Defeating Gummy Stem Blight: Strategies For Cucurbit Growers

“Chlorosis of leaf margins, wilting, oozing of gum, cracking of fruits” – Are you seeing these signs in your cucurbits farm? 

If yes, it’s high time to take immediate action against this highly destructive fungal disease: gummy stem blight. This fungus has the ability to spread rapidly, causing significant damage and loss to your crops. Visualize the devastating consequences of allowing this disease, caused by the pathogen Didymella bryoniae, to go unchecked. It can lead to substantial yield losses and a decline in fruit quality.  

Whether you’re already engaged in cucurbit farming, or if you’re planning to venture into it, it is crucial to familiarize yourself with the signs and causes of gummy stem blight and equip you with the tools to safeguard your harvest.  

Symptoms of Gummy Stem Blight in Cucurbits

Gummy stem blight symptoms can be observed on all parts of the plant except the roots. 

Leaves:

• Initially, water-soaked leaf spots can be seen, particularly near the leaf margins where chlorosis (yellowing) may also be observed.
• Infections can occur on young seedlings, presenting light to dark brown spots on the cotyledons.
• These spots may expand, merge together and result in leaf blighting and wilting.

Stems:

• If the infection occurs in the nursery, it can cause stem splitting, wilting and under severe conditions, the affected seedlings die.
• On the stems, the infection appears as brown water-soaked lesions that develop into stem cankers. These cankers exude a gummy brown fluid.

Fruits:

• Fruits of affected plants show cracking and rotting symptoms.
• Additionally, they may exhibit a characteristic black rot, which manifests as rotting with a black color.

Causes of the disease

Following are the conditions which create favourable conditions for the disease to develop and spread; 

• High humidity levels of around 85% and moist conditions, especially with frequent rains or overhead irrigation and poor drainage.
• Infected seeds used for planting.
• Wind and rain splashes facilitating the disease’s dissemination within and between fields.
• Undecomposed plant material provides reservoir for fungus survival.
• Alternate host plants and weeds.
• Contaminated tools, equipment or even through clothing of farm workers.

Ways to Prevent this disease

• Use disease free healthy seeds from reputed source. Treat the seeds before sowing to avoid infection.
• Take proper precaution measures during nursery, by cleaning and disinfesting the growing area regularly and inspecting seedlings for at least every 2 days for any signs of spots/patches and remove all infected seedlings and burn.
• Deep plough the soil during summer to expose and kill the fungal spores.
• Keep the field free from weeds.
• Avoid overcrowding of plants for allowing proper penetration of air and sunlight.
• Avoid overhead irrigation to avoid wetting of leaves and spreading of fungal spores to other healthy plants.
• Rotate the crop every 2 years with non-host crops like Brassicas, onion and legumes.
• Avoid any damage to the plants as well as fruits to avoid entry of fungus through wounds.
• Collect and burn all the plant debris after harvest.

Management of Gummy Stem Blight in Cucurbits

1. Biological Management

Spray or drench with Trichoderma viride or Pseudomonas or Bacillus spp, 15 days after sowing at every 15 days interval to prevent and manage gummy stem blight disease in melons and other cucurbits. 

Product name	Technical content	Dosage
Anand Dr Bacto’s Fluro	Pseudomonas fluorescens	Foliar: 2.5 ml/lit of water Drenching: 10 ml/lit of water
Multiplex Nisarga	Trichoderma viride	Foliar: 3 gm/lit of water Soil Application: 1 – 2 kg of the product + 100 kg of FYM
Mildown Bio Fungicide	Bacillus subtilis	Seed treatment: 0.15 – 0.2 ml/kg seed Seedling treatment/nursery bed: 5 ml/lit  Drip: 2.5 ml/lit of water
Multiplex Bio-Jodi	Bacillus spp. & Pseudomonas spp	Foliar: 5 gm/lit of water Soil Application: 2 – 5 kg of product + 120 – 150 kg of FYM

2. Chemical Management

It is recommended to apply fungicides preventively in combination, about 1 week after germination or when the plants have 3-4 leaves to minimize crop damage and losses to a greater extent. As a curative measure, spray fungicides after disease occurrence and at appropriate developmental stages of the crop. 

Product name	Technical content	Dosage
Krilaxyl Powder	Metalaxyl 35% WS	Seed treatment: 6 – 7 gm/kg seed
Amistar Top Fungicide	Azoxystrobin 18.2% + Difenoconazole 11.4% SC	1 ml/lit of water
Cabrio Top Fungicide	Metiram 55% + Pyraclostrobin 5% WG	3 – 3.5 gm/lit of water
Roko Fungicide	Thiophanate Methyl 70% WP	Foliar: 0.5 gm/lit of water or Drench: 2 – 4 gm/lit of water
Splash Fungicide	Chlorothalonil 75% WP	2 gm/lit of water
Kocide Fungicide	Copper Hydroxide 53.8% DF	2 gm/lit of water
Tata Master Fungicide	Metalaxyl 8% + Mancozeb 64% WP	1.5 – 2.5 gm/lit of water
Custodia Fungicide	Azoxystrobin 11% + Tebuconazole 18.3% w/w SC	1.5 ml/lit of water
Curzate Fungicide	Cymoxanil 8% + Mancozeb 64% WP	2 – 2.5 gm/lit of water