Tuesday, August 21, 2012

The Ugly American

American cockroach,
Periplaneta americana
If one were to poll pest control customers about what they thought was the most disgusting insect, there's a good chance the American cockroach would come out at top. First of all it's large and scary, it's very fast and, where it proliferates, it stinks. Add to this that the American cockroach is one of the few cockroaches that readily flies, and you've got a disgusting pest.

Since few people want to admit to having giant cockroaches in their homes, alternative names are often given to the American cockroach, waterbug and palmettobug being the two most common. One of our largest cockroaches (reaching lengths of just over two inches), they often look much larger to a surprised customer. They are often described as three or four inches long.

American cockroaches, while much longer lived and slower to reproduce than the more common German cockroach, can become quite prolific in the right environment.  While an American cockroach female only produces about 12 eggs per ootheca (egg case), compared to the German cockroach's 36, she lives much longer and produces more oothecae and potential offspring over her lifetime (an average 360 offspring vs the German cockroach's 320 offspring).  Left undisturbed, American cockroaches can build up impressive populations, as anyone who has opened an infested sewer manhole cover can attest.

Odors from the droppings and the insects
themselves can be noticeable in heavy
infestations of American cockroaches. Note
the stains from cockroach droppings on
these boxes in an infrequently used
storage area. Photo by Fudd Graham.
I guess one of the things that's always impressed me about the American cockroach is its ability to survive in places with little food.  They are relatively common in urban sewer and storm drain systems, as well as steam tunnels and basements and storage areas of institutional buildings like schools, hospitals, prisons and factories. These cockroaches are often living on the edge, nutrition-wise, making do with feeding on glues and starches associated with boxes and papers. They are opportunistic feeders and while they prefer fermenting foods, they will feed on dog food in the lab and will readily feed on various cockroach baits.

My colleague Dr. Fudd Graham, from Auburn University, was recently inspecting a courthouse with a chronic American cockroach infestation. Following his nose, his inspection led him to a storage room that hadn't been opened for over 18 months. The two tubes of  Advion cockroach bait Fudd applied were gone the next morning along with the cardboard on which the bait was applied. 

Typical of many infested areas of buildings, this room had a floor drain that, due to lack of use, was dry.  Dry floor drains are one of the most common entry points for American cockroaches to enter commercial buildings from sewage systems.  Many people, even building maintenance professionals, are unaware of the importance of periodically pouring a gallon or two of water into floor drains to fill the p-trap that is designed to block sewer gases and insects and other pests from entering buildings.  A dry p-trap allows cockroaches ready access to a utility room or food storage area in a building. Besides filling the p-trap, some companies have developed clever membrane devices that open for water flow, but close between use.  Trapguard and Sureseal are two commercial products and, while they can be expensive to install, provide a long term fix for gas and pest infiltration into storage and utility areas. 
The half-inch-long ensign wasp
(Evaniidae) is a sign of American
cockroach presence in a building.

Its important to remember that controlling American cockroaches has other benefits.  Eliminating American cockroaches helps reduce the potential food supply of rodents in a building. I'll guess that most PMPs have seen the disembodied wings and legs of American cockroaches left on sticky traps. This is often evidence of mice or rats, which are fond of snacking on live cockroaches plucked from sticky cards.  In addition, ensign wasps are a common parasite of American and smoky brown cockroach oothecae, and are often seen flying around buildings that have an American cockroach infestation.  While harmless themselves to people, the presence of these interesting insects is a sign of cockroach presence in a building.




1 comment:

Bryan Baker said...

I rummaged through my attic several months ago and found boxes with those same marking and droppings on them. I just assumed they were mice, but looks like i was wrong. thanks for the info.

Bryan Baker