Crabgrass & summer grasses (Digitaria/Setaria)
Fast-growing annual summer grasses that spread low and root at the nodes, quickly covering the ground between young crop rows.
- Type
- Grassy weeds (annual, summer)
- Life cycle
- Annual, seed-propagated
- Spreads by
- Seed; rooting at stem nodes
- Main harm
- Cover ground early; compete with young crop
Overview
Crabgrass (Digitaria) and the closely-associated foxtail/bristle grasses (Setaria) are common fast-growing annual summer grasses of maize, sugarcane, groundnut, vegetables and other warm-season crops. They germinate quickly with the crop, spread low and can root at the nodes of their stems, so they rapidly cover the open ground between young crop rows before the crop closes the canopy. They compete for nitrogen, moisture, light and space at the crucial early stage, and can carry a lot of seed to refill the seed bank.
Because they are annuals that germinate mainly from the surface seed bank and are most damaging early, they are best managed by not letting them get established in the young crop. Early inter-cultivation and hoeing, mulching, a competitive well-fertilised crop that closes the canopy, and timely pre- and post-emergence herbicides all help. Preventing seed set keeps the seed bank down for future seasons.
How to identify it
- Fast-growing annual grasses that germinate with the crop and spread low, often rooting at the stem nodes.
- Crabgrass (Digitaria): finger-like seed spikes radiating from the top of the stem.
- Foxtail/bristle grass (Setaria): a dense, bristly, cylindrical seed head like a small foxtail.
- Rapidly cover the open ground between young crop rows before the canopy closes.
Why it is a problem
- Compete strongly with the young crop for nitrogen, moisture, light and space at the crucial early stage.
- Spread quickly and cover the inter-row ground before the crop can close the canopy.
- Carry a lot of seed that refills the soil seed bank for future seasons.
- Worst in the early weeks of warm-season row crops before the crop gets ahead.
Cultural & preventive control
- Inter-cultivate/hoe early to remove the grasses while the crop is young and before they seed.
- Grow a competitive, well-fertilised crop and use proper spacing so the canopy closes quickly and shades them out.
- Mulch the inter-row (e.g. with crop residue) to suppress germination.
- Use clean seed and prevent seed set to run down the surface seed bank.
Herbicide control
- Use recommended pre-emergence herbicides (e.g. atrazine in maize, pendimethalin) and timely post-emergence grass herbicides for the crop.
- Apply at the correct early stage, dose and soil-moisture condition, and rotate herbicide groups.
- Combine herbicides with early inter-cultivation and a competitive crop for reliable control.
- Confirm the current herbicide, dose and timing for your crop with your local KVK.
Integrated management
- Combine early inter-cultivation, mulch, a competitive canopy-closing crop and timely herbicides.
- Prevent seed set to shrink the seed bank over seasons.
- Focus effort on the early weeks, when these grasses do the most damage and are easiest to control.
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
What are the fast-spreading grasses covering the ground between my maize/groundnut rows?
Fast-growing summer grasses that spread low and root at the nodes, quickly covering the inter-row ground, are usually crabgrass (Digitaria — finger-like seed spikes) and foxtail/bristle grass (Setaria — a dense bristly seed head). They compete hard with the young crop for nitrogen and moisture. Control them early: inter-cultivate/hoe while the crop is young, grow a competitive canopy-closing crop, mulch the inter-row, and use timely pre- and post-emergence herbicides.
Why is early control so important for these summer grasses?
Because they are most damaging in the early weeks, when they race to cover the open ground between young crop rows and compete for nitrogen, moisture and light before the crop can close its canopy. Once the crop shades the ground, new grass has much less chance. So the key is to keep the inter-row clean early — through inter-cultivation, mulch, a competitive crop and timely herbicides — rather than letting the grasses get established and then trying to remove a dense stand.
How do I stop these grasses coming back each year?
Since they are annuals that regrow from the surface seed bank, the key is to stop them setting seed and to run the seed bank down over time. Remove them early by inter-cultivation and hoeing before they seed, use clean crop seed, and keep field edges clean. Combine that with a competitive canopy-closing crop, mulch and timely herbicides each season. Over a few years of preventing seed set, the surface seed bank — and the weed pressure — falls.
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.