Congress put into place the Sequester which calls for extreme cuts to food safety, programs for children such as Headstart and grants for students with disabilities, the EPA, government programs for low-income families, national defense, and other essential programs.
The Sequester was not meant to go into effect, it was created as motivation for Congress to reach a deal on the budget. If they could not come up with a balanced approach, these automatic spending cuts would begin.
Since these horrible, deep spending cuts are not motivation enough, maybe threatening to withhold their pay will be better motivation instead of putting the economy at risk and affecting families that have nothing to do with the dysfunction in Congress.