The urbanised German cockroach
“If urbanisation or modernisation goes on, the German cockroach will be the major indoor pest,” declared Dr Tang Qian, Research Fellow at NUS Biological Sciences.
The German cockroach is one of three common pest cockroach species in Singapore, the others being the American cockroach and Australian cockroach. Even though it measures an average of only 1.1 to 1.6cm in length, the modern German cockroach is among the most common and pesticide-resistant creatures in the world. Always found indoors in human structures, its natural origin in the wild is not known.
Dr Tang’s research into the origin and spread of this prevalent pest, as part of his PhD degree, provides better understanding of this insect and can potentially lead to more effective pest management.
The investigator examined 599 German cockroaches from nine cities in China and discovered two regional specific genetic differences, which indicate that there were two periods of spread.
“Even though the German cockroach existed in both the North and South cities at a similar time, it was established in southern China cities later than in northern China cities,” said Dr Tang, who worked with researchers from China and Australia on the project.
The timing of the spreads was linked to the improvements of indoor temperature control systems; central heating systems in the north during the 1960s, and air-conditioning systems in the south during in the 1990s. The development of transport systems with heat supply also allowed the cold-intolerant German cockroaches to be safely transported, accelerating their spread. Studies have shown that these cockroaches dislike temperatures lower than 15°C, and will die below 10°C.
Future research plans involve the determination of the German cockroach’s full phylogeny, which could potentially help with pest control. Dr Tang has already established that its closest relative is the Asian cockroach and hopes to use the information to trace the German cockroach’s original habitat.
“Those Asian cockroaches may provide gene pools, because they probably have original genes or the whole spectrum of the German cockroach genes,” he said. “You can find some specific weakness of their genome to aim at to help in pest control.”
