It is India’s largest indigenous edible oil source farmed in nearly nine million hectares – mainly Rajasthan, Uttar Pradesh, Madhya Pradesh, Haryana and West Bengal.But mustard is also a crop increasingly susceptible to infestation by Orobanche aegyptiaca. This is a parasitic weed that attaches to the roots of mustard plants and extracts nutrients, carbon and water from them. By depriving the host crop of these, it causes wilting, yellowing and stunted growth of the plants and, thereby, lower mustard seed yields.“Till three years ago, there was no margoja (the local name for the root parasite) and my average yield was 9 quintals per acre. In good years with no disease, ola (hail) or pala (frost), it could be 12 quintals,” says Kokchand Sahu, a farmer from Gigorani village in Nathusari Chopta tehsil of Haryana’s Sirsa district.The 42-year-old harvested a mere 6 quintals per-acre average of seed in the 2024-25 crop season (October-March). “I followed the Haryana Agricultural University’s recommendation to spray glyphosate herbicide – first at 25 grams/hectare after 30 days of sowing and then 50 grams after 55 days. It made no difference,” he notes.Sahu has sown mustard on just six out of his total 32-acres holding in the current season, down from 14 in 2024-25 and 16 acres in 2023-24: “Farmers here traditionally grew mustard on almost three-fourths of their land. It requires only two irrigations, as against 5-6 for wheat. But margoja has dented our confidence. This time, I have planted wheat on 20, chana (chickpea) on four and jau (barley) on another two acres”.According to Bhagirath Choudhary, director of the Jodhpur (Rajasthan)-based South Asia Biotechnology Centre (SABC), Orobanche has become the “No. 1 hidden threat” in the major mustard-growing areas of Haryana and Rajasthan.The “hidden” threat is due to the weed’s underground location and its establishing connection with the host plant’s roots to steal nutrients and water. By the time the parasite’s shoots appear above the ground and become visible, the damage to the crop from diversion and undernourishment would have already occurred. Story continues below this adSABC conducted a field-based survey, including one-to-one interactions with 51 representative farmers, in Haryana’s Sirsa and Bhiwani districts to assess the severity and spread of the Orobanche infestation this season. The survey, undertaken between mid-December and first week of January, revealed heavy and uniform weed emergence in many fields. “The parasite density was markedly higher in repeatedly cultivated mustard fields,” informs Choudhary.The reason is simple: A single Orobanche shoot produces 40-45 purple-coloured flowers, each further containing 4,000-5,000 very minute seeds. These remain viable in the soil for up to 20 years and disperse by wind and water to other fields. Once a strong seed bank is built, it creates conditions for rapid infestation. Farmers usually give the first irrigation for mustard 25-30 days after sowing. The soil moisture from that is, however, also conducive for the germination of the Orobanche seeds, followed immediately by their underground establishment and attachment to the mustard plant roots.Mustard’s importanceMustard, as the accompanying table shows, is India’s biggest edible oil-yielding crop, accounting for over 4 million tonnes (mt) out of its 10.5-10.6 mt annual indigenous production.Mustard is, moreover, a target crop for yield improvement to reduce the country’s roughly 16 mt per year of edible oil imports (mostly palm, soyabean and sunflower), valued at $15.9 billion in 2023-24 and $18.3 billion in 2024-25.Story continues below this adThe mustard crop’s growing susceptibility to Orobanche and other pathogens – pests (especially aphids) and fungal diseases (white rust, leaf blight, stem rot and powdery mildew) – is, hence, a matter of concern. All the more reason why the worries of farmers like Sahu, who has sown mustard this season purely on “Ram Bharose (God’s mercy)”, need addressing.“Margoja is not new. But earlier it used to be seen 60-70 days after sowing (at the crop’s flowering stage) and only in fields having reteeli mitti (light sandy soil). Now, it comes within 40 days even in fields with upjau mitti (fertile soil),” Sunil Sihag (35), a 16-acre farmer from Shahpuria village in Sirsa’s Nathusari Chopta tehsil, points out.The damage potential of Orobanche has gone up with the development of viable seed banks facilitating early emergence.The herbicide optionOne solution may be to apply herbicides such as glyphosate.Story continues below this adBut glyphosate is a non-selective chemical that does not distinguish between crop and weed. It works by inhibiting the ‘EPSPS (5-enolpyruvylshikimate-3-phosphate synthase)’ enzyme. This enzyme is essential for all plants, including weeds, to produce aromatic amino acids that are the building blocks of proteins crucial for growth. Inhibiting EPSPS causes the plants to wither and die.Glyphosate and similar broad-spectrum non-selective herbicides (like glufosinate, paraquat and imazapyr) cannot be used on normal mustard plants to control Orobanche, as they would kill the standing crop along with the weed. The current recommended spraying levels of glyphosate are too low for its absorption by either the crop or weed and blocking the EPSPS enzyme.That’s where breeding for herbicide resistance comes. Out of the six acres on which Kokchand Sahu has planted mustard, two acres are under ‘Pioneer-45S42CL’. This is a hybrid mustard developed by Corteva Agriscience that can “tolerate” the application of imidazolinone herbicides, including imazapyr and imazapic. These herbicides would, then, only kill the Orobanche weeds and not the mustard plants.The US-based seed-cum-crop protection chemicals giant claims that the imidazolinone-resistant trait in its mustard hybrid has been introduced through the non-GM (genetically modified) route. The ‘Pioneer-45S42CL’ mustard hybrid seeds are being sold in 700-gram packs along with 80 grams of ‘Kifix’, a water-dispersible granule herbicide formulation of the German multinational BASF, containing 52.5% imazapyr and 17.5% imazapic.Story continues below this ad“The two packs suffice for one acre and together cost Rs 3,150. Kifix has to be sprayed once after 25 days. If this takes care of margoja, my confidence in mustard will be restored,” adds Sahu. Other farmers in his village, too, have sown the new herbicide-resistant hybrid in a total area of 20 acres “and the results seem good so far”.Mustard is generally sown from mid- to late-October and harvested after 130-150 days.Meanwhile, scientists at Delhi University’s Centre for Genetic Manipulation of Crop Plants led by its former vice chancellor, Deepak Pental, have developed GM mustard lines containing a ‘cp4 epsps’ and a double-mutant ‘als’ gene to control Orobanche. These confer resistance to glyphosate as well as imidazolinone and sulfonylurea herbicides.The potential for use of any of the three categories of herbicides is seen to address the problem of resistance build-up to a single molecule from continuous application.Story continues below this adGiven mustard’s importance as an oilseed and the growing threat from weeds, India’s policymakers would have take a considered decision on allowing GM breeding and crop cultivation. And it will have to be based more on science and farm economics than ideology.