There are several diseases that can affect eggplants, primarily caused by the decay of their stalks. Common issues include bacterial soft rot, black rot, stem rot, sclerotinia, and bacterial blight. In greenhouse settings, two major diseases are often observed due to decaying stalks.
**1. Bacterial Soft Rot**
This disease typically enters through wounds caused by pruning or harvesting. Initially, the infected area appears pale brown and soft. As it progresses, the epidermis and pith of the stem turn brown and begin to decay. The plant may become dehydrated and shriveled, though symptoms on the upper parts of the plant might not be immediately visible. Importantly, the vascular system remains unaffected at first. However, as the infection spreads, the upper leaves may wilt and die. A distinct, foul odor is often present in the affected areas. This disease tends to be more severe near the entrance of the greenhouse and in areas where condensation from the plastic film accumulates.
Bacteria thrive in moist conditions, so controlling humidity is crucial for prevention. Using drip irrigation, covering the greenhouse with a plastic film, and watering appropriately can help reduce moisture levels. After morning planting, short periods of ventilation can remove excess humidity and minimize condensation. Improving the greenhouse structure, such as using high-quality, non-drip films, can also significantly reduce disease occurrence.
If the disease has already developed, you can apply 72% streptomycin at a 1500-fold dilution, or 50% copper carboxylate (DT) at 200 times, or 47% mancozeb at 200 times. These treatments can be combined with 72% streptomycin diluted 4000 times and 47% mancozeb diluted 600 times. Apply every 7 to 10 days, repeating 2 to 3 times for best results.
**2. Black Rot**
Black rot mainly affects the base of the stem. The infected area becomes sunken and dark brown, with moldy growth appearing on the surface. The inside of the stem turns brown, and cracks may form at the base. At the onset, small dark brown spots appear, irregular in shape, and can spread along the veins. The center of the lesions may appear slightly lighter. Severe cases can lead to leaf death.
To prevent this disease, it's important to start with seed disinfection. For example, mix 10 ml of 2.5% Shilok with 150–200 ml of water and treat 5–10 kg of seeds. Once the disease occurs, you can use 75% chlorothalonil at 600 times dilution, or a combination of 50% carbendazim wettable powder at 600 times and 50% diclofenac copper (DT) at 500 times. When spraying, ensure even coverage, especially focusing on the base of the stems where the disease is most likely to occur.
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