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May 2008 / Vol.5 / Issue 5
Hello and Welcome to the May Greenpest News. Each month we aim to provide you with some useful information, keeping it short, sweet and pertinent.
Pest Talk
There is no 'Customer letter of the month' this month. Instead you will find an extended and we hope interesting article on termite behavior translated from several scientific journals into what we hope is layman's language.
How termites forage
We are going to address the specific issues of termite foraging behaviour as well as bait acceptance and we believe by the time you reach the end of the article you will appreciate why the Green Termite Bait System has significant advantages over ALL other commercially available bait systems.
Our evidence is based on currently available scientific research papers on termite behaviour that can readily be found on the internet. It is interesting to note that sometimes one scientist’s research conflicts with the research of another. Usually this is explained by the fact that they are researching different species of termites. This is significant, because there are over 2,500 known species of termite worldwide and some 300 species in Australia and their behaviour varies considerably. Only a small number of subterranean termite species are considered to be an economic threat to homes. In Australia this is limited to two families of subterranean termites:
- Rhinotermitidae, in particular the species Coptotermes acinaciformis & Schedorhinotermes spp, specifically Schedorhinotermes intermedius, and to a lesser extent depending on the area you live in, Coptotermes frenchi and Coptotermes raffrayi.
- Mastotermitidae, the primitive but voracious species Mastotermes darwiniensis.
Of these, only the first two genus damage homes across all of mainland Australia, whilst Mastotermes is only found in the northern tropics. Combined, they are responsible for over 99% of the damage caused to homes and property.
An interesting map that estimates termite distribution across Australia can be found here:
http://www.csiro.au/files/mediarelease/mr2000/Termite.htm
The reason Tasmania is safe is because environmental temperature is known to affect subterranean termite foraging activity. It’s simply too cold for the three major species of termite. In general, subterranean termite activity increases as soil temperature increases, (within the range needed for survival). This explains why a house in Canberra may be full of termites during the summer months and appear free of termites during the winter months.
Tip: If you are purchasing a house and your termite inspection and report is conducted on a particularly cold day, the house may get a clean bill of health when in fact it will be a disaster zone once summer returns. This is a reason why professionals don’t say the home has “no termites” but rather they say, “The termites appear to be inactive at the time of inspection.” Big difference, especially legally!
Moving on, research shows that there is a complex, ever changing relationship for different species of termites in any given area. Subterranean termite foraging activity is influenced by seasonal changes, and these changes vary between species, so that competing species may be accessing common food sources alternately. For example, Mastotermes foraging behaviour is reduced when the soil is laden with water as happens after heavy rain. On the other hand, Coptotermes activity increases with rising temperatures.
Coptotermes will build a central nest at the base of a tree or inside the walls of your home. The nursery in a tree is usually below ground level in cooler climates and higher up the tree in warmer areas. The nest in a home will be located either on a warm wall (north facing the sun) or a cool wall (south facing) depending on the climate as well as the construction material of the home.
Some trees such as Cypress Pine contain natural anti-termite chemicals to protect themselves from termites. Similarly our native Eucalypts also have resistance to termites but termites can still consume the heartwood (considered to be dead wood), because these anti-termite chemicals have naturally degraded through ageing as well as other decay organisms.
But do the termites kill the tree? Interestingly enough, there are some termite infested eucalypts that are over 200 years old. In fact the tree may even be structurally better off with the termites. The tree is able to limit the damage by compartmentalising scar tissue as the termites eat their way through the tree and out into the main branches. Should a branch break off in a storm, you’ll have what you need to make a genuine didgeridoo!
Are you surprised to know that worker termites are blind and work 24 hours a day? Did you know that the average worker/soldier termite has a life span of up to four years? Or that a termite can squeeze through a gap as small as 1mm?
Termites are sensitive to two critical environmental factors:
- Environmental temperature is known to affect subterranean termite foraging activity. In general, subterranean termite activity increases as soil temperature increases, within the critical temperature range for termite survival. Note that we are talking about soil temperature. This will vary with the season as well as the soil type. Sometimes termites may travel just below the surface or deeper at other times. On hot humid days you’ll find termites right up in the surface mulch commonly found on most gardens.
