Integrated Pest Management

IPM Manual for Structural Pests in British Columbia

Chapter 13: Commonly Used Pesticides

Learning Objectives

When you have completed this lesson, you should be able to:

1. Describe the properties and use of common insecticides, rodenticides and an avicide registered for use in structural pest management programs.

   In addition to the preferred pesticides described in Chapter 3, there are other chemicals used in structural pest control. These are insecticides, rodenticides and avicides (for birds). Among the insecticides, there are three main categories of chemicals:

   • organophosphates
   • carbamates
   • synthetic pyrethroids

   For each of the pesticides discussed in this section, information is included on the mode of action, properties, formulations and safety and use.

Insecticides

ORGANOPHOSPHORUS INSECTICIDES

The mode of action of organophosphorus insecticides is disruption of the insect nervous system. They are cholinesterase inhibitors, meaning that they stop the action of an enzyme (called the acetylcholinesterase enzyme) that has an essential role in normal functioning of the insect's nerves.

Chlorpyrifos

Properties

Chlorpyrifos is a broad spectrum, moderately toxic organophosphate insecticide. It is a contact residual insecticide with a longer residual life than most other insecticides when applied to nonporous surfaces (such as stainless steel and glazed tile). It is particularly persistent when applied to bare wood (activity lasts for several weeks).

Chlorine based cleaners will deactivate this insecticide. They can be used to clean up spills, but their use should be avoided where the residual insecticidal activity is needed.

Formulations

Chlorpyrifos is available as emulsifiable concentrates and microencapsulated formulations for use in non-residential buildings. Insect baits containing chlorpyrifos are registered for use in homes.

Safety

The solvents in some formulations have a strong odour that may last several days. These formulations are not recommended for use within buildings especially if the ventilation is poor.

Recent tests have raised concerns about the levels of chlorpyrifos remaining in the air of treated homes several hours after treatments. Although the tests are inconclusive at this time, it is recommended that the use of chlorpyrifos sprays be limited inside buildings to spot treatments and crack and crevice applications.

Notes on Use

Because many formulations of chlorpyrifos are not registered for use in or around in and around homes or other residential areas, it is not widely used.

The recommended concentration of active ingredient in a spray mix varies depending on the severity of the insect infestation and the length of residual activity that is needed.

Some product solvents have strong odours.

Diazinon (Diazinon 50®, Diazinon 50 0® or Basudin 50 EC®)

Properties

Diazinon was once widely used to control pests in and around buildings. It is no longer registered for indoor use. In residential areas, it may only be used outdoors as spot treatments for a very small number of land and turf pests.

Formulations

Many liquid formulations are available. Emulsifiable concentrates are the most common, but oil formulations are also used. Emulsifiable concentrates are usually packaged in 4 litre containers; these must be handled carefully to prevent spilling during use.

Dust formulations are available. As well, diazinon is available in a microencapsulated formulation (e.g., Basudin FM®) which has good residual action against many crawling insects on both porous and nonporous surfaces. Microencapsulated diazinon has a lingering odour which can last for several weeks, therefore would not be appropriate in situations where this is a concern.

Safety

For homes or offices that are sealed for spraying, there is some concern that diazinon application produces excessive vapour. It is particularly important that the rooms or buildings be well aired before residents or workers re-enter. A recent study found that vapour levels in unventilated rooms were high six hours after broadcast applications.

Notes on Use

Diazinon is a commonly used residual insecticide. It is most used for the control of crawling insects in homes.

Dichlorvos (DDVP®)

Properties

Dichlorvos is a contact insecticide and is also taken into the respiratory system as vapours. It is the fastest acting organophosphate and, in a spray formulation, has a short residual life of hours. Dichlorvos also has fumigant properties, but unlike a true fumigant will leave a residue. When impregnated in a resin strip, the release of dichlorvos vapours is maintained over long periods of time. It has a characteristic odour.

Dichlorvos is corrosive to iron and steel and may cause staining on carpets if the mixed product is stored in metal spray tanks.

Formulations

Dichlorvos is formulated in ready-to-use fogging solutions and emulsifiable concentrates.

Safety

Dichlorvos is highly toxic to mammals and is not registered for broadcast residual applications indoors. Resin strips are registered for use indoors, away from food preparation areas. Their use, however, is not advisable in living areas, especially where there is limited ventilation, because it may result in excessive human exposure (e.g., to children in bedrooms). Dichlorvos must not be used in dairy barns.

When applying dichlorvos as a spray, it is important to wear full protective equipment, including respirator.

Notes on Use

Dichlorvos has little or no place in an IPM program because it is so volatile and does not remain where it has been applied. It has a limited use as a broadcast spray where quick knockdown is required (e.g., outdoors for controlling wasps).

