Integrated weed-control strategies in sunflower

A vast field of bright yellow sunflowers stretches to the horizon under a clear blue sky with scattered white clouds on a sunny day.

Sunflower is a crop that is well suited to mechanical weed control. Due to the lack of effective chemical solutions against difficult weeds, mixed chemical-mechanical programmes often work better than herbicides alone. Being planted in wide rows, it is easy to pass through with a row-crop cultivator, which as well as killing weeds, also improves growing conditions and preserves moisture in the soil in dry years.

Integrated weed-control strategies in sunflower

Problem weeds: 

  • Ragweed 
  • Goosefoot
  • Jimson weed
  • Nightshade
  • Knotweed
  • Summer grasses (panic grass, foxtail, crabgrass)

Non-controlled weeds except for resistant varieties:

  • Three-lobe beggarticks
  • Thistle
  • Hedge bindweed
  • Wild sunflower 
  • Xanthium / Cocklebur

Agronomic context and challenges

Stale seeding, as part of a combination strategy, to reduce weeds before sowing the crop

Stale seeding is an agronomic lever that works well in sunflower crops. It reduces the seed stock in the plot before sowing the crop and warms the seedbed.

Comparing different weed-control strategies for sunflower

Terres Inovia has carried out several trials, at various sites in France, to compare weed-control methods in sunflower. Different chemical programmes were used alone or combined with 2 tine-weeder operations, and the results were compared.

Source: Itinéraires de désherbage mixte avec herse étrille, Terres Inovia, 2020
Sunflower (avg of 6 trials) Effectiveness (%) on all floraWithout tine weederWith tine weeder
pre-emergence
Pendimethalin 590 g/ha + Aclonifen 900 g/ha
6384

post-emergence

Imazamox 50 g/ha
6990
Imazamox 32 g/ha + adjuvant 1 L
6488
Tribenuron‑methyl 22 g/ha + adjuvant
6986
Tribenuron‑methyl 15 g/ha + adjuvant
4669
reference
No herbicide
066

A mixed weeding strategy was found to be 20% more effective, on average, than a purely chemical solution.

Possible treatment periods depending on mechanical weeding tools

Crop stagePre-emergenceGerminatedSternSpreading cotyledons1 pair of leaves2 pair of leaves3 to 4 pair of leaves5 to 8 pair of leavesRow-crop cultivator pass limitWeed stage
Rotary hoe🟠With care
15 km/h		🟠With care
15 km/h		⚠️Pass prohibited🟠With care
10 km/h		🟢Pass possible
10 – 15 km/h		🟢Pass possible
10 – 15 km/h		🟢Pass possible
10 – 15 km/h		🟠With care⚠️Pass prohibitedWhite filament to 1st leaf
Tine weeder🟢Pass possible
8 - 10 km/h

Aggressiveness:
●●●		⚠️Pass prohibited⚠️Pass prohibited🟠With care
3 km/h
max
Aggressiveness:
●		🟠With care
3 - 6 km/h
max
Aggressiveness:
●●		🟠With care
4 - 7 km/h
max
Aggressiveness:
●●●		🟢Pass possible
5 - 7 km/h

Aggressiveness:
●●● to ●●●●		🟢Pass possible
5 - 7 km/h

Aggressiveness:
●●● to ●●●●		⚠️Pass prohibitedWhite filament to 3–4 leaves
Row-crop cultivator⚠️Pass prohibited⚠️Pass prohibited⚠️Pass prohibited⚠️Pass prohibited🟠With care
3 km/h
with plant protectors		🟢Pass possible
4 km/h
Depending on guidance equipement		🟢Pass possible
4 km/h
Depending on guidance equipement		🟢Pass possible
5 to 10 km/h
Depending on guidance equipement		🟢Pass possible
5 to 10 km/h
Depending on guidance equipement		3 leaves
and more

Weed-control programmes for sunflower  

ModalityPre-emergenceCotyledons1 pair of leaves2 pair of leaves3 to 4 pair of leaves5 to 8 pair of leavesRow-crop cultivator pass limit
BBCH0-91011 - 1414 - 1818 - 1919 - 32 
Option 1 All chemical choice of resistances crops🟢💦  🟢💦   
Option 2 Mixed, with row-crop cultivator   🟢💦🟠💦  
   1–2 passes
🟢row-crop cultivator		1–2 passes
🟢row-crop cultivator		1–2 passes
🟢row-crop cultivator		1–2 passes
🟢row-crop cultivator
Option 3 Mixed, without hoeing🟢💦  🟢💦   
🟢↘ 🟢⚙️ or ↘🟢⚙️ or ↘   
Option 4 All mechanical🟠⚙️ or ↘ 🟠⚙️🟢row-crop cultivator
or tine weeder ↘		🟢row-crop cultivator
or tine weeder ↘		🟢row-crop cultivator 

🟠optional 🟢essential 💦chemical ⚙️rotary hoe or ↘ tine weeder

Purely chemical 

The conventional weeding strategy for sunflowers is a pre-emergence treatment. A second treatment can be applied post-emergence, after the 2-3 leaf stage, especially with Imazamox-resistant varieties.

  • Pre-emergence, several herbicides can be mixed depending on the type of weeds.
  • Post-emergence, when the sunflower crop is at around the 4-leaf stage, 1 month after seeding, several herbicides mixed can be effective against autumn grasses, summer grasses (panic grass, foxtail, crabgrass), and complex dicots.

Mixed strategy, with a row-crop cultivator

Row-crop cultivation can be combined with a post-emergence chemical herbicide to make it more effective. Classic pre-emergence herbicides are ineffective on grasses, so the plot needs to be clean for sunflowers, unless it is an imazamox-resistant variety of sunflower.

Row-crop cultivation improves growing conditions, especially when carried out before the summer.

Mixed strategy, with a tine weeder

A tine weeder or rotary hoe can be used blind, before crop emergence, at the 2-pairs-of-leaves stage. This enhances herbicide efficiency and makes it possible to reduce the dose.

Purely mechanical

It is possible to weed sunflowers without chemical products, using a rotary hoe, pre-emergence, or at the 2-leaf stage. A row-crop cultivator can be used from the 2-pairs-of-leaves stage until the tractor can no longer pass through.

A Rotary hoe Starliner churns through brown soil, kicking up dirt and debris in a farm field.
STARLINER Rotary hoe
row crop cultivator Rowliner with red and black components cultivates soil around young green corn plants in neat rows across a farm field.
ROWLINER Row-crop cultivator
A red and white tractor with a tine weeder Tineliner is working in a grassy field under an overcast sky, preparing soil for farming.
TINELINER Tine weeder

Recommendations

Mechanical weed control is a good solution in sunflower, as a substitute for the lack of herbicides available. Sunflower is also suited to row-crop cultivation which can catch weeds early and keep grass levels low until the summer. 

Sources:
Désherbage mécanique en tournesol, Terres Inovia, 2025
Désherbage mixte, l’alliance du chimique avec le mécanique, Chambre d’agriculture des Hauts de France, 2022
Stratégies herbicides en tournesol, Terres Inovia, 2025