Repellency of ethanol extracts of herbs to the German cockroach, Blattella germanica (Blattaria: Blattellidae), observed by feces distribution in the extract treated harborages

Ethanol extracts of some herbs showed strong repellency against the German cockroach, Blattella germanica, under laboratory conditions. Extracts of thirty-three herb species were applied to the surface of cockroach harborages made of 5 cm × 5 cm plywood panels with a 5-mm single void. The majority (90% or more) of cockroach feces was deposited in non-treated harborages when an extract among dill (Anethum graveolens), celery (Apium graveolens), caraway (Carum carvi), cumin (Cuminum cymimum), coriander (Coriandrum sativum), cinnamon (Cinamomum zeylanicum), mace (Myristica fragrans) and chili pepper (Capsicum annuum) was treated on the other side of the harborage in the same arena. The repellent efficacy was sustained with all the above extracts for at least one month, and caraway, cinnamon, chili pepper and celery were effective at 80 times dilution with water. The herbs, anis (Pimpinella anisum), sansyo (Zathoxylum piperitum), onion (Allium cepa), vanilla (Vanilla planifolia), mustard (Brassica hirta) and eucalypt (Eucalyptus radiata), showed an attractant effect to the German cockroach by the same method.