After nearly a decade of top-secret research, scientists in Israel have found a substitute for chemical pesticides that are sprayed on fruits and vegetables. The organic alternative involves the mass production of a particularly gluttonous female relative of the spider family
It’s tiny, frenetic and voracious, a single gram of it can cost $600, and for years Israel has been considered its top exporter. Meet Phytoseiulus persimilis, a predatory mite, and member of the arachnida class. In the Beit She’an Valley in northern Israel, thousands of them are packed in small salt shaker-type containers or tea bag-like packets for dispatch to strawberry fields in California, clementine orchards in Spain, berry bushes in Mexico and greenhouses in Colombia and Canada where roses and cannabis are cultivated. Thanks to the superb predatory abilities of persimilis, farmers raising these crops prefer deploying it over use of chemical pesticides.
Two prominent traits make the predatory mite a much-in-demand weapon against pests. The first is gluttony; the second, and complementary, attribute is an insatiable craving for its relative the red spider mite, well known among farmers as a noxious pest.
An Israeli innovation developed recently by scientists from the BioBee company, of Kibbutz Sde Eliyahu, makes it possible to mass-produce the predator, on demand, at any time and for any client. Another improvement is a sophisticated mechanism for scattering persimilis in fields, like an army deployed for battle, before a pest onslaught begins. So the way is open to grow ever more agricultural food crops that will contain far fewer chemical pesticides or none at all.
The antelope and the tiger
The usefulness of persimilis was first noted in the scientific literature in 1937. Farmers began employing it for pest control, and developed domestic methods of supply. For example, in summer, they “infected” eggplant bushes with persimilis from strawberry plants that had grown in the preceding winter, whose fruits had already been picked. However, they soon discovered that a home-grown supply is not enough to achieve pest control.
At the end of the 1960s, systematic rearing of persimilis, for sale by weight (one gram constitutes some 80,000 mites), began, by imitating natural conditions. Bean greenhouses served as a rearing platform; when the beans attained a suitable size, they were contaminated with the spider mite pest, which quickly multiplied. Once the greenhouse and its crop were teeming with the pests, persimilis was let loose on the sick plants until it too multiplied to a quantity that would justify harvesting for packing and sale to farmers. A greenhouse breeding cycle lasted about eight weeks, at the end of which a kilogram of predators had been produced from each greenhouse dunam (a quarter of an acre).
As demand for persimilis grew, year by year, a conglomerate of greenhouses sprang up around Sde Eliyahu, where temperature, humidity and lighting were controlled in accordance with the predator’s known preferences. But not even a greenhouse can escape nature’s sensitivities and vagaries. There are always surprises. A heat wave that causes extreme dryness will eradicate an entire promising generation of beneficial predators. A sudden cold spell or jump in humidity will eradicate the pests and leave sparse prey for persimilis. A fungus or insect that penetrates the greenhouse can unexpectedly change the delicate ecological balance, and thus disrupt the breeding process.
In such cases, a complete restart is required: A new round of plants must be planted, which require time to develop to an appropriate size to serve as a platform of infection for a new generation of pests, and so on and so forth. In the meantime, the farmers in the fields anxiously await the warrior that will vanquish the pest before their crops are wiped out – meaning now.
A decade ago, a secret project was launched to supplant the greenhouses, subject as they are to the caprices of nature. Success came after eight years of research: An industrial production line was established for creation of battalions of persimilis, ready to be sent into battle in the fields at any given time. What a team of 50 could once breed in 80 dunams of greenhouse agriculture, is now produced by 10 people in a closed structure of 1,000 square meters (one dunam). Bottles and bags of persimilis are on sale in all seasons, 365 days a year, indifferent to such external influences as the weather and other ecological vagaries.
The industrial system that is based on an unconventional idea for feeding the beneficial mite received the Bernard Blum Award from the Basel-based International Biocontrol Manufacturers Association in 2021, for leading innovative biocontrol solution of the year. The prize is considered the industry’s most important citation of merit.
