10 Tips for Dealing with German Cockroaches

1. German cockroach females carry and protect their oothecae (egg sacs) until right before nymphs hatch (Figure 1). Such gravid females tend to cluster together and stop feeding for long periods until after dropping the oothecae to hatch. It is important to be thorough so as to not miss any cracks or voids harboring gravid females.

2. German cockroaches breed faster than any other pest cockroach. You need to remove/kill 98-100% of a population within the first month to attain elimination, otherwise they simply repopulate through their high reproductive potential.

3. Cockroaches spend most of their time hiding in cracks and voids (Figure 2). Pest professionals should be using products designed mostly for crack and crevice and void treatments rather than formulations that are applied to exposed surfaces. It is far more effective to kill cockroaches in their harborages than to hope they pick up a lethal dose while crawling around.

4. German cockroaches travel only as far from harborages as they need to find food and water, so they tend to hide close to areas that provide both. Typically, if a German cockroach is seen on equipment or a wall, its harborage will be within 10 to 12 feet of that site.

5. Overpopulation and inadequate cockroach control efforts (i.e., space treatments) often move German cockroaches to seek less advantageous harborages. For example, false ceilings are not an ideal site for cockroaches, but they may be found there when forced to do so.

6. German cockroaches are fond of electric junction boxes and use conduits to move between areas. Cockroaches found on one floor of a facility have been traced to another floor, using electric conduits or wiring (or also plumbing lines).

7. Wall voids are commonly one site that goes untreated, which can lead to continued German cockroach infestations. Typically, those walls where moisture availability is higher and where plumbing pipes penetrate into voids should be targeted for periodic treatment when cockroaches are known in an area.

8. Incoming supplies should be spot checked for possible cockroach introductions, especially when cockroaches are found in rooms where supplies are stored.

9. Employee locker rooms can be a source for cockroach introduction, so employee lockers should be placed on a regular schedule for service.

10. When an infestation persists, it is usually because one or more active harborages are being overlooked. Have cockroaches been pushed into perimeter areas such as ceilings? Have key wall voids been checked and treated? Are cockroaches breeding beneath the slab floor? Are they infiltrating from pipe chases, crawlspaces or basements? These and other questions should be asked and investigated until the source(s) is found.

The author is owner of Stoy Pest Consulting and one of the country’s leading urban entomologists.