Biology and control of ring nematodes in stone fruit orchards

Mesocriconema xenoplax (previously known as Criconemella xenoplax) was found to be the only species of the ring nematode (RN) group (Fam. Criconematidae) to occur in large numbers in stone fruit orchards and to be associated with economic damage.

Root mass of Kakamas peach seedlings were reduced by 58% over a 6-month period.  On older plants the effect was less dramatic, but RN increased 18-fold on GF 677 rootstock and 64-fold on SAPO 778 rootstock over a 1-yr period.  Shoot lengths were reduced by 38-40% respectively.

RN numbers showed no seasonal fluctuations in established orchards of plum trees on Marianna rootstock.  Although RN occurred throughout the root zone to a depth of 1 meter, 48-56% of the population occurred in the top 40 cm soil.  Samples for diagnostic purposes can therefore be taken in the top 30 cm of soil at any time of the year.

Removing trees, fumigating soil and replanting in the same year gave poor control of RN.  This is due to (1) poor fumigation effect when large amounts of roots are still present at the time of fumigation and (2) RN occurring to depths of 1 m in the soil while fumigation is only effective to about 40 cm depth.  A substantial proportion of the nematode population in the deeper soil layers therefore survive the fumigation and recolonise the upper soil layers.

Post-plant treatments with the product cadusafos, or alternating cadusafos applications with fenamiphos applications gave good control of RN.