Evaluation of single and periodic applications of chlorpyrifos to control German cockroach (Orthoptera: Blattellidae) populations in multifamily dwellings.

Abstract

Multifamily apartment buildings were treated with formulations of chlorpyrifos by different treatment strategies. Single applications were made with a water emulsion spray of 0.50% chlorpyrifos or Killmaster II (a slow-release formulation containing 2% chlorpyrifos) to 79 apartments. Periodic reapplications (five) were made with a 0.25% water emulsion spray of chlarpyrifos on a monthly cycle to each of 14 apartments initially treated with the 0.50% spray. Populations of Blattella germanica (L.) were evaluated with sticky traps before treatment and reevaluated monthly for 7 months after treatment to determine insecticide efficacy. Reapplication treatments also included the use of a questionnaire to aid in efficacy evaluation. Single applications of the slow-release formulation and the periodic treatments with 0.25% chlorpyrifos yielded nearly twice the percent reduction in German cockroach numbers than did single treatments of 0.50% chlorpyrifos tor the 7 months of this study. Questionnaire results indicated a reduction in insecticide use by residents in the first 2 months of the study; however, there was a trend toward increased pesticide use by residents in the sixth and seventh months in those apartments that had received periodic retreatments. There was a general dissatisfaction by residents with the scheduled retreatment strategy because the cockroach populations did not appear to decline substantially through time.