Fumigant Toxicity Test. A paper disk (8 mm, Advantec) treated
with the essential oil or compound being tested was placed in the
bottom lid of a glass cylinder (diameter, 9.5 cm; height, 19 cm) with a
wire sieve fitted 9.5 cm above the bottom; thereafter, the lid was sealed
with Parafilm (Pechiney Plastic Packaging Company, Chicago, USA).
Ten adult male and female German cockroaches were placed on the
sieve. This prevented direct contact of the cockroach with the test
plant oils and compounds. The insects were maintained at 25 ± 1 °C
and 60% RH. The adult cockroaches were considered dead if their
appendages did not move when prodded with a brush. Cumulative
mortalities were determined 48 h after treatment. All treatments were
replicated 4 times.
Contact Toxicity Test. Appropriate doses of the test compounds
dissolved in acetone were topically applied to the thorax of the adult
male and female German cockroaches (anesthetized using CO2) with a
microapplicator (Burkard, Hertfordshire, U.K.). The controls received
acetone (1 μL). Batches of 10 treated adults were put into a Petri dish