Efficient resin production using stimulant pastes in Pinus elliottii × P. caribaea families

To address the increasing labor cost of resin tapping, more efficient methods for resin tapping need to be developed. This study aimed to evaluate the features of resinosis as affected by stimulant pastes in Pinus elliottii × P. caribaea, which is also one of the predominant resin-producing species hybrids in South China. The resin yields and resin compositions were assessed in 33 P. elliottii × P. caribaea F₁ families, with the application of four kinds of chemical stimulants, potassium (K₂SO₄) paste, naphthalene acetic acid (NAA) paste, benzoic acid (BA) paste and 2-chloroethylphosphonic acid (CEPA) paste. Our results showed that all four pastes significantly increased the resin yield by at least 20% at each tapping, and 3- to fivefold increases were detected at the beginning of each year. The correlations between resin yield and growth at each tapping ranged from uncorrelated to moderately positively correlated, indicating that resin yield was mostly but not always determined by tree size. The concentration of each resin component did not change with the stimulant applications. In P. elliottii × P. caribaea, selecting a larger tree diameter at breast height and employing the chemical stimulants at the first several tapping rounds are efficient tapping procedures. Moreover, the K₂SO₄-based stimulant can be recommended considering its promoting effects on resin yield and the low cost of the chemicals required to produce it.