Against this backdrop, natural pesticides based on
plant-essential oils may represent alternative crop protectants
whose time has come. Essential oils, obtained by
steam distillation of plant foliage, and even the foliage
itself of certain aromatic plants (notably in the families
Myrtaceae and Lamiaceae, but in other plant families as
well) have traditionally been used to protect stored grain
and legumes, and to repel #ying insects in the home.
Though some of the claims made for these crude preparations
have yet to be substantiated through controlled
experiments, scienti"c investigation into the biological
activities of these materials proliferated in the past decade.
The emerging picture is that certain, speci"c oils and
their chemical constituents have demonstrable contact
and fumigant toxicity to a number of economically important
insect and mite pests, as well as to plant pathogenic
fungi.