December 12th, 2017
A gel bait-resistant German cockroach, Blattella germanica (L.), strain Cincy was collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance toAvert (0.05% abamectin) and Maxforce FC (0.01% _pronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and _pronil. Resistance ratios (based on LD50 values from topical applications) to abamectin and _pronil were 2.5 and 8.7, respectively. The Cincy strain of had a signi_cantly lowerLD50 value to abamectin than a nonaverse _eld strain (Dorie) and similarLD50 values to _pronil as the Dorie strain. The aversion behavior (avoidance of gel baits) was therefore caused byfood ingredients in the gel baits.TheCincy strainshowedavoidance of agar containing fructose, glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. Modi_cations of the inert ingredients in the Maxforce FC gel bait signi_cantly improved the ef_cacy against the Cincy strain. The Cincy strain produced signi_cantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting _tness costs are associated with resistance.