Introduction
Recently, essential oils extracted from plants have been studied as
replacements for chemical pesticides due to their environmentally
friendly and biodegradable characteristics. Several essential oils
used as insect repellents have been studied by many researchers
(Ho and others 1996; Papachristos and Stamopoulos 2002;
Garcia and others 2005; Wong and others 2005; Liu and others
2006;Wang and others 2006; Negahban and others 2007). Among
them, thyme oil extracted from Thymus vulgaris was known to
have effective insect repellent activities. Cloyd and others (2009)
showed that the mixture of mint and thyme oil was effective with a
mean citrus mealybug mortality of 89%. Another work (Aslan and
others 2004) has shown that essential oil vapor from T. vulgaris was
toxic to the 2 spotted spider mites in greenhouse. However, most
essential oils are susceptible to oxygen, light, and are easily volatile
at high temperatures. Thus, their application has been limited in
the food and food packaging industries.
Microencapsulation technology has been applied to improve
the sustained release effect, stabilization from environmental damage
and for easy handling through solidification of essential oil.
There are 2 types of wall materials around the core materials:
natural and synthetic polymers.