Understanding Damping Off: A Plant Disease
Damping off is a disease that affects the growth of various crop seedlings. Plants like Amaranth, Brassica, carrot, tomato, cucumber, and melon are susceptible to this disease. Damping off can impact different parts of the plant, such as leaves, roots, seeds, stems, and the entire plant itself. The specific manifestation and timing of the disease vary depending on the type of crop.
In cabbages, damping off can occur during the heading stage, post-harvest, pre-emergence, or seedling stage. Fungal infestation leads to the collapse and decay of seedlings, sometimes resulting in a mass of fungal growth.
Causes of Damping Off
Many fungi are associated with damping off disease, with the most common being those in the pythium spp. These fungi thrive in conditions such as low soil pH, poor aeration, heavy seeding or high plant population, excessive soil moisture, low light penetration, and the presence of weeds. They depend on plant exudates for sustenance. The fungi can survive in the soil through mycelium, resting spores, or sclerotic (tiny brown resting fungal bodies).
Symptoms of Damping Off
The signs of damping off vary based on the affected plant part. Here are some common symptoms:
1. Leaves: Lesions, abnormal colors, and wilting may be observed.
2. Roots: Lesions can develop on the roots.
3. Seeds: Rotted or discolored seeds may be present.
4. Stems: Cankers may develop on the stems.
5. Whole Plant: The entire plant may dieback, indicating damping off.
Damping Off in Cabbage
When cabbage plants are affected by damping off, the following symptoms are likely to be observed:
1. Wire Stem: The stem above the soil line shrivels, darkens, and loses outer tissues, leaving a dark, woody inner stem. The plant appears stunted.
2. Bottom Rot: Lower leaves wilt, decay, and turn black.
3. Cabbage Head Rot: A slimy, dark decay occurs at the base of outer leaves, causing foliage leaves to die and drop off.
Controlling Damping Off
To prevent damping off, the following measures can be taken:
1. Use certified seeds known to be disease-free.
2. Raise nursery beds to reduce waterlogging and excess moisture.
3. Adjust soil pH to a slightly acidic or neutral level. HUMIPOWER, a soil conditioner from Greenlife Crop Protection Africa Ltd, can help regulate soil pH. It should be applied mixed with fertilizers or organic manures, at a rate of 1kg per 50kg bag of fertilizer or 1kg of humipower for 4 tons of organic manure.
Moiben Crop Protection Ltd offers two effective products for controlling damping off:
1. PYRAMID 700WP: This product can be applied by drenching at a rate of 100g/20L or through foliar application at a rate of 50g/20L.
2. GEARLOCK TURBO 250WP: Apply this product at a rate of 30g/20L.