CSIRO says over the past few months, thousands of new cars have been sitting on ships waiting to be offloaded at ports around Australia.

The delay has been caused by a backlog in vehicles waiting to be thoroughly cleaned and checked for biosecurity risk materials, including pests like the Brown Marmorated Stink Bug (BMSB) and weeds.

According to the Department of Agriculture, Fisheries and Forestry (DAFF), since 2021, Australian ports have seen an 88 per cent increase in new vehicles arriving with biosecurity risk material contamination.

Over the same period, there has been a 17 per cent increase in the total number of new vehicle imports into Australia.

CSIRO says these factors have combined to create a massive cleaning job for the commercial companies employed by car manufacturers to ensure new cars don't come with any ‘hidden extras'.

CSIRO says seasonality is responsible for some of the increased biosecurity threats, for example, BMSB is more likely to hide out in vehicles at certain times of the year.

However, the likely culprit is COVID as during the pandemic, many vehicles were stored overseas in paddocks waiting to be shipped. This exposed the vehicles to higher levels of plant debris and insects prior to export, resulting in a bigger cleaning job once they finally arrived in Australia.

CSIRO says a BMSB outbreak could be devastating. BMSB can breed huge populations that become both a household nuisance, as well as a major problem for crop growers.

According to CSIRO, if BMSB established in Australia, it would be extremely difficult and expensive to manage. Unlike native stink bugs, BMSB has no specialised natural enemies here to keep its population in check.

BMSB also isn't easily controlled with pesticides and feeds on more than 300 types of plant, so could spread rapidly.