I think these countries are in fact approaching this as a problem that has an obvious solution, as you suggest. The issue lies, however, with convincing their populace to work these seasonal jobs, and the inherent nature of seasonal agricultural work.
Firstly, the levels of unemployment are not necessarily going to be as bad as you might think, at least in some countries. Many western countries, including Norway, which you mention, and later, the UK, have implemented schemes which will allow companies to keep employees who have been furloughed due to the crisis on the payroll by covering a large portion of their wages. These schemes don't stop claimants from taking another job, at least in the UK's case, but potentially reduce the need for them to do so.
Secondly, the nature of this work means that for this to be a long-term job choice, workers need to be flexible and able to travel around the country. The BBC points out that
One reason overseas workers are recruited for these picking roles is
that farmers require temporary, flexible workers who will move around
the country following the crops.
It is often difficult for local people to fill these roles as they are
extremely busy for a short space of time - for example, two months to
pick apples - with no work for the rest of the year.
So while it might be easy to find workers in one area of the country, it is currently infeasible given the COVID-19 crisis for workers to travel around the country as previously. Therefore, a much larger number of local workers need to be found in order to meet with local demand, rather than smaller groups of seasonal workers meeting the demand nationally.
Additionally, western Europeans are unused to this sort of work. According to the Independent:
It's fair to say that British workers have turned their noses up at
seasonal farm work in recent years, perhaps partly due to the
availability of other, more secure jobs in more comfortable
"It's hard work and the Eastern Europeans are experienced at what they
do," says Oliver Shooter, owner of AE Lenton, which runs a group of
farms between Skegness and Boston in Lincolnshire, the centre of
England's vegetable production.
"It's not rocket science but it is quite a skilled job that these guys
do," he says. A top picker needs to know and apply supermarkets'
exacting standards for exactly how fruit and veg must look, as well as
how to cut it and pack it. For that they'll earn £12 an hour if
they're good. Many farms also provide free or subsidised
The seasonal workers that farms usually rely on, that know their trade and are experienced are unable to be used, so farmers are again being forced to engage a larger workforce than normal, in order to achieve a similar standard of work. This will, of course, entail higher costs, a longer training period, and presumably, a lower yield as mistakes are made.
Governments are trying to deal with this problem by pushing the solution you suggest - the Independent reports again:
So acute is the need that the government is reportedly readying its
own "Pick for Britain" campaign taking inspiration from the Land Army
that tilled the fields during the Second World War.
In Norway, the government has introduced a scheme which will encourage employees laid off by their employer to work in agricultural roles:
New legislation means that if a worker is laid off and takes up an
agricultural role, he or she will be able to earn both a salary from
the farmer as well as half his or her unemployment benefit.
It's not so much that the solution to the problem isn't obvious, it's that due to a combination of the nature of seasonal agricultural work, and the complications introduced by the current crisis, the problem is harder to solve than at first glance.