Predicting site hazard to fusiform rust.

Abstract

Nine plantations of slash pine Pinus elliottii var. elliottii were established in 1974 in S Mississippi to study conditions affecting incidence of fusiform rust (caused by Cronartium quercuum f.sp. fusiforme). Variables studied included climate, seed source, soil properties, pine growth, fungus and host phenology, abundance of aeciospore-producing galls and telia, number of basidiospores trapped, and the spatial relationships of oaks Quercus to the plantations. From 1974-1978, the amount of pine infection varied considerably by year according to frequency of rain or nights with prolonged high relative humidity. There also were large, but inconsistent, differences in annual infection among sites, due to a complexity of factors. Seed source, soil properties, and pine growth were unrelated to site hazard. The hazard of each area depended on the relationships of oaks to the pine plantations-how near they were, what directions from the plantation, and the number of oaks. Criteria are presented for differentiating among low-, medium-, and high-hazard sites for fusiform rust. -Authors