CARBAMATE INSECTICIDES (BENDIOCARB, PROPOXUR)

Carbamates have a mode of action similar to that of organophosphorus insecticides, which is disruption of the insect nervous system. They are cholinesterase inhibitors, meaning that they stop the action of an enzyme (called the acetylcholinesterase enzyme) that has an essential role in normal functioning of the insect's nerves.

Bendiocarb (Ficam)

Properties

Bendiocarb is a broad spectrum, residual contact insecticide.

Formulations

The three main formulations of bendiocarb are Ficam W® (a wettable powder), Ficam Plus® (bendiocarb with pyrethrins and piperonyl butoxide) and Ficam Dust®. Ficam® products are virtually odourless. This can be an advantage when treating living or working areas.

Safety

Avoid producing a cloud of dust when opening packages of wettable powder.

Notes on Use

Ficam products are broadly labeled and can be used to control most structural insect pests. They are especially effective against ants and wasps.

The wettable powder formulations are packaged in small packets that can be transported safely with little danger of accidental spills. They should be cut open carefully, however, as they are difficult to open and pour into a sprayer without spilling. Wettable powder formulations are classified as Restricted pesticides and so must only be applied by certified individuals.

High concentrations of Ficam W® may result in visible residues being left on dark wood or other surfaces. It is relatively easily removed from rugs with a vacuum cleaner, which cancels the residual effect.

Propoxur (Baygon LC®)

Properties

Propoxur is a moderately toxic, contact insecticide. It has moderate residual activity on many surfaces. When applied indoors, it has residual activity for several weeks. It has short residual activity outdoors.

Propoxur has a characteristic odour that can be noticed for up to 48 hours after spraying an enclosed area.

Formulations

Propoxur is formulated in liquid concentrates and in pressurized sprays.

Liquid concentrates are usually packaged in 4 litre containers; these must be handled carefully to prevent spilling during use.

Safety

Always wear an organic vapour respirator when applying propoxur.

Notes on Use

Propoxur is used as a residual insecticide in perimeter sprays, crack and crevice treatments and spot sprays. Its strong odour makes it unsuitable for use as a broadcast spray indoors.

The main use for propoxur is for control of cockroaches and other crawling insects. It's good flushing action and fairly fast knockdown effect can be used to advantage in cockroach cleanouts. The knockdown effect takes about 15 minutes so it is of limited use indoors for flying insect control.

SYNTHETIC PYRETHROIDS

Synthetic pyrethroids, such as allethrin and permethrin, have a structure similar to one of the active ingredients found in naturally occurring pyrethrins (extracted from pyrethrum daisies). The mode of action of pyrethroids is as a nerve toxin.

Allethrin

Properties

Allethrin was one of the first pyrethroids to be developed. It is a contact insecticide with a slightly longer residual activity than pyrethrins.

Allethrin formulations have a characteristic odour that is irritating to some people.

Formulations

Allethrin is usually mixed with a synergist in an oil-based formulation. It is usually used as a space spray.

Safety

Allethrin has low mammalian toxicity. Some people are allergic to it, however, so it is not recommended as a broadcast spray in homes. Where it is used, residents should be told to air out their homes thoroughly before they re-enter. Occupants should not re-enter closed buildings until extractor fans in the building have been in operation for a few hours.

A respirator must be worn while applying an ultra low volume (ULV) allethrin concentrate with an aerosol generator.

Notes on Use

The principal use of allethrin is as a knockdown agent in aerosols, particularly ULV applications.

Permethrin

Properties

Permethrin is a contact insecticide with fast contact action and moderate to good residual activity. It has a broad spectrum of activity against flying and crawling structural insects, such as flies and cockroaches.

Permethrin has low volatility and is soluble in water. It is virtually odourless.

Formulations

Permethrin is formulated as an emulsifiable concentrate (e.g., Dragnet®).

Safety

While permethrin has low toxicity to mammals and birds, it is extremely toxic to fish. Do not contaminate aquariums. It should not be applied near fish bearing waters outdoor and must be used with caution around backyard pools stocked with fish. Indoor aquariums should be removed from areas to be treated.

RODENTICIDES

Most rodenticides are anticoagulants, meaning that they prevent blood from clotting, which causes the rodents to die of internal bleeding. Some are effective when the rodent has eaten a single dose, others require multiple doses to reach a lethal level in the blood.

Brodifacoum (Talon, Final, Ratak)
Bromadiolone (Maki®, Bromone®, Rat-XB®, Contrac)
Difethialone (Generation)

Properties

Brodifacoum, bromadiolone and difethialone are all single-dose anticoagulants.

