Termicides (Termite Insecticides)

The development of insecticides and the Dirty Dozen

DDT Early chemicals

In our modern world we are surrounded by chemicals, we trust that we are being protected from dangerous substances but are we?

I remember as a child my father buying containers of a white powder he used to sprinkle on his roses, it was a sort of talcum powder to control unwanted insects. It was in fact DDT and was used to kill garden pests.

DDT was first synthesised back in 1874 but it was not until 1939 when its use as an insecticide was discovered and was used very effectively to control the spread of typhus and malaria during the second world war. After the war it was introduced as an agricultural insecticide and became very widely used. In 1948 Swiss chemist Paul Hermann Muller received the Nobel Prize for his discovery of the efficacy of DDT as an insecticide.

Dangerous Chemicals, Rachel Carson and the Silent Spring

In 1962 biologist Rachel Carson published a book called "Silent Spring" which examined the environmental impact of the widespread use of DDT and the lack of understanding of the risks to the environment and to people. The book suggested that DDT might cause cancer and be a threat to wildlife.

Rachel’s book was a major influence on the formation of the environmental movement and lead to the banning of DDT in America in 1972 which in turn lead to the creation of the Dirty Dozen which are toxic chemicals known as Persistent Organic Pollutants (POPs) and banned in 2001 by international treaty at the Stockholm Convention.

The dirty dozen

These are chemicals that are:

• 1. Are toxic to humans and wildlife.
• 2. Remain intact for exceptionally long periods of time.
• 3. Become widely distributed in the environment.
• 4. Accumulate in the fatty tissue or living organisms and become more concentrated higher up the food chain.

The Dirty Dozen

The dirty dozen are:

Aldrin, Chlordane, DDT, Dieldrin, Dioxin, Endrin, Furans, Heptachlor, Hexachlorobenzene (HCB), Mirex, Polychlorinated Biphenyls (PCBs) and Toxaphene

Of these DDT is still used in some parts of the world in the fight against malaria.

Most of these nasties are Organochlorides or chlorinated hydrocarbons which were widely used as insecticides. It is interesting to note how many of these nasty chemicals were sprayed liberally around and under houses for treatment against termites. A picnic on the lawn takes on a whole other meaning, “toxic sandwich vicar? Perhaps a chloride cookie”.

Organochlorides are not the only widely used nasties. Organophosphates are not exactly healthfoods. They work by irreversibly inactivating an enzyme which is essential to nerve function in insects, humans, and many other animals. They are used as insecticides, herbicides but also more notably as spyicides, they are the chemicals used as nerve gases (ever heard of Sarin?).

They easily degrade on exposure to sunlight, air, and soil (although small amounts can be detected in food and drinking water) which made them attractive when organochlorides were banned. Often banned for residential use organophosphates are still widely used in agriculture.

As the dirty dozen were identified and banned a new generation of insecticides were developed and banned chemicals were replaced by pyrethroids which now constitute the majority of commercial household insecticides. They quickly knock down flying insects but, in the concentrations used in such products, are generally harmless to human beings but can harm sensitive people. Normally they break down in one or two days by sunlight and the atmosphere. Pyrethroids are toxic to fish and other aquatic organisms but do not significantly affect groundwater quality.

Natural Pyrethrum was extracted from East African chrysanthemum flowers, a known natural insecticide. The active ingredients were identified and copied and in the 1960s 1st generation Pyrethroids were developed. By the 1970s more effective though more toxic and less biodegradable 2nd generation pyrethroids were developed that are more suitable for agriculture.

A new generation of chemicals for termite treatment

For many years termite insecticides have been an area of particular concern. The earlier chemicals were pretty nasty and pyrethroids provide safer, though still toxic, chemicals compared to the organochlorides.

In recent years a major change came and termite chemicals were developed that represented a different strategy for eradication. The earlier insecticides were repellent, termites could smell and taste them and were repelled by them. Termites that came into direct contact were killed while the rest were not. Termites simply went around the insecticide. The insecticide was used as an impermeable barrier around a building, any gap in the barrier and the termites would get through.

The latest chemicals use a more stealthy approach, they are non repellent. They are tasteless and odourless to termites which burrow through treated ground then later return to the nest taking the insecticide with them. This is then transferred from termite to termite killing the whole colony. To work effectively these are slow acting insecticides that allow time for dispersal through the termite colony.

Two of these new generation termite chemicals are Fipronil and Imidacloprid both of which work by disrupting the insects central nervous system.

Fibronil is manufactured by Bayer and marketed in different parts of the world under the names Termidor, Ultrathor, Taurus, Regent, Goliath, Nexa, Chipco Choice and Adonis. It is also used in flea control products for pets under the trade names Frontline and PetArmor.

Imidacloprid is manufactured by Bayer and is the active ingredient in insecticides sold under the trade names Admire, Condifor, Dominion, Gaucho, Premier, Premise, Provado, and Marathon

While highly toxic to termites and other insects both are classed as only moderately toxic to humans.

In animals and humans, Fipronil poisoning symptoms are vomiting, agitation, and seizures while Imidacloprid symptoms, including fatigue, twitching, cramps, and muscle weakness including the muscles necessary for breathing.

Fipronil is highly toxic to fish and aquatic invertebrates, to bees and to upland game birds, but is practically nontoxic to waterfowl and other bird species. Imidacloprid is toxic to upland game birds, highly toxic to bees but relatively harmless to fish.

Selecting a termite treatment company

To summarise when you are selecting a termite control company it is a good idea to check the chemicals they plan to use. Ask for the brand name of the chemical but also ask for the active ingredient which will tell you the type of insecticide and its toxicity. You may find they use one of the following five chemicals:

Chlorpyrifos - an organophosphate insecticide, nasty stuff and banned for use in residential areas in America, it is to be avoided.

Bifenthrin and Deltamethrin - pyrethroid insecticides much safer but still older generation, more toxic and less effective than new generation chemicals.

Fipronil and Imidacloprid - the latest non repellent termite treatment chemicals a lot more expensive but far more effective than the older chemicals.

Perhaps another insecticide to be aware of is the active ingredient commonly used for mosquito fogging which is a pyrethroid called cypermethrin.

A List of commonly used chemical insecticides

Here is a list of common chemical types and the active ingredients.