Purple Blotch is one of the most common and damaging diseases in onion farming. Many farmers first notice small purple spots on leaves. After some time, the leaves dry from the tips, and bulb size reduces.

If not controlled early, Purple Blotch can greatly reduce yield and profit.

Let us understand what Purple Blotch is, how it develops, the damage it causes, and how to control it effectively.

What Is Purple Blotch?

Purple Blotch is a fungal disease caused by Alternaria porri.

It mainly attacks:

• Onion leaves
• Flower stalks (in seed production)

The disease spreads easily in:

• Warm weather
• High humidity
• Rainy conditions
• Fields with poor air circulation

Stages of Purple Blotch in Onions

Purple Blotch develops in stages. Knowing these stages helps you act early.

Stage 1: Small Spots on Leaves

• Tiny white or pale spots appear on leaves.
• Spots enlarge and turn purple in the center.

This is the best time to control the disease.

Stage 2: Enlarging Purple Lesions

• Spots become bigger and oval-shaped.
• The center turns purple with yellow edges.
• Leaves begin to weaken.

The disease starts spreading quickly under wet conditions.

Stage 3: Leaf Drying

• Leaf tips dry from the infected areas.
• Entire leaves may collapse.
• Plant growth slows down.

When many leaves dry, bulb formation is seriously affected.

How Much Damage Can Purple Blotch Cause?

If left uncontrolled:

• Yield losses can reach 30%–70%.
• Bulbs remain small.
• Maturity is delayed.
• Storage life reduces.

In severe cases, most leaves dry before bulbs fully develop.

Since onions depend on healthy leaves to form bulbs, leaf damage directly reduces yield.

Agronomic Practices to Reduce Purple Blotch

Good farm management helps reduce disease pressure.

1. Proper Spacing

• Avoid overcrowding.
• Allow good air circulation.
• Leaves dry faster after rain or irrigation.

2. Avoid Overhead Irrigation

• Excess water on leaves increases infection.
• Use drip irrigation where possible.
• Irrigate early so leaves dry during the day.

3. Field Hygiene

• Remove infected leaves early.
• Destroy crop residues after harvest.
• Do not leave infected plants in the field.

4. Crop Rotation

• Avoid planting onions repeatedly in the same field.
• Rotate with non-host crops like cereals.

This reduces disease carryover.

5. Regular Field Scouting

• Inspect leaves weekly.
• Act immediately when small purple spots appear.

Early action gives better control.

Best Active Ingredient for Purple Blotch Control

One of the most effective active ingredients for controlling Purple Blotch is:

Difenoconazole

Difenoconazole is a systemic fungicide.

What it does:

• Penetrates into plant tissues.
• Stops fungal growth inside the leaf.
• Protects new growth.
• Slows down disease spread.

Because it works from inside the plant, it provides strong and reliable control.

Recommended Solution: Dewklin 250EC

For effective control of Purple Blotch, we recommend:

Dewklin 250EC

It contains:

• Difenoconazole 250g/L

Benefits of Dewklin 250EC

✔ Controls Purple Blotch effectively
✔ Stops further disease development
✔ Protects healthy leaves
✔ Improves bulb development
✔ Supports higher yields

When and How to Spray

• Spray at the first sign of purple spots.
• Do not wait until leaves are badly damaged.
• Ensure good coverage of all leaves.
• Follow recommended dosage and spray intervals.

Spraying early saves money and protects yield.

Final Advice to Farmers

Purple Blotch mainly attacks the leaves. And without healthy leaves, onions cannot form large bulbs.

To protect your crop:

• Maintain good field hygiene.
• Avoid overcrowding.
• Monitor regularly.
• Spray early using a reliable fungicide.

Using Dewklin 250EC with Difenoconazole 250g/L gives strong and dependable control of Purple Blotch.

Healthy leaves mean bigger bulbs.
Bigger bulbs mean better market prices.
Better prices mean better profits.

Act early. Protect your onions. Secure your harvest.