Farm state lawmakers are rushing to defend crop insurance again after President Barack Obama last week proposed chopping $18 billion from the program over 10 years in his 2017 budget plan.

The administration’s budget proposal reduces subsidies for harvest price option coverage on crop insurance policies and also makes changes to prevented planting coverage, including removing optional buy-up coverage.

Lawmakers from both parties said the cuts pose a threat to farmers at a time when farm incomes are plummeting.

"As farmers and ranchers are faced with the daily uncertainties of weather and volatile market conditions, the Obama...