Heisey (1996) isolated a quassinoid compound,
ailanthone, from bark and foliage of tree-of-heaven
(Ailanthus altissima (Mill.) Swingle). The compound
reported to possess pre- and post-herbicidal activity in
greenhouse trials. Ailanthone exhibited a strong herbi-
cidal activity when sprayed on soil before the seed
germination. It, however, also had dramatic effects
when sprayed onto seedlings after their emergence from
soil (Fig. 1). Although, not yet commercially exploited,
Heisey (1996) advocated the use of ailanthone as
potential herbicide due to its efficacy compared to
widely used herbicides such as glyphosate and paraquat.
Ailanthone is not commercially used as herbicide
because of its rapid degradation in soil (Fig. 2).
Although weed species present at the time of spray
may get killed, others may emerge once ailanthone
disappears from the soil (Heisey, 1999). Multiple
applications throughout the growing season of the crop
could be a solution, but certainly would not be costeffective or feasible.