Frequent heavy rains are a major hindrance for rubber harvests in the coastal zone of Cameroon, due to the pouring of latex out of cups as a result of water overflow. Lowering the pH of latex with acid to accelerate its clotting could be a solution. A factorial experiment in vitro was conducted to assess the pH and the corresponding coagulation times of different treatments obtained from three volumes of latex (40, 80 and 120 ml), four rubber clones (GT1, PB217, PR107 and RRIC100), and seven doses of formic acid (0, 1, 2, 3, 4, 5 or 6 ml). The three volumes of latex were tested pure (no addition of rain water) or diluted (with an addition of 120 ml of rain water). A RCBD experiment in vivo was also carried out to assess the percentage of trees with coagulated latex in their harvest cups 5 hours and 30 min after addition of acid. Both experiments were repeated weekly during four months in the rainy season. The use of formic acid had a highly significant effect (P˂0.001) on lowering the pH and accelerating the coagulation of latex in vitro and no significant effect (P˃0.05) in vivo. An adjustment of the doses of formic acid to be used in the field might be necessary for a successful acidification of latex.
