Agriculture: Floriculture and Ornamental Nurseries Pest Management Guidelines

Host-Pathogen Index

The host-pathogen index is a list of ornamental hosts not covered in the Disease Control Outlines and some of the pathogens that attack these hosts. Diseases covered in Key Diseases are noted with an asterisk.

African Violet (Saintpaulia ionantha)
Bacterial blight Dickeya (=Erwinia) chrysanthemi
Foliar nematode ** Aphelenchoides ritzemabosi
Gray mold * Botrytis cinerea
Phytophthora crown rot * Phytophthora parasitica
Powdery mildew * Odium spp.
Pythium root rot * Pythium spp.
Rhizoctonia stem rot Rhizoctonia solani
Ring spot physiological (cold water and light)
 
Christmas cactus (Schlumbergera bridgesii)
Crown rot * Phytophthora parasitica
Pythium aphanidermatum
Fusarium rot * Fusarium oxysporum
Gray mold * Botrytis cinerea
Root and stem rot Rhizoctonia solani
Root rot * Pythium irregulare
Stem rot Phytophthora spp.
Stem rot and leaf spot Bipolaris cactivora
Virus Cactus virus X
 
Candytuft (Iberis amara)
Alternaria leaf spot* Alternaria brassicae
Basal stem rot Phoma lingam
Club root
Plasmodiophora brassicae
Downy mildew * Peronospora parasitica
Gray mold * Botrytis cinerea
Phytophthora root rot * Phytophthora spp.
Powdery mildew * Erysiphe cruciferarum
Pythium root rot * Pythium spp.
Root knot nematode ** Meloidogyne sp.
White rust Albugo candida
 
Cineraria (Senecio cruentus)
Collar rot Rhizoctonia solani
Downy mildew * Plasmopara halstedii
Gray mold * Botrytis cinerea
Impatiens necrotic spot Impatiens necrotic spot virus
Leaf spot* Alternaria cinerariae
Powdery mildew * Erysiphe cichoracearum
Sphaerotheca fuliginea
Root and collar rot * Phytophthora spp.
Root rot * Pythium ultimum
Spotted wilt Tomato spotted wilt virus
Stem rot * Sclerotinia sclerotiorum
 
*For additional information, see section on Key Diseases.
**For additional information, see section on Nematodes.
 
Gardenia (Gardenia jasminioides)
Bacterial leaf spot Xanthomonas campestris pv. maculifoliigardeniae
Chlorosis iron deficiency
Petal blight (gray mold) * Botrytis cinerea
Phomopsis canker Phomopsis gardeniae
Root knot nematode ** Meloidogyne spp.
 
Gerbera (Gerbera jamesonii)
Bacterial leaf spot* Pseudomonas cichorii
Black root rot * Thielaviopsis basicola
Crown and root rot Rhizoctonia solani
Gray mold * Botrytis cinerea
Leaf spots Alternaria porri
Cercospora gerberae
Septoria spp.
Ascochyta gerberae
Phytophthora crown rot * Phytophthora cryptogea and others
Powdery mildew * Golovinomyces cichoracearum
Pythium root rot * Pythium spp.
Sclerotinia crown rot Sclerotinia sclerotiorum
Spotted wilt Tomato spotted wilt virus
Verticillium wilt * Verticillium dahliae
White rust*** Albugo tragoponis
 
German violet (Exacum affine)
Basal stem rot Nectria hematocca
Gray mold * Botrytis cinerea
Root rot * Pythium ultimum
Spotted wilt Tomato spotted wilt virus
 
Gloxinia (Sinningia speciosa)
Cottony rot and flower blight* Sclerotinia sclerotiorum
Crown rot Myrothecium roridum
Crown rot and tuber rot Rhizoctonia solani
Gray mold * Botrytis cinerea
Ring spot physiological (cold water and light)
Root and crown rot * Phytophthora cryptogea
P. nicotiana
Root rot * Pythium spp.
Southern blight * Sclerotium rolfsii
Spotted wilt Tomato spotted wilt virus
 
Hydrangea (Hydrangea macrophylla)
Gray mold * Botrytis cinerea
Powdery mildew * Golovinomyces orontii
Rhizoctonia stem rot Rhizoctonia solani
Ringspot Hydrangea ringspot virus
Root knot nematode ** Meloidogyne spp.
Root rot * Pythium spp.
Virescens Phytoplasma
 
*For additional information, see section on Key Diseases.
**For additional information, see section on Nematodes.
***Not reported in U.S.A.
 