Nourished by a leaf
BioBee was founded 40 years ago at Sde Eliyahu, a religious kibbutz situated in the Beit She’an Valley. Kibbutz member Mario Levy is considered the founder of organic agriculture in Israel. As early as the 1960s, Levy (who died in 2018) had spoken out against the use of toxic, synthetic chemicals in food-crop production. In 1983, at his inspiration, the Sde Eliyahu Biological Control Insectaries was established. Three individuals were instrumental in its creation: The founding CEO was Akiva Falk who, though a musicologist by training, served as the kibbutz treasurer and as such sought new sources of livelihood for the kibbutz. Yaakov Nakash, an autodidact and avowed lover of insects, engaged in the improvised breeding of beneficial insects in the kibbutz’s subterranean bomb shelters. The third was the late Prof. Dan Gerling, a world-renowned authority on biological control from Tel Aviv University, who was the company’s scientific adviser. The firm they created, today known as BioBee, is one of the three leading companies in the world in biological pest management, and it provides the kibbutz with its principal livelihood.
To understand the importance of the new invention, it’s necessary to know something about the exploits of the pest that the predatory mite eradicates. It’s no small matter: Both the red spider mite and the two-spotted spider mite (from the family Tetranychidae) have the ability to spread rapidly and constitute a serious global blight that is becoming more acute as the world’s population rises and agricultural crops are being raised in new areas. Spider mites are nourished from the leaf on which they settle, seizing the leaf’s flesh in their jaws, wounding its skin and drinking its liquid, thus drying it out and condemning it to death. The leaf is the plant’s unit of food production, and leaf loss reduces its ability to function: The plant will produce fewer flowers and less fruit. In addition, scratches caused by the mites’ mouthparts to a leaf are like an open wound – a breach that invites viruses, which weaken the tormented plant even more. Thus, leaf by leaf, the tiny creature vitiates the plant’s ability to grow, spinning long webs and using them to move to the next victim: the neighboring plant.
Inspirited by the leaf juice, the red spider mite multiplies. Within two weeks of a typical life cycle, it spawns hundreds of offspring, from which thousands more are born, that in turn produce tens of thousands more, a vast generation that devastates whole tracts of farm land. The spider mite establishes flourishing colonies in young cucumber plants, in watermelon and pumpkin fields, among pepper bushes and potato crops, and between the thin branches of pear and apple trees – wreaking havoc everywhere.
Spider mites are capable of wiping out many months of work that were invested in crops, doing away with a large part of the season’s expected fruits and devastating entire cultivated fields. Uncontrolled, their rampaging leads quickly to a decrease in agricultural produce, which in the end takes a toll on consumers. A shortage immediately drives up the price of a kilo of cucumbers or a basket of strawberries.
“Humanity is in a race to produce more food, in order to feed more mouths,” says Hagai Snir, a deputy director general of the Agriculture Ministry. “If we want to preserve fair prices for fruits and vegetables, there is no way at present that we can give up chemical pesticides, but at the same time we have to be careful about the price the public pays for its health.”
The law obligates farmers to wait a certain time between spraying and harvesting, in order to allow the poison to dissipate before the produce makes its way to stores and then on to the salad plate. Some summer crops, however, ripen at a pace that requires almost daily harvesting. If the farmer waits, the amount of marketable produce will be significantly reduced. The result is a loss for the farmer or higher prices for the consumer, or both. Under the pressure of this farmer-consumer business, effective pesticides that reach all parts of the plant end up in our digestive system.
Snir observes that recently Germany threatened to stop buying agricultural produce from Spain, unless that country reduces the volume of chemical pesticides it uses on its crops. In Israel, too, there is supervision and diminished use of chemicals, though substances that are banned for use in other countries remain part of the agricultural repertoire here. “Public opinion against chemicals is growing stronger, politics is doing its work and pesticide regulations are becoming ever stricter. Farmers, for their part, are at a loss,” Snir says.
Climate change is not making things better. The warming trend is beneficial for pests that in the past underwent natural diminishment in number in cold, rainy seasons. The spider mite is fond of heat and dryness, and the Negev and the Arava, where much of Israel’s agricultural produce is grown, offers an ideal climate for the pest’s growth.
Moreover, thanks to a short life cycle and abundant reproduction, the mite is capable of developing resistance to a pesticide during the very season it is exposed to it. As in Noah’s Ark, if within a swarm of pests one couple remains that underwent a genetic mutation that leaves it able to withstand the chemicals, it will be sufficient to produce entire new generation that will not respond to the substances. So, if at the start of the season, the grower sprays and the pest dies out, in the next treatment, or the one after that, its effect
With rapid steps, persimilis reaches its prey, seizes it with it long front legs, injects its mouth-parts into its body and sucks it dry. Within minutes it leaves behind a drained corpse, as it hurries on to its next victim.
will be like that of spraying water. The standard solution to this is to employ larger quantities and stronger chemicals. The material seeps into the groundwater and evaporates in the air – a point to be noted by all those who are drawn to the rural life. Green fields are perhaps a more pastoral-looking landscape than a cloud of smog over Metropolitan Tel Aviv, but they contaminate in their own way. Israel, it should be recalled, is a small country, and the farmland that is sprayed is often adjacent to residential communities and buildings.
