Root-lesion nematode, Pratylenchus thornei, a widespread pathogen of wheat in the subtropical grain region of eastern Australia, causes lost production of ~AU$38Million/year. We are investigating the biology of P. thornei for the purpose of modelling its population dynamics in cropping systems of this region. Population densities of P. thornei increase exponentially during crop growth then decline exponentially during fallow in all depths in the soil profile except in the topsoil where the decline is more rapid than exponential. An experiment was conducted to determine the potential contribution of elevated temperature and desiccation during summer fallow to this rapid decline. A vertisolic soil containing a high population density of P. thornei after wheat growth was subject to three moisture regimes and incubated at eight temperatures from 10 to 45ºC. Soil moisture regimes were (a) maintained at field capacity (pF 2.5), (b) initially field capacity allowed to dry during incubation, and (c) air-dried to pF5.6 before incubation. Survival of P. thornei was assessed at six intervals from 0 to 16 weeks incubation. P. thornei died out completely at 40 and 45ºC irrespective of the moisture regime and populations were substantially reduced at 35ºC and 30ºC. At lower temperatures, survival over a 16-week period was better in soil maintained at field capacity than in soil allowed to dry. Death of P. thornei in air-dried soil was rapid during incubation at all temperatures tested. Soil that dried slowly in treatment (b) in the course of the experiment resulted in longer survival of P. thornei than in treatment (c). Best survival was in soil at field capacity incubated at the lower temperatures of 10 to 25ºC. It is likely that elevated temperatures and desiccation during summer fallow contribute significantly to the poor survival of P. thornei in the topsoil to ~7 cm depth.