Christmas beetles
S. A. Lawson and J. King
Summary
Christmas beetles (Coleoptera: Scarabaeidae), mostly Anoplognathus species, are important pests of young eucalypt plantations and can cause severe defoliation of trees prior to canopy closure. Adult beetles emerge during the early-mid summer period from the soil and feed on eucalypt foliage. They are extremely voracious feeders and large swarms can rapidly defoliate trees. The biology and management of these beetles is reviewed in this note.
Damage
Adults. Adult beetles eat tree leaves and are voracious feeders. Trees can be severely damaged in a very short time, particularly by beetles feeding in swarms. Swarms can occur in 'waves' throughout the late spring - early summer season, depending on favourable weather conditions.
Beetles repeatedly swarming on trees can totally defoliate them. Repeated defoliations over several seasons can kill even mature trees, although in plantation situations it is young trees up to about three years old that are most at risk.
Christmas beetles feeding. Typical beetle feeding damage
Larvae. Beetle larvae live in the soil, where they eat decaying organic matter or roots. Larvae naturally feed on the roots of native grasses and other vegetation.With changed farming techniques and the introduction of improved pastures and some exotic crops, numbers of Christmas beetles and other scarabs have increased.
Larvae thrive on the roots of improved pasture grasses and turf. Some eat the roots of sugar cane, maize and other crops, and they can be serious pests. Affected plants yellow and wilt, and sometimes fall over. Larvae are not normally tree pests, but they occasionally damage the roots of newly planted trees and nursery stock.
Beetle species
Adult beetles are large, about 25-30 mm in length. So far, two species have been important in eucalypt plantations in Southeast Queensland. These are Anoplognathus porosus and A. boisduvali.These are similar in size, shape and colour and are often observed feeding together on the same trees.
Anoplognathus porosus
A. boisduvali
The species found in North Queensland are likely to differ. Other less common species recorded in trials and plantations have been A. viridiaeneus, a large iridescent species; A. pallidicollis and Repsimus aeneus, an iridescent, black species.
Host trees
Christmas beetles are capable of attacking a wide range of eucalypts and other tree species. Some eucalypts are more resistant to attack than others. Gympie messmate (Eucalyptus cloeziana) appears to be the species most resistant to beetle attack. Species that are known to be susceptible include Dunn's white gum (E. dunnii), spotted gum (Corymbia citriodora subsp. variegata), forest red gum (E. tereticornis), river red gum (E. camaldulensis), and flooded or rose gum (E. grandis ). Hybrids of the latter three species are also susceptible to beetle attack.
Distribution
Christmas beetles are widely distributed throughout eastern and southeastern Australia. Beetles are more common in the coastal, higher rainfall areas. However, beetles can be found almost anywhere suitable breeding material, mainly native and introduced pasture grasses, exists. Distribution of individual species is not yet known in detail, but Anoplognathus porosus, A. boisduvali and A. pallidicollis are the most commonly encountered species in southeast Queensland.
Life cycle
The life cycle extends over one or two years, depending on species (see the Figure below ). Eggs are laid into soil or compost in the spring and early summer. Females are capable of laying between 20 and 40 eggs each (Elliott et al. 1998). Newly hatched larvae feed on organic matter in the soil. Older larvae feed on organic matter and/or roots. In a one-year cycle, larvae spend one winter feeding in the soil and pupate the following spring. In a two year cycle, larvae spend two winters in the soil.
In late winter/early spring fully-grown larvae move close to the surface and hollow out a chamber in which they pupate. Pupation lasts several weeks. After pupation the new adults must wait in the soil for suitable conditions, usually when the soil is softened by rain, allowing them to dig their way to the surface. There can be mass flights of beetles after spring rains or thunderstorms. In very dry conditions the beetles cannot burrow to the surface, and die in the soil. In flooded conditions they will drown.
