Providing practical information to help you protect your farm from biosecurity risks

Nut pests

 

High priority exotic pests

The following are the high priority exotic pests of tree nuts (including almonds, chestnuts, hazelnuts, macadamias, pistachios and walnuts) as identified in the development of the Biosecurity Plan for the Tree Nut Industry.

All would have serious consequences should they be introduced into Australia. The severity of the impact may be dependent on rootstock-scion combinations and the presence or absence of pathogen vectors.

Implementing biosecurity measures to control endemic pests will go a long way towards preventing exotic pests from entering and becoming established on your farm.

The climate of Australia would allow each of these pests to survive, establish and spread, should they be introduced. Additional information on each of these pest threats is included in the fact sheets.

For a complete list of exotic pests, see the relevant industry page on the Plant Health Australia website.

Almond leaf scorch

almond leaf scorch-0162044

Xylella fastidiosa. Photo by Alex H. Purcell, University of California – Berkeley, Bugwood.org

  • Also known as Pierce’s disease
  • Bacterium – Xylella fastidiosa
  • Found in North and South America, and the Mediterranean
  • ‘Burn’ zones on leaves with golden margin; causing wilted, ‘scorched’ canopy resembling salt damage; and stunted trees
  • Spread by sap-feeding leafhoppers or by grafting of infected planting material
  • Pest of almonds and walnuts

Fact sheet

Glassy-winged sharpshooter

glassy winged sharpshooter-5382591

Homalodisca vitripennis. Photo by Johnny N. Dell, Bugwood.org

  • Sharpshooter insect (Hemiptera) – Homalodisca vitripennis
  • Found in the USA, Mexico and some Pacific islands
  • Vector of Xylella fastidiosa and also produces excrement showers
  • Large (13-14 mm) and dark, with yellow dots on head
  • Voracious feeder of a wide range of hosts
  • Eggs laid in side-by-side rows on underside of leaves
  • Good flyer that can spread quickly and eggs can also spread on plant material

Fact sheet

Brown-marmorated stink bug

Brown marmorated stink bug

Adult brown marmorated stink bug. Photo: Bugwood.org

 

  • Insect – Halyomorpha halys
  • Adult is a 12-17 mm long mottled brown coloured stink bug, shaped like a shield
  • Very wide host range and affects many plants, including tree nuts such as hazelnut, pecan and potentially walnuts
  • Originally from eastern Asia, but recently introduced to North America and Europe where it is having a significant impact on agriculture and as a nuisance pest
  • Saliva causes significant damage to plant tissues
  • Eggs are cream to yellow-orange and approximately 1.6 mm long and laid in clusters on the underside of leaves
  • Five nymph stages that range from less than 3 mm to 12 mm long. The nymphs are orange and black when they first hatch but quickly develop a similar colouration to the adults
  • The adults and larvae can be confused with a number of other brown coloured stinkbugs that are present in Australia
  • Hitchhikes in container shipments of a range of commodities, including plant material. Adults are capable of flight allowing localised spread of the pest
  • Pest of hazelnuts and walnuts

Fact sheet

Chestnut blight

Chestnut blight

Lethal canker on main stem. Image: Linda Haugen, USDA Forest Service, Bugwood.org

  • Fungus – Cryphonectria parasitica
  • Enters through wounds in the bark and grows underneath it causing a canker
  • Cankers are not easily seen on older thick barked trees until they crack open, exposing the buff-coloured inner bark and orange fungal fruiting structures
  • Eventually girdles and kills the branch above the infection point
  • Branch loss stimulates the tree to sprout from below the infection point or from the collar region
  • Can kill the tree if the trunk is girdled by a large canker or several cankers growing together
  • The first signs of infection are often wilting, yellowing and death of leaves and shoots. Yellow-brown to orange cankers on young smooth barked trees or branches may also be early signs of infection
  • The fungus is spread by animals that come into contact with the cankers and in the air after rain
  • Chestnut blight occurs in Japan, China, Korea, USA, Canada, Italy and throughout Europe and infects chestnut, oak, red maple, shagbark hickory and eucalypts
  • Pest of chestnuts

