Toxicity of the insect growth regulator novaluron to the non-target predatory bug Podisus maculiventris (Heteroptera: Pentatomidae)
Novaluron is a novel insect growth regulator that exhibits potent insecticidal activity against the Colorado potato beetle, Leptinotarsa decemlineata (Say). The predatory bug Podisus maculiventris (Say) is a natural enemy of the potato beetle found throughout North America, and is widely available commercially. Anticipating the use of novaluron in L. decemlineata management, we conducted laboratory experiments to determine the susceptibility of P. maculiventris to novaluron. Although there was a 2- to 3-day delay in the onset of toxic effects, second instars were susceptible by direct contact and through exposure to potato foliage treated with field rates. When P. maculiventris eggs were dipped in field rate novaluron solutions, there was no significant effect on percent hatch, but there was subsequently a sharp decrease in the ability of hatched nymphs to molt. Similarly, fifth instars actively preyed on L. decemlineata larvae dipped in field rate novaluron solutions, but were thereafter unable to molt into adults. Female P. maculiventris adults caged with L. decemlineata larvae and novaluron treated potato plants had reduced longevity compared to those caged with untreated potato plants. Further, oviposition and hatch of eggs from adults on novaluron treated plants was significantly reduced. Although novaluron has demonstrated selectivity in favor of beneficial insects in other studies, these results suggest that P. maculiventris would be adversely affected.