Secondary plant
metabolites can be small lipophilic molecules (SLMs) with
similar physicochemical properties and toxicities to pesti-
cides, and many have provided the lead structure or inspi-
ration for synthetic insecticides, for example, pyrethrum for
the pyrethroids [3], nicotine and other nicotinic acetyl-
choline receptor agonists for the neonicotinoids [4] and
stemofoline for the very recently introduced butenolides
[4]. Some insecticides are natural products, for example,
spinosad, which comprises the natural spinosyns A and D.
Thus, genes for the biosynthesis of the natural insecticidal
SLMs are available in nature for exploitation by genetic
engineering