Israel’s Agriculture Ministry supervises and finances biological pest-control projects to the tune of millions of shekels. Nonetheless, the territory involved amounts to only 260,000 dunams out of a total of 4.2 million dunams in use for agriculture, meaning that elimination of the use of synthetic pesticides will be a gradual process. Strawberry growers who do not spray in advance against the spider mite can forget about their crop. Tomato growers spray about eight times in each growth cycle. So too the cucumber growers in the Emek Hefer region, where 50 percent of Israel’s homegrown crop of the popular vegetable grows in the fields around Moshav Ahituv. For years, attempts were made – to no avail – to persuade them to forgo chemicals and shift to biological pest control. The solution inherent in the promise of an unlimited supply of persimilis finally succeeded in getting them to reduce the amount of chemical spraying by 60 percent.
In contrast to its relations with pesticides, a pest cannot develop resistance to a predator. When both predator and prey are insects or mites, the former searches out the latter actively, moving from one plant to the next like a guided missile, until it finds what it’s looking for. The antelope hasn’t yet developed resistance to the tiger.
Like the tiger, persimilis possesses sophisticated hunting skills. Other enemies of the red spider mite have a hard time getting to it – they get entangled in the webs it weaves – but the persimilis slides under the sticky web by means of hairs that grow on its exterior. With rapid steps it reaches its prey, seizes it with it long front legs, injects its mouthparts into its body and sucks it dry. Within minutes it leaves behind a drained corpse, as it hurries on to its next victim. It gorges on the spider mites at every stage of their development – as adults, in their nymphal stages when they haven’t yet matured to mating and when they hatch from their egg as larva. Persimilis gulps them down before they have fully hatched, thereby moderating the reproductive rate of the pest population.
Farmers’ holy grail
BioBee has 350 employees in insect-rearing facilities in Israel, and it has subsidiaries in Chile, Mexico, Colombia, the United States, Canada and South Africa. It rears sterile males of the Mediterranean fruit fly to reduce the population of the pest that causes rot among a wide range of fruit trees, and it sells a parasitic wasp that lays its eggs under the waxy shields covering the bodies of mealybug insects – the larvae gnaw at the mealybug from within, with the body of the latter acting as a shield that covers it until it reaches adulthood and becomes a wasp that will lay its eggs in another mealybug. Other BioBee products include mite and insect predators that operate against pests that harm vegetables and decorative flowers, and bumblebees that function as pollinators in greenhouses and fruit groves.
The production-line rearing of persimilis is a patented and closely guarded secret. Outsiders are not allowed to view the process, still less journalists. Whether with a camera or without, outsiders may not enter any of BioBee’s production facilities. We go through the packing house in which what looks like colorful forms of dust – but is actually clusters of beneficial mites, wasps and persimilis, among others – are weighed out by the milligram. Here, too we’re whisked from room to room, passing through doors, each of which opens with its own secret code.
“After 40 years, we have a biological control agent whose availability is equal to that of chemical pesticides and is far more effective,” says Dr. Shimon Steinberg, BioBee’s chief scientific officer, with unabashed pride.
How did they do it? Methods of feeding insects for industrial rearing, like the feed that cows and chickens eat in barns and chicken coops, have existed for some time. But to achieve that for the specialist persimilis, which feeds solely on the red and the two-spotted spider mites, was considered impossible. “It was the holy grail of the farmers – everyone was chasing it,” says Steinberg.
In the past, scientists in the United States were successful in confusing persimilis by means of artificially produced food. The warrior ate its fill, but there was one small problem: After gorging itself to the bursting point and reaching adulthood – when it’s supposed to lay eggs and reproduce – no offspring were forthcoming. That ruled out the prospect of pest control in field crops. Farmers determined to eradicate pests across the entire growing season rely on generational cycles that will follow each other in swift succession.
“Persimilis is a super-weapon that is not drawn to other foods, which is its well-known advantage in pest management – and is also its disadvantage in terms of mass rearing,” Steinberg says. “To extract commercial quantities in clean rooms instead of greenhouses, we decided to act against nature.”