- Soil moisture content is another influence that impacts subterranean termite foraging activity. Termites are prone to desiccation when exposed and can lose up to 10% of their body mass due to desiccation even when maintained at 98% atmospheric humidity for 24 hours. Access to water is critically important for the survival of subterranean termites; consequently lack of moisture is an important limiting factor that directly affects subterranean termite tunnelling activity.
Termite scouts are worker termites on an underground mission to find suitable food for the nest. When a scout finds some timber, in the ground or on the surface, it proceeds to throw a party.
Just kidding. In fact, what it does is lay a pheromone scent trail to tell the other termites from the colony about the food source. (Then they have a party). This scent trail is a crucial part of the colony's communication system.
Next, the worker termites use a mix of saliva and termite poo to construct a solid underground tunnel to link the nest to the new source of food. These tunnels are then able to insulate the termites from the outside world whilst maintaining close to 100% humidity levels and an optimum working temperature, which is pretty astounding when you think about it.
So… how do termites find a bait? To answer this we need to ask another question first. How do termites explore their neighbourhood?
If you had to travel underground, you would be seeking the path of least resistance. If you hit an obstacle you would go around it. Termites tend to behave the same way. Now consider the way a house on a slab is built. If the ground is hard, an earthmover is used to dig trenches for the laying in of plumbing lines linking the home to the sewer line. When it is backfilled, the soil around the plumbing is easier to travel through (path of least resistance) than the regular earth so termites will naturally follow the pipeline towards your home. The underground penetration point (where the plumbing enters your home) is oftentimes also the entry point that termites use to access your home.
On the same theme, different soils offer different levels of resistance to termites. Some species will prefer to travel through clay and others will prefer sand. Clay holds moisture better than sand but sand is much easier to tunnel through. Ideally termites prefer a blend of clay and sand better known as top soil or loam. Our observations over the past 20 years lead us to believe that Coptotermes can cope better with clay while Schedorhinotermes have little difficulty with sand.
Termites will follow a moisture trail. Moisture trails are created from poor plumbing so look for and fix:
- Dripping exterior taps.
- Hot water overflow pipes.
- Air-conditioning runoff pipes.
- Blocked drains that overflow.
- Cracked and broken underground run off drains. You can spot these by noting any permanently damp areas.
- Over-watered pot plants.
- Automatic watering and sprinkler systems.
- Leaky swimming pool pumps.
Termites will follow the root systems of trees. This week we core drilled some concrete to insert our Green Termite Baits. The nearest tree (a beautiful Poinciana) was 15m away, yet there were tree roots happily travelling in the damp sandy loam under the concrete. It’s ideal for termites and it’s why we placed the bait there.
Termites will follow pre-existing tunnels through soil. When you kill a nest, the tunnels remain. Later on, a new colony may discover these tunnels, repair them and put them to use. This is why we stress the importance of finding the termite entry point and disrupting it whenever we treat a home with pre-existing active termites inside.
Termites will avoid predators. They will avoid ant nests and detour around them. Note: Having lots of ants will NOT protect you from termites.
Now we understand that termites’ underground foraging is influenced by a combination of factors. No doubt there is a hierarchy to these factors which is likely to vary based on the species, the season, the soil type and the many other environmental conditions that the termites are facing.
Now we will return to the initial question, how do termites forage (find food or a bait)?
Now that we understand how blind termites travel in a dark underground world, how do they find timber that is on the surface? Why don’t they miss it and travel underneath it? Regular readers of this newsletter over the past 5 years may know the answer or part it.
Can you guess before you read on?
Well, here are the theories (by definition, theory: a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.):
- Theory 1: Termites find it by chance and simply blunder into it.
- Theory 2: Timber gives off a scent or juice that termites can detect.
- Theory 3: Decaying timber gives off decay gases that termites can detect.