Impatiens (Impatiens walleriana)
Bacterial fasciation Rhodococcus fascians
Bacterial leaf spot * Pseudomonas syringae
Black root rot * Thielaviopsis basicola
Brown crown canker Rhizoctonia solani
Crown rot* Pythium ultimum
Rhizoctonia solani
Downy Mildew * Plasmopara obducens
Gray mold * Botrytis cinerea
Impatiens necrotic spot Impatiens necrotic spot virus
Leaf spot Phyllosticta sp.
Root rot * Pythium sp.
Southern blight * Sclerotium rolfsii
Spotted wilt Tomato spotted wilt virus
Verticillium wilt * Verticillium dahliae
 
Kalanchoe (Kalanchoe blossfeldiana)
Aster yellows * Aster yellows phytoplasma
Edema Physiological; cause unknown
Fasciation Cercospora sp.
Impatiens necrotic spot Impatiens necrotic spot virus
Kalanchoe mosaic Kalanchoe mosaic virus
Leaf and stem blight Botrytis cinerea *
Leaf spots Stemphylium spp.
Powdery mildew * Sphaerotheca fuliginea
Root and crown rot * Phytophthora spp.
Spotted wilt Tomato spotted wilt virus
Stem rot Myrothecium roridum
 
Lilac (Syringa vulgaris and S. persica)
Armillaria root rot* Armillaria mellea
Bacterial blight* * Pseudomonas syringae pv. syringae
Crown gall * Agrobacterium tumefaciens
Gray mold * Botrytis cinerea
Leaf blotch Heterosporium syringae
Phytophthora blight Phytophthora spp.
Phytophthora root rot* * Phytophthora spp.
Powdery mildew * Microsphaera penicillata
Shoot blight* Sclerotinia sclerotiorum
 
Lilies (Lilium spp.)
Cottony rot and petal blight* Sclerotinia sclerotiorum
Foliar nematode * Aphelenchoides spp.
Gray mold* Botrytis spp.
Leaf spots* Cercospora, Heterosporium, and Ramularia spp.
Root knot nematode * Meloidogyne spp.
Rust * Uromyces spp.
Scale rots Colletotrichum spp.
 
Lisianthus (Eustoma grandiflora)
Foliar nematode ** Aphelenchoides spp.
Gray mold* Botrytis cinerea
Leaf spot * Cercospora eustomae
Powdery mildew* Leveillula taurica
Root knot nematode ** Meloidogyne spp.
Root and stem rot Fusarium avenaceum, Phytophthora, Pythium, and Rhizoctonia spp.
Viruses Tomato spotted wilt virus, Impatiens necrotic spot virus
 
Pouch Flower (Calceolaria x herbeohybrida)
Cottony rot * Sclerotinia sclerotiorum
Gray mold * Botrytis cinerea
Root and crown rot * Phytophthora spp.
Root rot * Pythium spp.
Spotted wilt Tomato spotted wilt virus
Stem rot Myrothecium sp.
Verticillium wilt * Verticillium dahliae
 
Primula (Primula x polyantha)
Crown rot Rhizoctonia solani
Fasciation Physiological; cause unknown
Gray mold * Botrytis cinerea
Leaf spot Ramularia primulae
Root rot * Pythium spp.
Spotted wilt Tomato spotted wilt virus
 
Protea (Protea, Banksia, Leucospermum, and other spp.)
Canker Botryosphaeria spp.
Gray mold * Botrytis cinerea
Leaf spots Colletotrichum spp., Mycosphaerella spp.
Root and crown rot * Phytophthora spp., Rhizoctonia solani
Root knot nematode * Meloidogyne spp.
Verticillium wilt * Verticillium dahliae
 
Queen Anne's Lace (Daucus carota)
Aster yellows * Aster yellows phytoplasma
Bacterial blight* Xanthomonas campestris pv. carotae
Black root rot Alternaria radicina
Early blight* Cercospora carotae
Leaf blight* Alternaria dauci
Powdery mildew* Erysiphe heraclei
Root and stem rot Fusarium spp.
Root, crown, and stem rots * Phytophthora, Pythium, and Rhizoctonia spp.
Southern blight* Sclerotium rolfsii
Tuber rot Rhizopus spp.
Viruses Celery mosaic virus, Carrot motley dwarf virus
 
Ranunculus (Ranunculus spp.)
Aster yellows * Aster yellows phytoplasma
Bacterial blight* Xanthomonas campestris pv. carotae
Cottony rot* Sclerotinia sclerotiorum
Downy mildew* Peronospora spp.
Gray mold* Botrytis cinerea
Leaf spots* Ramularia spp.
Powdery mildew * Erysiphe polygoni
Root rots* Pythium spp., Rhizoctonia solani
Rust * Puccinia spp.
Smut Entyloma spp.
Southern blight* Sclerotium rolfsii
Viruses Tomato spotted wilt virus, Ranunculus mosaic virus
 
Stephanotis (Stephanotis floribunda)
Crown rot Rhizoctonia solani
Gray mold * Botrytis cinerea
Powdery mildew * Oidium sp.
Stem dieback Glomerella cingulata
Virus Impatiens necrotic spot virus, Tomato spotted wilt virus
 
Sunflower (Helianthus sp.)
Aster yellows * Aster yellows phytoplasma
Charcoal rot Macrophomina phaseolina
Cottony rot * Sclerotinia sclerotiorum
Downy mildew * Plasmopara halstedii
Gray mold * Botrytis cinerea
Head rot Rhizopus oryzae
Leaf spots* Alternaria, Cercospora, and Septoria spp.
Powdery mildew * Golovinomyces cichoracearum
Root and stem rot * Phytophthora sp.
Rust * Coleosporium, Puccinia, and Uromyces spp.
Smut Entyloma calendulae
Southern wilt * Sclerotium rolfsii
 
* For additional information see section on Key Diseases.
Text Updated: 11/20