Bacterial Infections of Potato Tuber Moth Larvae in an Insectary1

Abstract

Larvae of Gnorimoschema operculella used as an insectary host for the mass production of the hymenopterous parasite, Macrocentrus ancylivorus, were regularly found dead in small numbers in their rearing trays. Microbiological examinations were negative for microsporidia and for poly-hedra but several strains of bacteria were isolated which apparently were at least a secondary cause of the deaths. Upon death, the larvae turned either dark brown to black in color or bright red. From the latter were invariably isolated strains of brilliantly red-pigmented Serratia marcescens. From the other dead and dying larvae 2 Gram-negative, nonsporeforming, small rods of the coliform group were isolated. One of these appeared to be a strain of Aerobacter, probably A. cloacae. Pathogenicity of these 3 strains was confirmed by a series of feeding and inoculation expts. Isolations were also made from washings of some of the insectary equipment and from potatoes used in rearing the larvae.