Boron Deficiency in Pines
Most species exhibit similar symptoms of boron deficiency including the cessation of growth of the main leader; terminal dieback is associated in some species with resin exudation; and crooked leader growth has been reported in several species of pine. The most characteristic symptom is the cessation of apical growth and the repeated death of the leading shoot. In P. radiata and P. taeda the growing points may become necrotic and the stem apex swell. Young needles adjacent to the apical bud may die and resin exude from the bud. In these two species the juvenile needles may be bluish-green color and the mature needles show a tendency to fuse.
Crooked leader growth has been especially reported on P. caribaea, P. khasya, and P. patula. P. khasya and P. patula seem less susceptible to boron deficiency than P. radiata and P. caribaea. In P. strobus the primary needles become light blue-green, with yellow/orange tips.