Repellency of essential oils
When cockroaches were used in a blank test with the T-tube
olfactometer, there was no difference in their choice of arm,
which indicates that the olfactometer did not have any bias.
When screening the seventeen selected essential oils, only five
oils showed significant repellent activity in the order of grapefruit
(96.7%), lemon (92.9%), lime (86.7%), orange (71.4%)
and clove leaf (70.0%) against B. germanica at 10m