Is Biflex Mikron Repellent to German Cockroaches?

The repellent qualities of Biflex Mikron have been tested in a laboratory trial, with the results outlined here (part one of two). 

German cockroaches (Blattella germanica) are a global pest. They have been very successful at establishing a presence alongside human habitation and are resilient in the face of many pest control measures. Reasons include prolific reproduction rates combined with a short reproduction cycle, sexual maturity within several weeks of hatching, the ability to hide in very small spaces, and the adaption and resistance to some chemical treatments.

Biflex Mikron is the newest dual-active formulation to the Australian market. With a number of dual-active products in the market already, which all include a synthetic pyrethroid, many pest managers are questioning whether they are repellent or non-repellent to the target pests, such German cockroaches.

A large volume of trial data was submitted to the APVMA to prove that Biflex Mikron works effectively. Yet FMC is committed to continuously increasing the knowledge base of what its products can and cannot do and delivering this information to pest managers to allow them to make informed decisions on how, when, and where to apply the product to achieve the desired treatment outcome.

A current example of this commitment was the engagement of experienced and respected pest researcher Scott Kleinschmidt from Australian Timber & Pest Research (ATP Research) to answer the question: “Are surfaces treated with Biflex Mikron repellent to German cockroaches?”

In early 2022, Mr Kleinschmidt set up multiple test arenas (large plastic boxes) that contained either a piece of plywood (porous surface) or a ceramic tile (non-porous surface) in the middle of the box.


Test arenas in the climate-controlled


These were either treated with Biflex Mikron at the label rate for the relevant surface, or treated with water only, and left to dry for 24 hours. Four replicates were carried out for each treatment on each surface type (16 test arenas in total).

After the 24-hour drying period, a food source consisting of dried dog food and a piece of cooked chicken breast was placed in the middle of each treated surface, and 20 German cockroaches, a mixture of adult and nymphs, were added to the corner of the box along with a piece of wet cotton wool as a moisture source. The cockroaches could then choose whether or not to travel over the treated surfaces to reach the food. The number of cockroaches present on each surface was counted every ten minutes for a total period of two hours. Cockroach mortality was also recorded.


German cockroaches presented on the Biflex Mikron treated surface


If the Biflex Mikron treatment was repellent to German roaches, it would be expected that fewer cockroaches would be present on the Mikron-treated surfaces compared to the water-treated surfaces.

The first two graphs show that the average number of German cockroaches on the Biflex Mikron and water-treated surfaces were very similar until the 40-minute mark for the porous surface (Figure 1) and the 30-minute mark for the non-porous surface (Figure 2). After these points, the cockroach numbers present on the Mikron-treated surfaces dropped off dramatically.



The mortality results can explain this observation. The second set of graphs show that at a similar time to when the cockroach numbers present on the Mikron-treated surfaces started to decline, the mortality rate started to increase (Figures 3 and 4). Whereas on the water-treated surfaces, the mortality rate stayed at zero. In other words, fewer cockroaches were present on the Mikron-treated surface was because they were either moribund or dead.



This independent trial indicates that Biflex Mikron is non-repellent to German cockroaches on both porous and non-porous surfaces.

The next question is, “Can Biflex Mikron be transferred from a treated German cockroach to untreated nestmates?” This will be answered in the next edition of Professional Pest Manager magazine.