Understanding German Cockroach behaviour
There seem to be no worries that German cockroaches are becoming extinct. In fact, the number and incidence of these pests on Pest Management Professional accounts is on the rise. Thus, it’s time to sharpen your knowledge and skills to take on this formidable foe.
Since one female German cockroach has the ability to produce as many as 500,000 offspring in a single year, it doesn’t take long for German cockroaches to give Pest Management Professionals a headache. To prevent a few cockroaches from quickly multiplying into a colony, PMPs should use the most effective tools to control these impressively productive pests.
Below are some behaviour facts that will help us better understand German cockroach traits and improve our chances of elimination:
- German cockroaches tend to exist within about 3 metres or less of their harbourage area. The use of sticky trap monitors can help you pinpoint their source. If this is unsuccessful, do not keep going to the client and redoing the same thing.
- These creatures are nocturnal and prefer to move around in darkness. When looking in a dark room or area, leave the lights off and use a flashlight to search. Once you find some German cockroaches, turn the lights on and watch where they scatter. They should lead you to their harbourage areas.
- The carrying capacity of a German cockroach population is usually dependent on the number of harbourage areas, rather than food and water. To reduce harbourage sites, seal cracks and crevices where the cockroaches most likely harbour, or bag and seal large harbourage areas like cardboard boxes. Areas that cannot be sealed, like electrical appliances, require the use of an insecticide product.
- Of all domestic cockroach species, German cockroaches have the highest reproductive rate. They mature very quickly (within 45 days) and continue to reproduce, so their numbers can easily skyrocket. Thus, until you completely eliminate a population, coming back on a quarterly basis is too long to wait between intervals. Don’t evaluate your control program by how many cockroaches are controlled, but rather by how many still remain. Use monitoring devices to prove you did a complete elimination job, or to pinpoint where more work is needed.
- German cockroaches prefer to feed on gel baits that retain their moist, soft gel texture. ADVION Cockroach Gel from Syngenta Professional Pest Management exhibits these characteristics with its excellent initial bait acceptance, as well as its ability to retain its palatability for up to three months.
- Since the 1990s, cockroach gel baits have become some of the most effective and preferred products for cockroach management. ADVION Cockroach Gel contains a highly palatable formulation with a low impact active ingredient, indoxacarb. Its formulation has the unique ability to cascade through a cockroach population at two levels – secondary and tertiary kill – to effectively overcome the reproductive potential of German cockroaches.
What is tertiary kill?
Tertiary kill (or transfer) is a type of horizontal transfer of insecticide. Horizontal transfer occurs when insecticide is passed among individuals of the same population. Research has shown a primary donor can transfer an active ingredient to primary recipients, which then become secondary donors. For example, a single adult cockroach can consume a lethal dose of ADVION Cockroach to kill many nymphs (secondary mortality). These nymphs then become donors and can kill other cockroaches (tertiary kill).
A laboratory study conducted at Purdue University found that excretions from a single ADVION Cockroach Gel fed cockroach adult killed 76 percent of nymphs within 72 hours. These dead nymphs then became an attractive food source for other adult cockroaches. The dead nymphs contained enough indoxacarb to kill 81 percent of adult cockroaches within 72 hours. Thus, the single bait-fed cockroach ended up controlling 54 members of its own family.1
What facilitates transfer among German cockroaches?
There are three main mechanisms that contribute to the effective transfer of insecticides among cockroaches:
Coprophagy is the ingestion of faeces. Cockroach nymphs readily feed on the faeces or rectal region of fellow cockroaches.
Necrophagy is the ingestion of dead cockroaches.
Emetophagy is ingestion of excretions from dying cockroaches.
All three mechanisms contribute to the transfer of indoxacarb throughout the cockroach population. Because of the slow-acting nature of indoxacarb, dying cockroaches can become walking bait stations as they return to harbourage areas and can share the product with difficult-to-reach stages, like nymphs, that often remain in the safety of cracks and crevices.
ADVION Cockroach Gel is highly attractive and palatable to multiple cockroach species, making it compatible with integrated pest management programs for both residential and commercial accounts. This makes ADVION Cockroach Gel a valuable tool to manage tough infestations and provide your customers with a cockroach-free environment.
By knowing your enemy and utilising their weaknesses, you can ensure success when implementing a program to control German cockroaches.
1 Buczkowski, G. Scherer, C. and Bennett, G. “Horizontal transfer of bait in the German cockroach: Indoxacarb causes secondary and tertiary mortality.” Journal of Entomology 101(3): 894-901.