The present invention provides natural and/or simulated, synthetic, synergistic pesticidal compositions comprising terpenes, such as extracts from Chenopodium ambrosioides near ambrosioides, or compositions based on those found in Chenopodium ambrosioides near ambrosioides. The present invention also provides methods of using said compositions to kill, inhibit, prevent and/or repel plant pests from contacting and/or damaging plants.