ABSTRACT The use of the Ethrel® stimulant on rubber cultivation has become essential to ensure greater rubber production. When applied on the cut of the tree, this stimulant releases the ethylene gas that causes an increase of the exudation period of the latex flow. Dilutions and applications should be performed correctly so that they do not cause tapping panel dryness, which would leave the plant unproductive for a long time. Thus, the objective of this study was to evaluate the effects of increasing doses of ethrel on tapping panel dryness and rubber production of rubber tree clones. Three experiments were conducted using a randomized block design with four treatments (ethrel doses) and three replicates. The clones used were RRIM600, PR255 and PB217 submitted to doses of the stimulant Ethrel 0%, 2.5%, 3.3% and 5% with an interval of application of 30 days. The d/7 bleeding system was used. The productive performance was evaluated monthly and the total of plants with tapping panel dryness at the end of the work. All clones presented a linear positive response to increasing doses. The dose of ethrel 5% favors higher rubber yields in the three evaluated clones, but is associated with high percentage of drying. Thus, it was concluded that the production of rubber is affected positively with the increase of ethrel doses, but this increase causes a higher incidence of panel drying. Thus, it is recommended to use the ethrel 2.5% dose so the production is guaranteed without causing the tapping panel dryness.

ABSTRACT The use of the Ethrel® stimulant on rubber cultivation has become essential to ensure greater rubber production. When applied on the cut of the tree, this stimulant releases the ethylene gas that causes an increase of the exudation period of the latex flow. Dilutions and applications should be performed correctly so that they do not cause tapping panel dryness, which would leave the plant unproductive for a long time. Thus, the objective of this study was to evaluate the effects of increasing doses of ethrel on tapping panel dryness and rubber production of rubber tree clones. Three experiments were conducted using a randomized block design with four treatments (ethrel doses) and three replicates. The clones used were RRIM600, PR255 and PB217 submitted to doses of the stimulant Ethrel 0%, 2.5%, 3.3% and 5% with an interval of application of 30 days. The d/7 bleeding system was used. The productive performance was evaluated monthly and the total of plants with tapping panel dryness at the end of the work. All clones presented a linear positive response to increasing doses. The dose of ethrel 5% favors higher rubber yields in the three evaluated clones, but is associated with high percentage of drying. Thus, it was concluded that the production of rubber is affected positively with the increase of ethrel doses, but this increase causes a higher incidence of panel drying. Thus, it is recommended to use the ethrel 2.5% dose so the production is guaranteed without causing the tapping panel dryness.