Week 5 - Day 22 - Termite Control

ESSENTIAL READING BEFORE COMMENCEMENT OF COURSE:

Urban Pest Management in Australia: 2004 Edition, UNSW Press, Sydney

by J Gerozisis and P Hadlington - Chapter 19 - Pages 233 to 240.

Chapter 19 – Termites -control of termites - the survey - eradication by use of dusts - location and treatment of termite colonies - prevention of attack - chemical soil treatments - existing buildings - buildings under construction - chemical moisture barriers - use of chemically treated timbers - use of naturally resistant timbers - the physical barriers - granite barriers - stainless steel mesh barriers - steel framed houses - use of timber bait monitors

Pest Species

Mastotermes darwiniensis

Cryptotermes
Schedorhinotermes
Coptotermes
Heterotermes
Nasutitermes
Porotermes
Neotermes
Microcerotermes

Mastotermes darwiniensis

Cryptotermes

Schedorhinotermes

Coptotermes lacteus

Coptotermes frenchi

Coptotermes acinaciformis

Heterotermes

Nasutitermes exitiosus

Nasutitermes walkeri

Nasutitermes fumigatus

Porotermes adamsoni

Neotermes insularis

Microcerotermes

Reference K Girard Training Notes
Timber Pests
Termites/Borers

Termites are the only members of the insect order "Isoptera".  This word means "equal winged" and refers to the fact that the winged reproductive adults (or alates') have two pairs of wings of similar shape and size.

Termites are closely related to the cockroaches (order Blattodea) both having an incomplete metamorphosis.  Termites date back at least two hundred million years and were in existence at a time when there were no flowering plants, butterflies, bees or birds.

In comparison to other insect orders, Isoptera have few species (approximately 2,000) of which about 200 are to be found in Australia.  Termites are especially abundant in the tropical and sub-tropical areas of the world.  A major distinguishing characteristic of termites is the fact that they live in communities and are thus termed "social insectsol.  The number of members of these communities may range from several million to fifty or less.
Every community, or colony, contains a number of different castes, which differ in appearance and function.  The four castes which may be found are:-

1. Primary Reproductives - (kings and queens) - which have arisen from the alates and retain wing remnants;
2. Supplementary Reproductives (neotenics) - which either have no traces of wings or have wing buds;
3. Soldiers - which are sterile males and females with heads modified for the purpose of defence; and

Workers - also sterile males and females but without any special modifications It is likely that immature stages of these castes will also be present in the colony. The main characteristics of the four castes are:

