Host Plants - Westcott's Plant Disease - page 611

WI; Potato Virus M; Potato Virus S, gen-
eral; Tobacco Veinnal Necrosis, Pacific
Northwest; Potato Virus A, WA; Tomato
Spotted Wilt, NC, TX; Potato Mop-Top,
ME, ND, WA; Impatiens Necrotic Spot,
NY, WA; Potato Yellowing, Ecuador.
W ART , Potato. Synchytrium endobioticum,
MD, PA, VA; see under

Prenanthes (Rattlesnake-Root)

D OWNY M ILDEW . Bremia lactucae, IA, MA, MN.
G ALL , Leaf. Synchytrium aureum, WI.
LEAF S POT . Cercospora brunnea, AR, NC, WI;
C. prenanthis, AL, IN, KS; C. tabacina, WI;
Laestadia prenanthis, AL; Septoria nabali,
NY to IA, WI, ME to VA.
P OWDERY M ILDEW . Golovinomyces
cichoracearum, IL, MD, NC, PA;
Sphaerotheca macularis,NYtoAL,IL,MN,
OH, PA.
R UST . Puccinia atropuncta (0, I), PA, VA; II, III
on Amianthium ; P. dioicae (0, I), IL, MN, NY,
VA, WI; II, III on Carex ; P. insperata (I, II,
III), OR; P. orbicula (0, I, II, III), ME to TN,
ND.

Galls ; Prince

▶

Edward Island, Canada.
W ILT . Verticillium albo-atrum, widespread.
W ILT ; Stem-end Rot. Fusarium spp.;
F. oxysporum, general but more frequent
East and South.
Potato growing is a highly specialized business
not well adapted to most small gardens. Use certi-
fied seed, resistant varieties where possible. Con-
trol insects spreading virus diseases.

Potentilla (Cinquefoil)

Prickly-Ash (Xanthoxylum
americanum)

D OWNY M ILDEW . Peronospora potentillae, IA,
NJ, TX.
L EAF S POT . Fabraea dehnii, IA, NY, VT;
Marssonina potentillae, CA, CO, MA, MI,
NM, NY, WI; Phyllosticta anserinae, IL;
Ramularia arvensis, WI.
P OWDERY M ILDEW . Erysiphe polygoni, CO;
Sphaerotheca macularis, CO, WI.
R UST . Phragmidiumandersonii (I, II, III), general.
V IRUS . Tomato Ringspot,NY.

C ANKER , Stem. Diplodia natalensis, TX.
L EAF S POT . Cercospora xanthoxyli, IN, TX;
Septoria pachyspora, IA, NE.
P OWDERY M ILDEW . Phyllactinia corylea,

widespread.
R OT , White Heart. Fomes igniarius.
R UST . Puccinia andropogonis var. xanthoxyli
(0, I), IA, KS, MO, NE, TX, WI; II, III on
Andropogon .

Pothos (Epipremnum)

Prickly-Poppy (Argemone)

R OT , Petiole, Leaf, Crown. Phytophthora
capsici,MA. D OWNY M ILDEW . Peronospora arborescens, TX.

L EAF S POT . Alternaria lancipes, KS, TX;
Gloeosporium argemonis, KS, TX; Septoria
argemones, NE, OK, TX.
R OT ,Root.Phymatotrichum omnivorum,TX.
R UST . Aecidium plenum (0, I), TX.

Pothos, Ivy-Arum (Scindapsus)

B ACTERIAL Blight. Pseudomonas cichorii, FL.
N EMATODE , Burrowing. Radopholus similis, FL.
N EMATODE , Lesion. Pratylenchus sp.
N EMATODE , Root Knot. Meloidogyne arenaria
thamesi; M. incognita.
R OT , Root. Pythium splendens, FL; Rhizoctonia
sp., foot rot, MO.

Primrose (Primula)

B ACTERIAL Leaf Spot. Pseudomonas primulae,CA.
B ACTERIAL , MLO. California Aster Yellows.