Developmental temperature effects on five geographic isolates of the entomopathogenic nematode Steinernema feltiae (Nematoda : Steinernematidae)

The development of five geographic isolates of Steinernema feltiae at 5, 8, 10, 15, 20, 25, and 28 degreesC in wax moth, Galleria mellonella, larvae w as examined. The isolates were from Mediterranean (Sinop from Turkey, SN fr om France, and Monterey from California), subtropical (Rafaela from Argenti na), and tropical (MG-14 from Hawaii) regions. All isolates caused 100% mor tality of wax moth larvae and developed and produced progeny between 8 and 25 degreesC. At 28 degreesC, mortality was 100%, but no progeny was observe d. The highest infective juvenile production was observed at 15 degreesC fo r all isolates. In general, the tropical isolate, MG-14, had the lowest pro duction of infective juveniles. The time of emergence of the infective juve niles from the host cadaver showed some differences among isolates, with th e Sinop isolate having the earliest emergence time from cadavers at 15 degr eesC (10 days) and 20 degreesC (8 days). At 25 degreesC, the infective juve niles of the Sinop, SN, and Rafaela isolates emerged from the cadavers from 5 to 7 days. Time of host death by all isolates showed no differences at 8 , 10, 15, 20, and 28 degreesC. At 25 degreesC for all isolates (except the MG-14), shorter times to host death were observed. Host death occurred at 1 2 days at 8 degreesC, 9 to 11 days at 10 degreesC, 4 to 5 days at 15 degree sC, 3 days at 20 degreesC, and 2 days at 25 and 28 degreesC. For penetratio n efficiency, the Sinop, SN, and Rafaela isolates penetrated their hosts at 5, 8, and 10 degreesC. Penetration of the infective juveniles was consiste ntly high for all isolates at 15, 20, 25, and 28 degreesC, but it was signi ficantly lower for the MG-14 isolate at 15, 25, and 28 degreesC. No progeny production occurred at 28 degreesC, but nematode penetration did occur wit h the MG-14 isolate having significantly lower penetration than the other i solates. When nematodes were produced at 8, 15, and 23 degreesC in wax moth larvae, all isolates had infective juveniles with longer body lengths at 8 degreesC followed by 15 and 23 degreesC. To further verify body length at the different temperatures, beet armyworm, Spodoptera exigua, larvae and do g-food agar medium were used, respectively, for in vivo and in vitro cultur e of the Sinop isolate. Infective juvenile body length showed the same tren ds, with the longest being at 8 degreesC and decreasing in length from 15 t o 23 degreesC. The data suggest that quality of food for the nematode and t emperature (that is, developmental time) influence the body length of the i nfective juvenile. (C) 2001 Academic Press.