In order to evaluate the improvement of rubber productivity of rubber trees by late upward tapping. A study was conducted at SCASO (Société Civile Agricole du Sud-Ouest) on the PB 260 clone of the active metabolic class. The experimental set-up is a Fisher block design with eight treatments and three replications. The treatments compared were bled in reverse in the eleventh year of harvest, in quarter spiral every 3, 4, 5 and 6 days, with stimulation frequencies of 6, 8, 10, 12 and 13 times a year. The parameters measured were rubber production, isodiametric growth, sensitivity to dry notching of trees and physiological profile. The results show that the different latex harvesting technologies improve the rubber productivity of PB 260 (5469 kg.ha-1.yr-1) with a low dry-nut rate (1.2%) and satisfactory radial vegetative growth (3.9cm.yr-1). The physiological profile of the trees is balanced, but the treatments significantly influenced the different parameters except sucrose. Trees bled in S/4U d3 gave better results due to their high yield with an acceptable dry notch rate. Late reverse tapping is therefore a good latex harvesting technology for improving rubber productivity after down tapping.

The classic latex harvesting system consists of top-down tapping for nine years before being immediately followed by reverse tapping. This period is often considered too long by the farmers. To address this concern, a study was conducted to determine the best period for down tapping to ensure good performance of agrophysiological parameters in reverse tapping of fast metabolising rubber clones. For this purpose, the PB 260 and IRCA 18 clones were used as plant material in Divo and Daoukro respectively, where the experiments were conducted. Five time frames for down-bleeding (5, 6, 7, 8 and 9 years = control) and two concentrations of ethephon (ET) stimulating paste (2.5 and 5% ET), except for the control which is stimulated only at 5% ET, were tested. The experimental design was a Fisher block design with 9 treatments and 4 replicates. Rubber productivity results (5262 ± 205 and 4951 ± 351 kg.ha-1.yr-1) showed that reverse tapping of these metabolically active clones preceded by 5 and/or 6 years of down tapping was the best (3723 ± 29 kg.ha-1.yr-1 ; control). Rubber production and average annual increment from these tapping periods (4.00 ± 0.42 and 3.60 ± 0.00 cm.yr-1 ; control) were the highest. Productivity gains were 41% for reverse tapping at 6 years stimulated at 5%. The dry notch rate was relatively low (3.30% LEM and 0% dry trees). The physiological profile was generally good. These results indicate that downward bleeding for 5 and/or 6 years allows these clones to express their best potential in reverse bleeding. These results are satisfactory and respond exactly to the concerns of the farmers.

In order to evaluate the effect of early upward tapping on rubber productivity of rubber trees and to determine its proportion relative to downward tapping, a study was conducted at SAPH Divo on the PB 260 clone of the fast metabolic activity class. The experimental set-up was a Fisher block with seven treatments and three replications. Tapping was carried out in d3 with 6 stimulations. Three upward tapping times at 6, 7 and 8 years, each coupled with two concentrations of the stimulating paste 2.5 and 5% of Ethephon and a downwardly tapped control stimulated with 5% of Ethephon were tested. The data collected were for rubber production, isodiametric growth, tapping panel dryness susceptibility and tree physiological profile. The results showed that the different treatments tapped in upward at 6, 7 and 8 years of age significantly improved the productivity of the PB 260 clone relative to the control by downward for nine years. All treatments combined, rubber productivity (4723 kg.ha-1.yr-1) and radial vegetative growth (3.8 cm.yr-1) were good. The gain in rubber productivity of the early upward tapping compared to the downward tapping was 42%. The tapping panel dryness rate was low at 2.6% and the physiological profile of the trees was well balanced. Our results suggest that PB 260, and therefore metabolically active clones, can be tapped in early upward tapping, especially at 6 years of age.