Resistance to diazinon in the German cockroach

Area of Science:

• Entomology
• Pest Management
• Toxicology

Background:

• German cockroaches (Blattella germanica) are significant urban pests, often developing resistance to commonly used insecticides.
• Monitoring insecticide resistance is crucial for effective pest control strategies in residential and commercial settings.
• Previous studies indicate widespread resistance to organophosphate insecticides in various cockroach populations globally.

Purpose of the Study:

• To determine the susceptibility of German cockroach populations from Owensboro, Kentucky, to diazinon and malathion.
• To quantify the level of resistance to these insecticides in laboratory-reared strains.

Main Methods:

• German cockroach specimens were collected from two distinct locations near Owensboro, Kentucky.
• Insects were reared in the laboratory for three to four generations to establish stable strains.
• Laboratory bioassays were conducted to assess resistance to diazinon and malathion using LC50 and LC90 values.

Main Results:

• Both German cockroach strains exhibited significant resistance to diazinon.
• Resistance ratios for diazinon ranged from 2.5 to 15.3 times the susceptible level, depending on the strain and sex.
• Neither strain showed any detectable resistance to malathion.

Conclusions:

• German cockroach populations near Owensboro, Kentucky, have developed resistance to diazinon.
• Malathion remains an effective control agent against these specific cockroach populations.
• These findings highlight the need for ongoing resistance monitoring and integrated pest management strategies.