Eighteen volatile monoterpenes, which are among the major constituents
of essential oils from plants, were screened for phytotoxicity to sev
eral crop and weed species. Several monoterpenes containing an oxygen
function severely inhibited germination of four different annual weeds
while concurrently displaying little effect on soybean germination. S
oybeans varied in their sensitivity to various monoterpenes (measured
by seedling growth), with alpha-terpineol and geraniol selectivity inh
ibiting weed seed germination while having little or no effect on soyb
eans. All of the monoterpenes tested exhibited relatively high germina
tion and growth inhibition to corn and wheat.