essential oil (eo) from the weedy shrub eupatorium glabratum was analyzed by gas chromatography/mass spectrometry and then evaluated as insecticide and repellent against sitophilus zeamais and as fungicide against fusarium commune, f. graminaearum, f. sporotrichum, penicillium expansum, and phoma herbarum. the eo was composed mainly by monoterpenes, with -pinene (29.5%) and -phellandrene (19.6%) as the most abundant. s. zeamais showed similar susceptibility to pure vapors of -pinene and -phellandrene, and to whole eo of eupatorium glabratum. the eo killed insects exposed to its vapors for 1 week (lc50=18.0 lml-1 air). the lc50 for daily female insect mortality was 16.0 l-ml-1 air, and for males 20 l-ml-1 air). the eo was repellent in olfactometry tests for females and males at 0.4 l oil cm-2, but attractive for males at 0.1 loil cm-2. the eo also was differentially antagonistic to fungi, inhibiting at various degrees spore germination, germinal tube elongation and mycelium growth.