Toxicity and repellency of essential oils in the management of Sitophilus zeamais

ABSTRACT This study had the following objectives: to identify and quantify the constituent compounds of essential oils from Cymbopogon winterianus Jowitt, Eucalyptus globulus Labill., Eucalyptus staigeriana F. Muell. ex F.M. Bailey, Foeniculum vulgare Mill., Ocimum basilicum L., Ocimum gratissimum L., and Piper hispidinervum C. DC., investigate their toxicity and repellency to S. zeamais and evaluate the toxicity of P. hispidinervum to immature S. zeamais. Individual tests for each essential oil were conducted with a completely randomized design with five concentrations for each oil and four replicates. Gas chromatography-mass spectrometry revealed the presence of citronellal in C. winterianus, 1,8-cineole in E. globulus, limonene in E. staigeriana, limonene in F. vulgare, linalool in O. basilicum, (E)-anethole in O. gratissimum, and safrole in P. hispidinervum. The median lethal concentration required to kill 50% of the insect (LC50) in contact and ingestion toxicity tests ranged from 5.12 to 78.89 μL 40g-1 corn in P. hispidinervum and C. winterianus, respectively. In adult fumigation tests, the LC50 ranged from 2.1 to 19.4 µL L-1 air, and in immature fumigation tests, the egg stage was susceptible to essential oil, whereas larval and pupal phases were tolerant. All of the oils repelled S. zeamais.