Primary Reproductives

While they are being reared, the future kings and queens or 'alates' have no duties to perform and are carefully tended by the workers.  The alates differ markedly in appearance from workers and soldiers inasmuch as they have pigmented bodies, well-developed compound eyes and two pairs of wings.  After landing from the nuptial flight, these wings break off at the base leaving small triangular stumps. Having established a colony, the king will alter little during the rest of his lifetime, becoming only slightly stouter whereas the female is transformed into an egg-laying machine.  In all species the queen's abdomen becomes swollen but, in members of the families Rhinotermitidae and Termitidae, it swells to enormous proportions completely dwarfing the head and thorax.  Such queens are called "physogastric" and are too large to move or to be moved easily by the workers.  Generally, she is kept in a specially constructed cell often attended by the king and a number of soldiers and workers.
Supplementary Reproductives
Most termite species are capable of producing supplementary or neoteinic reproductives.  Certain nymphs, before or after the appearance of wing buds, develop functional reproductive organs without becoming alates or leaving the colony.  The abdomen of a neoteinic queen will become swollen but will never reach the same size as that of a primary reproductive queen. Neoteinic are important because they enable a colony to continue when the original king or queen has died or when the reproductive efficiency of the queen has fallen below the standard essential to maintain the population of the colony.  Neoteinic are common in members of the family Kalotermitidae and in the species Mastotemes darwiniensis.  However they are not found in all species.
Soldiers
Soldiers are wingless and blind insects whose function is to defend the nest against invaders, primarily ants.  They can be distinguished from the workers because of their heads which are strongly chitinised'. (thick cuticle) usually pigmented and almost invariably larger than those of the workers and reproductives. Although they are genetically male and female, soldiers are sterile.
Two distinct types of soldier are recognisable:
imandibulate - with larger, prominent often grotesque jaws and
nasute - with heads being syringe - shaped, drawn out into a snout with the pore of the cephalic gland opening at the front. In addition, some species have two classes of soldier which differ not only in size but also in structure eg Schedorhinotermes species.
Colony Defence
Because of the modification or reduction of the mandibles, the soldiers of most species are incapable of feeding themselves and thus have to rely on the workers to obtain their nourishment.
Defence of the colony can be achieved in several ways - by biting, as in the case with mandibulate soldiers, by blocking galleries with heavily sclerotised (having a horny exoskeleton) heads specifically adapted for the purpose eg Cryptotermes; or bv chemical means as in the case with nasute soldiers.  The frontal gland secretion of the nasute soldiers may be toxic, repellent or adhesive, serving to entangle the legs and antennae of invading insects. Soldiers are most active during building or repair operations or when the alates are swarming from the nest.  In certain north Australian termites which habitually forage in the open, soldiers guard and also appear to direct the activities of the workers. Where soldiers occur, they usually constitute a small proportion of the colony.  The ratio of soldiers to workers may be as low as one to eighty. Workers serve in many capacities - foraging for food; feeding the immature termites as well as the soldiers and reproductives; caring for the eggs and building the nest and galleries. Workers are not found in the families Kalotermitidae and Termopsidae where the worker functions are carried out by the early nymphal stages of the reproductive caste or by late stage nymphs which have lost the ability to develop into alates.  In the species Mastotermes darwiniensis, the worker function is carried out by individuals who resemble and act like workers but whose precise status is still in doubt.

The Founding of the Colony
The well known phenomenon of the termites' colonising or "nuptial" flight can be observed during the two main flight periods - late spring to early summer and autumn.  The release of the winged reproductives may be in the form of several small batches over a period of weeks or one or two large batches over a few days.  The colonising flight will often take place after a thunder storm when the humidity is high.  The numbers of reproductives released may be in the vicinity of 70,000 as has been recorded in the case of Coptotermes lacteus.
Swarming cuts
The alates, with the sexes represented in approximately equal numbers, emerge from a swarming cut" opened and later sealed off by the workers.  This opening may be in a tree or other site of activity eg. wall or architrave in a building.  Soldiers guard the immediate area until the aperture has been sealed.
Predators
Depending upon the particular species, the alates may be weak or relatively strong fliers and the ultimate distance travelled depends upon the strength of the wind.  The vast majority of reproductives fall prey to birds, lizards, spiders, ants etc and so very few ever reach the next stage of founding a colony. After landing, the alates shed their wings and the females attract males to themselves by presumably emitting a sex­ attractant odour (pheromone).
Subsequently, they pair off, the male closely following the female with his head close to her abdomen.

Royal cell
The royal couple then found a new colony by excavating a shallow chamber in the soil under timber or vegetation.  Once this "royal cell" is constructed, they seal themselves in and copulation takes place.  The royal couple feed on wood during this time.
First broods
After the first brood has hatched, the young are fed by the parents apparently on the secretion of the salivary glands.  These first offspring never attain the size of a normal worker.  When they are sufficiently developed, these workers begin to forage for food, excavate new galleries and begin caring for the king and queen.  The queen then retires to a life of egg production. Only workers and soldiers are produced in the first few years of colony development and reproductives are only produced after this time.  Mature colonies may take several decades to reach their full growth potential and may comprise several million inhabitants.
Primary reproductives

The primary reproductives may live from 15 to 50 years in the higher termites and during this time the queen is periodically fertililised by the king.  There is usually only one primary king and queen per colony but, in the case of some Nasutitermes species, multiple primary queens have been found presumably as a result of fusion of adjacent colonies.  Where species can produce supplementary reproductives, the colony is potentially immortal.
Colonies may also be formed by a group of nymphs which split off from the main nest and subsequently develop supplementary reproductives.  This happens quite commonly in the more primitive termites eg: Mastotermes.

