Investigations into the survival of ring nematode (Criconemoides xenoplax) in soil

The objective of this project was to study the survival of ring nematode (RN) (Criconemoides xenoplax) in soil in the absence of a host.

Three separate studies were done.  In the first study, soil containing RN was stored in plastic bags at 0,5 -2,0 ^°C in a cold storage room.  RN numbers were monitored monthly.  After nine months 52% of the original population was still alive, indicating that RN can survive in adverse conditions and in the absence of a host for at least nine months.

In the second trial two orchards were studied where stone fruit trees were removed in March and replanted in August of the same year.  In both orchards the few months (March to August) were not long enough for the RN population to die out completely.  In the one orchard the RN numbers did initially decline, but reached damaging levels by the end of the first summer.  In the second orchard the RN did not drop below 500 RN/250 ^-3 soil in the period between tree removal and replanting.

In the third trial trees were replanted after 15 months of fallow.  In this case RN numbers stayed below damaging levels (< 500 RN/250 cm^-3 soil) for seven months after planting, when monitoring was terminated.  This aspect of leaving soil fallow for a year should be further researched, as it could possibly be one of the tools in our arsenal to manage RN.

The outcomes of this project are:

1. RN is hardy and can survive for at least nine months in the absence of a host;
2. We strongly recommend that stone fruit orchards are not replanted in the same year that the old trees are removed, as RN populations do not decline to acceptably low enough levels in such a short period.