However, volatiles produced by non-host plants often
affect the behavior of pests and their natural enemies,
these may vary genetically among plants (Bai et al.
2011). Intercropping with the non-host molasses grass,
Melinis minutiflora, significantly decreased levels of
infestation by stem-borers in the main crop and also
increased larval parasitism of stemborers by Cotesia
sesamiae. Volatile agents produced by M. minutiflora
repelled female stem-borers and attracted foraging female
C. sesamiae (Khan et al. 1997). Due to the inherent
variability, an important modification of this method
is the external application of volatile semiochemicals in
the field, which have a stabilizing effect and may reduce
populations of the aphids Diuraphis noxia (Prinsloo
et al. 2007), and Rhopalosiphum padi (Ninkovic et al.
2003). Essential oils, obtained by steam distillation of
plant foliage, and even the foliage itself of certain aromatic
plants have traditionally been used to protect
stored grain and legumes, and to repel flying insects
(Isman 2000). Diallyl disulfide, an essential component
of garlic volatiles (Edris and Fadel 2002), and in a
fumigation bioassay, had insecticidal activity on the larvae
of Japanese termite, Reticulitermes speratus (Park
and Shin 2005) and mushroom fly, Lycoriella ingenua
(Park et al. 2006). However, few studies have investigated
the effects of garlic oil blend and its components
on S. avenae control in wheat fields.