Bitter Gourd Diseases: Identifying And Managing For A Healthy Harvest

Bitter gourd (Momordica charantia), also known as bitter melon, is a tropical and subtropical vine that is widely grown for its edible fruit. It is an important vegetable crop in many regions of the world, including India. It belongs to the family of cucurbits that includes several other commonly grown vegetables such as cucumbers, pumpkins, squash and melons. Like other cucurbits, bitter gourd is also vulnerable to a range of diseases that can cause significant yield losses if not managed effectively. Bitter gourd diseases can be caused by bacteria, fungi, viruses and other pathogens and can affect all parts of the plant, including the leaves, stems, flowers and fruits. Effective management of bitter gourd diseases includes understanding of the diseases that affects the crop, their symptoms and the methods to control them.

1. Powdery Mildew

Causal organism: Podosphaera xanthii (formerly Sphaerotheca fuliginea) 

Powdery mildew is a common fungal disease in bitter gourd diseases. Its pathogen thrives in warm and humid conditions and can spread quickly in crowded plantings. 

Symptoms:  

• Presence of white powdery residue on upper surface of the leaves, stems and other growing parts. 

  

• The leaves of the infected plant may start turning yellow or brown, especially in areas with heavy fungal growth. 
• Eventually, it leads to drying and falling of leaves. 
• Infected leaves may shrivel and become distorted or misshapen. 
• Plants show stunted growth due to decreased photosynthesis caused by fungal growth. 
• Infected plants may produce smaller and less flavorful fruit. 
• In severe cases, the entire plant may be covered with the powdery growth, leading to the death of the plant. 

Management of Powdery Mildew in Bitter Gourd:  

2. Downy Mildew

Causal organism: Pseudoperonospora cubensis 

Downy mildew is favoured by cool, moist conditions and can spread rapidly in humid environments. 

Symptoms:

• Appearance of yellow angular patches or spots on the upper surface of the leaves. 
• As the disease progresses, brown spots may develop on the infected leaves, often surrounded by a yellow halo. 
• Under moist conditions, fuzzy grayish-white water soaked lesions appear on the underside of the leaves. 
• Causes rapid defoliation of affected leaves. 
• Affected plants becomes stunted and kills the plants in severe cases. 

Management of Downy Mildew in Bitter Gourd: 

3. Anthracnose

Causal organism: Colletotrichum spp. 

Warm and humid conditions provide favorable conditions for the growth and spread of the fungus that causes anthracnose. 

Symptoms:  

• Dark, sunken lesions develop on the leaves, stems and fruits of the bitter gourd plant. 
• These lesions or spots may be circular, oval or irregular. 
• As the infection progresses, small black spots/flecks may appear scattered on the affected parts. 
• Infected leaves may wilt, dry and fall off. 
• Petioles and stems may develop elongated dark spots with light centers, which can cause the death of surrounding tissues. 
• When the lesions on the stem base enlarge, it causes wilting and lodging of plants. 

Management of Anthracnose in Bitter Gourd: 

4. Angular Leaf Spot (Bacterial Disease)

Causal organism: Pseudomonas syringae 

The disease can be transmitted through contaminated seed, infected plant debris, or by wind-driven rain. Warm and humid weather conditions are conducive to disease development and once established, the disease can spread rapidly. 

Symptoms: 

• Appearance of small, angular, water-soaked lesions on the leaves which later expand rapidly under favorable conditions. 
• As the disease progresses, the lesions turn brown and necrotic, with a dark brown center and yellowish margins. 
• Affected leaves shrink and often tear away healthy leaf tissue forming irregular holes giving ragged appearance. 
• The disease can also affect other plant parts, including stems, fruits and tendrils. 
• Infected fruits will be small with circular spots. 

Management of Angular leaf spot in Bitter Gourd: 

5. Fusarium Wilt

Causal organism: Fusarium oxysporum f. sp. niveum 

It is caused by the soil-borne fungus which can infect the plant at any stage of its growth, but symptoms are most pronounced in the mature stage. The fungus can be spread through contaminated soil, water, and infected plant debris. Warm and humid weather conditions can also increase disease incidence. 

Symptoms: 

• Leaves of the affected plants show yellowing and drooping symptoms. 
• Infected plants may start to wilt, particularly during the hottest part of the day and may not recover even after watering. 
• The stem of the infected plant may show a brown discoloration, particularly at the base, which can progress upward. 
• Infected plants may exhibit dark brown or reddish-brown discoloration of the vascular tissue when the stem is cut open. 
• The plant shows stunted growth and later dies.  

Management of Fusarium Wilt in Bitter Gourd: 

6. Cercospora Leaf Spot

Causal organism: Cercospora citrullina 

The disease is most common in hot and humid regions. The fungus thrives in crop debris and weeds. Their spores can transmit through rain splashes, wind and tools/implements. 

Symptoms: 

• Small, circular or irregularly shaped spots appear on the leaves. 
• The spots are usually brown or gray in the center and have a yellow or reddish-brown border. 
• Under warm and humid conditions, the spots on the leaves may grow and merge, forming larger lesions that can cover most of the leaf surface. 
• The infected leaves may start to turn yellow or brown around the spots, and then dry up and fall off. 
• Causes premature defoliation of leaves. 
• In some cases, the disease can also cause dark, sunken lesions on the fruit, which can reduce the quality and yield of the crop. 

Management of Cercospora leaf spot in Bitter Gourd: 

7. Mosaic Disease

Causal organism: Cucumber mosaic virus (CMV) / Papaya ringspot virus (PRSV) 

Vector: Aphids 

This viral disease is transmitted by vector and by mechanical mechanical inoculation of plant sap. High temperatures and low humidity can increase the replication and spread of the virus. 

Symptoms:

• Appearance of alternate light and dark green (mosaic) patches on the leaves. 
• Reduction in leaf size. 
• The leaves may be distorted, wrinkled, or twisted. 
• Affected plant’s growth is inhibited thus giving bushy appearance.
• The fruits may develop raised bumpy protrusions that can make them unmarketable. 

Management of Mosaic Disease: 

The disease can be controlled by managing the vector, aphids which spreads the virus. In addition to spraying insecticides, spray Geolife No Virus at 3 – 5 ml/lit water which helps to increase plant’s resistance to the disease. 

(NOTE: Check the product label to know the right time of application) 

ITK Practices to control Diseases in Bitter Gourd 

• Spraying neem oil can control Powdery mildew, Downy mildew and anthracnose. 
• Sprinkling ash over the plants can help to control powdery mildew. 
• Buttermilk Fungicidal spray: 250 – 500 ml of 15 days fermented buttermilk + 15 liters of water can be used as foliar spray to control fungal diseases. 
• 20 gm of ginger powder mixed in 1 liter of water can be sprayed at an interval of 15 days. It is effective in checking the incidence of powdery mildew and other fungal diseases.  
• Leaf extract of Prosopis juliflora can be sprayed to control leaf spot and powdery mildew. 
• Following crop rotation with non-host crops like legumes or corn to reduce pathogen buildup in the soil. 

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