Onion Anthracnose: How to identify, prevent and control?

Onion Anthracnose is a worldwide threat, it seriously affects Onions yield. So, do you want to know how to identify, prevent and control Onion Anthracnose effectively? This article, Garden How will help you gain a lot of useful information about this disease.

What are the symptoms of Onion Anthracnose?

This disease can cause damage during the growth stage of the plant. However, it is most harmful in the period of tuber development until harvest and storage. 

Anthracnose fungi can attack parts of the plants. Symptoms of the disease vary depending on the temperature and humidity of the environment. 

The initial lesions are oval in shape, the average size of them is 4-5 x 2-3 mm, bright white in color, surrounded by a pale yellow border on the leaves. Besides, the first lesions usually appear in the middle of the leaves, rarely on the tips of the leaves. The disease then spreads to extend the length of the leaf.

On tubers and stems, the lesions are larger than those on leaves. The disease is gray and white spreading, accounting for half, even larger.

On the lesions appear many small black dots arranged in an enlarged concentric ring, which are the discs of the branches of the disease-causing fungus. Also, the disease thrives on dry leaves, easily blown tubers, and smaller than normal sizes.

What is the cause of Onion Anthracnose?

The cause of Anthracnose disease in onions is the fungus Colletotrichum circulars (Berk.) Voglino belongs to the family Melanconiaceae, order Melanconiales, class Incomplete fungi. Also, the sexual stage has not been discovered. Multicellular, branched hyphae have variable color and size, colorless when young, and dark color when old. 

• Single-celled meristem, small oval, colorless, with two oil drops at both ends, size 14 30 x 3 – 6 micrometers.
• The sporophyte branch is short and cylindrical, and unicellular and the sporophyte branch is closely arranged. The bristles have 0 – 3 horizontal compartments 80 – 315 micrometers long.
• The host spectrum of the fungus is onion, garlic, Chinese garlic, and green onion.

Developmental characteristics of Onion Smudge

Onion Anthracnose often causes strong damage in sunny and humid weather conditions. In storage when the temperature is above 20oC and high humidity, the disease develops and spreads quickly.

In the field, the disease appears and causes damage in the early onion crop or the main crop. Especially in the years with warmer winters, the temperature is 25-28oC, and in the fields that are too rich in urea, unbalanced with phosphorus and potassium.

In addition, Onion Smudge disease is easy to appear in onion plants that have the yellow curly disease (OYDV). If both diseases occur on the same tree, the disease is easy to spread and severely reduces yield.

When the temperature drops below 20oC, the disease does not develop. Anthracnose fungi exist in onions on storage platforms and in diseased plant residues in the soil. Japanese onion variety is seriously infected.

How to prevent and control Onion Smudge?

Prevent this disease

• It is better to rotate crops with other vegetables for about 2-3 years in severely diseased fields.
• You can choose healthy seedlings, and plant at the right density of 25 x 10 cm for an early crop. 
• Besides, you need to fertilize 1 ton of manure, 8-10 kg of urea, 25 – 30 kg of superphosphate, and 4-5 kg of potassium per pole. 
• In addition, you can add 50 kg of kitchen ash and lime powder to limit other diseases.

Control measures 

When a new disease arises in your field, it is necessary to immediately stop applying more urea, and you do not irrigate fertilizers. It is better to use stewed coal from ground rice husk grass sprinkled on the bed with the amount of 5 to 10 kg/pole and spray Sumi – 8 with a concentration of 1/800 – 1/600.

Besides, you need to spray evenly and drenched on leaves and stems with an amount of 1,2 to 1,5 kg of drugs/ha and fungicides such as Dconil Rovral, Score, and Aliette. 

Final Thoughts 

So, Garden How gave you all of the valuable information about How to identify, prevent and get rid of Onion Anthracnose effectively. We hope this information can assist you a lot in growing and caring for your Onion garden. Visit gardenhow.net to learn more about flowers and vegetables. Thank you for taking the time to read this! 

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