Biocontrol potential of Lariophagus distinguendus (Hymenoptera: Pteromalidae) against Sitophilus granarius (Coleoptera: Curculionidae) at low temperatures: reproduction and parasitoid-induced mortality

Lariophagus distinguendus Forster (Hymenoptera: Pteromalidae) has been suggested as a biological control agent against the granary weevil, Sitophilus granarius (L.), in grain stores. information on the effect of low temperatures prevailing in grain stores is necessary to be able to predict the potential of this parasitoid against S. granarius in temperate regions, where grain is cooled with ambient air to achieve safe storage conditions. The influence of constant temperatures of 16, 18, and 20[degree]C on life table parameters and parasitoid-induced mortality (PIM) was investigated in the laboratory. L. distinguendus is able to develop and reproduce at temperatures as low as 16[degree]C. The intrinsic rate of natural increase, rm was 0.0182,0.0222, and 0.0792 d-1 at 16,18, and 20[degree]C, respectively. The proportion of hosts killed due to parasitoid-induced mortality was highest at 200C. At this temperature, it amounted to 70% of the total mortality exerted by the parasitoid; at 18 and 16[degree]C, it was 57 and 42% of the total, respectively. L. distinguendus is a promising biocontrol agent for grain stores in temperate regions because it is able to develop and reproduce at temperatures down to 16[degree]C; its development is quicker than that of its host, estimated from the literature; and it kills many hosts in addition to those used for reproduction.