The bioassays were conducted to assess the biocidal activity of Annona coriacea seed extract on eggs and newly hatched nymphs of the vector Rhodnius neglectus two application methods, topical and contact. We evaluated the 25, 50, 100 and 200 mg/ml concentrations of extract/solution with the water control in DMSO (2%). The design was completely randomized with four replications, using 10 eggs with 1 day of age for each repetition. In the topical application method the eggs were treated after they were distributed on Petri dishes with filter paper, while in the contact application method the filter paper was treated 60 minutes before receiving eggs. The Annona coriacea extract inhibited the hatching of eggs up to 90% through the method of topical application. In the contact method up to 96.6% of nymphs died at the highest concentration, possibly after the contact with the impregnated paper extract residue. Thus, our conclusion is that the A. coriacea extract showed biocidal activity on eggs and R. neglectus first stage nymphs; the method of topical application was effective in inhibiting the eggs hatch and the contact method was sufficient to prevent the development of nymphs. Key words: biocidal action, plant extract, triatomines.