Cockroaches

Cockroaches are a common throughout New Zealand and are considered a low-level health threat. The American (Periplaneta americana) and German (Blatella germanica) are the main disease carrying species. Gisborne (Drymaplaneta semivitta) and Native Bush (Celatoblatta vulgaris) cockroaches mainly live outside and do not pose as much of a risk.

They have three stages of development: egg, nymph and adult. The nymph emerges from the egg and looks very similar to adult. Before becoming a fully reproductive adult, the nymph moults (sheds its body casing) several times. This process can take between a few weeks to a year  to complete. A mature female will lay hundreds of eggs in their lifetime.

Cockroaches are able to survive for long periods without food and water.

Gisborne Cockroach
jeans_photos / Creative Commons

The Gisborne cockroach arrived from Australia in 1949 and is now widespread. Adults are wingless and 30-35 mm long. Lives mostly outside in timber/bark but will enter buildings. It is harmless, cannot fly and does not spread disease.

German cockroach
plj.johnny / Creative Commons

The German cockroach is the most common species and breeds in large numbers. It is an indoor species favouring dark, moist shelter near food. It carries various diseases and can cause allergic reactions.

Native Bush cockroach
Jaco Grundling / Creative Commons

The Native Bush cockroach lives outside under the bark of trees, however it can be carried indoors on firewood. It is unable to survive indoors and does not infest food. 

You can reduce your chances of an infestation by doing a few simple things:

  • filling cracks in walls
  • keep living areas and kitchens dry and clean
  • dispose of rubbish often in a sealed bag and placing it in an outside bin
  • keep food in well-sealed storage containers
  • remove human and food waste quickly and efficiently.

Many home remedies can be found via a simple internet search, however many of these are ineffective and do not work. If you are finding these pesky insects inside your home on a large scale, then contact us for professional help. 

Further reading

  1. Landcare Research
  2. Ministry of Health