Title: A forgotten farming technique is making a big comeback – here’s why
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, despite intensive pesticide use. Pests are becoming immune to synthetic pesticides. According to the U.N.’s Food and Agriculture Organization, insect attacks now cause a loss of US$70 billion annually, while plant diseases cause a staggering loss of US$220 billion. Trap crops could lower these losses while reducing the need to use chemical pesticides, which in addition to harming health, also contribute to climate change.
Marigolds produce compounds that suppress the root-knot nematodes. The bright yellow and orange flowers also release compounds that deter aphids and whiteflies. The trap crop method is much healthier for farmers working the fields, people consuming the crops, and soil quality.
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 behaviour 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.
Trap cropping has given Danwade (pictured) 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 his 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 neighbours in Jambhali village in India, 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.
