SignificanceAmbrosia beetles are among the true fungus-farming insects and cultivate fungal gardens on which the larvae and adults feed. After invading new habitats, some species destructively attack living or weakened trees growing in managed and unmanaged settings. Ambrosia beetles adapted to weakened trees tunnel into stem tissues containing ethanol to farm their symbiotic fungi, even though ethanol is a potent antimicrobial agent that inhibits the growth of various fungi, yeasts, and bacteria. Here we demonstrate that ambrosia beetles rely on ethanol for host tree colonization because it promotes the growth of their fungal gardens while inhibiting the growth of “weedy” fungal competitors. We propose that ambrosia beetles use ethanol to optimize their food production.

Abstract. An incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for quantification of atmospheric trace gases that absorb in the cyan region of the electromagnetic spectrum (470 to 540 nm), including NO2 and I2, is described. The instrument uses a light-emitting diode coupled to a 1 m optical cavity consisting of a pair of mirrors in stable resonator configuration. Transmitted light is monitored using a grating spectrometer and charge-coupled device array detector. The average mirror reflectivity was determined from the N2∕He and Ar∕He ratios of scattering coefficients and was ∼99.98 % at its maximum, yielding an effective optical path length of 6.3 km. Cross sections of N2, O2, air, Ar, CO2, and CH4 scattering and of O4 absorption were measured and agree with literature values within the measurement uncertainty. Trace gas mixing ratios were retrieved using the spectral fitting software DOASIS (DOAS intelligent system) from 480 to 535 nm. Under laboratory conditions, the 60 s, 1σ measurement precisions were ±124 and ±44 pptv for NO2 and I2, respectively. The IBBCEAS instrument sampled ambient air in Ucluelet, BC, Canada, in July 2015. IBBCEAS retrievals agreed with independent measurements of NO2 by blue diode laser cavity ring-down spectroscopy (r2=0.975), but ambient I2 concentrations were below the detection limit.

Abstract. A cavity-enhanced absorption spectrometer (CEAS) for quantification of atmospheric trace gases that absorb in the cyan region of the electromagnetic spectrum (470 to 540 nm), including NO2 and I2, is described. The instrument uses a light-emitting diode coupled to a 1 m optical cavity consisting of a pair of mirrors in stable resonator configuration. Transmitted light is monitored using a grating spectrometer and charge-coupled device array detector. The average mirror reflectivity was determined from the N2/He and Ar/He ratios of scattering coefficients and was ~99.98 % at its maximum, yielding an effective optical path length of 6.3 km. Cross-sections of N2, O2, air, Ar, CO2, and CH4 scattering and of O4 absorption were measured and agree with literature values within the measurement uncertainty. Trace gas mixing ratios were retrieved using the spectral fitting software DOASIS from 480 to 535 nm. Under laboratory conditions, the 60 s, 1σ measurement precisions were ±105 and ±38 pptv for NO2 and I2, respectively. The CEAS sampled ambient air in Ucluelet, BC, in July 2015. CEAS retrievals agreed with independent measurements of NO2 by blue diode laser cavity ring-down spectroscopy (r2 = 0.975), but ambient I2 concentrations were below the detection limit.

Developing efficacious protocols for applying water disinfectants to reduce opportunistic pathogen‐associated mortalities during the Atlantic salmon Salmo salar fry stage would be highly beneficial for producers. Atlantic salmon fry (0.47 g ± 0.02) were exposed to daily stressors over four weeks while providing daily 30‐min bath treatments of 15 mg/L hydrogen peroxide (H2O2), 0.2 mg/L peracetic acid (PAA) or 0.5 mg/L PAA. Survival was tracked, and skin and gill samples were collected at 2 and 4 weeks for histopathology. Moribund fish were regularly assessed via wet‐mount microscopy, with organisms resembling Saprolegnia spp. routinely observed on gills of affected fish. Tanks treated with H2O2 had significantly (p < 0.05) higher survival (83.7% ± 1.7) compared to controls (69.5% ± 5.2) while no significant differences were observed between either PAA treatments (76.6% ± 0.6 and 77.4% ± 3.0 survival in the 0.2 mg/L and 0.5 mg/L PAA groups, respectively) and controls. Interestingly, no significant differences were noted among treatments for waterborne Saprolegnia spp. concentrations through qPCR quantification. Lower total suspended solids (TSS) were observed in both PAA treatment groups; no other water quality differences were noted. No treatment impacts were observed through histopathology at either sampling point. These results suggest that, at the dosage and treatment regime tested, H2O2 can be a safe and efficacious water treatment for reducing Atlantic salmon fry opportunistic infection‐associated mortality during periods of physical and environmental stress. Assessments of alternative PAA treatment regimens should also be considered in future research aimed at reducing early life‐stage mortality in Atlantic salmon.

Saprolegniasis is an important disease in freshwater aquaculture, and is associated with oomycete pathogens in the genus Saprolegnia. Early detection of significant levels of Saprolegnia spp. pathogens would allow informed decisions for treatment which could significantly reduce losses. This study is the first to report the development of loop-mediated isothermal amplification (LAMP) for the detection of Saprolegnia spp. and compares it with quantitative PCR (qPCR). The developed protocols targeted the internal transcribed spacer (ITS) region of ribosomal DNA and the cytochrome C oxidase subunit 1 (CoxI) gene and was shown to be specific only to Saprolegnia genus. This LAMP method can detect as low as 10 fg of S. salmonis DNA while the qPCR method has a detection limit of 2 pg of S. salmonis DNA, indicating the superior sensitivity of LAMP compared to qPCR. When applied to detect the pathogen in water samples, both methods could detect the pathogen when only one zoospore of Saprolegnia was present. We propose LAMP as a quick (about 20–60 minutes) and sensitive molecular diagnostic tool for the detection of Saprolegnia spp. suitable for on-site applications.