The surstimulation in exploitation of Hevea brasiliensis clones leads to a high rate of unproductive trees due to tapping panel dryness (TPD), and a drop of yield due to the unknown of their yield potential. This study was conducted during 9 years in the south eastern Côte d'Ivoire on clone GT1 of Hevea brasiliensis to determine the best regime of hormonal stimulation that can allow it to express its rubber production potentialities. The GT 1 is a clone at moderate metabolic activity, little susceptibility to wind breakage and TPD, it's the most widely planted clone in Côte d'Ivoire. The plot was planted at the density of 510 trees/ha (7 m x 2.80 m) according to a "one-tree plot design". Thirteen three trees per treatment were chosen in total randomization. Trees were tapped in S/2 d4 and stimulated with Ethephon 2.5 % at varied frequencies from 0 to 78 per year. The measured parameters included rubber yield, radial vegetative growth, physiological profile and the sensitivity to tapping panel dryness of trees. The results showed that 4 hormonal stimulations per year are sufficient to this clone, to reach its higher yield in tapping in S/2 d4 without causing prejudices on the vegetative growth, physiological profile and sensitivity of tapping panel dryness. This study can be lied down at other region of Côte d'Ivoire for the improvement of the exploitation of clones and optimize yield of plantations.

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The downward tapping on virgin bark of the lower panel (BO) is immediately followed by the upward tapping on virgin bark of the upper panel (HO), consecutively. To determine the agro-physiological advantages of one tapping over another, a study of the downward and upward tapping of the GT 1 and PB 260 clones of Hevea brasiliensis was carried out in southwestern Côte d'Ivoire. For this purpose, the rubber trees were tapped in a downward half-spiral (S/2) at the opening for nine consecutive years, followed by upward quarter-spiral tapping (S/4U) for four consecutive years. The agronomic parameters (rubber production and vegetative growth), tapping panel dryness and the latex micro-diagnosis, were evaluated. For GT 1 clone, the transition from the downward tapping panels to the upward tapping panels resulted rubber productivity gain of 35%. Meanwhile for PB 260, rubber productivity gain was 37%. Regardless of the clone and tapping direction, the higher the rubber productivity of a respective tapping panel, the lower the isodiametric growth of the tree trunk was recorded. Latex harvesting systems, and clone’s combination, did not influence the tapping panel dryness or the physiological profile of the trees. Finally, it should be concluded that upward tapping is more productive than downward tapping, but the quantification of the gains in this rubber production depends on the clone.

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