A forgotten farming technique is making a comeback—here’s why » Yale Climate Relations

Farmer Rafik Danwade has been spraying more pesticides on his one-acre field in Jambhali village in Maharashtra, India, but the chemicals are getting less effective at protecting his 3,200 chilli plants from nematodes and other pests. It's getting worse. So Danwade, 56, turned to a practice his grandfather had taught him in the 1970s: He planted 1,000 marigolds alternating between the edges and in the field.

“Sometimes you have to look to the past to find solutions to current and future problems,” Danward 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. Lessons must be learned anew now, as climate change increases temperatures and humidity, leading to increased pest attacks in many parts of the world.

Marigold produces compounds that inhibit root-knot nematodes, killing pests that enter its root system or come into contact with soil containing 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 pepper plants. Experiments conducted in India between 1990 and 1993 found that African marigold was also effective in controlling bollworm pests on tomatoes.

This eco-friendly approach significantly reduces the need for pesticides at a time when India and several parts of the world are reporting an increase in pest attacks. This approach is healthier for the farmers working the fields, the people consuming the crops, and the quality of the soil.

Global warming may expand the geographic range of pests, increase generation numbers, and make it easier for invasive insect species to survive the winter. Pests already destroy 20% to 40% of global crop yields each year. According to the Food and Agriculture Organization of the United Nations, insect attacks cause $70 billion in losses each year, while plant diseases cause a staggering $220 billion in losses. Trap crops can reduce these losses while reducing the need to use excess chemical pesticides, which in addition to damaging health, contribute to climate change.

global trends

Trap crops are helping farmers around the world. In Italy, a two-year study found that Brassicaceae (mustard family) trap crops help reduce flea beetle damage to sugar beets. Another paper found that broccoli produced high yields when grown with a variety of trap crops. A Chinese study found that using corn as a trap crop helped reduce whitefly intensity on cotton.

Shovon Chandra Sarkar, a researcher at Murdoch University in Australia, said: “Trap crops provide an environmentally friendly option for chemical control by controlling pest behavior and reducing reliance on pesticides. Alternatives.

He explained that many trap crops protect the main crop by creating “hot spots” that attract pests to specific areas, making it easier for beneficial insects to find and attack them. The paper compared the effectiveness of trap crops to pesticides, which are more harmful, more expensive and often less effective due to growing pest resistance.

Sorghum is an effective trap crop in cotton fields, and black mustard on sweet corn farms reduces kernel damage by 22%. The authors also suggest that, ideally, trap crops should attract at least twice as many pests as main crops during their vulnerable stages and should cover no more than 2%-10% of the crop area.

Danwad said he has witnessed severe changes in climate patterns over the past decade.

“Rainfalls become less and less, and the humidity and heat rise, making it a perfect breeding ground for pests,” he said, recalling the trap crops he learned from his late grandfather, Mohammad Danwad, while walking in the fields as a child. , this traditional knowledge was very helpful to him.

In recent decades, farmers have turned to the convenience of chemical pesticides. Global pesticide use has doubled since 1990 and will reach a staggering 3.69 million tons by 2022. However, the increased use of pesticides has increased farmers’ production costs while harming their health. There are approximately 385 million cases of pesticide poisoning each year, resulting in 11,000 deaths. Among them, 44% of farmers suffer from pesticide poisoning every year, with the highest number of cases in South Asia.

Trap farming provides Danwade with a sustainable way to protect his peppers and increase his profits. Marigolds not only repel pests, they also prevent them. They also attract bees and other pollinators that contribute to pepper production.

He also sells marigolds, which are necessary for daily prayers and decorative garlands in India.

“Thanks to marigolds, I'm seeing an increase in the pepper harvest…increased profits,” he said.

Among Danwade's neighbors in Jambhali village, 45-year-old farmer Shailaja Gaikwad fought the pest attack on sorghum in 2022 by growing hyacinth beans or Indian beans as a trap crop on the advice of her father-in-law.

“I thought I would eventually lose all the sorghum, but to my surprise, everything stayed safe,” she said.

This success lowered her production costs because she didn't even have to spray pesticides once. Prior to this, Gaikwad had lost a considerable portion of soybeans, groundnuts and leafy vegetables due to insect infestation.

“Even if the pests eat all the hyacinth beans, we still make money because the whole sorghum is safe,” she said.

Timing is of the essence

A government report states that 23 states in India suffered from pest attacks between 2015-2016 and 2021-2022, and trap crops are an important part of addressing these challenges.

Farmers usually use mung gram, black gram or hyacinth beans as trap crops for sorghum, while pigeon pea and hyacinth beans are more suitable for groundnut cultivation. Rice usually uses trap crops such as millet or moth beans.

“Farmers have used several combinations of this before,” Gaikwad said.

A 2019 review study published in Applied Soil Ecology looked at potential trap crops to reduce the risk of a plant-parasitic nematode that causes severe damage to a variety of crops around the world. In Northern Europe, yield losses of vegetables such as carrots, lettuce, onions and beets are as high as 40-80%. Research says trap crops like forage radishes can reduce nematode populations when mulched early, in which the trap crops are cut back before the pests trapped in the roots begin to reproduce.

Timing plays a vital role in trap cutting. Field trials have shown that legume grass cover crops can help reduce nematode populations by up to 90% if planted in the fall and covered in late spring or early summer. However, delayed planting or mulching may increase nematode populations as they reach temperature thresholds and reproduce. In addition, legumes provide additional benefits by enriching the soil with nitrogen, which helps improve soil fertility.

“Major challenges in designing knowledge-intensive trap planting systems include understanding pest behavior, optimizing plant species selection and integrating these systems into existing agricultural practices,” Sarkar said.

Effective trap crops require a deep understanding of pest-host interactions, the chemical ecology of attractant compounds and habitat manipulation techniques, he said. To address this problem, he recommends identifying complementary foods, trap crop colors and attractant chemicals to develop reliable attractants for pests and their natural enemies. Equally important “partnerships with governments and research organizations can ensure adequate support for farmers to integrate these strategies,” he adds.

Many farmers in Jambhali and several other villages, especially the younger ones, are reluctant to use trap crops and insist on using pesticides in the hope of maximizing the yield of a single crop without having to make room for trap crops . But Dhanwad said his sons Yunus, 35, and Shahid, 30, believed in trap farming.

“I'm not sure how long they'll continue this, but so far they're convinced of the results,” he said with a smile.