Polyphagous shot hole borer

Polyphagous shot hole borer

Polyphagous shot hole borer (Euwallacea fornicatus) (Figure 1.) is an exotic plant pest not present in Australia. It vectors fusarium dieback (Fusarium euwallaceae), which is also not present in Australia. Polyphagous shot hole borer and fusarium dieback are serious threats to Australia’s horticultural industries, amenity trees and native environment. They are listed on Australia’s Exotic Environmental Pest List.

Fusarium dieback associated with attack by polyphagous shot hole borer affects a wide range of species, with highly susceptible species killed.

Notifiable status

Polyphagous shot hole borer (Euwallacea fornicatus) is not a notifiable plant pest in NSW. However, if you suspect Polyphagous shot hole borer (Euwallacea fornicatus):

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

Description

The adult beetle is very small, 1.5 to 2.5 mm long, and black (Figure 2.)

Adult PHSB

The beetle bores about 1–4 cm into the tree; the exit hole is very small (<1 mm diam.); with many exit holes in an infested tree (Figure 3.).

beetle bores

The larvae are small, white, legless and “C” shaped (Figure 4.).

Larvae

Host trees

Polyphagous shot hole borer attacks a wide range of hardwood trees, including species within Acacia, Acer, Brachychiton, Casuarina, Liquidambar, Magnolia, Persea, Platanus, Populus, Quercus, Cupaniopsis, Salix, Ficus, Camellia, Fagus, Albizia, Corymbia, Alnus.

Damage

The beetle (Euwallacea fornicatus) inoculates the fusarium dieback fungus (Fusarium euwallaceae) into the tree. The larvae of the beetles feed on the fungus within beetle galleries. The fungus destroys the food and water conducting system in the tree, leading to stress and dieback, and death in severe cases.

Symptoms of infection include water-soaked lesions surrounding exit holes in the bark, which are often surrounded by a white powdery exudate (borer frass) (Figure 5.).

PHSB symptoms

Sometimes frass tubes (which resemble small matchsticks extending from the hole) can be seen (Figure 6.).

Visible frass tubes

Examination under the bark and in the wood reveals beetle galleries and brown to black discolouration caused by the fungus.

Affected trees might show signs of wilting and have dead branches.

In severe cases the whole tree dies.

Spread

Polyphagous shot hole borers may be introduced to Australia as eggs, larvae or adults concealed within raw timber materials. This could include whole plant parts, timber for construction, timber packaging, wood chips or any other material produced from host trees.

Distribution

Euwallacea fornicatus is native to Asia; it has been introduced to the USA, South Africa and Israel.

Lifecycle

Adult females disperse during the day and attack hosts within 30–35 m, but can travel up to 400 m. They bore into the branch or trunk. Eggs are then laid and take up to 1 month to develop into adults. Mating takes place within the galleries, then females disperse to new hosts.

Actions to minimise

Put in place biosecurity best practice actions to prevent entry, establishment and spread of pests and diseases:

  • practice “Come clean, Go clean”
  • ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements
  • monitor your crops regularly
  • monitor and control weeds that can harbour the pest
  • source plant material of a known high health status from reputable suppliers
  • keep records