Fact sheet

Eastern filbert blight or Hazelnut blight

Image: Joseph O’Brien, USDA Forest Service, Bugwood.org

Image: Joseph O’Brien, USDA Forest Service, Bugwood.org

  • Fungus – Anisogramma anomala
  • Fungal disease that causes potentially fatal cankers on the trunk and branches of hazelnut trees
  • In the United States, entire orchards have been lost to this disease
  • Cankers can expand at a rate of 30cm per year, causing canopy and yield loss
  • If mature trees become infected, death may result in 5-15 years: if trees are younger when they become infected, they may be killed within 4-7 years
  • New infections are usually as a result of infected nursery stock. Symptoms may not be seen for up to two years
  • As the canopy dies back, new shoots and suckers may emerge from the base of the tree base, which also become infected and die
  • Cool wet weather and rain splash is needed for dispersal
  • Pest of hazelnuts

Fact sheet

Green stink bug

Green stink bug

Image: Daren Mueller, Iowa State University, Bugwood.org

  • Stink bug – Chinavia hilaris
  • Feeds on a wide range of crops including grains, fruit and nuts (including pistachio, hazelnut and almonds)
  • Adults are 14-19 mm long, green coloured, and shaped like a shield
  • The head and thorax of nymphs are black and orange when they first hatch, becoming green as they mature. Nymphs have two black coloured patches in the middle of their abdomen, which become more obvious as they mature
  • Could be confused with the other green coloured stink bugs in Australia, but the most obvious differences are the colour of the nymphs and the shape and colour of the adult wing covers
  • Any unusual stinkbug sightings in your crop should be followed up
  • Can spread on plant material. The adults are also capable of flight allowing for localised spread
  • Currently only reported to occur in North America
  • Pest of almonds, hazelnuts and pistachios

Fact sheet

Gypsy moths

USDA APHIS PPQ, Bugwood.org

USDA APHIS PPQ, Bugwood.org

  • Butterflies & moths – Lymantra dispar asiatica and L. dispar dispar
  • Very wide host range, with over 650 known hosts
  • Egg masses laid on solid surfaces and covered in light tan fuzz
  • Mature caterpillars are large (50-65 mm long) and hairy with two rows of spots (red and blue) along their back
  • Moths have greyish-brown wings (30-40 mm wingspan) in males or white with grey markings (40-70 mm) in females
  • Causes heavy defoliation and larvae may produce webbing
  • Can spread large distances naturally or with infested plant material
  •  Pest of chestnuts, hazelnuts, pistachios and walnuts

Fact sheet

Khapra beetle

Khapra beetle 1

Trogoderma granarium: Photo by Ministry of Agriculture and regional Development Archive, Ministry of Agriculture and Regional Development, Hungary, Bugwood.org

  • Beetles & weevils – Trogoderma granarium
  • Adults are small (2-3 mm long) and do not fly
  • Spread in infested grain
  • Larvae are hairy and can survive for over a year without food
  • Phosphine fumigation gives poor control
  • If established, it would affect market access
  • Pest of almonds, pistachios and walnuts

Fact sheet

Leaf footed bugs

Western leaf footed bug

Image: Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org

  • The leaf footed bug (Leptoglossus clypealis), the western conifer seed bug (L. occidentalis) and the western leaf footed bug (L. zonatus)
  • All three species are similar in appearance and cause similar damage
  • Adult leaf footed bugs are approximately 19-25 mm long, brown coloured with a white band across their back. The hind legs have a widened area that resembles a leaf, giving these bugs their name
  • Eggs are brown coloured, rectangular and laid in a row on the leaves, fruit and nuts of the host plant.
  • Can spread on plant material. The adults are also capable of flight allowing for localised spread
  • Pest of almonds and pistachios

Fact sheet

Navel orangeworm

navel orangeworm

Amyelois transitella. Photo by Jack Kelly Clark, UC Statewide IPM Program

  • Larvae of moth (Lepidoptera) – Amyelois transitella
  • Found in USA and Canada
  • Moths lay eggs on new fruit or in mummies
  • Larvae feed on nut meat, leaving webbing and frass
  • Increases threat of aflatoxins in nuts
  • Orchard hygiene important for control
  • Pest of almonds, pistachios and walnuts

