The present invention provides natural and/or simulated, synthetic,synergistic pesticidal compositions comprisingterpenes, such as extracts from Chenopodium ambrosioides near ambrosioides, orcompositions based on those found inChenopodium ambrosioides near ambrosioides. The present invention alsoprovides methods of using said compositions to kill,inhibit, prevent and/or repel plant pests from contacting and/or damagingplants.