Fusiform rust (Cronartium quercuum f. sp. fusiforme)

LU&1U LL
Forest Health Fact Sheet

FOREST PEST
MANAGEMENT
GEORGIA FORESTRY COMMISSION

FUSIFORM RUST
(Cronartium quercuumf. sp. fusiforme)

RECEIVEb
2 DEC. 1 1994
UUCUMENTS
.

Figure 1

Fusiform rust, is the most
damaging disease of slash

and loblolly pines

throughout the southeastern

United States. This disease
causes stem, branch and tmnk cankers (galls) to fonn on

infected trees (Figures 1 and
2). The majority of infections

occur prior to age 5. In the

early spring active galls pro-

duce yellow-orange spores

(aeciospores) that are

windblown to young, tender

oak leaves. Water, willow and

laurel oaks are the most

susceptible species affected.
The fungus goes through three

additional spore stages

underneath the oak leaves.
(Figure 3) The fourth and final

stage results in basidiospores
being formed. The

basidiospores are windblown to new pine needles and/or succu-

Figure

lent green bark areas of young trees

thus completing the disease life

cycle.
The amount of infection in

planted and natural pine stands

varies considerably across the

South. Factors such as individual

tree resistance, site characteristics

and rust virulence all interact to

influence infection levels.
When regenerating sites to pine,

land managers must take steps to deal with fusiform rust. Below are

some practices that will help

minimize rust problems and protect economic investments.

These seedlings are the result of
many years o( valuable research
that hopefully will result in increased seedling resistance to the disease. Further protection from rust is provided by timed applications of fungicides to these
seedlings at the nursery. However, sometimes these fungicides do not get applied for one reason or another. Occasionally seedlings will
leave the nursery that are rust infected. Seedlings should be inspected for obvious stem swellings
and culled prior to planting (Figure 4). Infected seedlings should be
reported to the appropriate nursery

ARTIFICIAL
REGENERATION

officials immediately. Don't wait. In high hazard regions increase
planting densities to allow for

Use nist resistant seedlings (improved) that are available from state and privately owned nurseries.

anticipated losses. This will, o(
course, increase the number of
thinnings required throughout the

life of the stand. Consider site preparation
techniques that reduce oak trees unless they conflict with (
other management objectives
(prescribed burning, herbi-
cides, and intensive mechani-
cal preparation).
Use seed from a resistant source. Seed should be treated with an approved bird and
rodent repellent (see appen-
dix).
NATURAL
REGENERATION
If the seed tree or shelter-
wood method is used, select
disease-free seed trees.
TM MANAGING ESTABLISHED j STANDS Evaluate plantations at age 3-5
to ascertain the amount of rust
infection. Plantations that are
showing 50% or more infections
should be seriously considered for
clearcutting. If the decision is made
not to clearcut, a sanitation cut should be planned as soon as it is economical.
After age 5 it is usually
uneconomical to clearcut and start over. However, rotation ages will need to be adjusted in order to maximize on the establishment costs.
In older stands with less than 50% stem infections, remove as many
stem cankered trees as possible with each thinning. Try to maintain a basal area of 75-85 sq. ft. per acre or t at least 200 trees per acre.
When thinning plantations, be
sure to consider annosus root rot.

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YARD TREES

Photo, Dr. Harry Powers, retired USFS

Figure 4

Severely cankered trees often break at the canker during storms with 35 mph. winds or above. Although its hard

to predict breakage, trees closest to homes, powerlines etc. should be removed. Otherwise trees with cankers that do

not girdle more than 1/2 the stem's circumference usually pose no immediate threat

However, wind direction and tree location is critical, when predicting hazard.