Effect of recycling temperature on the infectivity of entomopathogenic nematodes

Abstract

Four strains of entomopathogenic nematodes were recycled in vivo for 2 years at temperatures ranging from 10 to 25 °C, then the infectivity of their infective juveniles was compared. Infectivity was examined by measuring LC50 values for wax moth (Galleria mellonella) larvae at bioassay temperatures ranging from 5 to 25 °C. Of the four strains examined, only the Umeå and NF strains of Steinernema feltiae that had been recycled at 10 °C infected and killed the insects at a bioassay temperature of 5 °C. The Steinernema carpocapsae All and Steinernema riobravis TX strains were infective at 10 °C only when the recycling temperature was ≤ 20 °C. The infectivity of the two strains of S. feltiae at 10 or 15 °C was compromised by propagating them at higher temperatures (20–25 °C). The Umeå strain of S. feltiae displayed an impaired capacity to infect hosts at higher temperatures (20–25 °C) when recycled at lower (≤ 15 °C) temperatures. The capacity of these nematodes to adjust to different recycling temperatures is discussed in relation to their infectivity in different field situations.