There is no chemical control for this problem. Leaves can be blighted by fungi in the genera Ascochyta or Septoria.
Infected leaves die.
The disease is not common and chemical control is not needed. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information becomes public property upon publication and may be printed verbatim with credit to MSU Extension. Reprinting cannot be used to endorse or advertise a commercial product or company.