Agnote
No: I58
July 2013
Management of the Giant Northern Termite
(Mastotermes darwiniensis)
B. M. Thistleton, M. J. Neal and E. S. C. Smith, Plant Industries, Darwin
INTRODUCTION
Termites are small, secretive insects that can cause
considerable damage to wooden structures and living
plants, particularly in tropical areas. The common name
"white ants" is a very poor choice since termites are not
ants and have been shown to be more closely related to
cockroaches.
Termites live in a complex, highly-organised social
group inside a nest which can be either above or below
the soil surface. Each colony consists of several castes:
a reproductive group, including an egg-laying queen,
soldiers to protect the colony, and worker termites
whose function is to gather food and tend both the
reproductive group and the developing young. The
worker and soldier termites are usually detected. They
have soft bodies, which can desiccate readily and they
are sensitive to light so they rarely venture from their
enclosed tunnels in the soil or the feeding galleries in
wood.
Food gathered by the workers can be consumed at the
feeding sites or carried to the nest. Some termites
forage above ground by covering dead or fallen timber
with a thin layer of mud, while others forage at night by
harvesting grasses and leaf litter which is then stored in
Figure 1. A soldier giant northern termite, about 12 mm long
the nest. Few species feed on living plants.
Some species build mounds or nests on or in the base of tree trunks or stumps, while others can be free standing
and remote from their feeding sites. Foraging tunnels from the nest to the feeding sites can, in some species, be
in excess of 100 metres away.
When termites feed, micro-organisms inside their gut produce enzymes to break down the plant material for
digestion. After the workers return to the nests, they share their digested food during mutual grooming activities
with other members of the colony.
The giant northern termite (Mastotermes darwiniensis), which is native to northern Australia, is the most
damaging species attacking plants in the Top End. This species is readily recognised since its workers and
soldiers are usually over 12 mm long, whereas all but one other species are less than 7 mm. The great majority of
small termite species do little damage to native plants, ornamentals or fruit trees and rarely need to be controlled.
Some species can attack timber in service (houses, sheds, pergolas, decking etc.). In these situations it is
recommended that you contact a Pest Control Officer.
The remainder of this Agnote deals only with the giant northern termite and its control in trees but not in timber in
service.
BIOLOGY OF THE GIANT NORTHERN TERMITE
Eggs (Figure 2) are laid in small batches and hatch into immatures (Figure 3). These can either develop into
workers and soldiers (Figure 4) or into nymphs (Figure 5) which produce winged adults called alates.
Figure 2. Giant northern termite eggs
Figure 3. Giant northern termite immatures
Figure 4. Giant northern termite workers, soldiers and eggs
Figure 5. A giant northern termite nymph
Alates (Figure 6) disperse, lose their wings and become primary kings and queens. However, the establishment
of new colonies by this method is uncommon. The workers can moult into wingless secondary reproductives,
called neotenics (Figure 7), and they are the main egg-laying caste in giant northern termite colonies. Colonies
increase in size by producing neotenics and budding off from the main colony. This is an important consideration
for control since a termite-free area is at the greatest risk of colonisation underground along its borders with
existing colonies.
© Northern Territory Government
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Figure 6. A giant northern termite winged adult
Figure 7. Giant northern termite secondary reproductives
(neotenics)
In native bush, colonies of the giant northern termite are small in extent and numbers of individuals, and most of
the hollow trees are caused by Coptotermes spp., not Mastotermes. However, in areas developed for horticultural
and forestry use, colonies can be huge, covering several hectares underground and consisting of large numbers
of individuals. These colonies often have many nests with secondary reproductives and nurseries of immature
termites, such as the one shown under an old mango tree (Figure 8). It has been demonstrated that nests are
connected by underground tunnels and that the termites move freely between them.
Figure 8. A giant northern termite nest under an old mango tree
SYMPTOMS OF GIANT NORTHERN TERMITE ATTACK
Trees infested with termites often show no external signs of their presence nor are adverse effects always
caused. The most common early symptoms of infestation are yellowing, wilting and drying of leaves, and the
death of shoot tips or whole branches on an otherwise healthy-looking tree. As the infestation progresses,
symptoms include occasional bursts of new growth that then wilt and die, branches that fold over (Figure 9) and
mud-covered galleries on the outside of the trunk.
Worker termites enter the tree through the root system or through the base of the tree below the ground. They
then move up through the heartwood and start to hollow out the upper branches weakening the structure of the
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tree. Sometimes they will move to the outside of the tree and run several deep grooves (Figure 13) around the
trunk which they cover with mud. This is referred to as ringbarking and, together with extreme internal damage
(Figures 10 and 11), can cause the death of the tree (Figures 12 and 14).
Foraging galleries radiating from the nest can be in excess of 100 metres and are usually found within 20 cm of
the soil surface although they have been recorded at depths of several metres following tree roots or sourcing
water.
.
Figure 9. "Folded” cashew branches
Figure 10. Damage to a Caribbean pine
Figure 11. Exposed galleries in a cut mango trunk
Figure 12. A mango tree killed by giant northern termites
Figure 13. Ring barking on a cypress
Figure 14. An African mahogany killed by giant northern
termites
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PLANTS ATTACKED
The great majority of common native trees, including (in order of preference) acacias, grevilleas, eucalypts and
terminalias are attacked. Most introduced plants are also susceptible. The more commonly attacked trees are
mango, cashew, citrus, poinciana, gmelina, aralia, African mahogany, and many palm species.
