kentucky pest news, november 12, 2013
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8/14/2019 Kentucky Pest News, November 12, 2013
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Online at:www.uky.edu/KPN
Number 1362 November 12, 2013
LANDSCAPE TREES
Stunted Pines and Brown Needles: Diplodia Tip
BlightNicole Ward Gauthier, Extension Plant Pathologist
Diplodia tip blight is a serious disease of matureAustrian, Scots (Scotch), and Mugo pines inKentucky. The disease is caused by the fungus
Sphaeropsis sapinea. In the landscape, tip blight isnormally not observed until pines reach about 12
years old and begin to bear cones. Continuousinfections (3 to 5 consecutive years) can greatlyweaken and eventually kill affected pines.
Infection occurs in spring; however, diseasesymptoms (Figure 1) become more obvious in mid-to late-summer and fall. Needles in early stages ofdevelopment stop growing as a result of shootinfections. These stunted needles eventually die andturn straw-colored (Figure 2). Infection progresses to
healthy needles and cones (Figure 3).
Disease Management
Apply fungicides (chlorothalonil,propiconazole, or thiophanate methyl) to
trees just as buds swell in spring. Apply asecond spray when the candles are about half
elongated and a third spray as needles beginto emerge from the needle sheaths.
Remove and destroy dead twigs, branches,and cones as they occur. Do not prune whentrees are wet.
Destroy all blighted needles, twigs, andcones debris as they fall to the ground. Thefungus overwinters in debris, especially
infected cones and diseased needles.
Trees under stress tend to be moresusceptible to tip blight. Fertilize and water
trees as needed to promote vigor.
Lexington, KY 40546
LANDSCAPE TREES-Stunted Pines and Brown Needles: Diplodia Tip
Blight
GREENHOUSE
-RecurringPythiumin the Greenhouse
DIAGNOSTIC LAB HIGHLIGHTS
Figure 1.
Symptoms of
Diplodia tip blight.
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Figure 2. Stunted needles turn a straw-color.
Figure 3. Cones may also become infected with the Diplodia tip
blight fungus.
For more information on tip blight or pine diseases:
Needle Cast Diseases of Conifershttp://www2.ca.uky.edu/agc/pubs/id/id85/id8
5.pdf Twig, Branch, and Stem Diseases of Pine
http://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdf
Department of Plant Pathology, ExtensionPublication page
http://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.html
GREENHOUSE
Recurring Pythiumin the Greenhouse
Nicole Ward Gauthier, Extension Plant Pathologist
One of our local greenhouse growers struggled withPythium infections in pansy earlier this year. Now,
poinsettia are infected with the same rootrotting/damping off fungus (Figures 4 to 7).
So, why wouldPythiumbe a recurring problem?Simple. Sanitation.
Sanitation is critical for greenhouse production,landscapes, orchards, and gardens. In this
greenhouse, fungal propagules are obviouslyspreading via debris, hoses, shoes, tools, drainagewater, and more. Also,Pythiumfavors soillessmixes, where there's no competition. Growers shouldverify that potting mix is not contaminated and that
containers are sterilized before reuse.
Moreover, greenhouses must be disinfested betweencrops, so that disease-causing propagules are notcarried over from one crop to another.
Once a greenhouse is infested withPythium,fungicides are required for disease management. A
single fungicide application will not be sufficient tomanage disease, so a regular schedule should be
employed. Rotate fungicides by FRAC group (mode
Figure 4.
Root
dysfunction
due to
Pythium
root rot
results in
wilting.
http://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdfhttp://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdfhttp://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.htmlhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.htmlhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.htmlhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.htmlhttp://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.htmlhttp://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdfhttp://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdf -
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Figure 5. Pythium root rot causes a discoloration and decay of
the small absorptive roots (feeder roots).
of action), avoiding two consecutive applications of
any particular group and observing maximumnumbers of applications per season. Fungicideseffective againstPythiuminclude:
mefenoxam (Subdue MAXX) FRAC 4 etridiazole (Truban/Terrazole) FRAC 14 propamocarb (Banol) FRAC 28 dimethomorph (Stature) FRAC 40 phosphorus acids (Aliette, Alude, Vital)
FRAC 33
etridiazole + thiophanate methyl (Banrot)FRAC 14 + 1
For more information on disease management ofpoinsettia or other greenhouse crops:
Greenhouse Sanitationhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdf
Fungicides for Management of Diseases inCommercial Greenhouse Ornamentalshttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdf
Poinsettia Diseaseshttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdf
Figure 6. Infections cause the outer layer of the root (cortex)
to easily strip off, leaving a narrow core of inner vascular
tissue.
Figure 7. Infections can extend up the stem.
http://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-2.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-3.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-4.pdf -
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DIAGNOSTIC LAB HIGHLIGHTS
Julie Beale and Brenda Kennedy, Plant DiseaseDiagnosticians
Recent samples diagnosed in the Plant DiseaseDiagnostic Lab have included anthracnose crown rot
on alfalfa; bitter rot on apple; brown heart fromboron deficiency on turnip; white leaf spot(Mycosphaerella) on Chinese cabbage; tomatospotted wilt virus on greenhouse tomato; Pythiumroot/stem rot on poinsettia; Cercospora leaf spot on
hydrangea; Botyrosphaeria canker on ash; tip blighton pine; and Rhizosphaera needlecast on spruce.
Note: Trade names are used to simplify the information
presented in this newsletter. No endorsement by the
Cooperative Extension Service is intended, nor is criticism
implied of similar products that are not named.
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