Shamiran Biswas

All vegetables like sweet pumpkin, brinjal, tomato, rice pumpkin, litchi, mango, cool, bitter gourd, gourd, shrimp, chichinga, and pumpkin. Yellowing of leaves is a problem. There can be various reasons behind the yellowing of the leaves of sweet pumpkin, potal, watermelon, cucumber, mustard, gourd, rice pumpkin, bitter gourd, dhundal, cucumber. Among these, the main cause of yellowing of pumpkin crops in Bangladesh is downy mildew, which is basically a fungal disease.

Causes of yellowing leaves:

Due to nutrient deficiency, waterlogging, over irrigation, lack of water, fungal diseases, powdery mildew, downy mildew, viral mosaic virus, insect attacks like aphids and whiteflies suck sap and spread from one plant to another. Due to all these reasons, the leaves of pumpkin plants turn yellow.

Downy Mildew:

Downy mildew is basically a fungal disease. Downy mildew causes heavy damage to farmers and fields in pumpkin crops from October to February. Today we will focus mainly on this downy mildew disease of pumpkin crops.

Disease symptoms:

The disease first appears on older leaves. White or yellow to brown palm-like angular spots appear on the affected leaves. Similar spots are also seen on the underside of the leaves. Gradually spread to other pages. Infected plants have fewer flowers and fruits and the fruit is tasteless. If the affected is more, the leaves turn yellow or black and die. The leaves gradually turn yellow and eventually wither. The disease can also affect the flowers, causing the flowers to become deformed and disrupt the normal growth of the plant.

Attack Time:

Downy mildew is more prevalent in cooler nights and warmer days. During periods of drought or low rainfall. Overuse of nitrogen. If there is a lack of light and air movement. The best time to spread this disease is from October to February. This disease is more common in winter. This disease can occur even if there is excess water in the crop field. Even if the drainage system of the crop field is not good and weeding is not done, the disease can spread.

Organic Management:

Sow seeds early. Use resistant varieties, do not collect seeds from infected fields. Use of mulching paper to eat, tilling the soil and drying it well in the sun, using trichoderma in the soil, cultivating cold tolerant varieties. Good drainage, adequate light and ventilation around the plant, Baking Soda Spray: Spraying a mixture of one spoon of baking soda and one liter of water can reduce the incidence of disease. Spraying neem oil, one kg of papaya leaves should be chopped and mixed with one liter of water, shaken well and soaked for 12 hours, then filtered and sprayed with 10 liters of water. Infected leaves should be removed promptly, the crop residue should be completely destroyed by burning or burying it in the soil. Using balanced fertilizers and regular crop monitoring.

Chemical Management:

Start applying fungicides as soon as the first symptoms appear.

1. Mencozeb group (contact) fungicide applications (two-three days apart)
2. Who should apply fungicides belonging to carbendazim (systemic) group (after seven days)
3. Ezoxystrabin + Ciproconazole (systemic) multipurpose fungicide application (after seven days)
Caution:
1. Spraying too much fungicide (contactor) can cause flower and fruit drop.
2. Excessive fungicide (systemic) sprays may stunt plant growth.
3. Fungicide will not work if washed off in the rain.
4. Practice good hygiene with any chemical spray.

The writer is a, Agriculture and Environment Specialist, Dhaka.