ISHS Acta Horticulturae 494: II International Symposium on Chestnut
A METHOD FOR EVALUATING THE DEGREE OF DEFOLIATION ON CHESTNUT TREES AFFECTED BY THE INK DISEASE |
| Authors: | M.T. Oliveira, L.M. Martins, C.G. Abreu |
| Keywords: | Castanea sativa, Phytophthora cinnamomi, Ink disease, Beer's law |
| Abstract:
The stands of chestnut trees (Castanea sativa) in Northeast Portugal are affected, with a different degree of severity, by the ink disease that leads to a general decline of the chestnut stands. The first visible results of the disease are the yellowing of the leaves and the partial defoliation of the canopy. In later stages the trees are killed. The evaluation of the yellowing and defoliation is visually based on a comparison with trees unaffected and classified within percentual classes of damages. The visual appraisal of the canopy aspect regarding the severity of the ink disease results in a subjective evaluation of the damages. The loss of leaves and their yellowing modify substantially the canopy's intrinsic properties of interception of the solar radiation and the principles of radiation geometry can be used to estimate the distribution of the solar radiation within a plant canopy. As the damage inflicted by the disease increases, the amount of radiation passing through the chestnut canopy will increase as well. Commercially available instruments can measure the total PAR and the PAR under the canopy at a given moment. We found a functional relationship, statistically reliable, between the amount of PAR passing through the tree canopy and the classes of combined damages. It provides a simple and fast process capable of reducing the subjectivity out of the visual evaluation. | |
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