Changing population patterns - when an alien pest becomes a problem at home? First recorded pest outbreak of the springtail Sminthurus viridis in Europe.

The springtail Sminthurus viridis (Collembola: Sminthuridae) is classed as an alien pest of economic importance in Australasia – costing over $50 million annum-1 in damage and control measures to the agricultural industry. Sminthurus viridis has never been considered a pest in its native Europe, where it has a ubiquitous distribution in grasslands, as native predators and environmental conditions keep abundances below damaging infestations. However, during an experiment assessing different cultivation practices for lucerne (Medicago sativa) in the UK, an abundant outbreak of S. viridis was observed in an initial field assessment, with a number of individuals visible per plant. Sminthurus viridis numbers were immediately quantified over a 24 hour period to ascertain whether this was comparable to any other reported outbreak; as well as sequence data obtained to compare to Australasian “pest” populations of S. viridis. As this outbreak occurred within a statistically-robust replicated experiment, we could also assess how different cultivation techniques affected the abundance of crop pests within ecosystems. Lucerne established by direct drilling with herbicide had the highest abundance of S. viridis compared to other treatments (lucerne established by direct drill or plough, with or without herbicide). The S. viridis population abundances were found to be ten-fold greater than populations found on a nearby site of established lucerne. Within the EU, over 60 million hectares are devoted to grassland containing clover and lucerne, the main food sources of S. viridis. If there were further outbreaks similar to our findings across Europe, allowing S. viridis to cause damage on a similar scale as Australasia (20-50% losses), it would cost millions to the European agriculture industry. Our findings highlight the need for greater monitoring of S. viridis within agriculture worldwide and that we need to increase awareness within the farming community of this potential future pest, to safeguard crops