Changes in the haemocytes of Agrotis ipsilon larvae (Lepidoptera: Noctuidae) in relation to dimilin and Bacillus thuringiensis infections.

Five types of haemocytes are observed in the fourth larval instar of the black cutworm, Agrotis ipsilon: prohaemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs), spherule cells (SPs) and adipohaemocytes (ADs). Infection of A. ipsilon fourth larval instar with Bacillus thuringiensis and dimilin resulted in a reduction of the total haemocyte count. Changes in the differential haemocyte population during bacterial and dimilin infections have been assessed. The PRs % decreased significantly while SPs, PLs, and GRs % increased significantly after the application of the two insecticides at 12 and 24h. Ultrastructural alternations and malformations have been observed in circulating haemocytes of A. ipsilon larvae treated with dimilin and B. thuringiensis.