Cockroach killing gels, food aversion and resistance to these baits

Synanthropic pests have accompanied man since he became sedentary, with the so-called agricultural revolution approximately 12,000 years ago. The sources of food, water and shelter areas provided by settled man favored the development and survival of pests, including cockroaches. To date, those cockroaches of importance to public health represent a real headache because there are many known and documented cases, over the years, of food aversion and resistance to numerous active ingredients present in commercial products intended for their control. Cockroaches are paurometabolous insects (egg-nymph-adult) belonging to the order Blattodea, with less than 1% of this order being considered domestic pests. Likewise, they are potential transmitters of various American acha" and Blattella germanica "German cockroach", both with cryptic behavior, nocturnal activity and omnivores. P. Americana typically lives outdoors, although it can also enter the interior of the facilities. This cockroach is characterized by its relatively large size, long development period and low reproductive potential. The survival of this species is not linked to human activity. On the contrary, B. germanica lives exclusively indoors, no populations living outdoors are known to date, it could be said that this is the most synanthropic cockroach of all, since it depends solely on food, shelter and the conditions provided by man. This cockroach is characterized by its small size, a relatively short development cycle, a high reproductive potential and a very marked resistance to various pesticides on the market, of which we can mention pyrethroids as an example. Resistance can be expressed in these individuals in the following way: greater metabolic degradation of the active ingredient, reduced cuticular penetration (thickening of the cuticle), lower sensitivity at the target site and behavioral (changes in behavior that allow evasion of pesticide residues). The aforementioned constitutes a real headache for PMPs (pest management professionals), who observe, often with frustration, that their efforts to control these insects do not yield the expected results when carrying out chemical treatments. Over time, the use of insecticides has been and continues to be an effective tool for controlling cockroaches under the integrated urban pest management (IUPM) approach. However, since the mid-1980s, conventional management programs stopped relying solely on liquid insecticides to include cockroach-killing baits. Various authors point out that a cockroach-killing gel should be a substance that incorporates an insecticide in an attractive and palatable, non-repellent food, effective in terms of causing high mortality including the cascade effect (through necrophagy and coprophagy) and easy to consume. The first gels developed had in their composition, among other components of the food matrix, glucose, which had the function of being the source of attraction (phagostimulant) for these insects, however, an aversion towards gels began to be observed in the late 90s. Silverman & Bieman (1993) were the first authors to demonstrate this aversion to glucose in B. germanica. Glucose aversion is an inherited behavior in cockroaches, which avoid foods or products based on this monosaccharide. In other words, cockroaches associate the glucose in the bait as a “bitter” compound. Subsequent studies in these populations of cockroaches with food aversion revealed the mutation in chromosome VIII, which caused those insects that did not eat the glucose gels, providing their offspring with this aversion capacity, therefore, they did not consume these hyperglusified baits. The baits currently used use other types of alternative attractive sources of carbohydrates, thus avoiding aversion. Now, it is worth mentioning that they are always pathogenic (which are generally present in the paws, mouthparts and excrement) and responsible for causing allergic symptoms in people, hence their importance in public health. In our environment, the most common cockroaches present in urban areas are Periplaneta Americana "cucarMIP must choose to use "new" gels since aged baits or exposed to high temperatures cause the hydrolysis of complex sugars (fructose and sucrose), once again causing the formation of glucose and again causing the aversion phenomenon. On the other hand, despite the fact that in the current market there are various gels with different active ingredients (i.a); the use indiscriminate, prolonged and without adequate rotation of baits with different mechanisms of action, have once again generated the development of resistant populations, thus making their control even more complicated. In fact, behavioral resistance in B. germanica results from continuous exposure to gels. In the same way as with the phenomenon of aversion, the resistance of B. germanica towards different i. a present in the gels is inherited to the following generations. The resistance to most classes of insecticides present in many commercial baits has been documented in various articles, such as that of Shao-Hung Lee. , et al. (2021), who demonstrated the resistance of various strains of B. germanica collected in the city of California, USA. Likewise, they concluded that these strains were resistant to those insecticides absent in the control programs in the areas from which they were collected, which could be explained, according to the authors, to a previous exposure that resulted in the development of stable resistance mechanisms, presence of broad-spectrum resistance mechanisms or cross-resistance. Baits are and continue to be a useful tool for cockroach management programs, however, if we do not have responsible use and an adequate rotation program of pesticides (with different mechanisms of action) we will logically have resistance problems in the populations, particularly speaking of B. germanica. Likewise, the use of other measures integrated in harmony, within a pest management program (IPM), such as cleaning, exclusion measures (hermeticity), among others, will greatly complement the use of these chemical products so as not to essentially depend on them.