ISHS Acta Horticulturae 184: I International Symposium on Computer Modelling in Fruit Research and Orchard Management
METHODOLOGICAL COMPARISON OF THREE APPLE SCAB SIMULATORS |
| Author: | R.C. Seem |
| Abstract:
Within the past ten years at least three major attempts have been made to develop apple scab disease simulators in North America. These include: VISIM, by A. L. Jones, T. B. Sutton, and J. Bobzin (Michigan State University, East Lansing, MI); APPLESCAB, by P. A. Arneson et al. (Cornell University, Ithaca, NY); and a simulator by K. P. Minogue (McGill University, Montreal, Quebec). All the simulators had common ancestry in the wealth of apple scab literature, and all were programmed in FORTRAN IV. However, the design and methodology of each simulator was uniquely different. VISIM is designed to address a major portion of the pathosystem, from ascospore dispersal to end-of-season disease levels. Considerable detail is given to the components of spore deposition, survival, germination, and penetration. Advantages of the simulator are the detail of the modeled components based on a very thorough examination of published information. Disadvantages include the need for large amounts of computer processing time, the exclusion of fruit disease, and the exclusion of the over-wintering phase of the disease cycle. APPLESCAB is a production system model designed as an instructional tool to demonstrate disease control decision-making. The apple scab simulator is contained within the production model. The simulator considers the whole pathosystem including fungicide management, fungicide resistance, and variable weather, however, it is in considerably less detail than VISIM. The main disadvantages are the many assumptions based on little or no supporting data. The unique feature of the Minogue simulator is its use of analytical equations to describe the major components of the disease system. The equations are time-varying distributed delays and are used to move the pathogen from one developmental stage to the next. The model also emphasizes spore dispersal and deposition. Disadvantages of the model include the use of a single-season time frame without over-wintering, and limited environmental and management constraints on the model. All three approaches offer significant insight into the simulation of the apple scab pathosystem, however none of them provide a complete simulator for research and management purposes. Because of improvements in technology and knowledge since the development of these simulators, a new, cooperative effort should be made to produce a comprehensive apple scab simulator that can be used for research and management decision-making. | |
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