PCOC - Fall 2015 - (Page 12)
German Cockroach Control:
Are Baits the Silver Bullet?
By Jules Silverman, Ph.D., North Carolina State University
The German cockroach, Blattella germanica, is a widespread pest found throughout the world. Interestingly,
unlike just about every other insect pest, it is almost never found apart from human-built dwellings. This
cockroach depends on us for its sustenance: it eats what we eat. Though there is evidence that cockroaches
can spread human pathogens, it is most notably a health hazard due to the production of allergens that trigger
asthma, which have particularly serious affects on inner-city youth. These allergens can build up rapidly due to
the high reproductive capacity of cockroaches, therefore it is imperative to eliminate these pests when detected.
Liquid residual spray insecticides were used almost exclusively
by pest management professionals to control German cockroaches
until the mid-1980s. These were primarily organophosphate,
carbamate or pyrethroid formulations that had varied impacts on
their cockroach target. Some were repellent, avoided by the insects,
while cockroach populations developed resistance to others. Then
baits, beginning with the active ingredient (AI) hydramethylnon,
were introduced to the professional and consumer markets. The
toxicant was mixed with food ingredients. Insects would detect,
then consume the food, while unwittingly ingesting a lethal dose
of insecticide. Other insecticides incorporated within baits that
are both very active and that go largely undetected by the cockroach include fipronil, indoxacarb, abamectin, dinotefuran and
Baits have another advantage over liquid residual sprays: they kill
cockroaches both directly and indirectly (secondary-kill, Domino
Effect™). Here, cockroaches directly consuming bait return to
hiding areas, excreting insecticide-laden feces, before dying. Other
cockroaches will consume these excretions and they, in turn, die. This
is an effective way of delivering insecticide to locations harboring
large cockroach numbers.
The hydramethylnon-based baits were initially very effective,
reducing cockroach populations by more than 90 percent. This
excellent performance continued throughout nearly all accounts
in the United States. However, in some locations, bait efficacy
declines became evident: despite persistent bait applications, cockroach populations were increasing rather than declining. After an
exhaustive search by the manufacturer to determine the cause of this
product performance decline (AI resistance?, AI and inert ingredient
repellency? other), we determined that surviving insects from these
accounts avoided eating the sugar glucose - the primary feeding
stimulant in the bait. Glucose aversion is a heritable trait, and thus,
we were skewing the populations toward glucose-averse individuals by applying bait with glucose as the feeding stimulant. We later
determined that glucose-averse cockroaches perceive glucose as a
deterrent, much like caffeine. Substituting fructose for glucose in
the baits improved product performance considerably.
There is recent evidence that certain populations of German cockroaches have become resistant to the active ingredients in some bait
products. We have identified field-collected cockroach strains with
individuals that are both insecticide resistant and glucose-averse. In
addition, secondary kill is compromised in these resistant strains.
www.pcoc.org / Fall 2015
Table of Contents for the Digital Edition of PCOC - Fall 2015
PCOC 2015 Pictorial Highlights
German Cockroach Control: Are Baits the Silver Bullet?
Is Bed Bug Heat Treatment Hot Enough for Multi-Unit Housing?
Insurance : Get the Facts Before They Get You: Accident Investigations & Employee Safety
State Capitol Report Do You Feel the Sunshine?
Firm Profile North American Home Services
Index to Advertisers
PCOC - Fall 2015