Purple Blotch Disease in Onion Crop: Identify Symptoms and Learn Easy Control Measures

Krishi Dunia

• 09 Feb, 2025 03:32 PM IST ,
• Updated Sun, 09 Feb 2025 06:40 PM

Purple Blotch Disease in Onion Crops: Symptoms and Control Measures

Onion Farming and Its Impact of Diseases:

Onion is an important cash crop for farmers, cultivated in both the Rabi and Kharif seasons. However, due to favorable weather conditions, various diseases can affect onion crops, with purple blotch disease being a major threat. This disease affects both the yield and quality of the crop, causing significant losses for farmers.

What is Purple Blotch Disease?

Purple blotch disease affects the leaves and stems of the onion plant, halting plant growth and reducing crop production. Effective management of this disease is essential to ensure good onion yield.

Symptoms of Purple Blotch Disease:

• Spots on Leaves – Initially, small, water-soaked, light yellow spots appear, which gradually turn brown or purple. A yellowish ring forms around these spots.
• Leaf Wilting – As the infection worsens, the leaves begin to dry and wilt. This disease can also affect the stems.
• Bulb Development Halts – Infected plants' leaves dry out prematurely, halting bulb development and leading to significant yield loss.

How Does the Disease Spread?

This disease primarily spreads through wind, infected plant residues, and moisture. High humidity (80-90%), temperatures between 18-25°C, rainfall, or excessive irrigation speed up the spread of the disease.

Management of Purple Blotch Disease:

1. Adopt Crop Rotation:

Growing onions in rotation with other crops can reduce the impact of this disease.

2. Maintain Field Hygiene:

Remove infected plant residues from the field, as they are the main source of disease spread.

3. Manage Drainage:

Ensure there is no waterlogging in the field, as excessive moisture promotes disease development.

4. Use Balanced Fertilizers:

Use a balanced amount of nitrogen, phosphorus, and potash. Excess nitrogen can exacerbate the disease.

5. Choose Resistant Varieties

Opt for onion varieties that are disease-resistant, to minimize crop damage.

Biological Control of Purple Blotch Disease:

• Use biological agents like Trichoderma, which help control pathogens.
• Apply 5% neem oil (Nimol) spray to reduce the disease’s impact.
• Using cow dung slurry as organic manure enhances the plant’s disease resistance.

Chemical Control of Purple Blotch Disease:

If the disease is severe, the following fungicides can be used:

• Mancozeb – Mix 2.5 grams per liter of water and spray.
• Propiconazole – Mix 1 ml per liter of water and spray.
• Chlorothalonil – Mix 2 grams per liter of water and spray.
• Apply these chemicals at 10-15 day intervals, twice.

Irrigation Management for Crop Protection:

Use drip irrigation in the morning for onion crops, which helps prevent excessive moisture and reduces the likelihood of disease development.

Purple blotch disease in onion crops is a serious problem, but it can be controlled with proper agricultural management, biological methods, and appropriate chemical control. Farmers can protect their onion crops and achieve good yields by adopting these measures in time.