Thus, a BioBee research and development team, led by two senior entomologists, Arnon Tabic and Tom Katz, embarked on a creative journey in a quest for an alternative predator. Katz took the role of the chef cooking up the food substitutes, Tabic monitored the biological effects of the diet, ensuring that the change in nutrition would not harm the well-known attributes of persimilis as an efficient predator.
Proper feed is based on several conditions. First, the possessor of the selective palate needs to be willing to eat it. That’s a necessary but not sufficient condition. The variation in food must not affect the rate of development. For example, the process persimilis undergoes from hatching to maturation lasts a week. If the new food extends the process to a month, this delays the reproduction rate and reduces the creature’s effectiveness as a weapon in the field. The idea is for it to go on laying eggs, not less frequently than twice than two a day, and if possible three or six; not to become climate-sensitive so that every minor shift in temperature or humidity saps it of vitality; and, naturally, for persimilis that developed on a feed substitute to pass on its culinary flexibility to its offspring, and they to their offspring.
When the coronavirus lockdown was declared, the first thing Tabic did was to pack persimilis of the type that eats the feed substitute and take it in a cooler to his home in the new section of Kibbutz Beit Keshet, in Lower Galilee. “I was really scared. That’s all I needed – for the whole team to be sent into quarantine and years’ worth of work to go down the tubes, with the enhanced persimilis dying because there was no one to feed them.”
Tabic likens himself to a herder in the African savannah: He too cultivates animals, enhances them, sees to it that they multiply and grow in order to fulfill their role in life. The difference is that the creatures Tabic is cultivating are very small, barely half a millimeter long.
It was evening, most of the staff had already left for the day. Just as Katz too was about leave, he glanced at a petri dish on which a few dozen persimilis were swarming around another type of food he had concocted for them.
“I have been following them for years and I know everything about them – habits and preferences, what temperature exhausts them down, the level of humidity that makes them active, and the level of lighting in which they proceed more energetically to mate and produce offspring, so as to increase the herd. I am a veterinarian of mites,” he says. “My life is more complicated, because not much research is devoted to problems of mites, so every problem that comes up I have to solve through experiments that we do ourselves. After so many years of cultivating a useful and effective species, I developed a truly deep rapport with them, like someone’s private creation.”
In the end, a precise recipe was found, for food that is both tasty and healthy, which the predator gobbled down without any alteration to its habitual development and reproduction. Katz, the chef who engineered the alternative food, remembers the day when he realized that he was on to something. It was evening, most of the staff had already left for the day. Just as he too was about leave, he glanced at a petri dish on which a few dozen persimilis were swarming ar
ound another type of food he had concocted for them.
“I’m looking into the microscope and I see that they are approaching the alternative prey and eating. I watched for about three minutes. Then I got up, waited a few minutes, sat down again and went back to viewing in order to make sure that what I had seen was really happening. It was a thrilling moment. What did I do? I emailed those who needed to know.”
Afterward came the moment of truth. As was to be expected, the development staff was filled with apprehension: Living beings tend to adapt to new conditions, adjusting to them as second nature. What would happen if persimilis, pleased with the food it was being given in this industrial habitat, were to lose interest in the very thing for which we all were gathered here? In other words, what if it were to forget its mission in the world as a predator of the red spider mite?
“It was a seminal moment,” Steinberg recalls enthusiastically. “On the petri dish we placed a leaf infested with the common red spider mite. We added to it persimilis that we had cultivated in the laboratory using the alternate food, and through the microscope we observed them attacking excitedly their favorite dish from the past. The sigh of relief that came out of here echoed across the whole Beit She’an Valley. Since that first generation that was reared on a substitute, hundreds more generations of persimilis have been born. To our delight, the genetics is strong enough, and their passion for the prey and their craving for the red spider mite haven’t diminished in the least.”
It soon turned out that albino persimilis is not a bug, but a selling point. When the industrial predator is released into the field and starts to prey on the pests just like in old times, the color returns to its cheeks and its body acquires the familiar red tint.
There was another obstacle along the way, one that worried the marketing and sales department more than it disturbed Steinberg’s research team. In the wild, persimilis has an orange-reddish color, whereas the persimilis that has supped on the alternative food during its mass rearing is – though still vital, fruitful and predaceous – snow-white with a beige “cap.”
“When we realized that this was the persimilis we would be getting, we wondered whether to invest an effort in repairing the ‘bug,’” reveals Steinberg. “We were apprehensive of commercial implications. Clients are clients. They need to be persuaded that it’s the same, well-known persimilis
from the past. The pale hue raised suspicions. Maybe it’s sick? Maybe its hunting skills are also pale? Selling albino persimilis to farmers who were used to bold orange would be like selling watermelons with yellow flesh in Israeli supermarkets. It may be sweet, but a watermelon that’s yellow inside will remain in the bin in the supermarket, alone and forlorn.