Nesting Habits
It is by virtue of their nesting habits that termites can be conveniently divided into two categories eg: soil-dwelling and wood-dwelling forms.  Wood-dwelling varieties can be further sub-divided into "dampwood" and "drywood" termites.
Soil-dwelling termites
Most Australian termites are soil - dwelling, many constructing no proper nest but living and breeding in a series of underground galleries.  Where a nest is formed, it is usually located at the base of a stump, pole etc or in the soil beneath.  Alternatively, the nest may be in the form of a raised mound or attached to the trunk or limb of a tree.  These tree nesters are still considered as soil-dwelling because they are always connected with the soil and only appear to be formed after several years of subterranean existence.
Coptotermes nests
An apparent exception to the rule is the genus Coptotermes which sometimes makes a nest in the centre of living trees usually at ground level.  However, when additional food is sought, underground galleries will reach this.  When a source of constant moisture has been present, C. acinaciformis has been known to establish colonies in buildings far above the ground level and to exist without ground connection.

Drywood termites
The wood-dwelling varieties, which all belong to the family Kalotermitidae, except P. adamsomi, do not construct nests but live entirely in galleries inside the wood on which they feed.  The dampwood dwelling genera (Neotermes, Kalotermes, Ceratokalotermes, Glyptotermes, Bifiditermes and Porotermes) generally live in damp rotting logs or rot pockets in dead or living trees.  Drywood termites (genus Cryptotermes) obtain water from the wood in which they feed and require no contact with the soil nor with any other source of moisture.

Drywood termites have become of greater importance in recent years with the introduction of several exotic species to northern Australia.  Eleven species, both native and exotic, are found in Queensland, generally confined to the coastal and adjacent tableland areas.  Each species usually has a relatively restricted distribution within these areas.
The Diet of Termites
Essentially, termites are cellulose feeders and this cellulose may be found in sources other than wood.  Many Australian termites are grass and debris feeders and of the few which attack wood, most feed on living trees, rotten wood or on weathered wood surfaces.  Most termites consume their food where it is found but the species, which consume grass, or plant litter, carry it back to the nest.  At times termites will attack a wide range of substances including some, which contain no cellulose eg. Bone. Mastotermes darwiniensis has extremely varied tastes.
Digestion by micro-organisms
As far as is known, the termites themselves lack the necessary enzymes to break down the cellulose and for its digestion they depend upon microorganisms.  In the family Termitidae it is thought that bacteria secrete the necessary enzyme or perhaps the termites themselves.  In all other families, protozoa in the gut provide the necessary enzyme.

Fungal gardens
The carbohydrate cellulose does not provide the proteins necessary for the maintenance of life. The source of these proteins is still open to conjecture. it has been suggested that fungal growths may be an important source of protein and that termites may have difficulty in establishing a colony on fungus - free wood.  The practice of cultivating fungi as food in special chambers of the nest as found among African and Asian species of the family Termitidae is not found in any Australian species.
Cannibalism

The phenomenon of cannibalism may be linked to protein starvation.  Under laboratory conditions, termites deprived of protein have been known to consume large numbers of their fellows.  This may also happen under natural conditions.  There is no direct evidence to suggest that termites habitually eat their dead but, accumulations of dead termites are rarely found and it would be logical to suppose that they would provide a ready source of protein.

Trophallaxis or Food Transfer
As previously noted, some colony members eg. soldiers, young nymphs, reproductive nymphs and the reproductives themselves are unable to feed and depend upon the workers to provide them with food.  This takes place in two ways i) mouth to mouth or "stomodaeal" and ii) anus to mouth or "Proctodaeal".  The recipient termite stimulates the prospective donor in the appropriate region with its antennae, mouthparts or front legs and a food droplet is disgorged or excreted.  The recipient immediately takes up this droplet.

In the case of proctodaeal feeding, this is essential to replace the gut protozoa, which have been lost during moulting.

Caste Determination
The one aspect of termite life which has aroused the most controversy is the problem of caste determination.  Most scientists now believe that all nymphs emerge from the egg with the potential to develop into any caste and that their final form depends upon external factors operating on the young nymphs.  It is not known for certain what these factors are nor is it sure if the same factor operates for all species.

