Timothy J. Gibb, Insect Diagnostician, Department
of Entomology, Purdue University
A cockroach is not very photogenic, at least I rarely
have photos sent to me here in the pest diagnostic laboratory.
I can think of several reasons why a roach may not be photographed
very often. ‘Flat
out ugly’ is probably the biggest single reason but the unpleasant
life cycle and living conditions where they thrive is also reason
for lack of photos. They require only food, water and a warm place
to harbor in between feeding events. They are able to eat whatever
food becomes available to them, commonly foraging not only on stored
foods, pet foods and table scraps that may be lying around but also
in uncleaned dishes or garbage receptacles. They usually only come
out at night when no one else is around but their presence can easily
confirmed by the mess that they leave after feeding and harboring
in an area. Signs are unmistakable and they emit a unique smell if
they have been around a while. So again, with such a disgusting life
style who would possibly want a photo, especially of one feeding
in your own kitchen. The fact is that most people typically go to
excessive lengths to eradicate them from their homes.
The German cockroach one of several species that can be found
inside homes but it is the species that gives all other cockroaches
a bad name. It occurs throughout the world primarily in association
with humans and often plagues multifamily dwellings in the United
States. Because it does not directly harm people it is considered
an aesthetic pest, and the action threshold for this insect depends
upon the tolerance of the people living in the infested dwelling.
That is why infestations in multifamily dwellings are so common.
The building is subject to the lowest common tolerance level. If
one apartment remains home to a large infestation, the entire building
remains infested regardless of control efforts in other areas.
The German cockroach has three life stages
typical of insects with incomplete metamorphosis: the egg, nymph,
and adult. Adult
German cockroaches are generally about 5/8 inches in length, are
light brown except for the shield behind the head that is marked
with two dark stripes running lengthwise to the body. They
have long antennae and can run in short bursts very quickly. Eggs
are enclosed in capsules that are light tan and usually yield about
36 young. Young roaches are wingless and nearly black with
a single light stripe running down the middle of the back.
The entire life cycle is completed in about 100 days and under
ideal conditions, population growth has been shown to be exponential.
Many classes of insecticides including organophosphates,
carbamates, pyrethroids, amidinohydrazones, insect growth regulators,
inorganics, microbial, and botanicals are available for controlling
German cockroaches. These are available in a wide variety of
formulations including baits, sprays (emulsifiable concentrates,
wettable powders, microencapsulated), dusts, and powders. Baits
and baiting technology have recently been improved such that
roach infestations have been eliminated rather than just reduced
in many buildings.
Non toxic and low toxic alternatives for German cockroach control
are available. Sticky traps can be used to monitor or reduce population
Improving sanitation by eliminating food and water sources and
clutter can have a significant impact on reducing populations.
Exclusion practices such as sealing cracks and crevices will reduce
harborage space and thus infestations.
Often a combination of the above tactics are
required to effectively manage an existing roach infestation. After
the roaches are eliminated, sanitation and exclusion techniques
usually are sufficient to keep them at bay.