Formulations

These rodenticides are formulated as meal or bait pellets or paraffin bait blocks.

Safety

All rodenticide baits should be used in tamper-proof bait stations. Pellets are more likely than other formulations to be moved by rodents to non-target areas and thus are not recommended. Diphacinone is highly toxic to dogs.

Notes on Use

Bait shyness in rodents usually does not develop. Multiple-dose anticoagulant baits can be useful in maintenance baiting programs, alternating with other baits, to ensure that the rodent population does not develop resistance to single-dose anticoagulants.

Warfarin was the first anticoagulant rodenticide introduced. With long use, populations of rodents can become resistant to it and such resistance has been reported in British Columbia. Where a rodent population has become resistant, other rodenticides must be used.

Bromethalin (Fastrac, Terminator, Rampage)

Properties

Bromethalin is not an anticoagulant. It is a highly potent rodenticide that can kill rats and mice after a single feeding. After ingestion, bromethalin is transformed in the liver to a toxic metabolite that leads to decreased energy production in cells. This, in turn, leads to a buildup of cerebral spinal fluid causing damage to nerves and resulting in paralysis, convulsions and death.

Formulations

Bromethalin is available as place packs and bait blocks.

Safety

Bromethalin can be absorbed through the skin so it is important to wear chemical-resistant gloves when handling the bait. Rats and mice can move place packs or pellets from place packs out of bait stations. Bait blocks, secured inside tamper-resistant bait stations is a safer way to use bait. Cats are particularly sensitive to bromethalin. There are no effective antidotes to bromethalin poisoning.

Notes on Use

Bromethalin baits are registered for indoor use only.

Cholecalciferon (Quintox®)

Properties

Cholecalciferol (vitamin D3) is a stable form of vitamin D. It kills by mobilizing calcium from the bones into the blood stream. Too much calcium in the blood stream causes calcification of soft tissues and eventual death, usually from heart failure. Rodents usually feed for several days on the bait before they lose appetite; they usually die within 3-4 days. It has a very slight odour.

Formulations

Cholecalciferol is formulated into meals, seed and baits. Sorexa® is mixed with an anticoagulant. Rampage® is a pellet formulation sold mainly in agriculture.

Safety

This rodenticide is less toxic to humans and pets than the other rodenticides described in this chapter. However, recent studies suggest that cats may have a low tolerance to cholecalciferol. As with all rodenticides, precautions must be taken to prevent exposure to people and other pets, preferably by securing the baits in tamper-proof bait stations.

Notes on Use

Pelleted formulations may be less attractive to rodents. Rats may only accept the bait when other food is scarce. Pellets are more likely than other formulations to be moved by rodents to non-target areas.

Zinc Phosphide (ZP®)

Properties

Zinc phosphide is a fast-acting, acute stomach poison that is very toxic to all animals. The action of stomach acids on the zinc phosphide results in the liberation of phosphine gas, which destroys the internal organs. When zinc phosphide is used as a 2% bait absorbed onto seed, it will kill a rat in 17 minutes.

Its unattractive dark grey colour and strong, garlic like odour make zinc phosphide repellent to most animals, although rats and mice do not seem to avoid it.

Formulations

Zinc phosphide is formulated in seeds and tracking powder. It deteriorates in exposed baits within two weeks.

Safety

This product is highly toxic to people and non-target animals. It must not be used where there is any possibility that rodents may track it or carry it to non-target areas.

Notes on Use

Zinc phosphide has little or no use in an IPM program. It may be necessary in a situation where a rapid reduction in a rodent population is required. It should then only be applied as a bait, in tamper-proof bait stations. All unused baits should be collected with a day or two after it has been placed.

AVICIDES 4-AMINOPYRIDINE (AVITROL®)

Properties

The active ingredient, 4-aminopyridine, has a strong excitatory effect on the central nervous system, probably enhancing the transmission of nerve impulses. Birds that have eaten baits containing this ingredient are in severe distress and their cries frighten and repel other birds in the flock from the area. Symptoms of exposure include hyper-excitability and tremors that progress to convulsions. Where death occurs, it is due to respiratory or cardiac arrest.

Formulations

Avitrol products are bait formulations in corn or grain. Concentrates are not available.

Safety

This is a restricted product and may only be used under permit from the Ministry of Environment. Permit conditions specify precautions that must be taken when using the product. Where the formulated product is used and how non-target organisms are protected is rigidly controlled.

Notes on Use

Avitrol treated grain is used for control of pigeons, starlings, sparrows and others on buildings. It is seldom, if ever, needed in an IPM program. If used, it must be applied in a manner that, as much as possible, prevents the death of birds.