KEY POINTS:
They are no longer just arguing about whether there is fire blight on New Zealand apples. The question being posed is whether a blight has now spread across overall trans-tasman relations given the intensity of Wellington's double-barrelled retaliation against Canberra yesterday.
First, the Prime Minister does not mince
words in telling Alexander Downer, Australia's Foreign Minister, to butt out of New Zealand's domestic politics after he considered her abhorrence at the idea of Air New Zealand flying Australian troops part way to Iraq as a slight on Australia.
Then the Cabinet decides to take Australia to the World Trade Organisation for the first time for blocking New Zealand apple imports.
Appearances deceive, however. Helen Clark's footstomping followed Mr Downer hauling in the New Zealand High Commissioner in Canberra for an official dressing down.
Once that became public knowledge, the Prime Minister had little option but to have a swipe at Mr Downer in return or risk looking weak. Naturally, she went for it. No New Zealand politician lost votes criticising an Australian one.
Her tone was in marked contrast to the much softer language used by Phil Goff and Jim Anderton, her trade and agriculture ministers, in invoking the WTO's dispute resolution procedures.
This is being done reluctantly, very much as a last resort and following extreme provocation.
After Canberra finally agreed last year to relax the ban on importing New Zealand apples - a ban which has been in place since 1921 - Biosecurity Australia then placed such stringent requirements on imports that it is not commercially worthwhile for New Zealand growers to make the effort.
The requirements - which stretch from the way apple trees are pruned through to the sampling of consignments for signs of disease such as fire blight - are a classic example of using so-called phyto-sanitary checks as de facto trade barriers. The paperwork alone would pose a nightmare for growers, while doing the obstructionist Brussels-based bureaucrats of the European Union proud.
Despite Australia's blatant protectionism, however, both countries have agreed to describe the problem as an "irritant". Both Mr Goff and Mr Anderton emphasised the dispute should not be blown out of proportion, given the potential gains to apple growers represent a drop in the financial bucket when overall trade between the two countries is taken into account.
It seems, however, that any sense of proportion is absent from the sniping between Helen Clark and Mr Downer.
A clue to why this tit-for-tat spat is happening lies in the fact that the pair's respective governments are battling the electoral odds. In that context, domestic politics come first, while the longer-term interests of the bilateral relationship lag someway behind.
However, the careful handling of the argument about apples is the better indicator that the relationship is essentially robust, if always fundamentally unequal.