Can tapping panel dryness of rubber ( Hevea brasiliensis) be minimised at field level with better management?

Abstract

This study attempted to find the significance of tapping panel dryness (TPD) of extensively grown new clones in Sri Lanka, with a view to find possible ways to minimise or overcome this disorder at field level. A survey done for clones RRIC 100, 102, 121 and 130 showed that the incidence of TPD was high when tapping is done in renewed bark compared to that of virgin bark and it increased with the advancement of the tapping panel from B0-1 to Bl-2. Also, % TPD increased with age, immature period, girth of plants, yield and with high intensity of tapping. Generally, the % TPD (partial + full) was high in RRIC 100 (22.5%) and RRIC 102 (19.7%) clones compared to the other clones surveyed. On average in any clone, 40% of the dry trees were with a partial dryness. The estimated average yield loss per tapping panel of RRIC 100 was ca. 20% and for the other clones surveyed it was ca. 15%. Morphologically, the majority of the TPD affected trees were without external symptoms (52%), whilst very few (3%) was with abnormal out growth on the trunk and the rest was with bark necrosis, which is irreversible. Since the TPD incidence was high in shallow areas (<10° land gradient) where water logging and occasional floods occur, such areas should be avoided in planting of rubber in future. Good quality planting material should also be used and the immature upkeep should be of good quality to minimise the immature period and any plant stresses. Implementation of low frequency tapping systems will also be helpful in controlling this disorder.