Development of a Prediction Model for Papaya Ringspot in Veracruz, Mexico. Gustavo Mora- Aguilera, Former Graduate Assistant, Centro de Fitopatología, Colegio de Postgraduados, 56230 Montecillo, México. Daniel Nieto-Angel, Daniel Téliz, and C. Lee Campbell. Graduate Assistant, Professor, Centro de Fitopatología, Colegio de Postgraduados, 56230 Montecillo, México; and Professor, Department of Plant Pathology, North Carolina State Univesity, Raleigh 27695-7616. Plant Dis. 77:1205-1211. Accepted for publication 24 August 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1205.

A model to predict incidence of papaya ringspot was developed and validated from 5 yr of field observations in central Veracruz, Mexico. The model was developed from 1 yr of data collected from papaya (Carica papaya) plantations in two different locations in Veracruz during 1985–1986. Incidence of papaya ringspot was evaluated every 15 days, and viral infection was confirmed by ELISA. Aphid vectors (Myzus persicae, Aphis gossypii, A. nerii, A. citricola, and Macrosiphum euphorbiae) of papaya ringspot virus were collected every 3 days from Moericke yellow pan traps placed at each location. The prediction model was obtained from an examination of the matrix of Pearson’s correlation coefficients and by simple and multiple regression analysis. Model selection was based on Mallow’s C_p statistic, proportion of variance explained, variance inflation factor, analysis of structure, and predictive capacity. The largest amount of variation in the data was accounted for by model y = – 1.45 + 0.42 AN₅ + 0.00016 PW + 0.116 AG₅ – 0.0058 AN₅² – 0.0057 MP₅², in which y was the incremental increase of disease ( y _t – y _t–1) at any given time (t); AN₅, AG₅, and MP₅² were the numbers of the alate aphid species A. nerii, A. gossypii, and Myzus persicae, respectively. PW was an interaction variable defined as the product of precipitation (P) and speed and duration of wind from the north (W). Values for independent variables were accumulated during a 4-wk period that ended 3 wk before the calculated incremental increase of disease. The equation accounted for 78% (R² ? 0.78) of the total variation of the change of disease incidence ( y _t – y _t-1) in the original data set. Validity of this model was tested with data obtained from 60 epidemics in papaya plantations established from 1987 to 1989 to represent different dates, plant densities, and plantation sites. The model predicted the relative rate of disease increase in 38% of the epidemics (23 of 60, R² ? 0.60). Three other models that accounted for less variance explained in the original data set than the first model (R² < 0.78) were also validated. One model predicted the incremental increase in disease incidence of 40% of the papaya ringspot epidemics (24 of 60) with R² ? 0.60. In this model, the disease incidence change was explained by the independent variables AN₅, AG₅, and PW.