- Theory 4: Timber on the surface casts a thermal shadow on the ground and termites can detect the difference in temperature.
- Theory 5: Termites follow pre-existing tunnels through the soil.
- A combination of the above that is influenced by termite species, and variable environmental factors.
- Some other theory yet to be thought up and tested.
Did you have the right answer?
None of the theories are proven (though No5 is pretty much accepted as fact). In all cases where tests have been done to establish these theories, the results are never 100% conclusive. What works for one species of termite may not for another. The best we can do is postulate, based on self-evident clues gleaned from each different species mode of behaviour.
Let’s examine the evidence and basis for each theory.
Theory 1: Termites find it by chance and simply blunder into it.
A large number of stakes were put into an area of known termite activity. Over an extended period of time quite a few of them were attacked but many were not. The fact that the termites went past one stake to get to another indicates that they don’t actually sense the timber in ground and that they simply bump into them.
However it’s possible that the large number of stakes in the ground overwhelmed the termites’ ability to sense an isolated timber stake.
Conversely, it’s possible (and more likely) that the stakes were too new to attract termites, based on the decay theory (3). It’s also been shown that once termites find a source of food they will allocate a set amount of resources to exploit it and reduce the amount of scouting in the meantime. When the source is near depletion they then start scouting for their next meal. So, another way of interpreting the results is to suggest that the termites merely bumped into a stake randomly then established a route to it and when it was near done moved on in search of their next meal and if the established route had already bypassed a stake it may remain missed whereas other stakes further afield that have not been bypassed are more likely to be discovered next by the scouting termites.
It seems pretty likely that termites do get lucky and simply blunder into food, but it’s unlikely to be the only way that they find food. As is often the case in science, observations can often be interpreted in many ways and there is often more than one right answer.
Sometimes, the obvious theory is completely wrong. For example: It appears to us that the sun circles the earth, which is a logical but wrong interpretation of the sun's movement across our sky each day.
Foraging activity decreases when a large food source is located. The bigger the food source, the greater the number of termites allocated to exploit it. Termites tend to cluster feed. This explains why a Green Termite Bait can be free of termites one month, yet a month later it is loaded with termites. This also explains why termites won't nibble on 100 stakes at once, but tend to knock them over one by one in proportion with the termite population. A large nest can supply enough workers to cluster feed on several stakes at once, whilst a small nest will feed on less.
Theory 2: Timber gives off a scent or juice that termites can detect.
If you’ve ever sawn or drilled timber, used wood in a fireplace or purchased unvarnished furniture, you‘ll know that each variety of wood has a distinct smell. Live trees produce resins and other compounds; some that may be attractive to termites and some that may be repellent. Many of these compounds break down over time which is why some termites can eat the dead heartwood inside a tree but not the live sapwood in the outer live part of the tree.
It’s possible that over time, a cut timber bait in the ground will leach out attractive molecular substances (in our ignorance and for fun we'll call it timber juice for want of a better name) into the soil which may be detectible by termites. The longer it’s in the ground the more this will increase. Termites are very sensitive to chemicals in the soil and this is the principle behind repellent termiticides such as synthetic pyrethroids. Termites sense the minute amounts of chemical around your house and turn away. This works well as a barrier until the chemical breaks down or unless there is a breach in the treated zone.
It’s possible that termites can sense timber in the soil, but from how far away is still speculative and no doubt affected by soil type, moisture content, and termite species. Different termite species have different preferences in timber which is why termites will bypass one type of timber left on the ground to reach another. Green Termite Baits are made from radiata pine and are a desirable food to all the high risk termites we mentioned at the beginning.
Theory 3: Decaying timber gives off decay gases that termites can detect.
Some think it may be carbon dioxide and this has been trialled in some plastic bait systems to try and attract termites. There is no solid evidence to show this actually works.
Most of us have been in a forest and smelt the musty earthy smell of composting trees that have fallen over. This is a mix of a variety of gases arising from fungal activity, bacteria and other compost organisms. It’s natural and it’s pretty likely that it attracts termites.
