LONDON — Prince Charles is urging the public to join a national effort to help farmers bring in the harvest, comparing the need to pick fruit and vegetables with World War II era programs that fed the nation.

The heir to Britain’s throne offered his support to a government’s initiative to bring UK workers and farmers together to ensure crops are not left to rot in the fields.

Travel restrictions due to the COVID-19 crisis have impeded the travel of seasonal workers who have done the hard work in the past.

The prince, who runs an organic farm, says in a video that “if the last few weeks have proved anything, it is that food is precious and valued, and it cannot be taken for granted.’’

He says food does not happen by magic and made no effort to gloss over the effort that would be required.

He says “it will be hard graft but is hugely important if we are to avoid the growing crops going to waste.”