| Dothistroma blight is a foliar disease of a number of
pine species throughout the Midwest. Austrian pine
is the primary host plant in Missouri. This blight is
caused by the fungus Dothistroma pini, which
infects and kills needles. The disease makes pines in
landscapes unsightly and successive years of
infection can result in decline and death of the tree.
Symptoms and Diagnosis
The earliest observable symptoms are dark-green
bands and tan spots or bands on the mature needles.
The spots and bands later turn reddish-brown. The
needles will begin to die back from the tip, but
needle bases usually remain green. From the time
symptoms are first noticed to the time of needle
browning may take 2–3 weeks. Infected needles will
drop prematurely. Infection typically is most severe
in the lower crown of the tree, closer to the
inoculum that spreads from infected needles that
have fallen from the tree.
Life Cycle
Dothistroma overwinters in infected needles. The
infective spores are released during wet weather and
dispersed by rain splash throughout the growing
season. Because of the continual release of spores,
infections can occur anytime from late April to late
October. The fungus attacks the mature foliage;
current season's needles are resistant until they are
fully mature. Symptoms on newly infected tissue are
especially obvious in early fall.
Integrated Pest Management Strategies
1. Live with the disease but monitor yearly. This
disease is slow to spread. Annual spraying is not
necessary in residential plantings. Wait and see
how serious the problem becomes in one season.
Serious infections can be prevented in the next
growing season with the use of fungicides.
2. Plant resistant pines.Research on Austrian pine
has determined that some populations are highly
resistant to Dothistroma. Ask for these at your
local garden center or nursery. Choose other nonsusceptible
evergreens.
3. Apply fungicides. Adequate control of
Dothistroma blight can be achieved with one or
two sprays in late spring using a Bordeaux
mixture. The first spray in early to mid-May
protects mature foliage. A second spray in mid-
June will protect the current season's needles
which are resistant until they are fully grown.
Other fungicides registered for use are mancozeb
and pentachloronitrobenzene. | 
