Host Plants - Westcott's Plant Disease - page 632

W ILT . Verticillium albo-atrum, CA, CT, ME,
MA, MN, NY, NJ, PA.
Rust is the most generally important
disease and can be prevented, to some extent,
by purchasing rust-resistant seed, but not all
such seed is resistant to all strains of rust.

Snapdragon (Antirrhinum)

A NTHRACNOSE . Colletotrichumantirrhini,general
in eastern and southern states to CO and TX.
B ACTERIAL Crown Gall. Agrobacterium

tumefaciens, NY.
B LIGHT , Gray Mold. Botrytis cinerea, cosmopol-
itan in greenhouses.
B LIGHT , Southern; Stem Rot. Sclerotium rolfsii,
CA, FL, MS, NJ, NY, TX.
C ANKER , Stem and Crown. Myrothecium
roridum, IL.
D AMPING -O FF ; Root Rot. Pythium spp., cosmo-
politan; Rhizoctonia solani, also collar rot.
D ODDER . Cuscuta sp., WA.
D OWNY M ILDEW . Peronospora antirrhini, CA,
NY, OK, OR, PA.
L EAF S POT . Cercospora antirrhini, FL, IL.
L EAF S POT ; Stem Rot; Canker. Phyllosticta
antirrhini, general in eastern and North cen-
tral states also TX and WA.
N EMATODE , Lesion. Pratylenchus pratensis.
N EMATODE , Pin. Paratylenchus penetrans, CA.
N EMATODE , Root Knot. Meloidogyne spp., gen-
eral in South and in northern greenhouses; M.
javanica, MD.
N ONPARASITIC . Fasciation. Probably genetic.
Tip Blight. Cause unknown CA, MD, OK, VA;
injury from peach aphid.
P ETAL S POT . Bipolaris

Snowberry (Symphoricarpos)

A NTHRACNOSE ; Black Berry Rot; Twig Canker.
Glomerella cingulata, widespread, MA to
VA, IL and WI.
B ACTERIAL Crown Gall. Agrobacterium

tumefaciens,MD.
B ACTERIAL Hairy Root. Agrobacterium

rhizogenes, IA.
L EAF S POT . Ascochyta symphoricarpophila,
NY; Cercospora symphoricarpi, MT, SD;
Phyllosticta symphoricarpi, NM, NY, WA;
Lasiobotrys symphoricarpi, black spot, CO,
UT, WY; Septoria oedospora, CO;
S. signalensis, WY; S. symphoricarpi,ND
to CO, CA and WA.
P OWDERY M ILDEW . Microsphaera diffusa, gen-
eral; Podosphaera oxya-canthae, WA.
R OT , Berry. Alternaria sp., CO, CT, MA, NY;
Botrytis cinerea, CT, MA, NY.
R OT , Collar. Fomes ribis, KS, MT.
R OT , Root. Helicobasidium purpureum, TX.
R UST . Puccinia crandallii (0, I), CA, CO,
ID, MT, ND, UT, WA, WY;

( Helminthosporium )

setariae, FL.
P OWDERY M ILDEW . Oidium sp., MA, NY, PA.
R OT , Charcoal. Macrophomina phaseoli, OK.
R OT , Root. Phymatotrichum omnivorum, TX;
Thielaviopsis basicola, CT, NJ.
R OT , Stem; Wilt. Fusarium sp., perhaps second-
ary; CT, FL, GA, OK, TN, WA;
Phytophthora cactorum, CA, IL, MN, NJ,
NY; P. cryptogea, CA, OK; P. parasitica,
GA; Sclerotinia sclerotiorum, CA, IN, MI,
PA, TX; S. minor, CT.
R UST . Puccinia antirrhini (II, III), general; 0,
I unknown.
V IRUS . Cucumber Mosaic, Mosaic, unidentified,
KS, NY, OH, PA; Ring Spot, unidentified,
OK; Impatiens Necrotic Spot, NC.

II, III on

grasses; P. symphoricarpi (III), MT to

CA, AK.
S POT A NTHRACNOSE ; Scab. Sphaceloma
symphoricarpi, ME to VA, AR, CA, CO,
OR, WA, WI.
Anthracnose and spot anthracnose, scab, com-
monly disfigure berries.

Snowdrop (Galanthus)

B LIGHT , Botrytis. Botrytis galanthina on

imported bulbs.