Bursaphelenchus aff. vallesianus/sexdentati – identification for dying Pinus spp. in Queensland.

Abstract

Through a combination of geographical isolation, effective quarantine and good fortune, Australia has remained free of many of the known species of forestry nematodes. However, with increasing volumes and sources of traded goods there is increased risk of these species gaining entry. The nematode Bursaphelenchus aff. vallesianus / sexdentati has been recovered from urban and plantation pine trees in Southeast Queensland. This nematode can affect pine seedlings in Europe during heat and drought, and may potentially be associated with pine-wilt disease.

The nematode was first detected in a dying tree in suburban Brisbane in July 2014. Wood samples from this tree were collected during response surveillance following emergence of adult Monochamus alternatus (Coleoptera: Cerambycidae) from imported timber pallets. Monochamus alternatus is the vector of pinewood nematode, Bursaphelenchus xylophilus, a major pest of Pinus spp. and cause of pine-wilt disease.

Wood samples were soaked for 24 hours and the extracted nematodes examined morphologically. Typical of the genus Bursaphelenchus, the female nematodes were slender, with a fine, but well developed stylet with small basal knobs, slightly off-set head, a large, angular median bulb, longer than wide, the oesophagus overlapping the intestine dorsally and with a posterior vulva at 70-80% of the body length. The female specimens were “hand-picked” and forwarded for molecular analysis at Australian National Insect Collection. The same nematode was subsequently found in NSW and an extensive surveillance program showed it to be widespread across a number of regions throughout the state and also at Passchendaele State Forest, near Stanthorpe, Qld. Molecular identification was confirmed by NSW DPI Plant Health Diagnostic Service.

Wood samples from unthrifty host trees will continue to be examined to contribute to our knowledge of the distribution of these nematodes and provide absence data in relation to B. xylophilus, the original target of the QLD surveillance.