Pyrethroids fail to repel German cockroaches in free-moving assays

Pyrethroids are synthetic insecticides which have low mammalian toxicity and broad-spectrum activity across insects. One major challenge with pyrethroids is their perceived repellency. For indoor pests, this perception often leads pest control operators to apply pesticides residually to try to prevent insects from getting into homes or certain areas. That said, for the German cockroach most experiments evaluating pyrethroid repellency employ Ebeling choice boxes, which only reports daily endpoint/positional data. While these assays have proven informative, they also do not capture data on the behavior/movement which led to the final position. To address this, we evaluated the kinetic behavioral response of German cockroaches to five pyrethroids based products and their active ingredients (A.I.) using advanced video tracking software (EthoVison XT) in open behavioral arenas for 30 minutes. To confirm the validity of the assay, we also used two positive controls (DEET and mint oil). Both positive controls were highly repellent towards German cockroaches, while all pyrethroid-formulated products and their A.I. failed to show repellency. To further investigate the discrepancy between the kinetic assays and previous work done with Ebeling choice boxes, we also performed harborage arrestment assays where German cockroaches were provided a choice between treated and control shelters. German cockroaches showed mixed results in arrestment assays, with all formulated products and two out of the five AIs preventing arrestment in treated shelters. In summary, these experiments confirm that pyrethroids are not repellent but cause irritation when harbored in treated areas, and the results will refine pest management strategies.