The group in society made up of the unemployed who can be put to work during times of high production and then laid off when they are no longer needed is called

Seasonally unemployed group

Explanation:

This group consist of people who are considered 'naturally' unemployed because of regular changes in the seasonExamples include construction workers who are hired mainly in the summer and laid off in the winter, ice cream vendors whose peak season is the summer and off-peak, the winters.