This observation and our results confirm that
thymol and carvacrol showed insecticidal activity against
German cockroaches by direct contact, and not via fumigation.
In our fumigant toxicity test, mortality with α-pinene, β-pinene,
and limonene was not higher than that with the other
compounds. This result did not agree with the results of
Phillips and Appel.12 The difference in the insecticidal activity
of these compounds might be because we used different strain
of German cockroach