New Economic Threshold for Striped Cucumber Beetle (Coleoptera: Chrysomelidae) in Cantaloupe in the Midwest

Abstract

Field experiments were performed in 2 locations in Indiana in 1993, 1994, and 1995 to determine the relationship between striped cucumber beetle, Acalymma vittatum (F.), density and the incidence of bacterial wilt in cantaloupe. The striped cucumber beetle is the primary vector of Erwinia tracheiphila (Smith) Holland, the causal agent of bacterial wilt in cucurbits, during the spring in the Midwest. Based on laboratory findings, initial densities of 0, 1, 5, and 15 beetles per cantaloupe plant were evaluated. Regression analyses showed that at beetle densities of 1–15 per plant there was a strong and significant linear relationship between numbers of beetles per plant and the percentage of cantaloupe plants with bacterial wilt. No cantaloupe plants developed bacterial wilt at a density of 0 or 1 beetle per plant during the 3-yr study at either location. To further define beetle density requirement, the densities of 0, 1, 2, 3, 4, and 5 beetles per plant were used in 1995. During these trials, there was no wilt at the 0 or 1 beetle per plant densities and significant wilt development did not occur until beetle densities reached 4 or 5 beetles per plant. Only 2 experimental trials showed significant yield losses from increasing beetle densities. In each trial, no yield loss was associated with beetle densities lower than 4 beetles per plant. Use of an economic threshold of 1 striped cucumber beetle per plant in the Midwest should greatly reduce insecticide applications in cantaloupe, while providing good control of the vector and bacterial wilt.