Cytopathological Impacts of Certain Plant Growth Regulators on The Circulating Hemocytes of Galleria mellonella L. (Lepidoptera: Pyralidae)

Abstract

The greater wax moth Galleria mellonella is a worldwide insect pest damaging wax combs and feeding on bee‐hive products. The objective of the current study was to investigate the cytopathological impacts of four plant growth regulators (PGRs), viz ., indole-3-acetic acid, indole-3-butyric acid, 2,4-Dichlorophenoxy acetic acid and 6-benzyladenine, on the circulating hemocytes of last (7 th ) instar larvae of G. mellonella . For this purpose, the 3 rd instar larvae were force-fed on diet supplemented with LC 50 values of these PGRs (0.24, 0.022, 0.16 & 0.085 ppm, respectively). These larvae were continuously fed on the treated diet throughout the larval stage. The important results could be summarized as follows. Five main types of the freely circulating hemocytes in the haemolymph of larvae had been identified as Prohemocytes (PRs), Plasmatocytes (PLs), Granulocytes (GRs), Spherulocytes (SPs) and Oenocytoids (OEs). Different qualitative disorders of the profile of each circulating hemocyte type were demonstrated in thelast instar larvae, such as destruction of cell nuclei and/or membrane, some extruded cytoplasmic contents, and production of some vacuoles in the cytoplasm. However, some of the tested PGRs failed to exhibit cytopathological impacts on certain hemocytes, since IAA and 6-BA failed to affect PLs, IBA and 6-BA failed to affect GRs, IBA and 6-BA failed to affect SPs and IBA and 6-BA failed to affect OEs. Therefore, IAA and 2,4-D may be recommended to use in the IPM program against G. mellonella