TPCP continues research on the Cossid moth Coryphodema tristis
The Cossid Moth, Coryphodema tristis (Lepidoptera: Cossidae) was identified in July 2004, extensively damaging mature Eucalyptus nitens in Mpumalanga. Damage by this
insect was first noted by Sappi staff and the insect was subsequently identified by Sappi Research Fellow and Entomologist, Dr. Solomon Gebeyehu and his colleagues at the TPCP. The insect
is a wood borer and is also known as the Goat moth or Carpenter moth. Since its first detection on Eucalyptus, Coryphodema tristis has attracted substantial interest and
concern from the forestry industry and private tree growers as well as Entomologists at TPCP. It damages trees by boring into the wood and causing loss of wood volume and quality as well
as tree death.
Dr. Solomon Gebeyehu and Maria-Noel Cortinas
Coryphodema tristis is native to South Africa and has long been associated with exotic plants such as vines, apples and quince in the Western Cape. It also feeds on a few
native trees in various families including Malvaceae and Combretaceae. However, its appearance of Eucalyptus is the first record of its association with Myrtaceae. What is
more interesting about this insect is that it appears to feed only on E. nitens and has not been associated with any of the other commercial Eucalyptus species. The
basis for this very selective preference for E. nitens is a subject of TPCP research. Research is also underway to determine the possible causes of this sudden host shift to
Eucalyptus, and the potential impact on native trees.
The Cossid moth has a very interesting biology. It has an extended larval stage of up to 18 months but the adult lives for a maximum of only 6 days. During this time the females lay up to 300 eggs and then they die. In the few months following hatching, the small larvae feed on the cambium of the infested trees. As they grow in size, they bore deep into the sapwood and heartwood. As the larvae mature and prepare for pupation, they establish an exit hole on the main stem or branch of the tree and then pupate inside the tunnels. As the adult is about to emerge, the pupa wriggles itself and protrudes halfway from the exit hole. Adult emergence is easily detected by the pupal case that protrudes from the exit hole. Oviposition starts on crevices and cracks on the bark soon after emergence. The eggs hatch in a few weeks.
Damage is done only by the larval stage of Coryphodema tristis. The adult does not feed at all. Larvae can grow up to 6cm in length. Contrary to the larval feeding behaviour on its other native and exotic hosts where it is known to be solitary, it manifests a gregarious feeding behaviour on its new host, E. nitens. It is common to find 50 or more mature larvae in a small section of an infested stem.
It is now known that Coryphodema tristis is distributed over hundreds of hectares of E. nitens plantations in the Mpumalanga region. Dr. Gebeyehu has been investigating various aspects of this pest including ways of managing it. During a recent field trip to infested sites to conduct area-wide surveys, it was clear that the problem is more serious than was anticipated at the end of the last growing season. The survey revealed that the pest is distributed over a wider area, and more importantly a striking finding was that high-value seed producing trees of 25 years of age are heavily infested by the moth. Some trees have already died and the damage is extending to new trees in the orchards. Since the value of each of these seed trees is much higher than individual trees grown for pulp or wood, appropriate management of the pest warrants considerations.
Currently Dr. Gebeyehu is investigating the application of chemical attractants, also known as pheromones, for use in monitoring and controlling the Cossid moth. Pheromone traps containing potential chemical compounds have been set up in infested compartments managed by TWK in the Carolina / Lothair area. Daily checking of the traps and evaluation is being undertaken by the area foresters. The result of this test will form the basis of a monitoring and controlling strategy. In this way, other management options such as restriction of movement of infested wood to other regions can be added.
The Cossid moth has a very interesting biology. It has an extended larval stage of up to 18 months but the adult lives for a maximum of only 6 days. During this time the females lay up to 300 eggs and then they die. In the few months following hatching, the small larvae feed on the cambium of the infested trees. As they grow in size, they bore deep into the sapwood and heartwood. As the larvae mature and prepare for pupation, they establish an exit hole on the main stem or branch of the tree and then pupate inside the tunnels. As the adult is about to emerge, the pupa wriggles itself and protrudes halfway from the exit hole. Adult emergence is easily detected by the pupal case that protrudes from the exit hole. Oviposition starts on crevices and cracks on the bark soon after emergence. The eggs hatch in a few weeks.
Damage is done only by the larval stage of Coryphodema tristis. The adult does not feed at all. Larvae can grow up to 6cm in length. Contrary to the larval feeding behaviour on its other native and exotic hosts where it is known to be solitary, it manifests a gregarious feeding behaviour on its new host, E. nitens. It is common to find 50 or more mature larvae in a small section of an infested stem.
It is now known that Coryphodema tristis is distributed over hundreds of hectares of E. nitens plantations in the Mpumalanga region. Dr. Gebeyehu has been investigating various aspects of this pest including ways of managing it. During a recent field trip to infested sites to conduct area-wide surveys, it was clear that the problem is more serious than was anticipated at the end of the last growing season. The survey revealed that the pest is distributed over a wider area, and more importantly a striking finding was that high-value seed producing trees of 25 years of age are heavily infested by the moth. Some trees have already died and the damage is extending to new trees in the orchards. Since the value of each of these seed trees is much higher than individual trees grown for pulp or wood, appropriate management of the pest warrants considerations.
Currently Dr. Gebeyehu is investigating the application of chemical attractants, also known as pheromones, for use in monitoring and controlling the Cossid moth. Pheromone traps containing potential chemical compounds have been set up in infested compartments managed by TWK in the Carolina / Lothair area. Daily checking of the traps and evaluation is being undertaken by the area foresters. The result of this test will form the basis of a monitoring and controlling strategy. In this way, other management options such as restriction of movement of infested wood to other regions can be added.
