella xylostella — after intensive, exclusive use is well documented. The lesson is not that Bt is fragile — it's that no tool should be used exclusively. Rotate Cry proteins. Combine mechanisms. Build a system, not a dependency..

[Audio] We've covered a lot of ground today. Let me bring it together with six key takeaways that I want you to carry out of this room. First: four classes, multiple mechanisms. Microbial, biochemical, PIPs, and semiochemicals each work differently. The fact that biopesticides collectively employ multiple mechanisms of action is their structural advantage for resistance management over single-site synthetics. Second: mechanism determines protocol. Bt must be ingested — so you target young larvae and ensure thorough leaf coverage. Entomopathogenic fungi work through cuticle contact — which is why they reach sucking pests that Bt cannot. Know your product's mechanism. That knowledge drives every decision. Third: timing is free efficacy. Shifting a fungal product application from 11 AM to after 5 PM costs nothing and can double the result. Scout early, apply proactively, and protect the investment you've made in the product by deploying it at the right moment. Fourth: storage is not optional. These are living products. Cold chain at 4 to 8 degrees Celsius, sealed packaging, and non-chlorinated water in your sprayer are non-negotiable. No storage protocol, no efficacy. Fifth: IPM plus biopesticides equals durable control. Biopesticides are most powerful as rotation partners and conservation tools within a managed IPM programme. Synergistic combinations and multi-mechanism rotations — including conventional chemistry where appropriate — are what deliver long-term, sustainable pest control. And sixth: the market is growing for good reason. 783 resistant pest species, a global market of eight billion dollars growing at 11% annually, and the regulatory withdrawal of key synthetic chemistry all point in the same direction. Biopesticides are not a niche alternative. They are an essential component of modern crop protection. Our next session — Module 3 — will cover regulatory approval, registration pathways, and how to read a biopesticide label. Before we close, are there any questions from today?.

[Audio] This final slide is your reference list for everything we discussed today. I want to briefly highlight a few sources that are particularly worth reading if you want to go deeper. Thakur and colleagues' 2023 paper in Diversity is an excellent recent review of microbial biopesticide mechanisms — open access and very readable. Wraight and Ramos 2005 is the definitive work on Bt and Beauveria synergy against Colorado potato beetle — the numbers I cited today come from that paper. The 2025 Frontiers in Sustainable Food Systems paper covers formulation advances and the cold chain issue in detail — it's current and practically focused. For up-to-date application guidance, the CABI BioProtection Portal is freely available online and regularly updated. It's an excellent field resource. All references on this slide have been verified as of May 2026. DOIs and PMC accession numbers are provided for peer-reviewed sources so you can locate them easily. Your training coordinator can answer questions about accessing any of these materials. Thank you for your attention today. I look forward to seeing you in Module 3..