P.C.N. Azevedo's scientific contributions

The production of oleoresin from Pinus trees is a relevant economic activity in developing countries, since it provides terpenes used in the chemical industry. The oleoresin production by trees of Pinus elliottii in southern Brazil was investigated. Trees of approximately 28 years of age were individually analyzed for oleoresin yield using the bark streak method of wounding for resin tapping. Plain wounding and wounding followed by application of commercial resin stimulant paste, composed of an ethylene precursor (CEPA) and sulphuric acid, were used as reference treatments. The optimum concentrations of CEPA and sulphuric acid in the stimulant paste were investigated in relation to oleoresin yield, as well as the shape of wound and tree diameter. The replacement of CEPA with auxin in the resin stimulant paste was also evaluated. The results showed that both horizontal and V-shaped streaks are equivalent for oleoresin yield. Trees with larger diameter at breast height, defined as the trunk diameter 1.4 m above the ground (22–23.5 cm) yielded more oleoresin than their smaller counterparts (18–19.5 cm). Oleoresin yield was equivalent with stimulant pastes containing between 1.5 and 4.5% CEPA. Trees exposed to stimulant pastes containing from 3 to 4.5% CEPA had average year oleoresin yield above 5 kg. The use of 20% sulphuric acid in the stimulant paste resulted in higher oleoresin yields. Auxin (2,4-D at 1 mM) was effective in replacing CEPA in the stimulant paste, particularly in smaller DBH trees or after 1 year of application in larger DBH individuals. In conclusion, cost reductions on resin tapping can be achieved by adjusting stimulant paste components and managing subsets of trees in specific fashion based on DBH ranges.