Modelling winter survival dynamics of Meloidogyne spp. (Nematoda) eggs and juveniles with egg viability and population losses.
Abstract
A theoretical model of winter survival dynamics of Meloidogyne spp. (Jeger & Starr 1985) was extended to incorporate the loss of egg viability and population losses due to predation or microbial decomposition. The model was used to estimate rates of egg hatching, egg viability loss, egg population loss and juvenile mortality; also, initial populations of viable and non-viable eggs and juveniles, and the cumulative number of eggs that lost viability of M. incognita in cotton field plots at College Station, Texas, and of M. hapla in rose (Rosa sp.) plots at Overton, Texas, in 1984-85. It was estimated that 47% of eggs lost viability during the winter at College Station and 19% at Overton. Egg population losses due to predation or microbial decomposition were important in the overwintering, but it is not known whether these affected viable and non viable eggs equally. There appeared to be a net migration of juveniles from shallow to deep soil profiles: a further complicating factor that is not accounted for in the current model. Problems in fitting the overwintering model to field data were encountered because of common parameters in the component equations comprising the model. Additionally, there were large sampling errors and biases encountered in nematode sampling that caused problems in fitting the overwintering model in some years and locations.