India depends significantly on cotton as a vital commercial crop. However, its slow growth in the initial growth stages and wider row spacing allows different weed species to grow and compete for water and nutrients, hindering cotton’s development and reducing crop yields. If the weeds are left unchecked, they could cause a yield loss of about 50 – 85%. To address this problem, effective weed management practices can be approached through integrated techniques including physical, mechanical, cultural, and chemical measures.
Major Weeds in Cotton Field
Weeds in cotton fields can be broadly classified into two main categories: grass weeds and broad-leaved weeds. Grass weeds typically have long, narrow leaves that are parallel-veined, while broad-leaved weeds have wider leaves that are often branchy-veined.
| Type of Weeds | Common weeds in cotton fields |
| Grass weeds | Cynodon dactylon, Echinocloa crusgalli, Dactyloctenium aegypticum, Cyperus deformis, Cyperus rotundus, Dinebra retroflexa |
| Broad-leaved weeds | Amaranthus viridis, Chenopodium album, Commelina benghalensis, Euphorbia hirta, Parthenium hysterophorus, Trianthema portulacastrum, Digera spp |
Preventive measures for weed management in cotton
Cultural
- Plough the land deeply during summer to uproot existing weeds. Expose the field to sun for at least 2 – 3 weeks.
- Grow short duration legumes such as cowpeas and lablab in between the wide-spaced cotton rows (inter-row cultivation) which can act as living mulch or cover crops to suppress weed growth and improve soil health.
- Use organic (paddy straw or dry leaves) or polyethylene mulch to suppress weed growth by blocking sunlight and reducing soil moisture.
- Follow crop rotation of cotton with non-host crops such as cereals or legumes to break the weed cycle.
- Follow other agronomic practices such as using ‘weed-seed free’ seeds, fertilizer and irrigation management.
- Plant the crop at the right time to take advantage of early season moisture and to minimize weed growth.
- Do timely hand weeding to keep the field weed free during initial days.
Mechanical
Manual weeding using hoes or sickles is important to be carried out to reduce the weed population in the field. Do one hand weeding at 45 DAS, after application of pre-emergence herbicide. If no pre-emergence herbicide is applied at the time of sowing, give two hand weeding at 18 – 20 DAS and other at 45 DAS. Or you can run blade harrows at 20-25 DAS and 45-50 DAS in between the crop rows to remove the weeds.
(*DAS – Days after sowing)
Chemical Management with Herbicides
Knowing the types of weeds, i.e., grass weed or broad-leaved weed present in cotton fields can help growers develop more effective weed management strategies tailored to the specific weeds present.
Herbicides can be applied pre- or post-emergence to control weeds in cotton fields. Care should be taken to select the appropriate herbicide based on the weed species and crop stage. The critical period for weed control in cotton fields is the first 45 days. Use selective herbicides to target specific weeds while reducing the risk of harm to non-target species and the surrounding environment.
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Pre-emergence Herbicides
Spray Pre-emergence herbicide Pendimethalin 30% EC at 1.2 liter per acre or 6 ml per liter of water, three days after sowing. It kills both grasses and broad-leaved weeds, thus protecting crops during early and critical days of their growth.
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Post-emergence Herbicides
Time of Application – Inter-row application at 15 – 30 DAS or at 2 – 4 leaf stage of weeds
| Product name | Technical content | Dosage | Type of weeds it controls |
| Agil Herbicide | Propaquizafop 10% EC | 2 ml/lit of water | Grass weeds |
| Dozo Maxx | Pyrithiobac sodium 6% + Quizalofop ethyl 4% MEC | 2 ml/lit of water | Both broad and narrow leaved weeds |
| Targa Super or | Quizalofop Ethyl 5% EC | 2 ml/lit of water | Grass weeds |
| Ryusei Herbicide | |||
| Hitweed Herbicide | Pyrithiobac sodium 10% E C | 1 ml/liter of water | Broad leaved weeds |
| Whip Super Herbicide | Fenoxaprop-p-ethyl 9.3 % EC | 1.5 ml/lit of water | Grassy weeds |
IMPORTANT NOTE:
- Herbicides can effectively manage weeds in cotton; however, relying solely on chemical methods may not be enough for optimal weed control. To achieve effective results, cultural practices and regular hand weeding, in addition to herbicides, should be employed.
- Make sure the soil is moist at the time of spraying of both pre and post emergence herbicides.
- Do not spray if the rain is expected.
- To prevent weed resistance, it is advisable to rotate herbicide products with different chemicals.
- Post-emergence herbicide application is recommended at the 2-3 leaf stage of the weeds to obtain favorable results.
- Use sticking and spreading agent like Multiplex Nagastha – 180 (0.4 – 0.5 ml/lit of spray solution) for herbicide mix for increased efficiency of post emergence herbicides.
- Spraying should only be carried out on clear and sunny days.
- It is advisable to avoid spraying herbicides in the direction of the wind to prevent the herbicide from drifting.
- Follow the herbicide label instructions carefully, including the recommended rates, application timing, and safety precautions.
- Do not tank mix with sulphur and copper-containing pesticides.
