VIEW ARTICLE

Disease Detection and Losses

Evaluation of a Mechanistic Model that Describes Potato Crop Losses Caused by Multiple Pests. Kenneth B. Johnson, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902; Phytopathology 82:363-369. Accepted for publication 11 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-363.

Potato yield and foliage loss expectations for solitary and concurrent infestations of potato leafhopper (Empoasca fabae), early blight (Alternaria solani), and Verticillium wilt (Verticillium dahliae) were developed with a crop growth simulation model and compared to data obtained when these same organisms were studied in a factorially arranged field experiment. The principal conclusion from both the field and simulation approaches was that concurrent infestations of potato leaf-hopper, A. solani, and V. dahliae result in yield and foliage reductions that are less than the sum of losses caused by a solitary infestation of each organism. The simulation model provided a mechanistic framework for understanding the basis and importance of various types of pest-pest interactions. This led to the conclusion that competition between the diseases and potato leafhopper to impact photosynthetic carbon assimilation was the dominant interaction in this system. Results obtained are discussed in relation to development of empirical, regression-based models for estimating the impact of multiple pests on crop productivity. Models based on cumulative radiation interception may be one of the few empirical approaches that can provide reproducible interpretations of the effects of multiple diseases, insect pests, and other constraints on potato crop yield.