A pot plant crosses the border carrying an unsuspecting hitchhiker.
And bang, that's all it takes and you have a new pest.
This week has proven exactly that.
For the first time there has been a detection of red imported fires ants in NSW, in which the nests have since been eradicated at South Murwillumbah.
But did the incursion need to occur?
As the latest in a string of pest and disease outbreaks, it is no great surprise questions are being raised as to whether the biosecurity plan in Australia is broken.
We could point the finger at Queensland because that state has had fire ants for years, and on they still breed.
Did Queensland not do enough? The NSW Department of Primary Industries appears so far to have stopped the ant in its tracks.
Either way, the awareness campaigns have clearly not cut through as well as needed.
They haven't stopped the ants from making their way across the border.
But what's the alternative - a COVID-style blockade at Tweed Heads to check everybody crossing into NSW.
All that extreme measure would do is anger people who would find ways around it and do the wrong thing anyway.
What is needed is better education about the fact that this tiny ant is not just a threat to farming, but to everybody.
People were more than eager to get a campaign going around "bin your thongs" for foot and mouth disease.
While that wasn't the ideal campaign, why is there so little interest in this damaging pest that is actually already on our shores?
What people don't realise is that these nippers are down-right nasty and when they sting it hurts, and not just in the hip pocket.
Everyone needs to take this threat seriously, know what the ants look like and pay attention to the signs.
When are we going to learn, especially given recent experiences with Varroa mite, that we need to jump onto these incursions hard and fast.
There seems to be this culture of conservatism around cost and control, but all that does is cost more money in the long run with ongoing expenses with a pest that becomes endemic.
It's not just about government actions. The responsibility needs to come back on individuals, including understanding their role in being aware of the risks in the first place.