Effects of Four Monoterpenoids on Growth and Reproduction of the German Cockroach (Blattodea: Blattellidae)

Abstract

The effects of the monoterpenoids d-limonene, linalool, beta-myrcene, and alpha-terpineol on the growth and development of the German cockroach Blattella germanica (L.) were examined. We evaluated the chemicals' attractiveness in cockroach diet, quantified growth effects induced by monoterpenoids, examined embryotoxic properties of the compounds, and examined their effects on reproduction when administered by oral, topical, and vapor routes of entry. Untreated diet was significantly preferred compared with diet treated with high levels of d-limonene, linalool, and alpha-terpineol. The threshold for acceptance was between 1 and 10% (AI). All four monoterpenoids significantly influenced the days required by nymphs to reach the adult stage; in general, higher monoterpenoid concentrations in the diet were associated with a reduction in the days required by nymphs to mature. Application of high doses of d-limonene or linalool to oothecae of gravid female cockroaches significantly decreased the probability of young emerging from them but did not affect female mortality. Feeding on diet treated with monoterpenoids during nymphal development and through the early, premating period of the adult stage did not significantly influence numbers of broods produced per pair, numbers of offspring per brood, days required to produce a brood, total offspring produced by a pair, or female life span. Topical applications of linalool, beta-myrcene, or alpha-terpineol at near lethal rates to adult cockroaches before they mated had no significant influence on the reproductive parameters examined. A single exposure to sublethal levels of monoterpenoid vapors before mating had no significant influence on any reproductive parameters examined.