Evaluation of the efficacy of lambda-cyhalothrin applied by three spray application methods for emergency control of Aedes aegypti in Costa Rica.

An extended duration formulation of lambda-cyhalothrin (Icon CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new hand-held sprayer (Twin-Fog) or as a low-volume spray (LV) from a backpack mist blower against Aedes aegypti was evaluated in Costa Rica. Spray applications were made at the front door for 1 min or to each room for 15 sec for the ULV and LV, and thermal fog applications were made to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and mosquito collections from within houses using hand-held, battery-powered aspirators. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for the ULV and thermal fog spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 3 wk of significant control (P < 0.05) based on adult Ae. aegypti house collections.