“In the field of chemicals, penetrating the market with a new product is a relatively easy task. You spray the field and immediately, you see the pests lying on their backs, legs twitching,” Steinberg laughs. He’s referring to the fact that chemical pest control generates an immediate reaction, compared to biological control, which requires forbearance on the farmer’s part. The natural enemy needs to establish itself on the ground, and the results are not immediately discernible.
It soon turned out that albino persimilis is not a problem, but a selling point. When the industrial predator is released into the field and starts preying on the pests, just like in old times, the color returns to its cheeks and its body acquires the familiar red tint. The case spawned an unexpected improvement; the production-line persimilis (now branded “BioPersi+”) includes a feature in the form of a visual indication. When the pest control kicks in, the “material” the farmer spreads morphs from white into pink and then into red, a transformation visible to the eye.
Mobilizing the army in advance
A farmer who relies only on biological pest control must take into account a certain adverse effect on the crop. A natural enemy has nothing to look for in a field without pests – it will simply die of hunger. Accordingly, the pursuit can begin only after the pest has multiplied and has already caused damage. A solution to this situation was found in the form of another improvement that came into being together with the substitute feed: a sachet that serves as a habitat for persimilis, which is hung on the plants and in which they wait in a state of readiness for the spider mites. Since they are nourished by the substitute feed, they’re in no rush, and only when the pests arrive do they emerge from the sachet to begin the hunt, in a mechanism similar to slow-release medications.
“It’s like advancing your well-equipped combat reserve battalion up to the border when intelligence discovers that the enemy is planning war,” says Tamar Keasar, of the Department of Biology and the Environment at the University of Haifa – Oranim, with a smile. Prof. Keasar heads an international research group for the Israel Institute for Advanced Studies, whose subject is the theory of biological pest control. She agrees that innovations of this sort hold out hope for a revolution that will reduce the use of chemicals in mass production of food crops.
Biological methods of pest control are being applied in greenhouses and in small farm plots where vegetables and fruits are grown. In a world shortage of bananas or strawberries, a fruit salad will be boring, but no one will die from it. On the other hand, without wheat and soy in sufficient quantities, hunger will prevail. Such food staples such as corn, soy, rice and the grains grow in immense fields that cover thousands of dunams, and it is thanks to chemical pest management that they can provide the world’s population with food in sufficient quantities. They occupy the vast majority of the world’s farmlands, which constitute 50 percent of the land suitable for habitation on Earth.
According to the accepted forecasts, the global demand for agricultural produce is expected to have doubled between 2005 and 2050, as a result of both population growth and a rise in the standard of living. Pests of various kinds currently cause the destruction of a quarter of the crops.
“Spraying causes considerable environmental and health damage, and it is not always effective,” Keasar notes. “In addition, it kills beneficial insects, such as bees, and natural enemies – predacious or parasitic – of pests, leaving the agricultural lands unprotected. Like antibiotics, which kill the bad bacteria but also the good types and leave the body without natural protection. Therefore, we need sustainable means that will make it possible to preserve the scale of agricultural produce and also reduce the damage to the environment.”
Industrial, cost-efficient production of a natural enemy enables biological pest control to be competitive with chemicals in terms of availability and price, and thus to become a realistic means of pest control even among massive, open field crops that until now did not seem to be within the horizon of possibilities for being freed from chemicals and genetic engineering. The challenge now, Steinberg says, is biological pest control applied with mechanical means, which will be required for the huge fields. Drones that will function as crop dusters to release beneficial insects are a realistic option.
If the spider mite is all that harmful, maybe it can be eradicated altogether, like smallpox?
Steinberg: “A smart natural enemy leaves itself food so that it will be able to go on living. When there are a lot of zebras, lionesses give birth to many cubs, and when the zebras decline in numbers the lioness bears fewer cubs. Spider mites are the food of persimilis, and persimilis is the food of other animals.”
In what was not a coincidence, just after the announcement last fall about the Bernard Blum prize for development of the substitute feed and the slow-release sachets, Kibbutz Mishmar Haemek acquired a quarter of the ownership of BioBee. Following the deal, the company is estimated to be worth $100 million. Turns out that persimilis is also the main nutrient of BioBee.