PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Not all termite species found in timber are a threat to
houses. Only a few of the species found in trees may
infest buildings. Of the few hundred Australian species
only about six are considered to be major pests of
buildings. Seek species identification and treatment
advice if buildings are close by to avoid unnecessary
treatments. Check pest species which occur in
your area.
Scientific name
Termite pests of living trees include:
Subterranean termites, eg Coptotermes spp.
Dampwood termites, eg Porotermes spp.
Drywood termites, eg Cryptotermes spp.
See also page 175
In Australia, subterranean termites are the most
destructive species, working from a central nest or
colony situated in the ground or in trees from which
subterranean tunnels radiate to food sources.
Host range
Timber, eg building timbers, fence posts, rail sleepers,
telegraph posts, wood chips and bark. Trees, shrubs,
fruit trees, vines, eg large and small trees and shrubs,
cashew, citrus, grape. Crops, eg potatoes, sugarcane.
Some species feed on grass, spinifex, and fungi in the
nest or on moist wood from which they get proteins, etc.
Description & damage
Adults (males and females) are winged insects
about 14 mm long (including wings). They leave the
nest, establish new colonies and become ‘king’ and
‘queen’ of the new nest. Workers are small,
wingless, sterile white-bodied (‘white ants’), blind,
with well-developed jaws for gnawing wood. About
80-90% of the colony in our common pest species are
workers. Soldiers, depending on the species, are
blind, sterile and have longer jaws than workers.
They protect the colony from invaders, and may
constitute as little as 2% of the colony. Termites
have a thin skin and desiccate readily.
Trees. Damage is caused by workers seeking food
for the colony traveling to and from the nest along
runways in a continuous stream. Large trees are
usually attacked through the centre of the trunk, often
with little external evidence of termite activity. They
do not normally affect the living part of the tree but
cause structural weakness in old slow-growing trees.
Termites work inside the trunk, along the grain,
eating out large runways. In one tree, there may be
several runways which are gradually widened and
extended until only thin layers of wood remain
between them (Fig. 118).
Firewood. Seek advice about local termite
species. Many termites found in firewood are feeding
workers from large colonies, unable to survive on
their own, in small pieces of wood or to invade
structural timbers. Some species found may not attack
buildings. Large blocks of firewood or intact logs
could possibly harbour a small nest. It is unwise to
stack large timber next to houses or fences. Some
species that can damage sound timber will dry out
and die in chopped wood.
Mulches and compost. Wood chips, bark
and neglected compost heaps can provide food and
shelter for some termite species. Finer mulches, eg
leaf litter, lucerne hay, break down too quickly to
provide enough food and shelter.
Termites
‘White ants’
Potato stems and tubers become tunneled, ‘honeycombed’
and spongy, skin is intact (page 175). Crops
are mainly reached by underground runways.
Diagnostics. Trees and other plants.
All tree assessments should be carried out by a
professional arborist.
Do not confuse termite damage to trees with
that caused by borers or wood rot (page 178,
Table 35). Termite galleries are constructed from soil.
Wood-boring moths often cover their activities at the
junction of branches with frass (silk and droppings).
Damage is difficult to detect in the early stages.
Unless runways are discovered during monitoring,
inspections or pruning, damage is not often noticed
until trees collapse, or crops harvested. Occasionally
runways can be traced back to the nest.
– Expert ID needed. It is usually easy to know
whether the pest is a termite or not but difficult to
distinguish one species of termite from another.
Collect several soldiers, put in methylated spirit in a
jar and take to a termite expert. Collect soldier caste
termites with as little disturbance as possible.
Termite diagnostics is offered by arborists and pest
control companies.
– Bait monitors alert tree growers to the presence
of termites and can be placed at various distances
from trees where termite activity is suspected.
– Wood chips. Water area well the evening before
gently scraping back the wood chips. During hot
and dry weather termites move deeper under-ground
to keep cool and damp.
– Inspection tools. Experience is necessary and
when used in conjunction with other technology
helps identify where termites might be.
Tappers (Termite Inspection Tools) or hammers.
As old living trees with fungal decay (page 361)
appear to be most susceptible to termite damage
(some exceptions in tropics), the analysis of
termite damage is the same as for fungal decay
hollows (Mann, 2009).
Drilling of trees to assess presence of termites
can be destructive to trees.
Temperature probes can locate termite colonies
in trees. The temperature of areas with termite
activity is generally several degrees higher than
‘normal’ tree temperature and can be detected. Noninvasive
Thermacam Technology can be used by
arborists to locate termites in trees. All material has
a unique thermal signature and when moisture, heat
or pests are introduced, thermal images change.
Moisture meters are non-destructive. Termites
need moisture to survive.
Termatrac technology (rather similar to radar),
can detect termites inside timber, plaster board etc.
Borescopes give a clear picture using mirrors and
a small light at the end of a flexible probe. They
are expensive and usually only used to check for
termites in inaccessible places in buildings.
Male winged form Worker Nymph Soldier
Fig. 119. Subterranean termite (Coptotermes acinaciformis).
Left: Male winged form. Upper: Female winged form. Lower left
to right: Worker (forages for food), nymph with wing buds; soldier
(defends the nest). Photo NSW Dept of Industry and Investment.
Insects and allied pests - Isoptera (termites, ‘white ants’) 177