Parasitism by Venturia canescens and Habrobracon hebetor on mono- and heterospecific populations of pyralid moths located in laboratory and experimental store houses

Abstract: Plodia interpunctella and Ephestia kuehniella are important pests of stored products that are both parasitized by Venturia canescens and Habrobracon hebetor. These two cosmopolitan larval parasitoids are found in large numbers in food processing facilities in north-eastern Spain. In laboratory, we evaluated their performance when mono and heterospecific populations of 3rd-4th larval stages of the two moths were offered. We also examined the dispersion capability of females when larvae of the two moths were offered also alone or in combination. For this purpose hosts were offered in the eight corners of experimental rooms of aprox. ≈ 30 m3 during three days; the experimental rooms had a window for considering the influence of natural light illumination on their dispersion pattern. Both parasitoids reduced the emergence of both moth species by half in the laboratory, in comparison with the controls, either when offered separately or in combination. Reproduction of H. hebetor was also similar in presence of both hosts, while V. canescens had a significantly higher reproduction on E. kuehniella than on P. interpunctella larvae. In experimental rooms both parasitoids were able to similarly parasitize larvae located in any of the eight corners, independently of the window situation. However, both parasitoids were more efficient parasitizing E. kuehniella than P. interpunctella larvae.