Knockout Roses: Yellow Leaves + Yellow "Gunk" at Base = Slime Mold, Not Virus

4 Knockouts, 2 years old. Leaves yellowing (fungicide applied). New growth/buds present but plants look terrible. Bright yellow wet powdery "gunk" at base. Gardener fears virus.

Yellow Gunk = Slime Mold (Harmless)

Not a plant pathogen. Just a soil organism appearing in mulch. More info.

Yellow Leaves = Water/Weather Stress

• Too much or too little water.
• Sudden heat.
• Not disease if new growth is healthy.

Action

Ignore slime mold. Fix watering. Yellow leaves will resolve.