Bumble bee parasite strains vary in resistance to phytochemicals

Nectar and pollen contain diverse phytochemicals that can reduce disease in pollinators. However, prior studies showed variable effects of nectar chemicals on infection, which could reflect variable phytochemical resistance among parasite strains. Inter-strain variation in resistance could influence evolutionary interactions between plants, pollinators, and pollinator disease, but testing direct effects of phytochemicals on parasites requires elimination of variation between bees. Using cell cultures of the bumble bee parasite Crithidia bombi, we determined (1) growth-inhibiting effects of nine floral phytochemicals and (2) variation in phytochemical resistance among four parasite strains. C. bombi growth was unaffected by naturally occurring concentrations of the known antitrypanosomal phenolics gallic acid, caffeic acid, and chlorogenic acid. However, C. bombi growth was inhibited by anabasine, eugenol, and thymol. Strains varied >3-fold in phytochemical resistance, suggesting that selection for phytochemical resistance could drive parasite evolution. Inhibitory concentrations of thymol (4.53-22.2 ppm) were similar to concentrations in Thymus vulgaris nectar (mean 5.2 ppm). Exposure of C. bombi to naturally occurring levels of phytochemicals—either within bees or during parasite transmission via flowers—could influence infection in nature. Flowers that produce antiparasitic phytochemical, including thymol, could potentially reduce infection in Bombus populations, thereby counteracting a possible contributor to pollinator decline

High efficacy of (Z)-γ-Bisabolene from the essential oil of Galinsoga parviflora (Asteraceae) as larvicide and oviposition deterrent against six mosquito vectors

The eco-friendly control of mosquitoes with novel and effective larvicides and oviposition deterrents is a crucial challenge to prevent outbreaks of mosquito-borne diseases. However, most of the herbal formulations tested in these years showed LC50 values higher of 10 ppm, and oviposition deterrent activity only when tested at relatively higher doses (>50 µg/ml). Here, we focused on the chemical composition of the essential oil (EO) of Galinsoga parviflora, an annual herb native to South America and naturalized all over the world, testing its larvicidal and oviposition deterrent action against 6 mosquito species. Totally 37 compounds were identified in the EO of G. parviflora by GC and GC-MS analyses. The major constituent was (Z)-γ-bisabolene (38.9%). The G. parviflora EO and (Z)-γ-bisabolene showed acute toxicity on An. stephensi (LC50=31.04 and 2.04 µg/ml), Ae. aegypti (LC50=34.22 and 2.26 µg/ml), Cx. quinquefasciatus (LC50=37.10 and 2.47 µg/ml), An. subpictus (LC50=40.97 and 4.09µg/ml), Ae. albopictus (LC50=45.55 and 4.50µg/ml) and Cx. tritaeniorhynchus (LC50=49.56 and 4.87 µg/ml) larvae. Furthermore, the oviposition deterrent potential of the G. parviflora EO and (Z)-γ-bisabolene was studied on six mosquito vectors, showing that 25 µg/ml of (Z)-γ-bisabolene led to Oviposition Activity Index lower of -0.79 in all tested mosquito vectors. Overall, all larvicidal LC50 values estimated for (Z)-γ-bisabolene were lower than 5 µg/ml, this result far encompass current evidences of toxicity reported for the large majority of botanical products currently tested against mosquito young instars, allowing us to propose this compound as mosquito larvicide and oviposition deterrent

Mangrove Helps: Sonneratia alba-Synthesized Silver Nanoparticles Magnify Guppy Fish Predation Against Aedes aegypti Young Instars and Down-Regulate the Expression of Envelope (E) Gene in Dengue Virus (Serotype DEN-2)

The control of dengue vectors with effective tools is crucial. Here, we fabricated silver nanoparticles (AgNP) using a cheap method relying to a mangrove extract (Sonneratia alba) as a reducing and stabilizing agent. AgNP were charac- terized by UV–vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. LC50 of S. alba extract against Aedes aegypti ranged from 192.03 ppm (larva I) to 353.36 ppm (pupa). LC50 of AgNP ranged from 3.15 (I) to 13.61 ppm (pupa). Sub-lethal doses of AgNP magnified predation rates of guppy fishes, Poecilia reticulata, against Ae. aegypti and Chi- ronomus kiiensis larvae. Mangrove-fabricated AgNP were evaluated for their antimicrobial potential against Bacillus subtilis, Klebsiella pneumoniae, and Sal- monella typhi, using the agar disc diffusion and minimum inhibitory concentration protocol. Notably, S. alba-synthesized AgNP tested at doses ranging from 5 to 15 lg/mL down-regulated the expression of the envelope (E) gene and protein in dengue virus (serotype DEN-2), while only little cytotoxicity rates (i.e.\15%) were detected on Vero cells when AgNP were tested at 10 lg/mL. Overall, this study pointed out the potential of S. alba-synthesized AgNP to develop eco-friendly nanoformulations effective against dengue virus and its mosquito vectors