Lawn Fungus
Brown Patch Disease

Lawn grasses, like people and pets, respond to the attention or abuse they receive. The lawn owner
must watch for symptoms of attacks by pests or signs of abuse in order to speedily correct the
trouble and maintain an appealing carpet of green.

Most diseases of lawn grasses are caused by fungi. They occur as microscopically small filaments
(called mycelia) that are parasitic within or on plant parts. Masses of these cobwebby or cottony
fungus filaments are sometimes visible on grass blades.

Many fungi reproduce by means of microscopic fruiting structures called spores. They are most
noticeable when infected grasses infected are being mowed and the spores are released like dust
into the air. Lawn fungus most commonly appears when the lawn is frequently cut too short.

The fungus responsible for brown patch disease, as pictured above, attacks most species of the lawn grasses during warm, humid
weather. Grasses which are growing rapidly following excessive application of nitrogen fertilizer are most severely damaged. Brown
patch also develops if a heavy swath of grass clippings is left on the lawn following mowing.

Brown patch occurs in irregular, circular areas varying from a few inches to several feet in diameter. If the grass is wet and the disease is
spreading, dead brown grass may be bordered by a narrow ring of dark-colored, recently infected grass. Sometimes only the leaves are
affected and the turf recovers within 2 or 3 weeks.

Infection in lawn grasses is most conspicuous on the leaves where reddishbrown spots develop. The leaf spots are often characterized
by lighter-colored centers. Diseased leaves usually shrivel and die prematurely. When the grass crown becomes diseased, the entire
plant dies.

A disease called dollar spot is most destructive on many species of grasses during spring and fall,
especially during seasons of low rainfall. Damage is usually greatest if nitrogen fertility is low. The
disease is characterized by development of bleached spots about the size of a silver dollar. Some-
times the individual spots become so numerous that they merge and form large irregular patches
of dead grass. Lesions that are light tan with a reddisbbrown border often extend across the entire
grass blade.

Fusarium blight occurs on several grasses but is most damaging to Kentucky bluegrass. The
disease occurs throughout the growing season although it is most noticeable in late spring and
summer when the temperatures exceed 75°F. and humidity is high.

Patches of diseased grass first become light green, then rapidly fade to tan and light straw color.
Dead areas may be circular, crescent-shaped, streaked, or in circles. A patch of live grass often
occurs in the center of a dead area.

About 60 species of insects injure lawn grasses by feeding on roots, stems, and leaves. This insect feeding weakens plants, causing
patches of grass to turn yellow or brown and die. A few insects damage lawns by their burrowing or nesting habits.

Grubs are the most destructive soil inhabiting pests. They are the larvae of several species
of beetles and in general are similar in appearance. They are whitish, soft bodied, usually
with brown beads, and generally found in a curled position. These pests feed on the roots
an inch or two below the surface, often destroying the turf.

The grubs hatch from eggs. They usually spend about 10 months in the soil, although some
species require 2 to 3 years to reach maturity and emerge as adults, Birds, skunks, and moles
feed on the grubs and often damage the lawn as they search for them.

White grubs are the most widely distributed in the United States. They are the larvae of the
familiar yellow-brown to blackish May beetles or June bugs that are attracted to lights.

Grubs of Japanese beetles are very damaging in some eastern areas. The adults are shiny metallic green with coppery-brown wing covers
and six patches of white hairs along the sides and back of the body. The beetles are active during the day and feed on many flowers and
fruits.

Grubs of the Asiatic garden beetle, masked chafers, European chafer, and the Oriental beetle are other important species that damage
lawns.

Since 1960, billbugs have been destructive to lawns. One species called the hunting billbug
has severely damaged zoysiagrass lawns in the East.

Billbugs are hard-shelled beetles 1/5- to 3/4-inch long with a long snout. The larvae are
legless, as much as 5/8-inch long, white with a reddish or yellowishbrown head. The adults
burrow in the grass stems near the soil surface and the larvae feed upon the roots, often
cutting them off so the grass can be easily pulled out.

Caterpillars of several species damage lawns. Sod webworms are the most important. These
are the larvae of small, whitish or grayish moths called lawn moths that are seen flying over
the grass in early spring evenings. They can be easily recognized by their habit of folding their
wings closely around their bodies when at rest. There are many species and one or more can be
found in all parts of the United States. Sod webworms may have several generations per year
depending on the species and location.

Larvae are about 3/4-inch long when mature, and are brown or gray and usually spotted. They
feed on grass leaves and are most active at night. The injury is first noticed as irregular brown
spots and later as patches of uneven growth.

Chinch bugs are the most important sap-sucking pests of grasses, particularly in the East
and the South. The hairy chinch bug is common in lawns in the Northeast and the southern
chinch bug is a major pest, especially of St. Augustinegrass, in Florida and along the Gulf
Coast.

The adults are about 1/6- inch long and black with white wings folded over their backs. The
nymphs are bright red when very small but turn gray as they grow older. They have a white
band across their backs.

Both the nymphs and the adults suck plant juices, causing the grass to turn yellow in irregular
patches. If feeding continues, the grass turns brown and dies.

The damage which insects cause to lawns can be reduced by following recommended cultural and maintenance practices.
A healthy, vigorous turf can support greater insect populations without serious harm.

When lawn insects become numerous they can be controlled with insecticides.

Lawn grasses tolerate a wide assortment of natural and mamnade contamination hazards.
Surprisingly few of these prevent grass growth, but they often do make growing good turf more difficult.