Recently, I've noticed many moss-green spots appearing on the trunk and leaves of my durian trees, which then turn reddish-brown. Some branches have cracked bark, and the trees are growing more slowly than before. Could you please tell me if this is algal spot disease and if it affects durian yield?
Le Thanh Tung (Cai Nhum commune)
Based on the symptoms described, it is highly likely that the durian tree has algal spot disease. The causative agent is the algae Cephaleuros virescens, which commonly appears on the trunk, old branches, and old leaves of the tree. The disease often thrives in dense, poorly ventilated orchards or those with inadequate care. Orchards with nutrient-poor soil, weak tree growth, and a lack of organic fertilizer are also susceptible to the disease. Furthermore, excessive use of foliar fertilizers or prolonged dampness in the orchard also creates favorable conditions for the algal bloom to develop.
On the trunk and branches, the disease initially appears as small green spots, then spreads into patches of mossy green, with the center turning reddish-brown. If the disease develops severely, the bark of the branches may crack, hindering plant growth. On the leaves, the disease forms slightly raised, round spots on the surface, reddish-brown in color like crab roe. Under favorable conditions, the lesions spread, reducing photosynthesis and affecting plant health.
To limit algal spot disease, preventative measures should be prioritized from the outset. During the rainy season, dig drainage ditches and pruning to improve aeration in the garden is essential. Avoid spraying NPK foliar fertilizers during prolonged periods of rain. Additionally, supplement with organic fertilizers, compost, amino acid preparations, and enzyme-based resistance enhancers to boost plant immunity.
In cases of severe disease development, fungicides containing copper, sulfur, mancozeb, propineb, or difenoconazole can be used as directed by technical staff. When spraying, focus on the trunk, branch axils, and severely infected areas for maximum effectiveness.
FARMER'S FRIEND
Source: https://baovinhlong.com.vn/kinh-te/nong-nghiep/202606/nha-nong-tim-hieu-phong-va-tri-benh-dom-rong-tren-cay-sau-rieng-618273a/
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