Abstract: Six desert plants were chosen to study their toxicity and effects on growth and metamorphosis to Heliothis armigera Hitbner. Artificial diet containing 5% water extracts of Cynanchum auriculatum Royle et Wight and Peganum harmala var. multisecta Maxim showing strong toxicity to the larvae and caused mortality of 100% and 55% respectively. Meanwhile the two extracts with the same dosage affects metamorphosis of the insect significantly. Artificial diet containing 1% water extracts of C.auriculatum and that containing 5% water extracts of P.harmala resulted in mortality of 85% and 55% and emergence rate of both 0 respectively. Different portions of the extracts of C.auriculatum were added to the diet to feed the larvae, the results shown that pH 3 and pH 10 portions of the extracts affected the larvae growth significantly.