Morphological characteristics of local entomopathogenic protozoan strains isolated from insect cadavers of certain stored-grain pests in Egypt

Abstract

AbstractThe present study has documented, for the first time in Egypt, the natural occurrence of four entomopathogenic protozoans (EPP) among five of the most abundant and damaging insect pests of stored grains or their products. These insect pests (Laemophloeus (Cryptolestes) turcicus (Grouvelle), Rhyzopertha dominica (Fabricius), Sitophilus zeamais (Motschulsky), Tribolium castaneum (Herbst), and Plodia interpunctella (Hobner) were infesting lots of crushed-maize grains, wheat grains, and wheat flour, brought, in 2015, from El-Behera Governorate, Egypt. The morphological characteristics, including spore size, of the entomopathogen infective units, spores, of the isolated entomopathogenic protozoans, were closely fit with the description to the following genera: Mattesia, Farinocystis, Adelina, and Nosema. The prevalence of these entomopathogens ranged between 9 and 89%. This study seems to be the first report of Mattesia sp. on S. zeamais; Adelina sp. on L. turcicus or R. dominica, and the second report of Nosema sp. on R. dominica. The rate of natural infection by the neogregarine, Mattesia sp. (tentatively, M. dispora), was the highest in L. turcicus beetles (89%) followed by that in P. interpunctella moths (48%), larvae (40%), and pupae (32%) and then in S. zeamais weevils (42%) and R. dominica beetles with a low rate of infection (9%). The microsporidian entomopathogen, Nosema sp., (tentatively, N. whitei) was naturally occurred in 11% of the examined adult cadavers of R. dominica. The coccidian entomopathogen, Adelina sp., was found, respectively, in 60% and 27% of larval and adult cadavers of T.castaneum, while the Adelina-natural infection rates in R. dominica and L. turcicus adult cadavers were 34% and 14%, respectively. A high rate of natural infection with another neogregarine, Farinocystis sp. (tentatively, F. tribolii), has also been recorded in T. castaneum adult (50%) or larval cadavers (36%).