Side effects of garlic extract on the life history parameters of the predatory bug, Podisus maculiventris (Say) (Hemiptera: Pentatomidae)

Abstract

As an organic insecticide, a sub-lethal dose of garlic causes disruption in the development and reproduction of insects and reduces fitness rate in some pest species. The aim of this study was to evaluate the side effects of garlic extract (GE) on the reproductive life table parameters of the predatory bug, Podisus maculiventris. The effects of different concentrations of GE were assayed on the fourth instar nymphs by topical application, a 10% v/v concentration being selected to evaluate life table parameters of the predator in comparison to the control. Data analysis used the age-stage, two-sex life table method and results showed negative effects of garlic on the intrinsic rate of increase (r), finite rate of increase (λ) and mean generation time (T) in the treated population compared with the control. There were no significant differences in net reproductive rate (R0) or the gross reproductive rate (GRR) between GE and control. In contrast with previous studies on pest insects, the present research showed GE should be considered as a botanical pesticide in cases where this natural enemy plays a main role in pest control. In addition, reviews have raised concern over the relationships between their sulphur-containing compounds and human health, but garlic extract would have no negative effects. Results suggested that as a green pesticide, GE presents a new and environmentally sustainable alternative for application in pest management programs where P. maculiventris or similar predatory bugs are important natural enemies.