Young loblolly and slash pines are very susceptible to fusiform rust – a fungus that results in tapered, spindle-shaped swells on branches and stems. Mortality is highest in stands younger than 10 years of age and might account for the second greatest loss of loblolly pine timber behind the southern pine beetle. The life cycle of the rust is associated with oak species, where the fungus develops before invading the pines. Rust ratings have been established to help with placement of plantations and genetic breeding of seedlings has helped produce future generations of rust-resistant pines. Most genetically improved stock is less susceptible to fusiform rust.
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