An insecticide oral-dosing method for the German cockroach (Blattodea: Ectobiidae).

BACKGROUND

Insecticide baits are commonly used to control the German cockroach [Blattella germanica (L.)]. Because bait performance is dependent on foraging and feeding behavior, forced external exposures with bait active ingredients are often used to estimate physiological susceptibility without behavioral confounders. However, relying on external contact methods may not be appropriate for baits because of their oral route of entry. To increase the utilization of oral exposures for German cockroaches, we describe a novel method of conducting precise oral dosing of insecticides in an accessible and practical manner.

RESULTS

Peanut butter was used as the delivery medium in quantities of 1.5 mg per adult male. Oral lethal doses of fipronil, indoxacarb, and dinotefuran were determined for the laboratory susceptible UCR and field-collected Dav strains, resulting in resistance ratios (RR50) of 14.4 (fipronil), 7.3 (indoxacarb), and 3.5 (dinotefuran) for the Dav strain. Bait bioassays using commercial fipronil, indoxacarb, and dinotefuran baits were performed to validate the method and compare with the lethal doses.

CONCLUSION

The oral-dosing method was compatible with both laboratory and field-collected strains, providing an accessible way to enhance the accuracy of German cockroach bait toxicity studies in the future. © 2026 Society of Chemical Industry.