Leaf Spot (fungus – Ascochyta phlogis): Remove spotted leaves. spray healthy leaves with recommended fungicide.
Powdery Mildew (fungus): Whitish, powdery mold patches on upper side of leaves and stems from midsummer on. Leaves may shrivel and drop early. Control with recommended fungicides.
Crown Rot (fungi – Sclerotium rolfsii, Sclerotium sclerotirum and Thielaviopsis basicola): Serious losses to phlox seedlings occur from these soil-borne fungi. Start in pasteurized soil.
Root Knot Nematodes (nematode – Meloidogyne spp.): (See the section on Root Knot Nematodes)
Root Rots (fungi – Thielaviopsis basicola and Phymatotrichum omnivorum): Not usually serious enough to warrant control.
Rusts (fungi – Puccinia douglasii and Uromyces acuminatus): Not usually serious enough to warrant control.