In the framework of the Local Group Census (LGC), a survey of the Local Group (LG) galaxies above Dec =-30° aimed at surveying the populations that have strong emission lines, we have searched for planetary nebulae (PNe) in the low-metallicity dwarf irregular galaxies IC 1613, WLM, GR 8. Two new candidate PNe have been found in IC 1613, one in WLM and none in GR 8. The observations presented in this paper, together with the previous results from the LGC, represent the first step in the study of the PN population in low-metallicity, dwarf irregular galaxies of the Local Group. These observations will be followed by deep spectroscopy to confirm the nature of these objects and to study their physical-chemical properties. We use the observed number of PNe in each LG galaxy to estimate a lower limit to the mass of the intermediate-age population, which is compared with the star formation rate (SFR) of LG dwarf galaxies. These results are in agreement with those from accurate star formation history (SFH) analyses for these small galaxy systems.