Threats

Eucalyptus long horn beetles \ Phoracantha spp.

Eucalyptus long horn beetles \ Phoracantha spp.
Phoracantha recurva (Newman) and Phoracantha semipunctata (Fabricius)

Phoracantha recurva (Newman); Phoracantha recurva papua (Gressit, 1959).

Phoracantha semipunctata (Fabricius); Phoracantha inscripta (Germar, 1848) and Phoracantha hospita (Pascoe, 1864).

Wood boring

The beetles tend to attack damaged and stressed trees. Emergence holes are visble on the bark of infested trees. Stains or gum exudates are common symptoms found on the limbs or trunks of trees. Foliage can become discoloured and wilted. The feeding of larvae results in galleries beneath the bark. Heavily infested trees exhibit a thin canopy with wilted leaves. The bark is cracked and contains frass.

Adults: The adults are approximately 14 to 30 mm in length. On their elytra (wing covers) they have shiny, dark brown and yellow to cream coloured areas. They have long antenna. The antennae are either the same length as their body or longer and the males have prominent spines on their antennae. The adults of both species are similar, however P. semipunctata is slightly larger and has more prominent markings on its wing covers. Their wing covers are mostly dark brown with a zigzag line that bisects the cream area in the middle. P. recurva are mostly cream to yellow and the dark areas are generally limited to the posterior end of the wing cover. Long, dense golden hairs can be found on the underside of each antennae segment of P. recurva.

Larvae: The larvae are cream coloured and legless.

Eggs: Ovoid and pale yellow.

Both species attack stems and branches that are stressed or dying, or newly felled trees (Ivory 1997, Paine & Millar 2002).

The female P. semipunctata lays approximately 40 eggs below detached bark of stressed trees. The eggs hatch from 1 to 2 weeks later depending on the weather. After the larvae hatch, they acquire nutrients from the cambium and phloem to assist its development. Larvae nearing development will move to the external layer of the sapwood and establish pupal chambers; the larvae will then pupate. It takes approximately 180 days to develop to an adult (Paine et al. 2019). The adult starts to dig itself out the pupal chamber, creating an emergence hole approximately 8 to 10 cm.

In South Africa there are two partially overlapping generations. The adults are present between September and November, and February and March (Kliejunas et al. 2001).

The female P. reurva lay approximately 40 eggs in bark crevices and branch stubs (Wang et al; Paine et al. 2000). The larvae hatch approximately 6 to 15 days later (Ivory 1977). The larvae bore under the bark and make irregular galleries containing frass. The larvae reach maturity between 4 to 6 months. When it reaches maturity it constructs a vertical pupal chamber and an exit plugged with frass. Adults emerge approximately 10 days later and can live for approximately 96 days. The beetles are nocturnal and hide under the lose bark during the day. In South Africa, the complete life cycle lasts between 208 to 355 days and contains between one to three generations depending on temperature (Ivory 1997; Paine et al. 2000; Farrow et al. 1996).

Chemical control: Chemical control is not efficient in the management of Eucalyptus borers (Paine et al. 2000).

Cultural Control: Avoid / minimize tree stress and remove infected trees (Paine et al. 2000).

Biological Control: Avetianella longoi, an egg parasitoid that is native to Australia, is one of the most important parasitoids used to control P. semipunctata. This parasitoid was intentionally introduced into South Africa, USA and Chile to control both species. It was noted to be more effective against P. semipuncata in California (Paine et al 2000). Tribe (2003),  provided details on the introduction of A. longoi to South Africa and noted that it is more effective against P. semipunctata than P. recurva, as reported in California.

The larval parasitoids, including Syngaster lepidus, Jarra phoracantha and Jarra maculipennis, were introduced from Australia to California for the biological control of Phoracantha spp. (Paine et al. 1995, Paine et al. 2000). Syngster lepidus, Jarra phoracantha and J. maculipennis were introduced into South Africa from California, but J. maculipennis did not established (Moore 2003). The braconid, Iphiaulax sp. has been recorded in South Africa but in very low densities (Ivory, 1977). The Pteromalid, Oxysvhus genualis, native to South Africa, has also been reported to attack Phoracantha sp. in South Africa (Moore 2003, Prinsloo 2004).

Megalyra fasciipennis is a pupal parasitoid that was introduced to South Africa in 1910 from Australia, reported to have established in the Western Cape in 1962 and rediscovered in 1993 when parasitism reached 50% (Moore, 1993).

Phorcantha recurva (Newman, 1937) and Phorcantha semipunctata (Fabricius, 1906)
Widespread.
Eucalyptus spp.
Australia

Gallery

Photo credit: Michelle Schroder
Photo credit: Michelle Schroder
Photo credit: Michelle Schroder
Phoracantha semipunctata
Photo credit: Michelle Schroder
Phoracantha recurva
Photo credit: Michelle Schroder
Eggs on the surface of the bark.
Photo credit: Michelle Schroder
Eggs
Photo credit: Michelle Schroder
Galleries
Photo credit: Michelle Schroder

Farrow RA (1996) Insect pests of eucalypts on farmland and in plantations in south-eastern Australia. Australia: CSIRO. 60ppMurphy ST, 1996. Status and impact of invasive conifer aphid pests in Africa. Impact of diseases and insect pests in tropical forests. Proceedings of the IUFRO Symposium, Peechi, India, 23-26 November 1993., 289-297.

Ivory MH, 1977. Preliminary investigations of the pests of exotic forest trees in Zambia. Commonwealth Forestry Review, 56:47-56.

Kliejunas JT; Tkacz BM; Burdsall HHJr; DeNitto GA; Eglitis A; Haugen DA; Wallner WE, (2001) Pest risk assessment of the importation into the United States of unprocessed Eucalyptus logs and chips from South America. General Technical Report - Forest Products Laboratory, USDA Forest Service, No. FPL-GTR-124:viii + 134 pp.

Paine TD; Dahlsten DL; Millar JG; Hoddle MS; Hanks LM, 2000. UC scientists apply IPM techniques to new eucalyptus pests. California Agriculture, 54(6):8-13.

Paine, T, Millar, J, Hanks, L , 1995. Integrated program protects trees from eucalyptus longhorned borer. California Agriculture, 49(1):34-37.

Paine TD; Millar JG, 2002. Insect pests of eucalypts in California: implications of managing invasive species. Bulletin of Entomological Research, 92(2):147-151; 38

Moore JA, 1993. Rediscovery and releases of parasitoid of eucalyptus borer. Plant Protection News, No. 33:4.

Moore, JA, 2003. Biological control of the Eucalypt borers, Phoracantha semipunctata (Fabricius) and P. recurva Newman (Coleoptera: Cerambycidae) in South Africa. MSc thesis. University of Stellenbosch, p1-96.