By Peter Keen
Biopesticides use nature’s resources to fight nature’s threats in farming. The threats are the competing creatures and organisms feeding on and destroying the health of plants. Unchecked, they wipe out 15-20% of tea crops. The resources are microbes, bacteria, viruses, plant extracts, and compounds that can counter the threats in a way that is different from relying on chemistry labs and factories. Biopesticides kill the target but leave the plant and ecology healthy. Synthetic pesticides have historically been very effective in the “-icide goals” but at the cost of escalating environmental damage.
Pest and disease control is a massive multidimensional challenge for tea growers. There are more than a thousand natural threats to bushes, with hundreds active in any tea garden. For North East India, which includes Darjeeling and Assam, a study cites 250 types of insects, 350 fungal pathogens and hundreds of parasites, and microbial threats. In China, representative figures from field surveys are 80 viruses, 49 fungi, 240 parasites, and 600 creepy-crawly and flying enemies. Studies in Sri Lanka show that uncontrolled weeds can reduce a tea plantation to “a totally unproductive and economically non-viable unit” in just 1-2 years.
Chemical pesticide defenses against these threats are analogous to broad-spectrum antibiotics. They are proven, relatively inexpensive and will wipe out a wide range of attackers with the equivalent of a chemotherapy radiation blast. But they too often add problems of overuse, residues in the soil and plant, chronic harm to workers’ health, water runoff pollution, and soil erosion and damage. Many pests develop resistance that escalates the complexity and consequences of treatment: the potato beetle, for instance, evolved immunity to over 60 previously effective insecticides.
Non-harmful insects increasingly become unintended victims. Combining “bee colony collapse” with “pesticides” generates over 600,000 Google search hits. An October 2020 study reports that the reproduction rate of female blue orchard bees in California drops by over a third when they are exposed to neonicotinoids, the most widely used insecticides in the world.
There’s a widespread agreement that synthetic pesticides now create more damage than benefit. They continue to improve short-term crop yields at the cost of long-term environmental harm. They became a necessary evil rather than a positive contributor to ecological balance and sustainable development.
Biopesticides are the most effective alternative and are organic in the technical sense of the term: free of synthetic compounds and derived from plant, bacterial, and animal origins with a carbon base. Organic does not mean simple, instant, or easy to develop and apply. All pesticides are toxic and dynamic in their interactions. The suffix “-cide” equates to killing, ranging from suicide to homicide to, say, avunculicide (killing your uncle) and episcopicide (a bishop).
Organics are biologically vicious “-cides”, in the same way that chemical ones are, but toxic to the predator’s insides not the external environment. A core trick is to get a munching caterpillar to happily chow down on what its digestive system takes as a nutrient but which destroys its cell walls, disrupts internal defenses, and induces apoptosis – self-programmed death. A core problem is that such a bio rather than chemo killer narrowly snipes only this target; the mosquito sunbathing alongside is left daydreaming and abuzz. The most widely used synthetics have the widest impact so that a harmless butterfly gets its insides eviscerated in killing the target caterpillar.
Public opinion is increasingly opposed to such synthetic chemical -cides. “Organic” is now the synonym for “good” and “glyphosate” for “evil” in the press and among consumers of tea. Glyphosate is the core ingredient in Roundup, the synthetic that has generated organized public opposition plus large damage awards in civil lawsuits for its carcinogenic and neural impacts. The science is not as absolutely clearcut in its conclusions here as proponents and opponents of glyphosate claim and counterclaim. Regardless, consumers increasingly see chemical farming as harmful and regulators are more and more looking for fertilizers and pesticides that contribute to environmental, personal and worker health. Government policy ranges from national banning of some synthetics to region, state, and city restriction to open markets and use.
What makes biopesticides different is how they interact with the environment and predators. They are analogous to narrow spectrum antibiotics and are very much following the same development path as immunotherapy versus chemo: selective, targeted, less damaging to their ecology, and reliant on biological manipulation and undermining of the cells and molecules of specific host predators.
That makes it more expensive to produce effective new ones and their pest-specific specialization narrows down the market size and shoots up the price. They are biologically active and thus have a shorter life span than chemical synthetics, making stocking of inventory a risk for sellers, but of course their being biodegradable is part of their positive value in protecting the environment. Most must be produced in vivo rather than in vitro – bred on live plants rather than synthesized in labs. That’s one of the many factors that adds to cost and complexity.
Progress is ongoing and sustained with the caveats above. The high-end estimates of the 2019 biopesticide market are around $4.4 billion, out of a global total of $84 billion. The consensus seems to be 1.0-2.5% market share and 10-15% increase per annum. The fastest growing segment has been for microbial products, which are relatively inexpensive and very effective for targeting specific pests.
The field is broad, specialized, and packed with very long and very obscure terms. It’s impossible to provide a summary that both simplifies the core principles while doing justice to the complexity of their implementation. The simplification too easily encourages the idea that switching to biopesticides is easy — just a different spray. Or, better, no spray. The complexity can be discouraging. Roadblock after roadblock on the path from research to application and more blocks from there to commercialization and even more to everyday adoption.
Here are four general examples that may help balance the two perspectives: one from longest-established practice (botanicals) and the other from what is very much the mainstay of current practice (microbes and bacteria) and a glance at the emerging advanced application of genetic engineering.
Phytochemicals and botanical biopesticides
The history of biopesticides goes back several millennia. It rested on phytochemicals. These are compounds naturally produced by plants. Around 25,000 have been discovered. They are very much the ideal for biopesticides: as natural as can be. Estimates are that about 6,500 species have been tested for anti-insect properties, with 2,500 of them — belonging in 200 families of plant — showing some degree of activity. The number of patents for new botanical pesticides more than halved in the early 2000s but is now back to an average of 80 a year. The market is growing and the chemical giants increasing their development activity, with BASF, Certis, Bayer Crop Science, and Monsanto (now merged) signaling the growing potential of bio- versus chemo-.
