EVALUATION OF 2 LEAFHOPPER SAMPLING METHODS FOR PREDICTING THE INCIDENCE OF A LEAFHOPPER-TRANSMITTED VIRUS OF MAIZE

Two sampling methods for estimating the abundance of corn leafhopper, Dalbulus maidis Delong & Wolcott, were evaluated for predicting the incidence of maize rayado fino virus (MRFV), a virus transmitted to maize in a persistent manner by D. maidis. Leafhoppers were sampled weekly using both counts of insects on plants and yellow sticky traps in maize planted at two densities, and the incidence of MRFV was recorded twice during that period. There were fewer leafhoppers per plant, a lower incidence of MRFV, and fewer virus-infected plants per square meter in maize planted at a higher density, but there were no differences in the number of leafhoppers caught per trap or in the number of leafhoppers per square meter. Multiple regression analysis revealed that the number of leafhoppers per plant was a reliable predictor of disease incidence, but no relationship between trap catch and disease incidence could be detected. These results suggest that counts of vectors on plants may be more reliable than sticky traps for predicting the incidence of persistently transmitted plant pathogens.