Leaf spot in cotton shows up as circular to angular brown lesions scattered across the canopy, often alongside grey mildew when humidity stays high through the boll-development stage. Left unmanaged, it thins out the leaf area the plant needs to fill its bolls, cutting directly into lint yield. Three fungicides are confirmed for leaf spot control on cotton, and here's how each one works.
Signs of Leaf Spot to Watch For in Cotton
- Small, circular to angular brown or reddish-brown spots scattered across the leaf surface
- Spots that enlarge and develop concentric rings or a grey centre as the infection matures
- A yellow halo often visible around younger lesions
- Premature yellowing, drying, and shedding of heavily affected leaves
- Grey mildew developing on the same leaves under humid conditions
What Causes Leaf Spot in Cotton
- Warm, humid weather with extended periods of leaf wetness
- Frequent rain or heavy dew during the boll-development stage
- Dense canopy growth that traps humidity and limits airflow
- Infected crop debris left in the field from a previous cotton season
- Nutrient stress, particularly potassium deficiency, which makes plants more susceptible
Solutions to Control Leaf Spot in Cotton
1. Azoxystrobin 18.2% + Difenoconazole 11.4% w/w SC
This combination pairs a systemic strobilurin with a triazole, giving both protective and curative action against the fungus. The strobilurin component disrupts the pathogen's respiration and keeps spreading to new growth as the plant develops, while the triazole works from within tissue already infected, making the mix effective whether applied ahead of an outbreak or once spots have already appeared. It also covers grey mildew, which commonly shows up on the same leaves.
Product Recommendations
2. Carbendazim 50% WP
A systemic benzimidazole fungicide that's absorbed into the plant tissue and interferes with the fungus's cell division, stopping it from spreading further once inside the leaf. It's one of the older, well-established options for cotton leaf spot and remains a dependable choice for growers rotating away from newer chemistries.
Product Recommendations
3. Kresoxim-methyl 44.3% SC
A strobilurin fungicide that inhibits fungal respiration on contact and moves translaminarly through the leaf, giving protection to both treated and adjoining tissue. It also holds up against grey mildew on the same crop, making it useful where the two diseases show up together.
Product Recommendations
Note: Rotate between different modes of action across the season rather than repeating the same one, and clear infected crop debris from the field after harvest, since it's one of the main ways the fungus survives to infect the next planting.
Disclaimer: Always confirm current label registration, approved dosage, water volume, and pre-harvest interval (PHI) for your state before using any product - labels are periodically revised by regulatory authorities.
This guide is a general advisory. Do your own research and verification before using any product. Always confirm suitability for your crop stage, region, and field conditions before making any purchase, spray, or crop-management decision.