Our policy is to leave the Green Termite Baits in the ground for a long as possible (3 – 5 yrs) before replacing them with new baits. In general if there is an old bait alongside a new bait, it is the old bait that gets termites first. It isn’t proof, but it’s reasonable evidence that termites can home in on a source of timber decay gases.
Theory 4: Timber on the surface casts a thermal shadow on the ground and termites can detect the difference in temperature.
This is a great theory. It easily explains why termites can so quickly invade a timber pallet when it is dropped off on someone’s lawn. One of our customers had a pallet of bricks dropped off so he could build a back yard BBQ. It took him two week-ends. When he went to drag the pallet out to the footpath for the pick-up it was riddled with termites.
Here’s one suggested explanation: It’s well known that temperature plays a critical part in a termite colony’s activity level. Materials such as timber are a heat sink. In other words they absorb heat and don’t radiate it back out. Hence a log on the ground would cast a thermal shadow or cool spot. The soil under the log will be cooler than the surrounding soil. It’s postulated that termites can sense this cool spot and will rise up to investigate.
It goes a long way to explaining the termites’ quick invasion of the pallet on the lawn.
There are some non-professional people out there putting forward a theory (as fact) that a termite bait need only sit on the surface to be effective. This is misleading the gullible, and it is not a very logical argument for three reasons:
- A scouting termite needs to travel under the timber bait to sense a thermal shadow (obviously, since that is where it is). So, if the same timber bait was in the ground, the termite would have discovered it anyway.
- A thermal shadow needs to be cast by a large object, at least the size of a dinner plate. This is evident by the fact that termites are often found in large isolated pot plants (on the ground without saucers) but not in small pot plants.
- Termites are cautious about predators. A loose bait on the surface is much more likely to be exposed to predators than a secure bait in the ground. Entering an 'on ground' bait would be tenuous, unless the bait is weighted down heavily (as in a pallet or large pot plant). Directly entering an in-ground timber bait is safe and secure for a termite. It's ideal. It's why the Green Termite Bait System works so well.
It would be impractical and visually ugly to make a large bait that simply sits on the surface. Plus it would be easily knocked about by a lawn mower or whipper snipper and it would pose a tripping hazard. If it was accidentally disturbed (as is likely), then the termites would quickly abandon it.
As we’ve said many times before, if all you want is a termite monitor, simply shove a timber stake in the ground, but if you want a monitor that can be effectively treated without disturbing the termites, then you need a Green Termite Bait.
A Green Termite Bait could cast a larger thermal shadow if a polystyrene fruit box lid was placed over it, but this would be very unsightly. And why bother when they work perfectly just the way they are? (We will clearly demonstrate this in next month’s newsletter.)
A quick digression to discuss some ideas suggested to improve bait acceptance and discovery.
It has been suggested by some in the termite industry that underground plastic wings attached to a bait might improve the chances of a bait being found by a termite scout. The idea is that the termites will bump into the wing and travel along it until they locate the bait. However, scientific tests have shown that termites will treat it as an obstacle and rather than go along it, will simply go over or under it. A timber wing may be better, but then it may become the food source itself and not the bait. More importantly, installing wings would be an expensive and difficult exercise. If you are going to trench to install wings, then you might as well trench and flood with termiticide.
As mentioned earlier, termites will follow a moisture trail or a path of least resistance through the soil. Above or in-ground slow release soaker hoses could do the trick, but it too would be labour intensive. Another method would be to dig a shallow trench between baits and fill it with top soil. Both these methods would enhance a scouting termite’s chances of finding a bait quickly, but it’s a lot of trouble just to speed up discovery, and does it really matter if a bait is found in 1 week or 4 weeks? No.
One must remember that the systematic way termites scout a set area will in most cases ensure that a correctly installed bait will be found anyway. Scouting termites don’t travel in straight lines. It’s been shown that termites radiate out from a nest in all directions and that minor exploratory underground trails are continually branching off, then branching off again and again so that nothing is missed. Once a food source is found the trail from the nest to food is converted into a major lead and the other minor trails are temporarily abandoned. The termites focus their energy into taking full advantage of the new food source while they can. This clearly explains why a bait placed next to a railway sleeper full of termites may take months before it becomes active, yet if the railway sleeper is removed, the bait will become active in as little as two weeks.
