5.1. Limitations
There are certain limitations for using allelochemicals
as natural herbicides. High cost, limited activity and
selectivity restrict the use of natural herbicides e.g.,
maize gluten (Bhowmik, 1992) and pelargonic acid
(Duke et al., 2001). Natural herbicide may also be toxic
to non-target organisms. For example, a natural
compound, alpha-terthienyl, isolated from the roots of
the common marigold (Tagetes erecta L.) was originally