Plant Disease Management Handbook

See:

Grass for Seed - Damping-off

Hosts Many. Ryegrass and bluegrass species are particularly susceptible to damping-off.

Damping-off caused this poor stand of Kentucky Bluegrass.

Alec Kowalewski.

Damping-off of Kentucky Bluegrass.

Alec Kowalewski.

Slide reads Fusarium crookwellense, which has been renamed to F. cerealis, from bentgrass.

Richard Smiley collection.

Hosts Common on bluegrass and fescue.

Cause Fungi, Curvularia spp., about nine species in all. They live on diseased grass and organic debris at the soil surface. The disease is most destructive in warm weather, from May to October and on compacted soil. These fungi are weakly virulent, commonly isolated from turf with problems and may be components of disease complexes.

Irregular reddish brown dead patches 2 to 3 inches in diameter appear.

OSU Extension Plant Pathology Slide Collection.

See:

Lawn and Turf - Yellow Patch

Hosts Annual bluegrass, creeping bentgrass, and rough bluegrass. The pathogen does not appear to affect perennial ryegrass, fescues, or Kentucky bluegrass.

Thin yellowing that can turn brown or necrotic.

OSU Plant Clinic image, 2011.

The fungus can colonize the foliage in affected areas.

OSU Plant Clinic image, 2011.

The fungus colonizes the foliage, crowns, upper roots, and thatch in affected areas.

OSU Plant Clinic image, 2011.

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.

Image related to Lawn and Turf-Brown Patch

Brown patch of this bluegrass turf.

OSU Plant Clinic collection, 2012.

Note the thick layer of thatch under this bluegrass turf.

OSU Plant Clinic collection, 2012.

Rhizoctonia sp. was isolated from this plant.

OSU Plant Clinic collection, 2012.

See:

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

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

Image related to Lawn and Turf-Brown Blight

Girdled leaves become yellow and die back from the tip.

Photo by Ralph S. Byther

Tiny, chocolate-brown spots to large, dark-brown streaks appear on perennial ryegrass leaves.

Richard Smiley, 1974.

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.

Anthracnose symptoms on annual bluegrass putting green turf.

C. J. Schmid.

Symptoms of both the foliar and basal rot phase of anthracnose on an annual bluegrass tiller. (A) note the black fruiting bodies called acervuli with (B) hair-like setae.

C. J. Schmid

Image related to Lawn and Turf-Anthracnose

The yellow blades of this Poa annua are typical of both the foliar and basal phases of anthracnose.

WSU Extension Plant Pathology Slide Collection.

Note the black fruiting bodies, acervuli, of the fungus.

Photo by R. S. Byther, 1992.

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.

Dark green to black mass in the center of the image is an algal growth on the surface of the ground.

Jay W. Pscheidt, 2017.

Cross section shwing the greenish algal growth is only on the surface of the light brown soil below.

Jay W. Pscheidt, 2017.

Growth on soil surface is composed of several single cell and filamentous photosynthetic organisms.

Jay W. Pscheidt, 2017.

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.

This plant had Phytophthora.

Melodie Putnam, 2010.

This plant had Pythium.

Melodie Putnam, 2010.

This plant had black root rot (Berkeleyomyces sp. formerly Thielaviopsis basicola).

OSU Plant Clinic Collection, 2011.

Go to:

Delphinium

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

Symptom Needles turn brown and fall off the tree in fall. May seem to be very sudden to those who are unaware of the species' deciduous habit.

Cultural control None needed.

Along highway 18 in Oregon's coast range is a smiley face in the hills made using larch and Douglas-fir. When the larch go dormant and the leaves drop in the fall, the evergreen Douglas-fir stand out to make the smiley face.

Jay W. Pscheidt, 2018.

Larch stand out in this image as brown trees as they go into winter dormancy.

Larry Moore, 1992.

Image related to Larch (Larix spp.)-Needle Drop

A larch that retains needles, as in this picture, would be unusual. Brown needles are due to Hypodermella laricis from Northern Idaho.

Photo by Lew Roth, 1965.