yellow patch

noun2

1. •
   (historical) A yellow badge.
2. •
   A disease affecting several varieties of grasses, including bentgrasses, annual bluegrass, some perennial ryegrass and Kentucky bluegrass, which results in the development of yellow or brown rings.

   • Yellow patch, sometimes called cool-temperature brown patch, develops during prolonged cool (50-65°F; 10-18°C), overcast, and moist periods from late autumn to early spring. — 2013