Parasitic weeds (Striga, Orobanche, Cuscuta)
Weeds that attach to and feed off the crop itself — witchweed, broomrape and dodder — drawing nutrients directly from the host.
- Type
- Parasitic weeds (attach to & feed off the crop)
- Life cycle
- Huge, very long-lived seed; host-triggered
- Spreads by
- Tiny seed in soil, crop seed, water; Cuscuta by seed & stem
- Main harm
- Draw nutrients directly from host; severe loss
Overview
Parasitic weeds are a special, damaging group that do not just compete with the crop — they attach to it and feed off it directly. The three important ones in India are Striga (witchweed), a root parasite of sorghum, maize, pearl millet and sugarcane that emerges as small plants (often with bright flowers) near the crop base after doing most of its damage underground; Orobanche (broomrape), a leafless, chlorophyll-less root parasite of mustard, tomato, tobacco and brinjal that appears as pale/fleshy flowering spikes at the crop base; and Cuscuta (dodder, amarbel), a leafless yellow/orange thread-like stem parasite that twines over and sucks from the shoots of many crops, fodder and ornamentals.
They are especially hard to control for three reasons. First, they draw water and nutrients directly from the host, so damage is done before you even see them — Striga and Orobanche do most harm underground before they emerge. Second, they produce huge numbers of tiny, extremely long-lived seeds (Striga and Orobanche seeds survive many years and germinate only when they sense a host). Third, because they are attached to the crop, you cannot simply spray them without harming the crop. Control combines clean crop seed, resistant/tolerant varieties, trap and catch crops, hand-removal before they seed, and specialised methods for each.
How to identify it
- Striga (witchweed): small plants, often with bright (purple/pink/white) flowers, emerging near the base of sorghum, maize or millets, with the host stunted and yellowed.
- Orobanche (broomrape): leafless, pale/fleshy, chlorophyll-less flowering spikes at the base of mustard, tomato, tobacco or brinjal.
- Cuscuta (dodder, amarbel): leafless yellow/orange thread-like stems twining over and matting the crop’s shoots.
- Hosts stunted, yellowed and low-yielding because the parasite is drawing their nutrients.
Why it is a problem
- They attach to and draw water and nutrients directly from the crop, so they are far more damaging than ordinary competing weeds.
- Striga and Orobanche do most of their damage underground before they even emerge, so the crop is hurt before you see the weed.
- They produce huge numbers of tiny, extremely long-lived seeds that survive many years and germinate only when they sense a host.
- Because they are attached to the crop, you cannot simply spray them without harming the crop.
Cultural & preventive control
- Use clean, parasite-seed-free crop seed — infested seed is a major way Cuscuta and others spread to new fields.
- Grow resistant/tolerant varieties where available, and rotate with non-host crops to starve the parasite’s seed bank.
- Use trap crops (that make the parasite germinate but cannot be parasitised) and catch crops as recommended, and hand-remove and destroy the parasite BEFORE it flowers and seeds.
- For Cuscuta, remove and destroy the twining stems (and the affected crop patch) before it seeds, and never let it set seed.
Herbicide / specialised control
- Because the parasite is attached to the crop, control uses specialised, crop-specific recommendations — not a general spray.
- Certain crops/varieties allow specific herbicide or seed-treatment strategies against Striga/Orobanche; Cuscuta patches may be spot-treated in some crops.
- Combine any chemical method with rotation, resistant varieties, trap crops and preventing seed set.
- Confirm the current, crop-specific parasitic-weed package for your situation with your local KVK.
Integrated management
- Never let the parasite set seed — its huge, long-lived seed bank is the core problem, so stopping seed set is essential.
- Combine clean seed, resistant varieties, rotation with non-hosts, trap/catch crops and hand-removal.
- Be persistent over many seasons, because the seeds survive for years in the soil.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
A small bright-flowered weed is coming up at the base of my sorghum/maize and the crop is stunted. What is it?
Small plants with bright (purple/pink/white) flowers emerging near the base of sorghum, maize or millets, with the host stunted and yellowed, are usually Striga (witchweed), a root parasite that attaches to the crop and draws its nutrients — doing most of its damage underground before it emerges. Control it with resistant/tolerant varieties, rotation with non-host crops, trap crops, and hand-removing it before it flowers and seeds; its seed survives many years, so never let it seed.
What is the leafless yellow-orange thread twining over my crop?
A leafless, yellow or orange, thread-like stem twining over and matting the shoots of your crop is Cuscuta (dodder, amarbel), a parasitic weed that has no roots or leaves and sucks water and nutrients directly from the host plant’s stems. Because it is attached to the crop, you cannot simply spray it off. Remove and destroy the twining stems (and the affected patch) before it sets seed, use clean crop seed, and never let it seed — its seed can persist in the soil.
Why are parasitic weeds so much harder to control than ordinary weeds?
For three reasons. They attach to the crop and draw its water and nutrients directly, so they are far more damaging than weeds that merely compete — and Striga and Orobanche do most of that damage underground before they even emerge. They produce huge numbers of tiny seeds that survive many years and germinate only when they sense a host, so the seed bank is enormous and persistent. And because they are attached to the crop, you cannot just spray them without harming the crop. So control relies on clean seed, resistant varieties, rotation, trap crops and never letting them seed, kept up over many seasons.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.