Cross sectional life table analysis of fusiform rust incidence and severity among slash pine plantations in north florida usa
Applied Agricultural Research 5(4): 302-308
A cross-sectional life table analysis of fusiform rust incidence and severity was performed among living hosts in a narrowly defined geographic area in northern Florida which had been rated high-hazard for the disease. One 0.1-ha plot was selected from each of two separate but equally aged slash pine (Pinus elliottii var. ellottii) plantations in 10 different age classes, i.e., 1-7, 10, 13, and 20 years. Disease incidence was initially low (3%) but increased in year two (52.1%) and was consistently high (47.5-82.9%) among the remaining age classes. Branch symptom frequencies were predominant among the hosts in the younger age classes but decreased over time. Branch-stem combination and stem symptoms increased from intermediate and low levels, respectively, to levels approximately equivalent to branch symptom frequencies by year 20. Except for negligible infection levels in year one, 50 + % of the trees in all remaining age classes exhibited five or fewer symptoms even through occasional individual trees in several age classes possessed as many as 18 symptoms. Eight symptom types were recognized and their probabilities of occurrence were computed at each symptom level in each age class. Cross-sectional life table analysis proved a useful means of describing the dynamics of fusiform rust symptom development among living hosts in this composite data set but specific restrictions must be applied to its use and interpretation of results.