Nine of them were treated using a 1.5 cm, lightly scrapped suber strip beneath the next tapping cut, similar to that described by Tungngoen et al. (2009), with 1 g of crude palm oil emulsion containing 0.05% Tween 20 and about 70 μmoles of either 4-chlorophenoxyacetic acid (4-CPA) (synthetic auxin), ABA, or SA, for 4, 8 and 16 h before the first tapping.