We hate them, they are filthy and annoying. We want to see them dead but recent research suggests that they are getting stronger. They are here to stay.
The German cockroach (Blattella germanica L.) is a worldwide pest that lives exclusively in human environments. B. germanica threatens human health by producing asthma-triggering allergens, vectoring pathogenic/antibiotic-resistant microbes, and by contributing to unhealthy indoor environments.
There’s a study titled ‘Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach (Blattella germanica L.)’, which focused on the resistance of cockroaches on different chemical products used on them.
The study led by Michael E. Scharf from Purdue University represented a seminal effort to assess trans-generational impacts of different resistance management strategies on resistance evolution in B. germanica cockroaches.
There were three focus objectives;
- Use pre resistance-monitoring data to make informed insecticide choices,
- Compare three resistance intervention strategies in the field and
- Assess resistance evolution in surviving cockroach field populations.
The results, according to the report show clear links between predicted resistance levels and field performance of insecticides, poor efficacy of insecticide deployment strategies on populations with evolved resistance, and unexpected selection of field populations for broad cross-resistance across insecticides.
Three resistance intervention approaches were compared in “low-rise” housing facilities in Danville, IL and Indianapolis, IN (in the Midwest USA) that included rotation, mixture or single active ingredient (AI) treatments.
All products were E.P.A. registered (that is the U.S Environmental Protection Agency), purchased from retail vendors and applied in collaboration with licensed pest management professionals.
The study was conducted with human subjects’ research approval by the Purdue University Institutional Review Board. Untreated control apartments were not permitted, which necessitated comparisons only among the three treatments (i.e., rotation, mixture and single AI).
Cockroach population monitoring and density assessment was done with glue traps to determine the amount of insecticide products to apply and to assess treatment impacts.
To account for potential cockroach movement between apartments and buildings, all apartments within study buildings, whether initially infested or not, received identical treatments. All buildings receiving the same treatments were clustered together.
The researchers in this study were able to maintain the level of cockroach populations through the rotation of insecticides, but didn’t really reduce their numbers.
It was pointed out that resistance within a single generation of cockroaches sometimes increases four or six fold.
It was concluded that the problem is worse in low-income areas and other places where effective pest control is not available.
The researchers suggests that the best way to combat these creatures is to diversify pest treatment methods, this could include physical methods such as traps and vacuum cleaners, and preventive measures such as cleaning.