Host Plants - Westcott's Plant Disease - page 594

C ANKER , Stem Wilt. Coniothyrium sp., CA on
tree peonies.
L EAF S POT . Alternaria sp., occasional in north-
eastern and central states; Cercospora
paeoniae, IL; Pezizella oenotherae,MD,
PA; Phyllosticta sp., NJ, PA, VA, Septoria
paeoniae, also stem canker, ME, MI, MN, NJ,
NY, OR, RI, WA, WI; Cryptostictis
paeoniae, IL.
N EMATODE , Leaf and Stem. Ditylenchus dipsaci,
NJ, WA.
N EMATODE , Root Knot. Meloidogyne spp., wide-
spread; M. hapla; M. incognita.
N EMATODE , Spiral. Rotylenchus buxophilus.
N ONPARASITIC . Bud Blast. Various causes, some-
times potassium deficiency.
Le Moine Disease; Club Root. Cause unknown,
possibly virus.
P OWDERY M ILDEW . Erysiphe polygoni, TX.
R OT , Root. Armillaria mellea, CA, IA, MI, OR;
Fusarium sp., CO, IN, MO, NE, NJ, OK;
Phymatotrichum omnivorum, AZ, TX; Rhi-
zoctonia solani, CT, IL, MN, NY, PA, VA;
Thielaviopsis basicola, CT.
R OT , Stem; Wilt. Sclerotinia sclerotiorum, IL,
MD, MN, NJ, NY, OH, OK.
V IRUS . Peony Ring Spot, MA to VA, CA, KS,
MI, WA; Tobacco Rattle, AK; Witches'
Broom, Crown Elongation. Cause unknown,
MD, NY, VA; Hosta Virus X, Tobacco Rat-
tle Virus; Helleborus Net Necrosis;
Nemesia Ring Necrosis, Diascia Yellow
Mottle, Pacific Northwest.
W ILT . Verticillium albo-atrum, IL, KS, MD,
NY, OH.
Botrytis blight is doubtless the best-known
peony disease. Young shoots are rotted at base;
buds turn black, flowers are blasted. Cutting
down all tops at ground level in fall and spraying
in spring when reddish shoots first show will
reduce blight. Anthracnose, blotch, sometimes
leaf spot, may be serious occasionally. In humid
summers Sclerotinia sclerotiorum frequently
kills stalks, filling the pith with very large
sclerotia. Sickly plants may have root-knot
nematodes. Lack of bloom may be due to too-
deep planting, growing in shade, Botrytis blight,
or nematodes.

Penstemon (Beard-Tongue)

B LACK M ILDEW . Dimerium alpinum, CA.
L EAF S POT . Cercospora penstemonis, AL, IN,
KS, MT, NE, ND, OK, SD, TX, WI;
Cercosporella nivosa, CO, ID, OH, WA;
Phyllosticta antirrhini, IL; Ramularia
penstemonis, CA; Septoria penstemonis,
CA, IL, ME, MI, MS, MO, NY, OK, TX,
WA, WI.
L EAF S POT ; Stem Spot. Ascochyta penstemonis,
CA.
N EMATODE , Root Knot. Meloidogyne sp.
N EMATODE , Stem. Ditylenchus dipsaci, VA.
P OWDERY M ILDEW . Golovinomyces

cichoracearum, WA.
R OT , Crown, Stem. Sclerotium rolfsii, CT, IL,
MA, NJ, TX.
R OT , Root. Phymatotrichum omnivorum,TX.
R OT , Root, Crown. Phytophthora citrophthora,
CA.
R UST . Puccinia andropogonis (0, I), widespread;
II, III on Andropogon ; P. confraga (III),
AZ; P. palmeri (0, I, III), AZ, CA, ID, WA,
MT, to NM; P. penstemonis

(III), AZ, CA,

OR, UT.
V IRUS . Cucumber Mosaic, OR; Turnip Vein-
Clearing,MN.

Peony (Paeonia)

A NTHRACNOSE . Gloeosporium sp., IL, KS, MD,
MA, NJ, NC, PA, VA.
B ACTERIAL Crown Gall. Agrobacterium

tumefaciens, MD, MI.
B LIGHT , Early Bud Rot. Botrytis paeoniae,
general.
B LIGHT , Late; Gray Mold. Botrytis cinerea, also
leaf rot, general.
B LIGHT , Southern. Sclerotium rolfsii, MS, TX.
B LIGHT , Tip; Crown Rot. Phytophthora
cactorum, CT, IL, IN, KS, NJ, NY, OH.
B LIGHT , Twig. Pestalotiopsis paeoniicola, CT.
B LOTCH , Leaf, Stem; Measles. Cladosporium
paeoniae, general.