Fact sheet

Oriental chestnut gall wasp

Image: Ayanava Majumdar, Alabama Cooperative Extension System, Bugwood.org

Image: Ayanava Majumdar, Alabama Cooperative Extension System, Bugwood.org

  • Ants & wasps – Dryocosmus kuriphilus
  • Also called Asian chestnut gall wasp
  • A small 2.5-3 mm long black wasp that lays its eggs in the buds of chestnut
  • Egg laying induces the formation of green to rose coloured galls up to 20 mm in diameter. In cross section, small white grubs may be visible inside the gall. After the adult wasps emerge these dry out and eventually fall from the tree
  • Any galls on chestnut trees should be reported for diagnosis
  • Severe infestations can cause up to 70 per cent yield losses and in some cases the death of the tree
  • Considered to be the most significant insect pest of chestnuts worldwide
  • Can be spread by the movement of grafting material. The adults are also capable of flight allowing for localised spread
  • Native to Asia (china, Japan and Korea): recently introduced into the United States and Europe
  • Pest of chestnuts

Fact sheet

Sudden oak death

sudden oak death-1427111

Photo by Joseph O’Brien, USDA Forest Service, Bugwood.org

  • Fungus – Phytophthora ramorum
  • Infects over 130 tree and shrub species
  • Symptoms in shrubs: blackened shoots, diffuse dark brown spots or blotches with fuzzy margins, starting at the leaf tip
  • Symptoms in trees: stem canker with red to black thick sap oozing on the bark surface. Stem necrosis leads to the death of whole crown
  • Spread with infected plant material, or water, growing media and compost that has been in contact with infected plants
  • Pest of chestnuts, hazelnuts and macadamias

Fact sheet

Tropical nut borer

Damage to a macadamia shell. Image: Vincent P Jones

Damage to a macadamia shell. Image: Vincent P Jones

  • Beetles & weevils – Hypothenemus obscurus
  • The most important pest to macadamia production in Hawaii
  • It can damage up to 60% of the crop in heavily infested areas where harvesting is not strictly managed
  • Damage is usually seen as abundant 0.5 mm holes in the husk of the nut
  • Extensive tunnelling is visible throughout the husk, shell and kernel
  • Damaged kernels are open to further spoiling through fungal infection. The beetles are very small and up to 190 have been found in a single macadamia nut
  • Widespread in North America (including Hawaii), Central and South America where it attacks several tree species
  • Pest of macadamias

Fact sheet

Tropilaelaps mites

Tropilaelaps mite-5459547

Photo by Pest and Diseases Image Library, Bugwood.org

  • Mites – Tropilaelaps clareae and Tropilaelaps mercedessae
  • External parasitic mites that feed on the haemolymph of both drone and worker bee larvae, pupae and adult bees
  • Detection possible by close examination of brood or testing of adult bees
  • Symptoms include deformed pupae and adults (stunting, damaged wings, legs and abdomens), Parasitic Mite Syndrome and colony decline
  • Tropilaelaps mites can also spread viruses, further affecting the colony’s health and disease susceptibility
  • Pest of almonds and macadamias

Fact sheet

Varroa mites

Varroa mitea-1317031

Photo by Scott Bauer, USDA Agricultural Research Service, Bugwood.org

  • Mites – Varroa destructor and  Varroa jacobsoni
  • External parasitic mites that feed on the haemolymph of both drone and worker bee larvae and pupae, and adult bees
  • Detection possible by close examination of brood or testing of adult bees
  • Symptoms include deformed pupae and adults (stunting, damaged wings, legs and abdomens), Parasitic Mite Syndrome and colony decline
  • Varroa mites can also spread viruses, further affecting the colony’s health and disease susceptibility
  • Pest of almonds and macadamias

Fact sheet

Verticillium wilt

verticillium wilt-5365934

Verticillium dahliae: Photo by Howard F Schwartz, Colorado State University, United States; Bugwood.org

  • Fungus – Verticillium dahliae (defoliating strain)
  • Risk is from new, defoliating strains establishing to which the local cotton varieties have little or no resistance (non-defoliating strains present in Australia)
  • Extremely wide host range, including vegetable, fruit and broadacre crops
  • Leaf mottling, vascular peppering, total defoliation, boll shedding
  • When the stem is cut lengthways, vascular discolouration exhibits flecking of the inner tissues
  • Spread by spores in water, soil and infected plant material, clothing and equipment
  • Non-defoliating strains of Verticillium dahliae occur in Australia. The defoliating strain VCG 1A is known to occur in Australia and is currently under review
  • Pest of almonds, chestnuts, pistachios and walnuts

Fact sheet