Citrus decline a fast spreading disease of Citrus reticulate in South East Asia a quick diagnosis and management technique
P Raja: College of Horticulture and Forestry
<div><em>Citrus reticulate</em> is widely cultivated in south east Asian countries. The pest and diseases are major production constraints in this region. Out of diseases, decline leads to death of hundreds of mandarin trees in north eastern states of India. <em>Citrus tristeza virus</em> (CTV) was contributed 30-50, 60-80 per cent decline in 5-10 and 10-15 year old trees respectively. The key symptoms are veinal chlorosis, vein corking, gradual wilting on the tip and branches. For quick detection, the branches are soaked in water with tabolene solution(0.5%) for 48 hrs, upon peeling of stem zonal lines, stem pitting are seen. In India, <em>Toxoptera citricida, Toxoptera aurantii</em> is spreading the CTV and active in Dec to March. Upon releasing of viruliferous insects into <em>Citrus limon</em> seedling, similar symptoms were observed. Early detection and replanting with pre-immunized seedling could reduce 90 % incidence followed by 0.01% dimethoate spray (60%). Citrus trunk borer caused 40-60 % decline in 4-10 year old trees during Sep-Oct months. The grub of the trunk borer bores the tree trunk near ground level horizontally up to the pith and then tunnels vertically and again horizontally for exit during September to November months. Presence of chopped saw dust outside the hole is the key symptom to identify this pest. Gradual drying and sudden drooping of premature leaves are common symptoms observed during the study. Experimenting with various management treatments depicted that stem injection with 0.5% Dichlorvos was the best treatment followed by cent per cent kerosene or petrol then covering with clay. Painting with 10% Bordeaux mixture with 0.5% Dichlorvos in the trunk region up to 30-40 cm height significantly reduced egg laying in the month of June-July. Further works are in progress to develop integrated pest and diseases management modules specific to north eastern states of India</div>
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