to the empty granaries and warehouses, to bags or
directly to grain (Snelson 1987, White and Leesch
1996). Malathion has been used extensively to control
stored-product insects, but there is now widespread
resistance worldwide to this insecticide and other insecticides
in stored-product insect populations (Subramanyam
and Hagstrum 1996, Perez-Mendoza 1999).
In general, parasitoids are more susceptible to contact
insecticides than pest insects (Scho¨ ller and Flinn
2000), although there are a few cases where a parasitoid
has developed resistance to an insecticide
(Baker et al. 1998). Therefore, alternatives to chemical
insecticides are needed to control pests in stored products.
There is a long tradition of subsistence farmers using
whole plants or parts of plants to protect stored products
from insect attack (Golob et al. 1999). For example,
neem (Azadirachta indica A. Juss.) is commonly
applied to grain and acts as a repellent,
antifeedant and insecticide to several insects (Makanjuola
1989, Gerard and Ruf 1995, Senthil-Nathan et al.
2009, Kebede et al. 2010). Pyrethrum is another widely
used botanical insecticide (Snelson 1987). It is extracted
from chrysanthemum [Tanacetum cinerariae