Yves here. With Hair Furore pre-inauguration furor getting more intense, perhaps another break from reguar programming is in order. However, to be a stickler, “forgotten farming technique” is clearly a misnomer since the central figure in this article remembered it!
As do some of our readers. lyman alpha blob discussed the limits of marigolds last August:
I had been planting marigolds for years around my gardens since they are supposed to repel insects and animals too. And they probably do. But after a few years, I noticed my marigolds slowly being eaten away every single year. Turns out that marigolds are an earwig’s favorite food, so I had likely been inadvertently breeding them for many years. I discovered they also love bok choi and the first small leaves on bean plants.
If anyone knows how to get rid of earwigs other than by going outside at night with a flashlight and squashing them like a crazy person, well, I’m all ears.
By Sanket Jain, an award-winning independent journalist and documentary photographer based in Western India’s Maharashtra state. Originally published at Yale Climate Connections
Farmer Rafik Danwade had been pumping more pesticides on his acre-long field in Jambhali village in India’s Maharashtra state, but the chemicals were getting less effective at protecting his 3,200 chili plants from nematodes and other bugs. So Danwade, 56, turned to a practice his grandfather taught him in the 1970s: He planted 1,000 marigolds on the border and alternating rows of the field.
“Sometimes you must look into the past to find solutions for the present and future problems,” Danwade said.
He and other farmers around the world are relearning the ancient wisdom of sowing plants known as trap crops to protect their harvests from pests. The lessons must be relearned now because climate change has raised temperatures and humidity, leading to increased pest attacks in many regions of the globe.
Marigolds produce compounds that suppress the root-knot nematodes, killing the pests that enter their root systems or contact soil containing a marigold’s bioactive compounds. The bright yellow and orange flowers also release compounds that deter aphids and whiteflies. For Danwade, marigolds also act as a natural barrier, confusing pests looking for his chili plants. Experiments conducted between 1990 and 1993 in India found that African marigolds also effectively managed the cotton bollworm pest on tomatoes.
The eco-friendly method vastly reduces the need for pesticide use at a time when several parts of India and the world have reported increased pest attacks. This method is much healthier for farmers working the fields, people consuming the crops, and soil quality.
Global warming could expand the geographic range of pests, increase the number of generations, and make it easier for invasive insect species to survive the winter season. Pests already destroy 20% to 40% of crop production worldwide every year. According to the U.N.’s Food and Agriculture Organization, insect attacks cause a loss of $70 billionannually, while plant diseases cause a staggering loss of $220 billion. Trap crops could lower these losses while reducing the need to use excess chemical pesticides, which in addition to harming health, also contribute to climate change.
A Global Trend
Trap crops are helping farmers all over the world. In Italy, a two-year study found that Brassicaceae (mustard family) trap crops helped reduce the damage caused to sugar beets by flea beetles. Another paper found that broccoli yield was high when cultivated with diverse trap crops. A Chinese study found that using maize as a trap crop helped reduce the intensity of whiteflies on cotton.
“Trap cropping offers an environmentally friendly alternative to chemical controls by manipulating pest behavior and reducing reliance on pesticides,” said Shovon Chandra Sarkar, a research fellow at Australia’s Murdoch University who coauthored a paper on trap crops published in the Journal Insects in 2018.
Many trap crops protect the main crop by creating “hot spots” where pests are attracted to specific areas, making it easier for helpful insects to find and attack them, he explained. The paper contrasted the effectiveness of trap cropping to insecticides, which are more harmful, more expensive, and often ineffective due to growing pest resistance.
Sorghum is an effective trap crop in cotton fields, and black mustard in sweet corn farms reduced kernel injury by 22%. The authors also suggest that a trap crop should ideally attract at least twice as many pests as the main crop during the vulnerability stage and shouldn’t cover more than 2%-10% of the crop area.
Over the last decade, Danwade said he has witnessed severe changes in climate patterns.
“Rains have become infrequent, followed by a rise in humidity and heat, a perfect breeding ground for pests,” he said. He recalled learning about trap crops from his grandfather, the late Muhammad Danwade, when he roamed the fields as a child, and the traditional knowledge has served him well.
In recent decades, farmers turned to the convenience of chemical pesticides. Globally, pesticide use has doubled since 1990, reaching a staggering 3.69 million metric tons in 2022. Yet rising pesticide use has increased production costs for farmers while hurting their health. Some 385 million cases of pesticide poisoning occur every year, leading to 11,000 mortalities. Of this, 44% of farmers are poisoned by pesticides yearly, with the highest number of cases in South Asia.
Trap cropping has given Danwade a sustainable way to protect his chilies and boost his profits. Marigolds not only deter pests; they also attract bees and other pollinators that aid chili production.
He also sells marigolds, which are essential for daily prayers and decorative garlands in India.
“Because of marigolds, I have seen an increase in chili harvest … adding to the profits,” he said.
Among Danwade’s neighbors in Jambhali village, farmer Shailaja Gaikwad, 45, battled pest attacks on sorghum in 2022 by following her father-in-law’s advice of cultivating hyacinth bean or Indian bean as a trap crop.
“I thought I would end up losing all the sorghum, but to my surprise, everything remained safe,” she said.
This success reduced her cost of production as she did not spray pesticides even once. Before this, Gaikwad lost a considerable part of her soybean, peanut, and leafy vegetables to pest attacks.
“Even if the pests eat all the hyacinth beans, we can still earn money as the entire sorghum remains safe,” she said.
Timing Is Crucial
A government report pointed out that 23 states in India witnessed pest attacks between 2015-2016 and 2021-2022, and trap crops are an important part of the response to these challenges.
Farmers typically use green and black gram or hyacinth beans as trap crops for sorghum, while pigeon peas and hyacinth beans are favored for peanuts. Trap crops such as finger millet or moth bean are commonly used for rice.
