Molecular evidence for dual pyrethroid-receptor sites on a mosquito sodium channel.

Pyrethroid insecticides are widely used as one of the most effective control measures in the global fight against agricultural arthropod pests and mosquito-borne diseases, including malaria and dengue. They exert toxic effects by altering the function of voltage-gated sodium channels, which are essential for proper electrical signaling in the nervous system. A major threat to the sustained use of pyrethroids for vector control is the emergence of mosquito resistance to pyrethroids worldwide. Here, we report the successful expression of a sodium channel, AaNav1-1, from Aedes aegypti in Xenopus oocytes, and the functional examination of nine sodium channel mutations that are associated with pyrethroid resistance in various Ae. aegypti and Anopheles gambiae populations around the world. Our analysis shows that five of the nine mutations reduce AaNav1-1 sensitivity to pyrethroids. Computer modeling and further mutational analysis revealed a surprising finding: Although two of the five confirmed mutations map to a previously proposed pyrethroid-receptor site in the house fly sodium channel, the other three mutations are mapped to a second receptor site. Discovery of this second putative receptor site provides a dual-receptor paradigm that could explain much of the molecular mechanisms of pyrethroid action and resistance as well as the high selectivity of pyrethroids on insect vs. mammalian sodium channels. Results from this study could impact future prediction and monitoring of pyrethroid resistance in mosquitoes and other arthropod pests and disease vectors.

Parasitoids and hyperparasitoids (Hymenoptera) on aphids (Hemiptera) infesting citrus in east Mediterranean region of Turkey.

The aphids, aphid parasitoids, and hyperparasitoids found in citrus orchards, the parasitoids' and hyperparasitoids' seasonal abundance, and the plant-aphid-parasitoid relationships in Hatay, Osmaniye, Adana, and Mersin provinces of the east Mediterranean region of Turkey are presented in the present 2-yr study. Aphidius colemani Viereck, Binodoxys angelicae (Haliday), and Lysiphlebus confusus Tremblay and Eady (Hymenoptera: Braconidae: Aphidiinae) were encountered as the most common parasitoids among 10 identified aphidiine and aphelinid taxa on different citrus species. Hyperparasitoids belonging to the genera Alloxysta, Phaenoglyphis, Asaphes, Pachyneuron, Syrphophagus, and Dendrocerus are reported for the first time emerging from aphids feeding on citrus in Turkey. Among them, Asaphes spp., Pachyneuron spp., and Syrphophagus spp. were recorded as the most common ones. Citrus reticulata Blanco and Citrus limon (L.) Burm. fil. were recorded as main hosts for the aphid parasitoids and their hyperparasitoids.

Capsella bursa-pastoris Is a Key Overwintering Plant for Aphids in the Mediterranean Region.

The reproduction of aphids depends to a great extent on their host plants, an integration that impacts on the successful expansion of overwintering populations. Therefore, a survey was conducted to evaluate the globally distributed Capsella bursa-pastoris as an overwintering host of economically important aphid species, their parasitoids and hyperparasitoids in the southern and western regions of Turkey from November to March in 2006 to 2013. During this survey, 395 samples of C. bursa-pastoris were collected with 25 aphid species recorded. Among aphids that feed on this host, Myzus persicae, Aphis gossypii, Rhopalosiphum padi, Aphis fabae, Aphis craccivora, Lipaphis erysimi, and Brevicoryne brassicae were the most frequently recorded. In total, 10,761 individual parasitoids were identified. Binodoxys angelicae, Aphidius colemani, Aphidius matricariae, Diaeretiella rapae, Ephedrus persicae, and Lysiphlebus confusus were the most abundant aphidiines that emerged from the aphids collected from C. bursa-pastoris. Alloxysta spp. (Hymenoptera: Cynipoidea), Chalcidoidea (unidentified at genus level), and Dendrocerus spp. (Hymenoptera: Ceraphronoidea) were identified as hyperparasitoids on the parasitoids. These findings indicate that C. bursa-pastoris is a key non-agricultural plant that significantly contributes to the overwintering of numerous aphids and their parasitoids, which should be given serious consideration when biological control strategies are designed.

Some Demographic Parameters of Lysiphlebus confusus, L. fabarum, and L. testaceipes (Hymenoptera: Braconidae: Aphidiinae).

Lysiphlebus confusus Tremblay and Eady, L. fabarum (Marshall), and L. testaceipes (Cresson) (Hymenoptera: Braconidae: Aphidiinae) are important biological control agents for aphids. To select the appropriate biological control agent for a target pest, an understanding of the demographic parameters is essential. Therefore, a study was conducted to determine the effect of five temperatures, 12, 17, 22, 27, and 32°C, at 60% RH and 5.0 Lux photoperiod of 16:8 (L:D) h, on the parasitism rate, development, and fecundity of these three parasitoids of Aphis gossypii Glover (Hemiptera: Aphididae). Only L. fabarum parasitized at 12°C and the rate was low. None of the parasitoids was able to develop at 32°C. Lysiphlebus testaceipes had the shortest developmental period at the other temperatures. Lysiphlebus confusus and L. fabarum had similar developmental times at 22 and 27°C, with L. confusus completing its development faster at 17°C. The mortality rate of the three parasitoids varied between 3 and 20% at 17, 22, and 27°C, except for L. testaceipes which had about 53% mortality at 27°C. Lysiphlebus testaceipes had the highest net reproductive rate at all temperatures for the 2.5 and 97.5% bootstrap CIs. Lysiphlebus fabarum had the highest intrinsic rate of increase at 22°C and L. testaceipes had the highest at the other temperatures. The best temperatures for fecundity were 17 and 22°C for L. testaceipes and 22°C for the other species. Lysiphlebus testaceipes appeared to be the most suited biological control agent for A. gossypii in southern Turkey, but its intolerance to high temperature could prove problematic for its establishment and persistence in this region.