Biology
The German cockroach has three life stages typical of insects with incomplete metamorphosis: the egg, nymph, and adult. The entire life cycle is completed in about 100 days. However, factors such as temperature, nutritional status, and strain differences may influence the time required to complete a life cycle.
German cockroaches breed continuously with many overlapping generations present at any one time.
Under ideal conditions, population growth has been shown to be exponential. Actively growing field populations are comprised of 80 percent nymphs and 20 percent adults.
The German cockroach is omnivorous, eating table scraps, pet food, and even book bindings.
Adult size: 13 -16 mm
Number of moults: 5 - 7
Development time (Egg to adult): 1 - 3 months
Length of adult stage: 3 - 6 months
Number of ootheca produced in female lifetime: Average 5
Number of eggs produced per ootheca: Average 30 - 40
How they affect you
Cockroaches can carry dysentery, gastro-enteritis typhoid and food poisoning organisms.
Germs can be spread from the body of the cockroach or from the droppings they leave behind. Cockroaches will feed on almost anything including faecal matter. Contamination occurs when the cockroaches come into contact with foodstuffs.
Control Methods
An established cockroach infestation is likely to be difficult to control. This is because the cockroaches will be distributed throughout the building in difficult to reach harbourages.
Furthermore the phenomenal breeding potential and production of many egg cases by each female cockroach means that unless a very high proportion of the population is eliminated, numbers will continue to increase.
An integrated programmed approach is essential.
Spot treatments will be completely ineffective for all but a small, localised infestation. Before a treatment is carried out, it is important to identify the cockroach species. This will provide details of the biology, life cycle and habits of the pest,
which can be exploited in the control programme. Monitoring the extent of the infestation by visual inspection of voids, potential harbourages and the use of traps will help identify hotspots of infestation.
Inspections are best carried out at night when the cockroaches are more active. A torch fitted with a red filter should be used, as cockroaches do not respond to red light.
When using sticky traps, suitable placement sites would be underneath equipment, behind counters, in roof spaces and in ducting and electrical trunking.
As cockroaches become trapped, the trap becomes more attractive to other cockroaches because of the effects of aggregation pheremones exuded by the trapped cockroaches.
Adjoining building and areas sharing services should be included in the monitoring.
If chemical control is needed, a combination of different formulations for different areas will give the most effective treatment.
Insect growth regulators, baits, residual insecticidal sprays, insecticidal dusts and ULV formulations may all be considered and most usually a combination of all or some of them will be selected.
Use of one type of formulation alone in a complex building is unlikely to achieve a sufficiently high level of control. Re-treatment of all or some areas will almost certainly be needed.
A thorough treatment is needed.
After insecticidal application, post treatment monitoring should be carried out and steps should be taken to prevent re-infestation, by attempting to determine the source of the original infestation.
Continued use of sticky traps as a permanent early warning system may also be useful.
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