“There are several such combinations which farmers used earlier,” Gaikwad said.
A review study published in Applied Soil Ecology in 2019 looked at potential trap crops for reducing the risk from a species of plant-parasitic nematode that causes significant damage to a variety of crops globally. In Northern Europe, yield losses are as high as 40-80% for vegetables like carrots, lettuce, onion, and sugar beet. The study said that trap crops like fodder radish can reduce the nematode populations when mulched early, a process in which the trap crops are cut before the pests trapped in the roots start reproducing.
Timing plays a crucial role in trap cropping. Field trials have shown that if legume-grass cover crops are planted in autumn and mulched in late spring or early summer, they help reduce the nematode population by up to 90%. However, a delay in planting or mulching can increase the nematode numbers as they reach the temperature threshold and proliferate. Moreover, legumes also provide additional benefits by enriching the soil with nitrogen, which helps boost soil fertility.
“The main challenges in designing knowledge-intensive trap cropping systems include understanding pest behavior, optimizing plant species selection, and integrating these systems into existing farming practices,” Sarkar said.
Effective trap cropping, he said, requires a deep knowledge of pest-host interactions, the chemical ecology of attractant compounds, and habitat manipulation techniques. To address this, he suggested identifying supplementary food, the color of trap crops, and attractant chemicals to develop reliable attractants for pests and their natural enemies. What’s also essential is “establishing partnerships with government and research organizations can ensure adequate support for farmers to integrate these strategies,” he added.
Many farmers in Jambhali and several other villages, especially the younger ones, are reluctant to use trap crops and are sticking to pesticides, hoping to maximize yields of a single crop without having to devote space to the trap crop. But Danwade said his sons Yunus, 35, and Shahid, 30, trust trap cropping.
“I am not sure for how long they will continue this practice, but as of now, they are convinced of its results,” he said with a smile.
Trap-cropping is a form of interplanting, practiced by every small farmer in the world. (I wrote my dissertation about a group of Black peasant farmers in Grenada who revived a tradition of interplanting sugar can with both “provision” (basic food) and “cash” crops, thus lifting the economy of four or five communities across the island. But the simpler truth is that the lack of diversity that monocultures implies leaves single crops open to many predators and disease and biodiversity–the hallmark of food sovereignty, indeed (ahem) of nature, makes food crops healthier. Something every peasant knows.
So–“discovery. . .” You’ll find that when non-experts seize on almost any idea, it’s a discovery for them!
Yves, thank you for this article. Not sure if Lyman AB found a solution for the earwigs. Beer traps work.
Trying to revive family farmland in Greece. My biggest issue is water quality as the drought has changed the water table and salinity has entered the aquifer (alas our land is near the coast). Switching from citrus my father planted in early 80s to olive varieties that are less affected by salt. Will look into any salt tolerant trap plants that help phytophthora and various insect pests of olive (dacus – the olive fly and leaf hoppers that transmit the dreaded xyllela virus).
Please keep these articles coming! NC is truly a treasure!
My solution so far has been to stop planting marigolds to see if that will reduce the earwig population. I also made sure to clean up any small piles of dead leaves that accumulate in corners around the yard since they create the little damp, dark spots that make prime earwig habitat. I did try beer traps last year and did not get any earwigs or slugs in them, but I did notice fewer earwigs overall around the yard. Besides the earwigs, I had also been inadvertently breeding a few different beetle species which also like to eat similar plants. Work in progress – just glad that I don’t depend completely on my vegetable garden and there’s still a grocery store nearby!
Also, from the article above –
“Marigolds not only deter pests; they also attract bees and other pollinators that aid chili production.”
Since Yves remembered my comment in the intro (thank you!), I did want to point out that the earwigs only chew the marigold leaves, and very slowly. So they’re really only a problem if they get out of control – a few won’t do much damage. They leave the blossoms alone, so even if you lose some greenery, they’ll still bring in pollinators with the blossoms. Definitely give marigolds a try!
Cover crop Rye is a great nematode trap crop. They crawl in early spring and then the crop is turned under. A single Rye plant has an almost unbelievable amount of root length for them to climb into.
I thought Marigolds were a repellent crop? And then only certain species…
Some other terms to look into related to this would be “companion planting”, and “integrated pest management”.
Companion planting is similar to pest management but less of a trap and more symbiotic.
Integrated pest management can incorporate non-biological controls but has concepts like using insects to control pest insects.
Another thing you might want to look into if you’re interested in this sort of thing is the concept of “the three sisters”. In North America this is typically Corn, Squash, and Beans. What’s interesting is that these three foods contain most of the nutrition needed for people to survive.
From Wikipedia: “In a technique known as companion planting, the maize and beans are often planted together in mounds formed by hilling soil around the base of the plants each year; squash is typically planted between the mounds. The cornstalk serves as a trellis for climbing beans, the beans fix nitrogen in their root nodules and stabilize the maize in high winds, and the wide leaves of the squash plant shade the ground, keeping the soil moist and helping prevent the establishment of weeds.”
In South America and Asia I believe there is a similar trio that is common to the diets, but I’m not sure about the history of companion planting them. Im basing this off the Blue Zones miniseries that talks about areas that people live longer on average and I just noticed the similarities in stable foods. (Spoiler: exercise was a massive factor)
We’d used companion planting 40yrs ago, due to unusual consensus of elder refugees trying to survive Reagan, by community gardens (foraging, fishing, dumpster diving & varmint hunting). Seemed to be pretty widely used (SE Asians, Jews from Ukraine, Lebanese & West Africans) Wonder, if robotic trimmers can outdo predators & microorganisms, before agribusiness GE monoculture, AGW, agri-business & fracking brine kills us all?