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The plant products are the most promising source for their biological activity against various pests. The strong inhibition of Acetylcholinesterase (AchE: EC 3.1.1.7) is the principal underlying mechanism of action of most of the potential pesticides. In the present study, the newly moulted penultimate instar nymphs of the desert locust Schistocerca gregaria were treated with methanolic (at concentration levels: 7.5 or 3.7%), petroleum ether or n-butanolic (at 30 or 15%) extract from the wild herb Fagonia bruguieri. The AchE activity was determined in the haemolymph and fat body of the last instar nymphs and newly formed adult females. Along the nymphal life, remarkably induced AchE activity was unexceptionally observed in the haemolymph, especially of the early- and mid-aged nymphs. With regard to the enzyme activity in the fat body of S. gregaria nymphs, pronouncedly inhibited activity in the early-aged nymphs, regardless of the extract or its concentration level. The strongest prohibiting effect was exhibited by both the petroleum ether and n-butanolic extracts. On the contrast, AchE activity was enhanced in the fat body of all nymphs other than the early-aged ones. The F bruguieri extracts exerted a potent inhibitory action on the AchE activity in the haemolymph of the newly emerged adults of S. gregaria. Such action was reversed on the AchE activity in the fat body of adults, whatever the extract or concentration level. The present results suggest that the wild herb F. bruguieri may prove to be a probable candidate for the development of biopesticides to control the populations of the desert locust as safer, ecofriendly and economic alternatives to the synthetic pesticides.