Nutrient Variables Associated with Tapping Panel Dryness and Necrosis Syndromes in Rubber Tree Clones RRIM600 and RRIT251

Tapping panel dryness (TPD) and tapping panel necrosis (TPN) are syndromes that reduce the yield of rubber trees. Their causes are associated with factors such as clone type, tapping system, and environmental stress and are potentially linked to nutrient deficiencies. This study aimed to investigate the causes of these disorders, with particular focus on their relationship with nutrient fluctuations in plant tissues. The experiment was conducted at rubber plantations owned by local farmers in Pakkhat District, Bueng Kan Province, Thailand, where soil fertility is generally poor. The plantations were 14–16 years old and had been tapped for 7–9 years. Two rubber tree clones (RRIM600 and RRIT251) were used to evaluate three different tree types: healthy, TPD-affected, and TPN-affected. For each clone, five plantations were sampled. The measurements included the incidence of abnormalities; trunk girth; yield; and nutrient concentrations in the soil, top shoot, bark, and latex. The nutrient analysis focused on nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and boron (B). The results showed that the incidence of abnormalities (both TPD and TPN) was higher in clone RRIT251 than in RRIM600. Yield was reduced in trees affected by TPD and was dramatically reduced in those affected by TPN. In RRIT251 trees affected by TPD, the lowest concentrations of K, Ca, and B were found in the bark, along with the lowest Ca concentration in the top shoot. These findings indicate that RRIT251 is more susceptible to bark necrosis than RRIM600 and that reductions in K, Ca, and B may be associated with development of the syndromes.