Integrated Pest Management

IPM Manual for Structural Pests in British Columbia

Chapter 4: Cockroaches

Learning Objectives

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

Describe the life cycle of the German cockroach.
Describe two methods of monitoring cockroach populations.
List preventative measures used in cockroach control.
Describe the use of vacuuming to control cockroaches.
Describe the use of boric acid and hydramethylnon for cockroach control.
State three reasons why post-treatment evaluation of a cockroach control program is important.

Identification

Drawing of lifecycle of cockroach The most common pest species of cockroach in British Columbia is the German cockroach, scientific name Blattella germanica. The brown-banded cockroach (), a serious pest elsewhere, can also occur in B.C., as can other species on an occasional basis.

Notes on Biology: Cockroaches have three stages in their life cycle: the egg, nymph and adult. The females carry the egg cases around until just before the eggs hatch, which increases the chances of the eggs surviving. Over their lifetime, females can produce four egg cases of about 40 eggs each. German cockroaches develop more quickly than other cockroaches; their eggs hatch in 16 to 28 days, depending on the temperature. Nymphs develop to the adult stage in 74 to 103 days, again depending on the temperature.

Monitoring

German cockroaches are mostly active at night, therefore when cockroaches are seen moving around during the day, it can indicate a very large population is present.

German cockroaches have aggregation pheromones in their excrement.

Pheromones act like chemical messages from one insect to another. In this case the message attracts more cockroaches to the same area. This means the cockroaches are not evenly distributed throughout
a room or building. Instead, they will be more concentrated in certain areas.

Regular monitoring is used to find where cockroaches are concentrated and in what numbers. Ways to monitor populations include:

At specific locations, spray pyrethrins and count the number of cockroaches flushed out. This helps find the main areas of aggregation.
Place cockroach sticky traps (triangular or rectangular boxes with sticky glue on the inside surface) throughout the facility and record the number of cockroaches captured. Traps should be placed in areas where cockroaches travel and near any potential shelters, such as:
- along the edges of walls or counters
- near cracks and crevices
- in the motor compartment under refrigerators
- inside electrical devices or wall sockets
- under stoves
- near plumbing fixtures and under sinks

Action Decisions

Tolerance for cockroaches depends on the client and the sensitivity of the site. Some people will be concerned over a single sighting of a cockroach, while in some situations this may not be a problem.

As with any pest that has a high reproductive rate, cockroach control will be easier if populations are not allowed to build to high levels. A regular monitoring program should be maintained so that re-infestation can be detected while the numbers are still low.

Prevention

Barriers to the movement of cockroaches, such as screening on vents and windows, exclude them from buildings. Sanitation measures remove their sources of food and water. Water is more important to their survival than food. German cockroaches can survive about 12 days with food and no water, while they can live 42 days with water, but no food.

Sanitation measures include:

repairing moisture leaks
storing food in insect proof containers
storing garbage in insect proof bins
removing grease and food debris from all kitchen surfaces
flushing drains with hot water
sealing cracks and filling crevices to remove hiding places

Although it has wings, the German cockroach does not fly. It is usually moved to new areas by the movement of furniture, cartons, bottles, etc., in which it is hiding. An example of how this may be important in a control program would be in facilities where cans and bottles are stored for recycling. These sites may require separate treatment to ensure cockroaches are not hiding in the containers and being moved to other areas.

Control

It will seldom be necessary to resort to pesticides, other than the controls listed below. Most pesticides repel cockroaches, which causes them to disperse.

Mechanical Control (Vacuuming)

A backpack mounted vacuum cleaner is useful for knocking down high populations. It can also be used in combination with a flushing agent (such as a pyrethrins spray) that drives the insects out of their hiding places so that they can be captured. Because the dust from cockroaches can cause severe allergic reactions, the vacuum should be fitted with very fine dust filters, a water filter or, even better, a HEPA filter.

Preferred Pesticides

Abamectin: Abamectin is an extract from the naturally occurring soil micro-organism Streptomyces avermitilis. It is available as a bait formulation in bait stations or as a gel bait to be applied with special bait guns into cracks and crevices.

Boric acid: Boric acid does not repel German cockroaches but is repellent to brown-banded cockroaches. It is slow-acting, but is readily available in bait, dust or aerosol formulations. The dust is limited to use in cracks and crevices where it won’t filter out over time. It cannot be used in most vertical cracks or in suspended ceilings, but is ideal for use in wall voids, hollow equipment legs and in voids under cabinets.

Where boric acid cannot be applied as a dust, it can usually be applied as a bait. Some baits are formulated as pastes to be applied with special bait guns into cracks and crevices. Other baits are formulated as a fine granular material to be applied with dusters and some baits come in ready-to-use bait stations. The key to using bait effectively is to ensure that cockroaches find and eat the bait instead of other food. To make this bait effective, it is important to:

place the bait where cockroaches are most likely to find it,
use good sanitation to make sure that the insects have no other sources of food, and
not contaminate the bait with insecticides after the bait is applied as this will repel the cockroaches.

Female German cockroaches have been found to eat less when they are carrying egg cases. This means they will visit bait stations less frequently than nymphs and males and will be removed from the population at a slower rate.

Hydramethylnon: This chemical is available as a bait formulation in a bait station and as a paste to be applied with bait guns into cracks and crevices. It is slow acting and works by taking advantage of the aggregation behaviour of cockroaches. The cockroach does not die until several days after it has returned to its hiding place. It has time to excrete the chemical in its faeces, which kills other cockroaches attracted to feed on the toxic faeces.

Pyrethrins: Crack and crevice sprays of pyrethrins are effective when quick population reduction is essential. Pyrethrins are especially useful for flushing cockroaches out of hiding. Used alone, pyrethrins usually will not eliminate cockroach infestations, but they can be used in combination with other controls, such as vacuuming or other pesticides.

Other Pesticides

Residual insecticides are seldom needed to control cockroaches. The may be of some use in situations where rapid control of large cockroach populations is needed, but a combination of vacuuming, good sanitation and baiting can also provide fast cockroach control. The most commonly available residual sprays for cockroach control are cyfluthrin (Tempo®) and permethrin (Dragnet® and Prelude™).

Treatments for the Future

The following products are not yet available in British Columbia but watch for them in the future.

Insect Growth Regulators: Hydroprene and fenoxycarb eventually produce sterile adults with twisted wings. These should be used in combination with other types of controls for adults because these are juvenile hormones that affect only the immature stages.

Biological Controls

A microbial control, containing the green muscardine fungus, a species of Metarrhizium, is available in the United States. The fungus is on an agar block inside a plastic bait station with four entrances (Bio-PathTM Chamber). When the cockroach walks into the bait station it comes in contact with the spores of the fungus, then spreads the disease to other cockroaches.

Evaluation

Cockroach control programs should be followed up with regular monitoring to evaluate their success. This is extremely important:

to detect progress when using products that take several weeks to eliminate the population,
to locate areas of cockroach activity and aggregation that may have been missed,
to improve placement of baits and bait stations.