Essential oil components in superabsorbent polymer gel modify reproduction of Blattella germanica (L.) (Blattodea: Ectobiidae)

The use of essential oil components (EOCs) against the German cockroach, Blattella germanica (L.), has increasingly received attention from researchers. However, the determination of lethal doses/concentrations alone does not provide enough information on the range of biological effects of these EOCs. To improve our understanding of the potential effects of EOCs, we examined biological parameters of B. germanica exposed to sublethal EOCs formulated in gels. This study employed superabsorbent polymer (SAP) gel to prolong bioavailability of limonene, carvacrol, and β–thujaplicin, and evaluated how these EOCsshape biological parameters of B. germanica. Overall, median survival days ranged from 57 – 69.5 d for males and 73 – 99 d for females. The survival day ranking for the EOCs was limonene > β–thujaplicin > carvacrol. Carvacrol and β–thujaplicin gels reduced male longevity by at least 34% and 39%, respectively, while limonene had no effect. The longevity of females was reduced by limonene, but not carvacrol and β–thujaplicin gels. EOCs significantly suppressed overall adult females’ reproductive period, oothecal hatchability, reduced fecundity, and interoothecal period. The preoviposition period (mean: 2 – 25 d) ranking was limonene < carvacrol < β–thujaplicin. Based on these results, limonene, carvacrol, and β–thujaplicin in superabsorbent polymer gels show promising potential to reduce adult male survival/longevity, suppress egg hatchability, and female fecundity, and to delay the interoothecal period. These findings may represent the basis for the practical use of EOCs as a tactic in integrated pest management systems for B. germanica.