T. Confusum Case Study

Results and discussions
The experiment was conducted in order to determine the activity of plant extracts on the adult and last larval instar of T. confusum. In all cases, considerable differences in insect mortality were shown with different plant extract, different concentration at the same exposure period 24 hrs.
The 24 hrs bioassay is a major tool for evaluating the toxicity of phytotoxins, and a number of researches have been applying this method to assess the toxic effect of different plant extractions against T. confusum (Hana, 2013 and Kundu et al., 2007). The T. confusum larvae that exposed to the plant extracts showed significant behavioral changes. The changes were observed within 30 minutes of exposure. The larvae showed restlessness,
confusum depend on several factors among which are the chemical composition of the crude plant extracts and insect susceptibility (Casida, 1990). Crude plant extracts contain components that increase their repellency and /or toxicity. The highly toxic and repellent effects of the main constituents of these oil are the cymol, 1,8-cineole, terpineol and a-pinene, which have been demonstrated against T. confusum by researchers (Ojimelukwe and Adler, 1999 and Tapondjou et al., 2005). Repellency could be due to the blend of oil constituents or to minor compounds present in oils and characterized by a significant biological activity (Cosimi, et al., 2009). Various biological activities have been reported for some plant species e.g. Mentha, antibacterial (Oyedeji and Afolayan, 2006), antifungal (Bouchra et al., 2003), insecticidal properties (Akrami, 2008) and repellency effect against storage pest (Mahmoodvand, 2012, Saeidi and Moharramipourm, 2013). Many researchers pointed that some of plant essential oils showed strong repellency effects against storage pests (Liu and Ho, 1999; Akrami, 2008; Caballero-Gallardo,et al., 2012 and Saeidi and Moharramipour,
The insecticidal activity depends on the crude plant extracts concentration and insect stage. A concentration of 113.15 ppm of R. officinali extract was necessary to cause 50% mortality for the last larval stage, while a concentration of 135.18 ppm for the adult stage. The same result obtain in O. basilicum extract when concentration of 148.38 ppm of O. basilicum extract was necessary to cause 50% mortality for the last larval stage; a concentration of 218.78 ppm for the adult stage (Table 1). Moreover, slopes estimated that any increase in crude plant extracts concentration, inflicted the highest mortality on last larval stage when compared with the