The three factors postulated are:-
Hormonal control

1. Hormonal control - which suggests that the colony is regulated by the circulation of a pheromone within the colony.  This short-lived material must be produced continuously and is passed among the colony members by licking or by food exchange.  It is assumed to be able to induce specific actions eg. Stimulating the development of reproductive organs or inhibiting the development of certain structural characteristics.  This theory has been supported by experimental work carried out with the production of supplementary reproductives in some primitive genera.

Nutritional control

1. Nutritional control - which theorises that it is the quantity and type of food given to the nymphs, which determines which caste, they will eventually become.  There is little experimental evidence to support this view.

Sensory control

1. Sensory control - which suggests that odours or tactile communication between colony members may determine the distribution of castes.

Economic Importance
Termites are economically important as a result of damage done to timber in service or structural timber and to forest trees, fruit trees and crops.  It is this destructive action, which brings them into conflict with mankind.

Damage to Structural Timber
It is difficult to estimate the amount of damage done annually to timber in buildings, bridges, wharves, poles, posts, sleepers etc but recent estimates have put the sum at approximately $5,000,000 per annum.  Most of this damage can be attributed to the actions of soil-dwelling, particularly subterranean, species.  Wood-dwelling species cause little damage by comparison.  Most of their destruction is wrought by the drywood species, Cryptotermes, with occasional infestations by Porotermes and some of the Kalotermitidae family in poles and rarely, construction timber.

Damage to Forests, Fruit Trees & Crops
Termites are relatively scarce in the rain forest areas of Australia and consequently, little damage is done to forest trees in these areas.  However, in the coastal and near coastal hardwood forests of eastern Australia much damage (also approximately $5,000,000) is done yearly.  The incidence of infested trees may be very high sometimes ranging upto 75% and many trees are rejected because of heavy internal attack.  Those species of termites most responsible for this damage are - C. acinaciformis, C. frenchi, N. insularis and P. adamsoni
The tropical termite M. darwiniensis is the only serious pest of fruit trees and crops in Australia.  In some areas it is also impossible to produce supplies of domestic vegetables.  Mastotermes has been found to attack such crops as citrus, pineapple, banana, paw-paw, melon, pumpkin, carrot, potato, tomato and many kinds of shade and ornamental plant.  C. acinaciformis has also been recorded infesting fruit and almond trees in the Adelaide district.
Damage to Pastures
This aspect of damage has not been fully investigated but the few studies which have been carried out suggest that the grass-eating termites of the tropics are most usually found in poor pastoral country and thus present little competition to grazing cattle.  In the southern states, some areas of grassland have been found to be visibly affected by species of Amitermes and it is possible that grass-eating varieties may be of greater significance than previously realised.
Damage to Subterranean Cables
An interesting phenomenon which has often been noted is the termites' habit of attacking the lead sheathing of subterranean cables.  Perforation of the lead permits the entry of moisture and subsequently a breakdown of the insulation.  It is not known for certain but all evidence suggests that the termites are merely congregating in areas of higher humidity such as would be found in conduits wherein the cables are laid.  How the termites actually penetrate the cables is not certain.  It is evident that the lead is chewed through although some sources suggest that the secretion of the cephalic gland could aid this action. Termites have also been found attacking such items as fibre and particleboards, plastic piping and plastic - sheathed cables.

Beneficial Functions of Termites

Despite all the damage done by termites in Australia, they do act in some beneficial manner viz. soil formation.  This comes about by their breaking down of plant tissues of all kinds into their constituent materials so that they may be re-used repeatedly for the nutrition and growth of new plant life.  This is more especially true of the subterranean species which, by virtue of their tunnelling activities, facilitate the penetration of air and water to the deeper soil layers.  In Australia's arid and semi-arid regions they carry out the role fulfilled by earthworms in other areas.
Studies have also shown that termites produce very large amounts of methane and carbon dioxide as a result of cellulose digestion.  These gases are incorporated into the earth's atmosphere and thus help to retain the earth's heat.

Useful website links:

http://www.ipminstitute.org/school_biblio_buildings.htm#Wood