Why German cockroaches are a formidable foe, Part III


March 15, 2023

Photo: © Gene White

Photo: © Gene White

Editor’s Note: In Part I of this series, Dr. El Damir explains the biology and behavior of German cockroaches. In Part II, he looks at what goes into making assessment-based management decisions for this persistent pest. Now, in his final installment in this series, he examines other facets of best practices for German cockroach IPM.

German cockroaches (Blatella germanica) are persistent pests that require time, patience and an integrated approach for complete control. In addition to inspecting and assessing the individual account in which you are trying to bring a German cockroach population under control, consider the following additional steps:

  1. Sanitation: Keeping the area clean and free of food and water sources that can attract cockroaches. Durbin and Cochran (1985) conducted research on the effect of food and water deprivation on German cockroaches and found that it reduced reproduction in female cockroaches and increased mortality. This highlights the importance of removing food and water resources to help control German cockroach populations. Removing food and water resources can force cockroaches to move around more than usual in search of these resources. This increased movement can eventually expose them to pesticide residues or the vacuum, making it easier to control their population.
  2. Exclusion and harborage modification: Sealing cracks and crevices in walls, floors, and other areas to prevent cockroaches from entering the area. Finding and sealing cracks and crevices important steps in controlling German cockroach infestations, as these areas provide hiding spots for insects. However, finding and removing harborage is a continuing effort that can be time-consuming. It’s important to establish good communication with customers and work in partnership with them to identify and eliminate harborage sites
  3. Physical control: Using methods such as vacuuming, trapping, and flushing to physically remove cockroaches from the area. Vacuuming is a highly effective method for reducing German cockroach numbers, as it physically removes the insects from the environment. It’s important to use a vacuum with a HEPA filter to prevent the insects and their debris from being released back into the air. Regular vacuuming, along with other pest control measures, can help to keep German cockroach populations under control.
  4. Chemical control: Chemical control is one of the methods commonly used to manage German cockroach infestations. Using targeted pesticide applications is necessary, as general and broad applications of baits can be ineffective and may even exacerbate the infestation. Baits and non-repellent sprays that are specifically formulated for German cockroaches are effective because they are designed to not alert the cockroaches, who will expose them and bring them back to their harborage areas, which can help to eliminate the entire population. In contrast, repellent sprays can cause cockroaches to scatter and avoid the treated areas. Scattering cockroaches to non-target areas can indeed cause unintended infestations, making it difficult to control and treat the infestation. Some examples of non-repellent insecticides that are commonly used for German cockroach control include fipronil, imidacloprid and hydramethylnon. These insecticides can be applied as sprays, baits, or dust, depending on the situation. When applying pesticides, it is important to consider safety and to apply them only to areas where German cockroach activity has been identified, such as areas where they hide, travel and feed. This can include cracks and crevices, under appliances, behind baseboards, and in other areas where cockroaches are likely to be present. This can help to minimize the amount of pesticide used and reduce the risk of pesticide resistance. It is also important to rotate the types of baits and pesticides used to prevent resistance from developing. This involves alternating the use of different types of baits and pesticides with different modes of action so that cockroaches are not exposed to the same type of control measure repeatedly. By doing this, the likelihood of cockroaches developing resistance to any one type of control measure is reduced. It is generally recommended to rotate the mode of action every three months or so, as this is the approximate length of a cockroach’s life cycle. However, the specific timing and frequency of rotation may vary depending on the severity of the infestation and the specific products being used. It is also important to follow label instructions and use pesticides only as directed to minimize any potential risks to human health and the environment.
  5. Education: Educating building occupants on proper sanitation practices and ways to prevent cockroach infestations can help reduce the cockroach population and prevent future infestations.

In conclusion, regular inspections and preventive measures can also help to prevent German cockroach infestations from occurring in the first place. German cockroaches are known for their ability to hide in hard-to-reach areas, such as cracks and crevices in walls, floors, and cabinets. This can make them difficult to locate using conventional inspection methods. However, the “3S process” — scatter, suck and seal — can be effective in eliminating German cockroaches from these hard-to-reach areas. By using a flushing agent to scatter the insects out of their hiding places, a HEPA filter vacuum to suck up the insects, and sealing off the hiding places to prevent the insects from returning, it is possible to eliminate German cockroach infestations.

Other than flushing cockroaches from hard-to-reach areas, use non-repellent insecticides as the basic chemicals to properly deal with German cockroaches. Non-repellent insecticides are specifically designed to be transferred from one cockroach to another, which can effectively control the entire population. These types of insecticides are generally the better choice than repellent insecticides, as they don’t cause cockroaches to scatter and spread the infestation to other areas.  However, rotating the mode of action of baits and pesticides is an important strategy to prevent the development of resistance in cockroach populations.

Cleaning and removing clutter can help eliminate hiding places and food sources for cockroaches, while sealing cracks and fixing leaks can make your customers’ homes or workplaces less appealing to these pests. Baits, traps and insecticides can also be effective when used correctly and in combination with other control methods. It’s essential to remember that prevention is key when it comes to cockroach infestations and taking proactive steps can help you avoid the problems that come with these pests.


About the Author

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Dr. Mohammed El Damir, BCE, is technical and training director of Adam’s Pest Control, Medina, Minn.

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