Effect of propagation temperatures on temperature tolerances of entomopathogenic nematodes

Abstract

Swnmary - Four isolates (= three species) of steinernematids were propagated at 25, 20 and when possible, 15 and 10°C for 2 years, then their capacities for tolerating high temperatures and freezing determined. In all isolates, the temperature at which 50 % of the infective juveniles died (LT50) increased with an increase in maintenance temperarure. Sleinernema riobravis had the highest LT 50 values, Sleinernemafeltiaestrains the lowest, while Sleinernema carpocapsae Ali strain displayed an intermediate degree of tolerance to high temperatures. Tolerance to freezing, as measured by times at which 50 % of the infective juveniles were killed by a -5 oC regime, was diminished at higher maintenance temperatures. The infectiviry of nematodes that survived freezing was at least 90 % that of unfrozen nematodes (controIs) . Two strains of S. feltiae were the most cold tolerant of the four isolates, but their capacities to withstand freezing were diminished by propagation at warmer temperatures. (\) Elsevier ­ ORSTOM