Maintained and supported by the Forest Health Technology Enterprise Team, the White Pine Blister Rust Model available as an extension to FVS is based on the original work of Geral I. McDonald, Raymond J. Hoff, and William R. Wykoff, documented in USDA Forest Service Research Paper INT-258 (1981). It simulates the life cycle of cronartium ribicola and the resulting mortality of white pine.
The original computerized version of the model was translated to FORtrAN and linked to FVS in 1990. A workshop was held in Spokane, Washington, in 1991, at which the implementation and operation of the model was demonstrated and reviewed. The results of that workshop were the basis for modifications to the model and its parameters in the following years. The model has recently been enhanced to also recognize sugar pine, but specific model parameter values for sugar pine have not yet been developed. This enhancement was designed to facilitate the inclusion of additional pine species as research findings become available. The incorporation of new ideas and recent research findings has brought the model to its current state.
The blister rust index, a measure of white pine blister rust infection level or potential for a site, area, or stand, drives the model. The initial value of the blister rust index can be provided by the user, calculated from current infections provided with inventory data, or calculated based on Ribes populations (white pine blister rust-Cronartium ribicola-is heteroecious and its alternate host is Ribes). Three principle Ribes hosts are represented in the model: Ribes hudsonianum, Ribes lacustre, and Ribes viscosissimum. Population control of the alternate host is one option available in the model to affect the pine infection rate.
Pine infection rate is also dependent upon target (leaf/needle) area as well as the blister rust resistance of the pine stock. Pine species is represented in the model with four stock types per pine species. The user can specify resistance factors of the stock types and also use these values for calibration. Options available to manage existing infections on trees include pruning of branch cankers and excising of bole cankers. The white pine blister rust model causes top kill and tree mortality, but does not impose reductions to FVS estimated height and diameter growths.