Pyrethrins are an instance of botanical pesticides. They are found in the seed cases of the perennial chrysanthemum flower, known to have been used in powdered form as an insecticide as early as 1000 BC in China and 40 BC in Persia. Kenya is the largest producer today. Pyrethrins bind to the sodium channels along a weed’s nerve. Death is quick.
This “ethnobotanic” approach is closest in ethos and aims to the commonsense view of organic farming. It often produces surprises. One discovery in the late 1990s, for instance was that fungal yeast cells could trigger a plant’s defense responses against certain pathogens. The result was a commercial bio-fungicide. The source is now listed as one of only 18 approved substances in an EU database of low toxicity and high potential for plant protection: beer.
Arazadirachtin is one of the most successful botanical insect deterrents. It’s derived from the neem tree, a fast-growing evergreen native to the Indian subcontinent that can grow to 65 feet in height. It contains over 250 bioactive compounds. Arazadirachtin is one of the most effective. It is an antifeedant that inhibits and stunts the growth of around 200 insects and an egg-laying deterrent. Neem is tricky to grow, standardize, and harvest the seed. Arazadirachtin degrades quickly in sunlight. It’s an insecticide and ineffectual as a fungicide and herbicide, both of which are needed to provide a comprehensive protection.
Neem has also been used as a general pesticide in the fields and inside homes for thousands of years. It was an early part of Ayurvedic medicine in India. That was the basis for the Indian government winning a challenge to a US patent for an anti-fungal product derived from neem; its successful case was that the neem process had been in continuous use for 2,000 years. The US firm’s counter that it had not been published in any modern scientific research journal was snickered out of court.
Microbes and viruses: Bacillus thuringiensis
Microbes have a long history in bio-pesticides. Most experts see them as the likely main growth area for both revenues and new products. They include a wide range of microorganisms: bacteria, fungi, viruses, and nematodes – microscopic worms.
There are more than 700 viruses known to be insect-infecting. Only a few dozen of these have been turned into patented products with a broad market. A distinguishing characteristic of all microbial biopesticides is how specialized they are. They are uniformly non-toxic and non-pathogenic — not causing or originating disease — to non-targets. This adds to their safety strength.
Bacillus thuringiensis (Bt) is by far the most widely used biopesticide globally, with over 90% of the microbial segment and 75% of the overall market. It is a bacterium commonly found in soil. Ingested by a host insect — its particularly deadly to mosquitos and caterpillars — Bt wrecks their digestive system and kills them in as little as 48 hours. Baculoviruses attack only invertebrates. Birds are immune. The name comes from the town where the German scientist who first isolated the bacterium obtained his first sample from a flour mill in 1910. It took 50 years for Bt to become part of the mainstream of farming. It is now mass produced through fermentation and costs a few cents per liter to make.
Bt can be sprayed directly on crops or — and this is where it becomes contentious — added to the DNA of genetically modified crops. That means that the mainstream of biopesticides is becoming fused with the mainstream of genetically modified (GM) organisms.
Around 20 insect species have been reported as developing resistance to Bt.
RNA interference
Much of the future of agriculture will be driven by manipulating genes. That raises many issues that go beyond the science, which is spectacular with much of it creating entirely new possibilities. That’s both the plus and expanding innovation) and the negative for many (unconstrained and expanding risks to nature and humans). Proponents of GM seeds point to the improvement in yields (an average of 22% for the top crops of corn, soy and cotton) and reduction in chemical pesticides use (37%). Sceptics and overt opponents highlight the unknown second-order effects of the combination of GM, glyphosate, lack of effective regulation, byproducts of application, such as soil contamination, etc., etc.
A growing area of development in agriculture is gene splicing and editing. CRISPR is becoming a practical and powerful tool. In October 2000, the Nobel Prize for physics was awarded to the two women who developed genetic scissors. Science has moved over millennia from the leaf as the unit of tea development to its chemical compounds to its molecular structures and now to its genome and genes.
Double-stranded DNA-mediated gene silencing (RNAi) is an instance in biopesticides. RNA is a molecule in all living organisms that handles the messaging of instructions from DNA cells in building the body’s proteins. RNAi silences a selected gene in the targeted pest that is critical to its growth. The predator dies but the plant remains healthy. The messenger RNA molecules are entirely carbon-based so that they leave minimal chemical residues in the soil. Progress in production is reducing costs, that can be as high as $10,000 a gram for batches of new candidate treatments.
GMO is here and now and commonplace. RNAi is coming.
From lab to market
The formulation of a pesticide is a complex topic in itself. Biopesticides are more volatile than most synthetic ones because so many are based on living organisms and sensitive to environmental conditions.
The costs of pesticides and fertilizers are a major burden on smallholders, especially as loan financing shrinks, driven by banks being unwilling to take on the growing risks of default and governments facing the massive economic disruptions of the Covid pandemic. Only 4% of Indian farmers surveyed view biopesticides as affordable, versus 16% for chemicals. A number of studies estimate the use of spurious, substandard, and banned pesticides as being at least 25% of the total and probably.
A problem in incorporating the complex issues of pesticides in their choices is simply the lack of information. This isn’t just a matter of putting a broad “organic” and “natural” label on a tea or garden. It’s far more a combination of management and science, with IPM – integrated pest management - being the extension of organic farming to incorporate care of plant, environment and the natural defenses of birds, fauna and botany. Sophisticated IPM implies sophisticated use of biopesticides.