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Missouri Environment and Garden	Volume 6, No. 2
News for MissouriÂ’s Gardens, Yards and Resources	April 17, 2000

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Brown evergreens?! What's happening to my tree?

In the past several years, pine and other evergreens have been the most
common plants submitted to the Extension Plant Diagnostic Clinic at the
University of Missouri. Regional Horticulture Specialists Tom Fowler and
Polly Kaufmann are already receiving numerous inquiries about browning pine
trees. Pine wilt disease, caused by the nematode Bursaphelenchus
xylophilus, has received much attention in the press recently, because the
disease is responsible for death of Scots pine throughout much of Missouri.
But there are other less destructive pine diseases that can be managed with
accurate diagnosis and proper timing of fungicide applications and cultural
practices.

Sphaeropsis tip blight (formerly Diplodia tip blight) is one of
the more common diseases of pine in Missouri. It is most severe on
Austrian pine, but infection can also occur on Scots, ponderosa and mugo
pines. The fungus infection results in death of shoot tips. Over a period
of years, whole branches or the entire tree may be killed. Symptoms
include brown tips, stunted needles within the tip and excess resin
associated with the dead tips. Fruiting bodies (pycnidia) of the causal
fungus are abundant at the base of dead needles and twigs and on the cones.
Pruning out dead branches can improve the tree's appearance, but doesn't
provide much protection from infection because of the presence of inoculum
on the cones. Fungicide applied when this year's candles are about 2
inches long, followed by a second application 10 to 14 days later can
reduce the number of new shoot infections. Proper timing and thorough
coverage are essential for satisfactory control. Products containing fixed
copper, Bordeaux mixture, propiconazole (Banner Maxx) or thiophanate methyl
are labeled for control of Sphaeropsis tip blight.

Another common disease on Austrian pine is Dothistroma needle blight. The
symptoms on mature needles first appear in late summer or fall as tan or
yellow bands, often with a red border. In the spring, the spots will begin
to coalesce, causing the needle to turn brown from the tip back. Fruiting
bodies of the fungus will erupt through the epidermis and are often
concentrated at the transition zone between brown and green tissue.
Infected needles will drop prematurely. Infection is most severe in the
lower portion of a tree and on trees planted on sites where air circulation
is restricted. Newly emerging needles are not susceptible to infection
until fully expanded. Fungicide should be applied once in mid-May,
followed by a second application in mid-June. Products labeled for control
of Dothistroma include Bordeaux mixture or copper materials. In landscape
plantings where trees are widely spaced, fungicide may not be necessary.

Brown spot needle blight results in symptoms similar to Dothistroma, but
the disease is most commonly observed on Scots pine. Ponderosa pine is
also susceptible. The disease is most severe in pine plantations, but it
can occur in the landscape also. The symptoms on needles become evident in
late summer as reddish brown spots with yellow margins. Fungicide should
be applied once when needles are about half grown. A second application
may be needed in three to four weeks, if weather is rainy. Labeled
fungicides are chlorothalonil, Bordeaux mixture, or mancozeb. The longer
needled varieties of Scots pine are more resistant to brown spot infection.

Although white pine in Missouri has no needle diseases, numerous problems
are causing death and decline of white pine in the state. We have
confirmed Procera root rot (white pine root decline) or Phytophthora root
rot in a few samples, and identified pine wilt nematode as a contributor to
decline on one specific site in southeast Missouri. In many other
situations, including Columbia sites visited by Plant Diagnostic Clinic
personnel, no pathogens have been identified. It's likely that site-
related conditions and fluctuating environmental conditions the past
several years are contributing to the loss of established white pines. To
adequately investigate a white pine problem, the clinic needs to look at
samples from the lower trunk and roots.

There are a number of different diseases affecting pine in Missouri.
Accurate identification is critical to deciding the proper timing of
fungicide application. Samples can be sent to the Extension Plant
Diagnostic Clinic through your local University Outreach and Extension
office. Visit the clinic web site at http://agebb.missouri.edu/pdc for
more information on pine diseases.

Barb Corwin and Laura Kabrick of the UMC

Extension Plant Diagnostic Clinic and Tom Fowler, Regional Horticulture

Specialist, University of Missouri Extension

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