Mulch preferences of the Asian cockroach (Dictyoptera: Blattellidae).

Mulch preferences of the Asian cockroach, Blattella asahinai Mizukubo, were determined in a series of laboratory experiments. Because this species is a peridomestic pest, mulch preferences may be a key part of an integrated pest management program for homeowners. Five mulches were used: cypress, oak leaf litter, pine straw, rubber, and topsoil. Large arena experiments showed that adult male Asian cockroaches preferred oak leaf litter and pine straw, while adult females preferred oak leaf litter and rubber mulches. Nymphal stages preferred rubber (48.3-62.5% for small and medium instars, respectively) to all other mulches. All stages of the Asian cockroach showed very little preference to topsoil (0%) and cypress mulch (6.3%). Ebeling choice box tests confirmed lack of preference or repellency of adult males to topsoil (17.8 +/- 3.6%) and rubber mulch (15.7 +/- 3.6%). Continuous exposure experiments indicated that pine straw was significantly more toxic to adult males than other mulches (66.7 +/- 18.4% mortality at 7 d). Mulch preferences of the Asian cockroach may be mediated by characteristics of the interstitial spaces in the different mulches. Rubber mulch afforded smaller, more humid spaces that were inaccessible to adults. Because cypress mulch was least preferred by nymphs and adults, use of cypress mulch in an integrated pest management program around homes may help to reduce Asian cockroach populations and limit insecticide exposure to humans, animals, and the environment.