Plant Disease Management Handbook

Hosts Bentgrass lawns are especially susceptible.

Cause A fungus, Rhizoctonia solani, that lives in soil and on diseased vegetation of nearly any kind. Brown patch is rare west of the Cascade Range and not common east of the Cascade Range. Hot (82°F or above) humid weather favors the disease.

See:

Grass for Seed - Drechslera Leaf Blights (Helminthosporium Net Blotch)

Hosts Primarily perennial ryegrass and some fine fescues, but other grasses may be affected.

Hosts Annual bluegrass is most severely affected, especially in putting green turf. Red fescue and bentgrass also are susceptible but are more resistant than annual bluegrass. This disease is not much of a problem on bentgrass in the Willamette Valley of Oregon.

Cause Algae (aquatic plants). Two genera are common: Symploca sp. and Oscillatoria sp. Algae grow where conditions are unsuited for growing a dense, healthy turf. Shaded areas with poor drainage, little air movement, and compacted soils are ideal for algal growth. Under those conditions, algae grow better than turfgrasses. The only permanent algae control is to correct the conditions unfavorable for grass growth.

Cause The OSU Plant Clinic has found Fusarium, Phytophthora, Pythium and Rhizoctonia associated with rotting roots of lavender. These pathogens, including Fusarium avenaceum, P. megasperma from field grown plants and P.

Go to:

Delphinium

See:

Larch (Larix spp.) -Needle Cast

Cause Larch are deciduous: they lose their needles each fall. People who think they are evergreen conifers wonder why their trees have died suddenly.

See:

Larch (Larix spp.) - Needle Drop

Cause The fungus Hypodermella laricis infects newly emerging needles in the spring from dead infected needles that remain on the tree. More of a problem when spring and summer weather is cool and moist for years, or when larch grows on foggy, cloudy mountain sides.

See:

Fir, Douglas and True - Dwarf Mistletoe