INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT Behavioral and Physiological Resistance of the German Cockroach to Gel Baits (Blattodea: Blattellidae)

Agel bait-resistantGerman cockroach,Blattella germanica (L.), strainCincywas collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance to Avert (0.05% abamectin) and Maxforce FC (0.01% Þpronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and Þpronil. Resistance ratios (based on LD50 values from topical applications) to abamectin andÞpronilwere 2.5 and 8.7, respectively. TheCincy strain of had a signiÞcantly lowerLD50 value to abamectin than anonaverseÞeld strain (Dorie) and similarLD50 values to Þpronil as theDorie strain. The aversion behavior (avoidance of gel baits) was therefore caused byfoodingredients in thegelbaits.TheCincystrainshowedavoidanceofagarcontainingfructose,glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. ModiÞcations of the inert ingredients in the Maxforce FC gel bait signiÞcantly improved the efÞcacy against the Cincy strain. The Cincy strain produced signiÞcantly smaller oothecae and lower numbers of eggs in each egg capsule than thenonaverse JwaxandDorie strainsofcockroaches, suggestingÞtnesscostsareassociatedwithresistance.