After emerging, beetles fly a short distance to food plants to feed and mate. The females then return to the soil and lay eggs, although some lay eggs before feeding. Feeding and egg-laying may continue for several days. Adults may live for some weeks. Each species is active at about the same time each year. In those with a two-year life cycle the generations overlap and adults fly every year.
There are differences in behaviour between species. Some form large swarms, others feed singly or in small groups; some are active during the day (diurnal) and others in the evening or at night (crepuscular or nocturnal). Crepuscular and nocturnal Christmas beetles are often attracted to lights and will fly into homes in large numbers.
Life cycle of the christmas beetle in southeast Queensland
Management
General
Christmas beetles are very difficult to control. It is difficult to kill larvae in the soil because the larvae are resistant to some insecticides. The adults fly and can emerge within plantations, but they also come in from surrounding areas. They appear suddenly and do a lot of damage in a short time. Continuous chemical treatment, 'just in case' can mean time and money wasted, as well as having detrimental side effects on the environment. A more directed approach to management, based on knowledge of the pest, and a combination of non-chemical and chemical techniques, can give better results.
Efforts should concentrate on reducing the numbers of adults, thereby reducing egg-laying. Record keeping, and regular inspection at possible emergence times are important. Inspection should probably be daily at critical periods such as after the first heavy spring rains. If possible, get the beetles identified.
Non-Chemical
At new sites cultivation of soil, where possible, will help to control larvae, by killing them and attracting birds such as ibis and magpies, which eat very large numbers of larvae. Adult beetles can also be controlled manually by knocking them into a bucket containing soapy water.
Chemical
At the time this guide was prepared, only products containing the systemic insecticide dimethoate at 400g/L (e.g. Saboteur 400) were registered for use against Anoplognathus species of. beetle in eucalypt plantations in Queensland. This product can be applied with a spray pack or a mister. Note: This information was correct at the time of publication. However, it is the user's responsibility to ensure that registered agricultural chemicals are used in accordance with legal requirements (see Further Information). Always read the label.
Plantations should be checked regularly after rain during late spring - mid summer for populations of these beetles. Chemical applications should be considered only if defoliation is severe enough to cause an unacceptable loss of growth or tree mortality. Most eucalypts can tolerate levels of defoliation of up to 40-50% without serious loss of growth. A range of chemicals for registration against eucalypt pests is currently being evaluated.
Tree vigour
Plantation management that promotes tree vigour is of vital importance in lessening the effects of leaf feeding insects. Effective weed control and fertilisation during the early period of plantation growth is of particular importance for tree health. Trees that are growing vigorously are better able to compensate for leaf loss and will achieve canopy closure earlier, reducing the period of exposure to the pest. However, fast grown trees of species susceptible to stem borers, such as rose wood (E. grandis), are more likely to be attacked by giant wood moths and longicorn beetles and some caution is therefore necessary when these trees are grown for timber production.
Long term
Long-term management of these pests will ultimately be achieved by using resistant tree species, provenances and/or hybrids in plantations. Leaf chemicals which help confer resistance to Christmas beetles, have been identified in some eucalypt species, particularly in E. camaldulensis, and resistant provenances are now being developed. Screening techniques, which will lead to easier and earlier identification of resistant biotypes, are also currently being developed.
Further Information
Infopest CD-ROM contains current national information on registered agricultural chemicals and is available from Infopest, DPI, GPO Box 46, Brisbane Qld 4001 or by email from infopest@dpi.qld.gov.au.
Elliott, H.J., Ohmart, C.P and F.R. Wylie (1998) Insect Pests of Australian Forests: Ecology and Management. Inkata Press. 214pp.
Farrow, R. (1996) CSIRO Identification Leaflets - Insect pests of eucalypts on farmland and in plantations in southeastern Australia. No. 7. Christmas beetles. 4pp. CSIRO Publishing.
State Forests of NSW (1995). Christmas beetles. Forest Protection Series Leaflet E2, 4pp.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
File No: FOR0047
Last updated February 2005
