Comparison of intercept trap fluids and aerial spore collectors to survey fungal spores

Abstract

Surveillance for early detection of non-native, invasive pathogens requires simple, sturdy, and easy-to-use collecting devices. In this study, we compared the fungal species detected in wet collection cups of Lindgren traps vs. those detected on slides with oiled cheesecloth as aerial spore collectors. DNA was extracted and amplified from both using the primers ITS1F and gITS7, and Illumina sequencing was used for the metabarcoding of fungi present in samples. In 90 samples, there were 1,277 fungal operational taxonomic units (OTUs). For fungal OTUs only detected by one collection method, insect traps had three times the number of fungal OTUs compared to slides, and this pattern persisted when analyses were restricted to pathogens and forest pathogens. Annually, thousands of insect traps are deployed in North America and the associated trap fluids have added value to forest disease research and monitoring.

High throughput screening of fungal phytopathogens caught in Australian forestry insect surveillance traps

“…Our results do, however, substantiate the utility of preservative fluids for forest surveillance activities. This substrate provides a consistent and stable source from which to sample when targeting fungi and other microbes, allowing for standardization of an approach that extends beyond only screening for insect-vectored pathogens (Berube et al, 2022). While both the anti-freeze and glycol mixtures used in the current study showed no apparent difference in their efficacy for long-term storage (>300 days at 4 • C), further investigation is needed to test for within sample differences that might exist for these substrates.…”

“…Considering that the traps are currently used to monitor insect pests, our methodology focused on speed, scalability, and compatibility for targeting phytopathogens, and consequently incorporated non-destructive approaches when working with the insect specimen subsamples. Previous studies have established that semiochemical-baited insect traps are effective for fungal surveillance, whether sampling the preservative fluids alone (Tremblay et al, 2018(Tremblay et al, , 2019Berube et al, 2022) or through destructive sampling of the insect-specimens (Malacrino et al, 2017;Miller et al, 2019;Rassati et al, 2019). To our knowledge, however, the impact on recovering targeted fungi from insect trap subsamples (i.e., extracting from preservative fluids vs. insect specimens) is yet to be assessed.…”

“…Both diagnostic approaches are, however, limited by their targeted nature and not well suited for early detection during general surveillance activ to detect fungal pathogens that may be cryptic during the early stages of invasion. To this end, innovative approaches which rapidly screen for forest phytopathogens using high-throughput molecular techniques are increasingly desirable (Tremblay et al, 2018;Aguayo et al, 2021;Berube et al, 2022).…”

“…At present, diagnosis of trap catches during forest biosecurity surveillance is only conducted on insects, leaving an opportunity for Australian biosecurity agencies to improve their capacity by incorporating methods that can simultaneously screen for phytopathogens within the same traps. It is well established that semiochemical-baited insect traps are effective for fungal surveillance (Malacrino et al, 2017;Tremblay et al, 2018Tremblay et al, , 2019Berube et al, 2022).…”