Fertilization and inoculum density affect susceptibility to fusiform rust and gall development in slash pine and loblolly pine seedlings
Plant Disease Reporter 61(7): 609-612
Susceptibility of Pinus elliottii var. elliottii and P. taeda seedlings to Cronartium fusiforme was significantly influenced by fertilization, inoculum density (ID), host species, and the interaction of fertilization and host species. Fertilization also interacted with ID to affect the susceptibility of slash, but not loblolly, pine seedlings. Susceptibility tests should include seedlings both fertilized and not fertilized before inoculation with a specified inoculum density to ensure reliable data for comparisons of slash and loblolly progenies. Seedling height and top weight growth were increased by fertilization. Increase of the ID, and consequently the number of infected seedlings and probable number of infections causing each gall, did not reduce seedling growth. Slash pine seedlings were taller than loblolly seedlings at inoculation and 9 mo. after inoculation. Fertilized loblolly grew faster than fertilized slash seedlings. Galls grew faster on fertilized than nonfertilized seedlings of both species, on slash than loblolly, up the stem in slash than downward, and down the stem in loblolly than upward.