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.
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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.
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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.

kentucky pest news, november 12, 2013

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