Disease	Symptoms	Pathogen/Cause	Management
Alternaria Leaf Spot	Brown specks form on florets and the leaves. Centers become white on the leaf spots.	Alternaria sp.	Maintain low relative humidity and avoid overhead watering. Apply azoxystrobin or fludioxonil to protect leaves.
Bacterial Leaf Spot	Small to large spots are circular at first, then become irregular and dark brown to black. May have a concentric ring pattern.	Pseudomonas cichorii	Maintain low relative humidity. Avoid overhead watering.
Botrytis Blight	Petioles have long brown spots. Leaves yellow and die. Petals have tan spots. Stems at soil level are killed. Infected tissues become covered with gray fungal growth.	Botrytis cinerea	Space plants to insure good air circulation. Maintain low humidity. Avoid watering late in the day. Remove crop debris. Apply azoxystrobin, vinclozolin, copper, chlorothalonil, or fludioxonil to protect healthy plants.
Powdery Mildew	White fungal growth develops on the surface of leaves.	Erysiphe cichoracearum	Apply triadimefon, kresoxim methyl, or piperalin to protect plants.
Pythium Root Rot	Plants wilt and die as roots rot.	Pythium sp.	Plant in pasteurized potting media. Apply etridiazole or etridiazole + thiophanate methyl to protect healthy plants.
Phytophthora Crown Rot	Plants wilt suddenly. Leaves brown. Roots are rotted and a crown rot develops.	Phytophthora cryptogea	Plant in pasteurized potting media. Avoid overhead watering. Apply etridiazole or etridiazole + thiophanate methyl to protect healthy plants.
Powdery Mildew	White, powdery fungal growth spots or covers leaves. Leaves yellow and die.	Erysiphe cichoracearum	Apply Ampelomyces, azoxystrobin, kresoxim methyl, or triadimefon to protect leaves.
Rhizoctonia Crown Rot	Stems at the soil level have a brown lesion. Plants wilt and die.	Rhizoctonia solani	Plant in pasteurized media. Apply etridiazole + thiophanate methyl azoxystrobin, or PCNB to protect healthy plants.
Thielaviopsis Root Rot	Plants yellow, wilt, and die. Roots are dark brown to black as thick-walled dark spores form in the cells.	Thielaviopsis basicola	Plant in pasteurized media. Apply etridiazole + thiophanate methyl to protect healthy plants.
Viruses	Leaves may be mottled, have yellow spotting, dead flecks, line or ring spot patterns. Plants may be distorted or have flower color breaking.	Impatiens necrotic spot, tobacco rattle, gerbera mosaic, and cucumber mosaic viruses.	Maintain good insect and mite control. Plant in pasteurized media. Destroy infected plants.

Fungicides mentioned above:

COMMON NAME	TRADE NAME
Ampelomyces quisqualis	AQ10 (biological control agent)
azoxystrobin	Heritage
chlorothalonil	Daconil
copper	Phyton 27
etridiazole	Terrazole, Truban
etridiazole + thiophanate methyl	Banrot
fludioxonil	Medallion
kresoxim methyl	Cygnus
PCNB	Terraclor
piperalin	Pipron
triadimefon	Bayleton, Strike