On funding of community gardens and their being a "Biosecurity risk"

On funding of community gardens and their being a "Biosecurity risk"

The view of Ausveg, the peak body for the vegetable industry in Australia, that community gardens are a risk of spreading infestations of either pests or diseases to commercial crops which need to comply with strict adherence to quality assurance guidelines at least for export. Likewise farmers' markets have a food safety issue, because of insufficient identity checking of vendors at those markets, and that these dodgy vendors might sell poor food. (Ive reconstructed the argument here; I think this is their claim. The text is "We've seen a litany of examples where people have passed themselves off as other growers," he said").

The press release:
http://ausveg.com.au/media-release/risky-project-funding-cut-gets-vegetable-industry-support

Tony Abbott has killed funding for community gardens - the feds have saved $1.5 million that was going to the Community Food Grants program, created by the former Labor government under the National Food Plan, and AUsveg supports the cessation of funding. I don't have strong views to express about the political judgement of supporting community gardens with an amount of cash this small, except to say that it is trivial compared to the millions going to public sporting grounds and various sporting leagues, and various other forms of wasted expenditure.

My interest is rather in this claim that community gardens pose a "biosecurity risk" to commercial agriculture, especially export agriculture. Some comments by celeb gardener Costa here:
http://www.abc.net.au/news/2014-02-28/costa-says-community-gardens-no-threat/5289184

He's rejecting the contentions of Ausveg on "biosecurity risk", but no actual refutations of particular claims. He makes the important wider claim that community gardens generate a sense of community. He could have added they are good for communal health, and take the pressure off the industrial food system, and encourage some degree of resilience among the gardeners. He could have said that the term "Biosecurity risk" is a vague, stupid and manipulative phrase, tagging along credibility from the war on terror, and either too vague to be useful in this context or just plain wrong. (It might be a commercial agriculture risk, but it isn't obviously a biosecurity risk, except in the very loose sense that the risk of death of a (monoculture, non-threatened, commercially grown, globalised) plant is involved. There is no suggestion that death to humans or animals is involved either).

Neither side has offered much evidence and science for their claims in either direction. Costa has offered none, but merely asserted a negation; Ausveg has offered some conjectural assertions based on what might possibly occur as a result of neglected or run-down gardens. Neither has discusses location and transmission issues - how do the bugs/gribblies/germs/fungi etc get from Concrete City to FarmerLand, and how distances affect transmission probabilities. Neither has dealt with the appeal to consistency on whether a kitchen garden in a rural area comes under the same strictures, because it would seem to have the same possibility of neglect (possibly a stronger possibility, given rural population aging, and single-gardener maintenance issues).
 
So is there any science behind the Ausveg claim?

In the wider context, is this a case of the Australian commercial sector wanting to be maximally lazy and not actually deal with crop resilience issues (except to dump more chemicals on things, plant more marginal land, drain more aquifers, demand more handouts - in short, to keep doing industrial farming the good old way, but with more tech and scale,  etc etc)?