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Benzaldehyde and 2-hexanone are allomones produced by beagle dogs that reduce infestation by Rhipicephalus sanguineus sensu lato on these animals and on susceptible dogs which artificially release these repellents. These observations were obtained in previous laboratory tests or artificial infestations of susceptible dogs under controlled conditions. Here we evaluated the efficacy of collars delivering these repellents for suppressing the loads of R. sanguineus s.l. on naturally infested mixed-breed dogs under field conditions. Thirty dogs naturally infested with R. sanguineus s.l. were separated into two groups with 15 dogs each. The dogs from the treatment group received the collars with slow-release formulations of the allomones, and the dogs from the control group received collars without such compounds. Collar effectiveness tests were carried out over 30 days. All ticks found were removed from each dog, identified, and counted every collection day. The density of the different life stages of R. sanguineus s.l. varied greatly between groups and across evaluation times. Adult ticks were the stage most abundant and prevalent on infested dogs. The counts for larvae, nymphs and adults were similar between the control and the treatment groups within each tick collection day. Conversely, when we considered the total number of ticks over 30 days and gathered all life stages collected in the same animal, the dogs from the control group had significantly higher loads (35.3 ± 4.27) of ticks than the dogs from the treatment group (21.8 ± 2.96) (P0.01). In addition, the efficacy of treatment with repellent collars was high for adult ticks (30.8%) but was extremely low for reducing larval or nymphal infestation (0 or 2.6%, respectively). The present study demonstrates, for the first time, the efficacy of these volatile compounds on naturally infested dogs under field conditions. The development of a technologically enhanced device for slow release of the allomones tested here can be an advantageous alternative for reducing R. sanguineus s.l. infestation on dogs in residential environments.

Aims Control of diurnal Aedes aegypti with mycoinsecticides should consider the exposure of fungus-treated adults to sunlight, and especially to UV-B radiation that might affect activity of conidia applied on the mosquito′s surface. Methods and results Germination of M. anisopliae s.l. IP 46 conidia on SDAY medium was not affected at the lowest level of radiation with UV-B, 0.69 kJ m−2, but was retarded and reduced at higher 2.075 and 4.15 kJ m−2, and completely inhibited at ≥ 8.3 kJ m−2. In contrast, germination of conidia applied onto fiberglass nettings and exposed from 0–16.6 kJ m−2 did not differ significantly among among levels of irradiance exposure and the controls. There was also no significant impact of UV-B up to 16.6 kJ m−2 on adulticidal activity of IP and on the subsequent conidiogenesis on cadavers. The Quaite weighted UV-B irradiance in the laboratory (1152 mW m−2) was higher than the natural sunlight irradiance observed in the city of Goiânia in Central Brazil on midday (706 mW m−2 in August to 911 mW m−2 in October 2015). Conclusions UV-B does not impair the activity of IP 46 conidia applied previously to radiation on A. aegypti adults. Significance and Impact of Study Findings contribute to a better understanding of the effectiveness of M. anisopliae against day-active A. aegypti and its potential for biological mosquito control. This article is protected by copyright. All rights reserved.

Aims: The effect of nutritional supplementation of two Metarhizium species with riboflavin (Rb) during production of conidia was evaluated on (i) conidial tolerance (based on germination) to UV-B radiation and on (ii) conidial expression following UV-B irradiation, of enzymes known to be active in photoreactivation, viz., photolyase (Phr), laccase (Lac) and polyketide synthase (Pks). Methods and Results: Metarhizium acridum (ARSEF 324) and Metarhizium robertsii (ARSEF 2575) were grown either on (i) potato dextrose agar medium (PDA), (ii) PDA supplemented with 1% yeast extract (PDAY), (iii) PDA supplemented with Rb (PDA+Rb), or (iv) PDAY supplemented with Rb (PDAY+Rb). Resulting conidia were exposed to 866·7 mW m−2 of UV-B Quaite-weighted irradiance to total doses of 3·9 or 6·24 kJ m−2. Some conidia also were exposed to 16 klux of white light (WL) after being irradiated, or not, with UV-B to investigate the role of possible photoreactivation. Relative germination of conidia produced on PDA+Rb (regardless Rb concentration) or on PDAY and exposed to UV-B was higher compared to conidia cultivated on PDA without Rb supplement, or to conidia suspended in Rb solution immediately prior to UV-B exposure. The expression of MaLac3 and MaPks2 for M. acridum, as well as MrPhr2, MrLac1, MrLac2 and MrLac3 for M. robertsii was higher when the isolates were cultivated on PDA+Rb and exposed to UV-B followed by exposure to WL, or exposed to WL only. Conclusions: Rb in culture medium increases the UV-B tolerance of M. robertsii and M. acridum conidia, and which may be related to increased expression of Phr, Lac and Pks genes in these conidia. Significance and Impact of the Study: The enhanced UV-B tolerance of Metarhizium spp. conidia produced on Rb-enriched media may improve the effectiveness of these fungi in biological control programs., Instituto de Investigaciones Bioquímicas de La Plata

It is already known that the beagle breed of domestic dogs produces semiochemicals capable of repelling the brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.). With a view to discovering new non-host semiochemicals as tick repellents, we compared the semiochemicals produced by a putative tick-resistant breed of dog, miniature pinscher, with known tick-resistant (beagle) and tick-susceptible (English cocker spaniel) breeds. Two non-host compounds produced by beagles, i.e. 2-hexanone and benzaldehyde, were shown to be present in samples collected from all three breeds. Furthermore, two compounds, 6-methyl-5-hepten-2-one and 1,2,4-trimethylbenzene, were found in higher amounts in samples collected from miniature pinscher dogs. The mean amounts of benzaldehyde, 2-hexanone and 1,2,4-trimethylbenzene were similar for beagles and miniature pinschers (P > 0.05) and higher than the means observed for cocker spaniels (P < 0.05), whereas the mean amount of 6-methyl-5-hepten-2-one produced by miniature pinschers was significantly higher (P < 0.05) than for the other breeds of dogs. In Petri-dish assays with adult R. sanguineus s.l., 6-methyl-5-hepten-2-one was repellent for all observation periods evaluated for the two highest concentrations (0.100 and 0.200 mg.cm-2, P < 0.01). The obtained results support our hypothesis that miniature pinschers are a tick-resistant dog breed and agree with previous observations of miniature pinschers being the breed least parasitized by ticks. Furthermore, the non-host semiochemical 6-methyl-5-hepten-2-one has potential to be developed for use as a repellent for the protection of susceptible dogs from R. sanguineus s.l. ticks.