Termite Monitoring Systems; On Ground or Below Ground?

Termite monitoring has a worrying practice returning of the selling and marketing of Termite Monitors for placing on the ground.

One such marketing press release stated the following;

Termite Monitoring why On-Ground?

Termite monitoring trials in the USA (carried out in the ’70s) indicate stations that are located on or above the ground are found much sooner than stations which are placed in the ground.

The termite monitoring study referred to was made over 40 years ago (using cow dung pats and termites which ate them).Since being replicated on a much greater scale with more relevant termites with much greater statistical significance.

This newer study was actually one of the first studies showing that termites follow thermal shadows (cool/warmer areas) and will climb to close to surface looking for moisture and food but certainly not leave it unless certain ideal conditions exist (warm wet dung). A plastic monitor unless appropriately treated offers the opposite temperature differential that a cow dung does and will actually repel termites.

Several field studies have suggested that subterranean termites attack food items located on the soil surface more frequently than they attack similar items buried in the soil (Santos, 1979; Ettershank et al., 1980). In studies since it has been shown that much of this preference was due to the condition of the food source than the placement, with the timber buried very quickly becoming wet, mouldy and unpalatable.

In another field study, French (1991) found that baits located below the soil surface were more likely to be discovered by several economically important Rhinotermitidae (termites that attack our homes not cow dung) when positioned within the root systems of woody plants.

Organic objects on the soil surface like wood and animal carcasses tend to have high moisture content and may absorb environmental moisture (Corey and Kemper, 1968). Organic materials have a high heat capacity, and therefore they warm slowly when exposed to solar radiation and cool slowly when no external source of heat is present. Thus, organic objects on the soil surface act as heat sinks (objects that radiate heat at a slower rate than the surrounding substrate). The temperature of the soil below organic features is buffered from changes in the atmospheric temperature (Ettershank et al., 1980; Haywood et al,1997). A single layered plastic box which heats and cools quickly on the surface does not act as a thermal shadow and therefore offers little stimulus to attract termites for termite monitoring. Insulating and adding an air lock as in the Termite Mansion however does create a similar stimulus as does an organic object.

And then this little piece of wisdom has recently appeared;

Termite infestations in Australia have told us, there is no need to bury your house for termites to find it.

It makes sense when you think about it – all timber that is damaged in service is above ground, because termite scouts have come from the soil to find it.

By installing stations containing timber on surfaces on ground, you can intercept them in places where they are foraging – on ground.

If we just look at the termite family Rhinotermitidae which cause over 90% of all termite damage in Australia and only enter homes via a water leak, timber/ground contact or through a crack or protected area that maintains a high 95% humidity environment. So realistically the majority of termite attack is due to a home being partly buried. Further these termites spend the majority of their life protected within tree roots and deeper in soil and only leave when conditions offer protection from their major predator, common ants. These termites simply will never forage on ground by choice and although they do build mud tubes above ground to maintain the humid environment they live in, this is because they are following dominant pheromones laid by thousands of other members of their colony and already know that food exists above, found via another route with ground contact.

Subterranean termites are sensitive to disturbance while feeding. Replacement of the bait matrix in an active station, or replenishment of a depleted bait frequently resulted in abandonment of the station by foraging termites (Nutting and Jones, 1990; Su and Scheffrahn, 1996; Su, 2001). An unattached, floating monitor offers none of the protection required to maintain feeding.

Termite monitoring studies have shown that no practical attractant exists for subterranean termites. Subterranean termites are incapable of detecting volatiles emanating from food items, through even a few millimeters of substrate (Campora and Grace 2001; Cornelius and Osbrink, 2001; Puche and Su, 2001b). That is without actually running into something that resembles food or moisture termites will not secrete the pheromones necessary for recruitment, an air gap will make discovery impossible.

If the food is accepted and consumed, the forager lays a pheromone trail back to the nest. A primary gallery then is constructed around this recruitment trail (King and Spink, 1969; Goldberg, 1973b; Lys and Leuthhold, 1991; Reinhard et al., 1997). Therefore the laying of pheromones by multiple termites becomes more difficult with the more remote food sources such as those located at the extremity of foraging (surface).

Studies have found that termites are more likely to be located in areas with vegetative cover than open areas (Light, 1934c; King and Spink, 1969; Jones et al., 1987). For example, French (1991) noted that Australian Coptotermes colonies were frequently located in or closely associated with living trees and that monitoring stations located in the area of trees were recruited to preferentially over stations located in the open.

There are a number of reasons why termites may prefer to tunnel beneath vegetation, including abundance of forage, increased humidity, structural protection and thermal shadows.

Building a tunnel directly beneath a root allows subterranean termites to exploit voids in the soil created around the root as it grows or decays (Mun and Whitford, 1998).

Exploitation of such voids could provide easier passage through layers of substrate that might otherwise be resistant to tunneling. For example, a root is likely to lead to fallen wood under the canopy of a tree OR more importantly the root may follow a leak from a bathroom or crack in a slab BUT never leave the surface or even get close to it.

Termites’ behavior in dishes containing PVC guidelines raises serious questions about the use of plastics to construct guidelines and even monitoring stations (Swoboda, 2004). The Termite Mansion has a Lower Timber Device as the first point of contact for termites, who can continue to the feeding chamber without ever needing to contact plastic. This is not possible in the plastic casing of the On-Ground Stations or most of originally designed monitors.

In summary termites are effected by many stimuli in their environment which creates their foraging behavior and whether or not they will enter a Monitor. To misinterpret one of those stimuli without even considering many others is a recipe for failure in the design of a Termite Monitor.

2 Comments. Leave new

That old study of food sources ‘on’ the surface ruled out the ‘condition’ of the food source as being a discovery factor. The test ‘pads’ were placed on sheets of plastic proving the the discovery factor was the temperate differential ( ie Thermal Shadow ). Ultimately, of course, termites will ‘discover’ food on or in the soil but the primary food source they ‘instinctively’ seek out is ‘on’ the ground. They are not called nature’s recyclers for nothing. Without the likes of termites ( recycling fallen wood and releasing nitrogen into the soil ), our forests would die.

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Yes but No ! To actually form a thermal shadow, ‘onground’ with associated airgaps must be converted to a sealed with ground structure. To become nature’s recyclers is much more complex than simply placing timber on the surface and to date nobody has been able to confirm the exact stimuli and importance of each one over another. However much more important in Termite Treatment is not getting termites to eat but keeping them eating long enough to destroy the Queen. Such additional stimuli as how termites actually vibrate the food source by tearing and determining how big and structurally solid the food source is may be more important than previously thought. Our ongoing trials continue to demonstrate that it is not just the food condition but how it is presented that is preferenced. Darren

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