There is an important principle at work here and it is worth noting. If you place termite baits in area of known termite activity and none of the baits become active for a considerable time, it’s very likely that the termites are busy and contented feeding at another food source. Find that food source and treat it directly if you can or alternatively remove the food source. For example, if you have termites in a pile of firewood and place a bait beside the firewood you’ll more than likely be wasting your time. If you can directly treat the firewood or the soil that the firewood is resting on; that would be the correct procedure. If the firewood is stacked off the ground and unsuitable for direct treatment, place a Green Termite Bait nearby, then relocate the firewood away from the termites. In our experience the bait will be pounced on in a very short time.
Another way to improve the likelihood of a bait being found by scouting termites is to install them in places where termites are likely to go. That’s easier said than done which is why we advise the general public to engage a professional termite company to install the baits. Good placement will make a big difference over poor placement.
Here are some placement tips:
- Near taps
- Near drains
- Near cracks or expansion joints in concrete
- In gardens
- In mulch
- In damp spots
- In freshly dug soil
- Near plumbing lines
- Along the edge of concrete paths and driveways
Theory 5 (Fact??): Termites follow pre-existing tunnels through the soil.
It’s well known that termites sometimes intercept old abandoned termite tunnels and follow them. If these tunnels lead into your home, then the termites are led straight in. It’s important that one part of a treatment plan for the management of active termites in a home should involve a sensible effort to find, treat and disrupt the termite’s entry point. This is usually step (2) of a treatment plan. Typically, step (1a) is the initial treatment; usually the application of a transferable termiticide to the active termite leads within the home followed by step (1b) a follow-up in around 4 - 6 weeks to check and see if the termites are gone. If the initial treatment was successful, the termite nest will be dead or dying. If it was unsuccessful as is sometimes the case (a clumsy operator or insufficient leads/termites to work with), then the termites were merely harassed and disturbed and may have only abandoned the leads. Abandoned leads misinterpreted as a successful treatment is very unpleasant because the termites are still alive and very nearby often still in the house but moving in a new direction. It’s during step (2) that you may have a second chance to treat them.
Returning to the subject, there are a veritable host of other insects that tunnel underground (e.g. earthworms, beetles, various insect larvae). Any of these tunnels can facilitate ease of movement for a termite.
And then there are man-made tunnels. The most notable man-made tunnel that termites occasionally use to enter your home is the underground power line which is sheathed in a tough plastic tube. There is plenty of room inside for termites. It offers them top protection from predators and the threat of desiccation. Interestingly enough, this gives the termites direct access through even the best chemical treated zone. To be fair, it would give termites a path past a bait also. What can you do about it? If you have underground power, then you need to check where the power lines enter your home. If you can’t see because the cables are enclosed within a wall, then have an electrician install a removable wall air-vent. It’s then easy to pop it off to check now and again.
In conclusion: It would be foolish to say that termites forage by one method alone or that one method of foraging takes precedence over another. Many factors influence their behaviour.
If you are unsure which bait system works the best, then next month’s newsletter will clearly show why the Green Termite Bait System stands out from the crowd. For the moment we will put it into a few succinct words:
A Green Termite Bait is much more than just a monitor. It’s an ideal termite accumulation point where they can be easily and effectively treated without disturbance just by adding a suitable transferable termiticide.
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The Greenpest News is Published by J & A Furnell Nominees P/L; Shop 23a Franklin Square, 60 Railway Street, Mudgeeraba, Gold Coast, Queensland, Australia. The opinions expressed in this newsletter are those of Jerry Furnell. The reader is encouraged to seek further information from appropriate government and statutory departments before taking any action based on this material alone.
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See you again next month.
Always... At your service,
Jerry Furnell
Green Pest Control & Green Termite Bait Systems.
Phone 1800 6 12345.
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