Management of pre- and post-harvest diseases of mango (Mangifera indica L.) cv. 'carabao' using its natural resistance mechanisms
2006
Porras, M.J.P., Philippines Univ. Los Banos, College, Laguna (Philippines)
The study was conducted in Davao del Norte and Davao del Sur, representing a wet and a drier mango production systems respectively, to assess the field efficacy of resistance-enhancing treatments in reducing the pre- and post-harvest losses due to mango diseases. Three resistance-enhancing materials were used, namely Bion (Boost 500 SC or Acibenzolar-S-methyl), Kasil, (silicon-based formulation) and rice hull ash (RHA). Bion was applied as foliar spray, kasil as soil drench and RHA as mulch. The efficacy of these materials against pre- and post-harvest diseases of mango was evaluated under high and minimized (with fungicide spray) disease pressures. Results showed that the application of fungicide spray consistently reduced the severity of blossom blight and scab. When subjected to high disease pressure, the resistance-enhancing treatments failed to show suppressive effect on both diseases. Under minimized disease pressure, however, a reduction in disease severity was observed but only Bion provided a profound decrease in disease severity as compared with the control. The significant reduction of blossom blight severity due to fungicide and Bion was significantly translated into higher fruit yield. The other treatments did not improve fruit yield and quality of mango. Chemical analysis of fruits (peel and pulp) revealed that the resistance-enhancing treatments did not influence any change in the silicon content or the pH level of fruit peel and pulp. Fruits from trees sprayed with fungicide incurred lower and less severe fruit rot incidence and severity as compared to those with no fungicide spray. A remarkable reduction of fruit rot incidence and severity was found among fruits associated with Bion, Kasil and RHA. Such findings, however, were not consistent in another experimental site. Mango stem-end rot incidence was generally low in both sites, hence, the effect of resistance-enhancing treatments can not be reliably demonstrated. The failure of resistance-enhancing treatments to provide sufficient protection against fruit rot and stem-end rot had led to poor fruit quality. The saleable life index (SLI) was relatively short (1-3 days) and the visual fruit quality was rated very low. Fruit peel color development and physico-chemical changes in the fruit did not significantly differ among treatment combinations.
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