Pine nematode

Radiata pine tree with all needles and branches completely brown

Current situation

Bursaphelenchus pine nematodes were detected in Sydney at the beginning of 2016. Whilst these initial infestations were quickly destroyed, surveillance and testing of pine trees across Sydney and other parts of NSW found further infestations in locations at long distances from the initial detection. By the end of 2016 Consultative Committee on Emergency Plant Pests recommended that it would not be technically feasible to eradicate the Bursaphelenchus pine nematode from Australia.

Notifiable status

One species of pine nematode Bursaphelenchus vallesianus has been found in the Sydney basin and parts of northern NSW. Other Bursaphelenchus species are not present in Australia. Only exotic species of Bursaphelenchus are notifiable plant pests in NSW.

All notifiable plant pests and diseases must be reported within 1 working day.  You can report notifiable plant pests and diseases by one of the following methods:

A full list of notifiable plant pests and diseases can be found in Schedule 2 of the NSW Biosecurity Act 2015.

Description

Pine nematodes are microscopic, wormlike organisms. They are invisible to the naked eye and require technical expertise and molecular methods for identification. However, the progression of symptoms in a pine tree may indicate a nematode infestation.

How to spot a tree infested with pine nematode

The first symptoms of a pine nematode infestation include brown and dry needles in the tree branches.

Tree death usually progresses from the top of the tree downward.

A serious nematode infestation can result in rapid dieback of the pine tree, sometimes within a few weeks.

Many pine trees normally have dead needles present in the canopy and the odd dead branch. It is considered relatively normal for up to 15% of the tree canopy to be affected by dead tips or dead older needles caused by environmental factors other than nematodes. Suspected nematode presence needs to be confirmed by a technical expert.

Host trees

Of over 100 known speciesof Bursaphelenchus approximately 70% are associated with conifers, mainly pines (Pinus species).

Common trees in Australia known to be hosts of Bursaphelenchus nematodes include:

  • Aleppo pine (Pinus halepensis)
  • Austrian pine (Pinus nigra)
  • Common spruce (Picea abies)
  • Maritime pine (Pinus pinaster)
  • Ponderosa pine (Pinus ponderosa)
  • Radiata pine (Pinus radiata)
  • Stone pine (Pinus pinea)
  • Scots pine (Pinus sylvestris)
  • Turkish pine (Pinus brutia)

Damage

Pine nematodes may be linked with rapidly dying pine trees. Most pine nematodes feed on fungi inside the tree without causing problems. There are a few species of pine nematodes including some Bursaphelenchus species which feed directly on plant cells. In these cases feeding by pine nematodes can lead to rapid wilting and tree death.

Pine nematodes move within infested host trees in the water transport system. Nematodes feeding on plant cells cause air pockets to form, disrupting water uptake by the tree. Death of the tree is rapid, often within a few weeks or months.

Pine nematode is a threat to softwood forestry plantations.

Spread

Most pine nematodes are carried from infested trees to new host trees by vector beetles. A number of beetle species including native species belonging to the Scolytidae, Cerambycidae, Curculionidae, and Buprestidae families are known to vector pine nematodes.

Pine nematodes and their beetle vectors can be spread over long distances inconifer wood chips, logs, unseasoned timber, untreated wooden pallets, crates, packing-case material and dunnage.

Lifecycle

The pine nematode has two lifecycles: one completed inside the host tree and one inside the vector beetle.

In the host tree, the lifecycle occurs in the sapwood and involves the egg, four larval stages and the adult. A complete cycle can take only 4−5 days under favourable conditions.

Infestation of the vector beetle occurs after tree death. Nematode larvae infest beetle pupae present in the tree and undergo a non-feeding larval stage for transport. These larvae enter the respiratory system of the young beetle when it emerges and are vectored by the beetle to new host trees.

Management

Control of pine nematode is limited to prevention. Chemical control is impractical, expensive and ineffective.

Infested trees should be removed (PDF, 156.82 KB) Wood chipping a pine tree suspected of being infested with Bursaphelenchus nematodes is recommended. Wood chipping reduces the risk of survival of both the nematodes and any beetles which could carry the nematodes from infested to healthy pine trees in the area.

Grind the stump to ground level or remove by excavator if other pine trees are nearby.

If possible pile the woodchips back over the stump and cover the pile with black plastic.

Covering the pile with black plastic has a number of advantages. The black plastic traps any beetles which survive the chipping process, increases the internal temperature of the pile to assist in killing the nematodes and begins decomposition of the woodchips.

If it is not practical to retain the woodchip pile on site the woodchips could be relocated to another site but must not be placed near living pine trees. Nematodes may move into living pine trees through wounds in the trunk or roots.

Nematodes in the woodchip pile are likely to die within four to six weeks.

Woodchips could be used as garden mulch after six to eight weeks.