Reversibility of the knockdown effect at application of aerosols against pyrethroid-resistant house flies

Knockdown resistance to pyrethroids and pyrethrins is the first sign of insecticide resistance, suggesting a decrease in insect nervous system sensitivity. On the Russian market of insecticides, there are many products in the aerosol package intended for the destruction of flying insects, which include pyrethroids, which provide a quick knockdown effect in insecticide susceptible insect strains. In resistant populations, in many cases, the reversibility of paralysis is observed, which indicates insufficient effectiveness of insecticidal products. The insecticidal activity of four products in aerosol package containing pyrethroids or pyrethrins in various concentrations on houseflies in natural populations was studied in comparison with the insecticide susceptible against laboratory on strain S-NIID. The most effective formulation was on the basis of natural pyrethrins. The reversibility of paralysis of resistant populations was detected using all aerosols and amounted to 0–37 % for the Kaluga strain, 10–93 % for the Krasnogorsk, KSK-1 0–87 %, KSK-2 20–99 %, S-NIID 0 %.

Life and Death at the Voltage-Sensitive Sodium Channel: Evolution in Response to Insecticide Use

The voltage-sensitive sodium channel (VSSC) is a critical component of the insect nervous system. Pyrethroids and DDT are insecticides that have been widely used, and they kill insects by perturbations of the VSSC. Decades of insecticide use selected for mutations in Vssc that give rise to resistance in almost all pest insects. However, the mutations responsible for the resistance are not always the same, and some unusual patterns have emerged. This review focuses on what pyrethroid/DDT selection has done, in terms of Vssc changes that have occurred, using four well-studied species as examples of the differences that have evolved. Information is provided about the mutations that occur, potential pathways by which alleles with multiple mutations arose, the relative fitness of the alleles, the levels of resistance conferred, and the geographic distribution of the mutations. The lessons learned and exciting new areas of research are discussed.

Odourant dominance in olfactory mixture processing: what makes a strong odourant?

The question of how animals process stimulus mixtures remains controversial as opposing views propose that mixtures are processed analytically, as the sum of their elements, or holistically, as unique entities different from their elements. Overshadowing is a widespread phenomenon that can help decide between these alternatives. In overshadowing, an individual trained with a binary mixture learns one element better at the expense of the other. Although element salience (learning success) has been suggested as a main explanation for overshadowing, the mechanisms underlying this phenomenon remain unclear. We studied olfactory overshadowing in honeybees to uncover the mechanisms underlying olfactory-mixture processing. We provide, to our knowledge, the most comprehensive dataset on overshadowing to date based on 90 experimental groups involving more than 2700 bees trained either with six odourants or with their resulting 15 binary mixtures. We found that bees process olfactory mixtures analytically and that salience alone cannot predict overshadowing. After normalizing learning success, we found that an unexpected feature, the generalization profile of an odourant, was determinant for overshadowing. Odourants that induced less generalization enhanced their distinctiveness and became dominant in the mixture. Our study thus uncovers features that determine odourant dominance within olfactory mixtures and allows the referring of this phenomenon to differences in neural activity both at the receptor and the central level in the insect nervous system.