The Behavioral Response of Blattella germanica (Blattodea: Ectobiidae) Exposed to DEET Varies Throughout Its Life Cycle

Abstract

The German cockroach, Blattella germanica L., is a hemimetabolous insect pest of economical and medical importance. N,N-diethyl-3-methylbenzamide (DEET) is an insect repellent whose effect on this species has received very little attention. The objective of this work was to determine whether the behavioral response of B. germanica to DEET varies along its life cycle. DEET repellence was assessed in small, medium, and large nymphs, and in adults of both sexes, all originated from the same laboratory colony (CIPEIN). The experimental arena consisted in a piece of filter paper treated with repellent on one half (195 µg/cm2) and solvent alone on the other half. A cockroach was placed on the filter paper, and its behavior was filmed. An image analyzer was used to quantify how long the insect spent on each side of the paper. As a control, a cockroach was exposed to a piece of filter paper treated with solvent (acetone) alone. Each assay was repeated independently six times. Distribution coefficient (DC) values were calculated, a parameter that ranges between 0 (attraction) and 1 (repellence). Small nymphs were more sensitive to DEET (mean DC = 0.93). The mean DC values of the other groups varied between 0.62 (medium nymphs) and 0.71 (male adults). The group of medium nymphs was the only one whose behavior was not significantly altered by exposure to DEET. The results show the importance of assessing insect repellents at different stages of the insect’s life cycle in order to obtain a complete panorama of its effect.

Behavioral responses of field‐collected German cockroaches to pyrethroids and pyrethroid‐formulated insecticides

“…However, it should be noted that the assays used in this study did not evaluate behavior without direct contact. It should also be noted that contrary to a recent report that showed adult male German cockroaches spend approximately 30% of their time on DEET treated surfaces at a concentration of 195 μg/cm 2 , 39 we found adult males spent less than 2% of their time on DEET treated surfaces at a similar concentration (170 μg/cm 2 ), as would be expected with a repellent such as DEET.…”

“…Therefore, we assessed the response of German cockroaches to pyrethroids using advanced video tracking in free‐moving arenas, where one side was treated with chemicals and the other is treated with solvent control. This experimental design has been used previously to measure the repellency of chemicals against other species of cockroaches 38,39 . Prior to testing pyrethroids, we validated the experimental design using both DEET and corn mint oil, which were previously reported to repel German cockroaches 39–41 .…”

“…This experimental design has been used previously to measure the repellency of chemicals against other species of cockroaches. 38,39 Prior to testing pyrethroids, we validated the experimental design using both DEET and corn mint oil, which were previously reported to repel German cockroaches. [39][40][41] In our study, both DEET and corn mint oil significantly reduced German cockroach movement on treated surfaces, in a dose-dependent manner.…”

“…38,39 Prior to testing pyrethroids, we validated the experimental design using both DEET and corn mint oil, which were previously reported to repel German cockroaches. [39][40][41] In our study, both DEET and corn mint oil significantly reduced German cockroach movement on treated surfaces, in a dose-dependent manner. In addition, cockroaches were shown to travel a shorter distance at a higher velocity in the area treated with DEET and corn mint oil, further supporting a direct/immediate behavioral response that would be expected of a true repellent.…”