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Control of stem-end rot disease in mango fruit cultivar ‘Karuthacolomban’ using non-agrochemical methods

Nimal Adikaram: National Institute of Fundamental Studies

<div>The local mango cultivar ‘Karuthacolomban’ is highly susceptible to stem end rot (SER) and presently the disease is controlled by synthetic fungicides. The study investigates alternate methods to reduce SER in mango. At the pre-harvest stage, the amount of potassium fertilizer added to trees was altered. Fifteen year old fruit-bearing trees (6 per treatment arranged as a CRBD) were provided with soil fertilizer at the fruit development stage as recommended, but varying the level of potassium. SER development was assessed in harvested fruits from both natural infections and following artificial inoculation. In a separate postharvest dip application, the effect of selected essential oils (EO) in reducing SER was tested. Six EOs were tested at concentrations 500-1000 μl l-1 by <i>in vitro</i> Poisoned food bio-assay against <i>Lasiodiplodia theobromae</i> causing SER. The essential oils that gave a significant reduction (P<0.05) of radial mycelial growth in three replicate trials were used in <i>in vivo</i> fruit dip-treatments (3 min). In field trials, potassium at 3 x recommended dose reduced natural SER development, but reduction was not significant. SER was reduced significantly (P<0.05) in artificially inoculated fruits. The essential oils Basil, Cardamom (700 μl l-1) and Citronella (400 μl l-1) significantly reduced the <i>L. theobromae</i> growth<i> in vitro</i> and Cardamom oil at 700 μl l-1 significantly reduced the severity of SER <i>in vivo</i>. Neither pre nor postharvest treatments significantly affected sensory properties except for external peel appearance which was altered by EO treatment as indicated by a Principle Component analysis (PCA). Potassium is known to increase firmness of plant organs while EOs act directly on the pathogen in reducing SER in mango fruit.</div>