Pratylenchus penetrans (root lesion nematode)—cause of patch chlorosis of Pinus radiata seedlings

Summary

The root lesion nematode Pratylenchus penetrans was recovered from the roots of stunted, chlorotic, wilting and recently dead Pinus radiata seedlings growing in a forest nursery located on deep sands in south-western Victoria adjacent to the South Australian border. Although specimens of the genus Pratylenchus were recovered from P. radiata nursery soils in this region about 20 years ago, this is the first record of the species P. penetrans parasitising P. radiata in Australia.

Greenhouse and phytotron tests showed that P. penetrans could, by itself, cause the disease symptoms observed in the nursery and that other soil pathogens, which produce similar symptoms, contributed insignificantly.

P. penetrans was controlled by a single application of readily available proprietary brands of either liquid or granular nematicides shortly after seedling germination. A 10–15% improvement in seedling height was obtained even in healthy-looking seedlings infested with nematodes.