MONITORING FOR TERMITES
Termites can be monitored by looking for the symptoms described and illustrated above. However, external signs
are often only evident when the internal damage is already extensive. Trunks of larger trees, such as mature
mango, can be drilled into the centre using a 13-mm bit to locate the central galleries (Figure 15). If termites are
active in the tree, they will seal the hole with mud within 24 hours. This process can be carried out on groups of
trees in areas where termite infestation is suspected
Where monitoring is required along borders between uninfested and infested blocks, rows of sacrificial plants,
such as cassava, grevilleas or acacias can be planted or wooden billets placed in the ground. These should be
monitored for damage every two to three months and, if infestations are found, the termites should be aggregated
(see below) and controlled.
Figure 15. Drilling a cashew tree to detect a giant northern termite infestation
TERMITE CONTROL
Termiticides
Since worker termites radiate from the central nest to forage for food, the application of fast-acting insecticides to
the feeding sites will kill them at that site but few others will be affected. However, if a slow-acting insecticide is
used, the workers will carry it back to the nest and, by transferring it to other members during grooming and
feeding, the colony can be greatly reduced.
The recommended termiticide with such properties is fipronil (Termidor® or Regent®). Its use in horticultural
crops is covered by a number of Minor Use Permits issued by the Australian Pesticides and Veterinary Medicines
Authority (APVMA). These permits give detailed directions on how to apply the termiticide for a variety of
situations. These methods include soil injection, trunk injection and application to aggregation drums. Since these
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permits change over time, they are not listed here, but current ones can be downloaded from the APVMA website
(http://www.apvma.gov.au) or can be obtained by contacting DPIF.
Soil and trunk injection
The Minor Use Permits allow fipronil to be applied to some species of infested trees by injecting into the soil
around the roots or directly into the trunk through the holes drilled for monitoring purposes. Since fipronil is carried
to adjacent trees up to 25 m away and sometimes farther, it is often not necessary to treat all trees in infested
groups.
Where it is possible, the trunk injection method is preferable as the chemical runs down inside the trunk and
directly into underground galleries in the roots or the soil. Termites in these galleries do not contact the insecticide
so readily when it is injected into the soil.
Details of tree species, concentrations and amounts of chemical to use are given on the Minor Use Permits.
Aggregation drums
To maximise the transfer of the chemical to the colony, it is advantageous to apply it to as many termites as
possible. Often when the infestations are in small trees, the number of termites in each tree is relatively small. In
such a situation, it is far better to aggregate the termites into aggregation drums (Figures 16 and 17).
Figures 16 and 17. Aggregation drums
This method involves locating active galleries in trees, under mulch, or under timber or old logs and placing drums
from 20 L to 200 L in size with 12 to 15 finger-sized holes in their bases. The drums are filled with untreated
timber (e.g. from old pallets or packing crates, not hardwood) or forest mulch, which is moistened and covered
with a plastic bag and a lid. After four to six weeks the drums should be highly active with termites and can be
treated by pouring the diluted chemical into the drum. The lid should be left off at this stage as the treated
termites will move away from the light and back towards the nest.
This technique is described in more detail in a poster and a booklet which can be downloaded from:
Poster – www.nt.gov.au/d/Content/File/p/Plant_Pest/Termites_booklet.pdf
Booklet – www.nt.gov.au/d/Content/File/p/Plant_Pest/Termites_poster.pdf
It is important to allow an adequate time (four to six weeks) for the drums to become highly active. While there will
be termites present long before this, treating too early will reduce the amount of chemical taken back to the
colony.
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Management of colonies before planting horticultural crops
It is advisable to control giant northern termites in native vegetation prior to and during clearing of the potential
orchard area. If this is not done, the expense and difficulties of subsequent management in the fruit trees may be
much greater than that of the initial control. Moreover, the investment in nurturing trees for several years to
bearing stage may be wasted.
Monitoring can include checking for dead or dying trees, ringbarking or muddying on the outside of larger trees,
dying or folded branches on grevilleas or acacias and other smaller trees, and under fallen timber. Larger trees
can also be drilled and checked after 24 hours for muddying as described above. In large areas, it is often useful
to set up a grid of about 50-m spacing and monitor each of the lines.
When drilling the trees, re-walk the grid after 24 hours and check for mud in the holes. A muddied hole indicates
termite activity. Push a metal rod or wooden stick into the hole to clear out the mud, then insert a grass stem or a
very fine stick into the hole and move it vigorously, then leave it for a few seconds. If the tree is infested, the
soldiers will grip the grass with their mandibles and can be extracted. The majority of the muddied holes will be
caused not by giant northern termites but by Coptotermes spp. These are easily recognised as they are much
smaller. Only the giant northern termites need to be treated as most Coptotermes mounds will be destroyed
during the clearing process. The active sites should be marked with a GPS, tape or paint ready for treatment by
trunk injection.
During clearing, infested trees can also often be detected since the trunk or larger branches break apart more
readily than those of un-attacked trees and the damage can be easily inspected in felled timber. Active sites
should be marked and treated.
Please visit us at our website:
www.nt.gov.au/d
© Northern Territory Government
ISSN 0157-8243
Serial No. 734
Agdex No. 622
Disclaimer: While all care has been taken to ensure that information contained in this document is true and correct at the time of publication,
the Northern Territory of Australia gives no warranty or assurance, and makes no representation as to the accuracy of any information or
advice contained in this publication, or that it is suitable for your intended use. No serious, business or investment decisions should be made
in reliance on this information without obtaining independent and/or professional advice in relation to your particular situation.
© Northern Territory Government
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