WATER-CONTENT AND FATTY-ACID COMPOSITION OF INFECTIVE JUVENILE ENTOMOPATHOGENIC NEMATODES DURING STORAGE

Limited shelf life of infective juveniles is a major obstacle in reali zing the full biological control potential of entomopathogenic nematod es. We studied some of the physiological parameters affecting storage stability. Heterorhabditis bacteriophora, Steinernema carpocapsae, and Steinernema glaseri were cultured in the wax moth larva, Galleria mel lonella, and the freshly emerged infective juveniles were stored in wa ter at 25 C. Shelf life, estimated by a minimum of 20% survival, varie d among species: infective juvenile S. glaseri survived for 36 wk, whe reas S. carpocapsae and H. bacteriophora survived only 16 and 7 wk, re spectively. Water and lipid contents of infective juveniles were deter mined during storage. The rate of increase in water content differed a mong species, and at the end of their shelf life all species contained 14-16% more water than the freshly emerged infective juveniles. When lipid content was analyzed, a positive correlation between fatty acid composition of the total lipid and increase in the water content was o bserved. With advancing storage, the percentage of unsaturated fatty a cids increased, whereas saturated fatty acids decreased. We suggest th at poor storage stability of H. bacteriophora may be due to the presen ce of large quantities of unsaturated fatty acids in the freshly emerg ed infective juveniles.