Population Dynamics of Heliothis virescens (F.) (Lepidoptera: Noctuidae) in a Host-Species Rich Agroecosystem: Implications for Insecticide Resistance Management

Abstract

A three-year evaluation of crop host utilization by the tobacco budworm, Heliothis virescens (F.), was conducted from 2001 to 2003 in the central coastal plain of North Carolina. Monitoring of commercial tobacco and non-Bt cotton fields revealed spatial and temporal patterns of host use, and showed that tobacco budworm may be produced in tobacco throughout the growing season. Small plot trials conducted in 2002 and 2003 demonstrated a strong oviposition preference by tobacco budworm for tobacco when located adjacent to alternate crop hosts. The bodies of individual moths were analyzed for the presence of a cotton-specific analyte, gossypol, using high-pressure liquid chromatography—mass spectrometry⁄mass spectrometry (HPLC-MSMS). This technique provides a conservative estimate of tobacco budworm production on hosts other than cotton. Analysis of feral moths revealed that <10% of tobacco budworms collected in North Carolina contained gossypol. Isotope ratio mass spectrometry (IRMS) analysis of 13C⁄12C ratios of moths reared on four crop-plant species and two common weed species revealed a range of d13C values within that expected for plants utilizing the C3 photosynthetic pathway. Feral tobacco budworm moths collected over three years were found to have carbon isotope ratios consistent with those having fed on C3 plants. No unique carbon isotope signature was discovered that would enable a reliable determination of natal origin of feral tobacco budworm with current IRMS technology. Dose-mortality studies were conducted in 2004 to determine the susceptibility of two North Carolina strains of tobacco budworm to cypermethrin. LD50 values were 4 and 9 times greater for tobacco budworms collected in June and August respectively than for a susceptible laboratory strain. Foliar applications of pyrethroid insecticides were made to flue-cured tobacco for control of the tobacco budworm in 2001, 2002, and 2003. Pyrethroids provided significant control of tobacco budworm when compared to untreated checks in all three years of the study; however, they were generally less efficacious than the standard insecticides tested.