Observations On the Biology and Ecology of Paralongidor Us a Ustralis On Rice in North Queensland

Abstract

Few P. australis were associated with rice roots in non-flooded fields following planting, but nematodes aggregated around roots and poor growth symptoms became apparent when fields were inundated with water. Pot experiments designed to investigate the effect of soil moisture on nematode movement and symptom development showed that P. australis did not move towards rice roots and cause damage unless clay soils were flooded. When water was drained from fields prior to harvest, nematodes became inactive and frequently assumed a coiled form. Inactive females produced eggs but the first-stage juveniles hatching from them remained clustered together and entwined with the coiled adults. P. australis remained viable for at least 14 months in fallow soil, surviving mainly at depths of 15-25 cm. Nematodes added to rice seedlings in pots matured no more than one developmental stage by the time plants ripened, suggesting that in the field P. australis required several rice crops to complete its life cycle.