Influence of Oak Control and Pine Growth on Fusiform Rust Incidence in Young Slash and Loblolly Pine Plantations

Abstract

Abstract The influence of oak control and pine growth on fusiform rust incidence (percentage trees infected) on rust-susceptible slash and loblolly pines was evaluated at age 5 yr at seven potentially high-rust-incidence locations in the Coastal Plain of FL, GA, and MS. Rust-susceptible oaks were reduced or eliminated in a 9 ac treatment block and the surrounding 500 ft border zone of an oak-free (OF) area; oaks were not controlled in an adjacent oak-present (OP) area. At four of seven locations, rust incidence was significantly greater on the OF areas compared with the OP areas, and among all locations, average rust incidence on pine was greater (Pr > F = 0.06) on the OF areas (51.4%) than on the OP areas (40.0%). Greatly reducing rust-susceptible oak stems in the treatment blocks and in a surrounding 500 ft border did not reduce rust incidence on rust-susceptible slash or loblolly pine. Inoculum to infect pine came from beyond the 500 ft border zone. Greater pine height, associated with reduced competition from oaks, likely contributed to the greater rust incidence on pine in the OF areas. South. J. Appl. For. 19(4):151-156.