ENTOMOLOGY TODAY - Originally from central Asia, the house fly (Musca domestica) is found pretty much anywhere humans live. In large numbers it can be a nuisance, and it is known to transmit more than 200 pathogens to humans and animals.
One of the most common methods to control house flies are toxic baits, which contain a phagostimulant (a substance that induces feeding, in this case usually based on sucrose) and toxic insecticide. Overuse and misuse of insecticides, however, have resulted in resistance to every major insecticide class.
Insecticide resistance can take two forms—physiological or behavioral. Physiological resistance involves mutations that modify the insecticide’s target site or boosting expression of genes to produce enzymes that detoxify insecticides. Behavioral resistance is the evolution of responses to toxicants that help the insect avoid the lethal effects of the insecticide and reduce exposure to the chemicals.
Neonicotinoid (neonic) pesticides are commonly used against insect pests. Imidacloprid is the most common of these insecticides, routinely used in baits against house flies. However, house flies have developed both physiological and behavioral resistance to imidacloprid. Other neonics could be used that are chemically different from imidacloprid. A team from the University of California, Riverside, decided to investigate whether flies that were resistant to imidacloprid could show “cross-resistance,” that is, resistance to other members of the same insecticide class. Their study, published in August in the Journal of Medical Entomology, shows that, at least in their sample of house flies resistant to imidacloprid, the flies showed no behavioral cross-resistance to other neonicotinoids.