Control of the Colorado potato beetle (Leptinotarsa decemlineata [Say]) on potato under field conditions: a comparison of the efficacy of foliar application of two strains of Steinernema feltiae (Filipjev) and spraying with thiametoxam

Abstract

The efficacy of entomopathogenic nematodes in controlling Leptinotarsa decemlineata on potato was tested in a field experiment. A Slovenian strain of Steinernema feltiae (B30) was used with the commercial product Entonem and the insecticide thiametoxam. The application of the nematodes and thiametoxam was repeated twice. In the second application half of the first dose (250.000 infective juveniles m–2) was used. Observing the population dynamics of the pest, it has become apparent that entomopathogenic nematodes significantly decreased the number of larvae, while no effect on their eggs and adults was confirmed. In controlling larvae in both years thiametoxam showed the best results in general, meanwhile treatments with EPNs showed no differences. In both years the highest yield was obtained when thiametoxam was used (2008: 24.38 t ha–1; 2009: 21.60 t ha–1), while the lowest yield was in the control treatment (2008: 7.65 t ha–1; 2009: 6.94 t ha–1). Different treatments of EPNs showed differences, and yields ranged from 16.44 (S. feltiae B30 low concentration) to 17.81 t ha–1 (Entonem high concentration) in 2008, and between 11.06 (S. feltiae B30 low concentration) and 14.88 t ha–1 (Entonem high concentration) in 2009. Both strains of entomopathogenic nematodes showed sufficient activity when controlling larvae, but unfortunately the high price of these biological agents at the moment makes it difficult for their broader implementation in the systems of potato production.