Disease	Symptoms	Pathogen/Cause	Management
Alternaria Leaf Spot & Stem Rot	Large reddish brown or purple spots (leaf on the right), at first round to oblong but becoming irregular in shape have gray or tan centers that may drop out leaving a hole. Severely affected leaves brown, dry, and become brittle. Seedlings can be killed when stems are attacked.	Alternaria zinniae	Apply chlorothalonil, iprodione, mancozeb, fludioxonil, or thiophanate methyl + mancozeb at 1- to 2-week intervals during warm wet weather or during warm dry weather if frequent sprinkler irrigation is employed. Whenever possible, water in a manner that keeps the leaves dry to inhibit this seedborne disease.
Aster yellows	Leaf-like tissue forms where flower parts should be located. Flower-like parts remain green or light green. Often flowers on only one side of the spoke show symptoms Sepals may be very large or dwarfed.	Phytoplasm	Destroy infected plants. Control leafhoppers.
Bacterial Leaf Spot	Spots reddish brown to dark brown, angular, and with a prominent yellow halo (leaf on the left) form on leaves.	Xanthomonas campestris pv. zinniae	No sprays are effective. Whenever possible, water in a manner that keeps the leaves dry to inhibit this seedborne disease.
Powdery Mildew	White fungal growth forms on the upper surface of leaves and may form on flower petals.	Erysiphe cichoracearum	Apply Ampelomyces, piperalin, fenarimol, mancozeb, thiophanate methyl + mancozeb, triadimefon, kresoxim methyl, myclobutanil, paraffinic oil, or triforine to protect plants.

COMMON NAME	TRADE NAME
Ampelomyces quisqualis	AQ10 (biological control agent)
chlorothalonil	Daconil 2787, Exotherm Termil
etridiazole	Terrazole, Truban
etridiazole + thiophanate methyl	Banrot
ferbam	Carbamate
fenarimol	Rubigan
fludioxonil	Medallion
fosetyl-Al	Aliette
iprodione	Chipco 26019
kresoxim methyl	Cygnus
mancozeb	Dithane, Mancozeb, Protect T/O
metalaxyl	Subdue
myclobutanil	Systhane
paraffinic oil	SunSpray UltraFine oil
PCNB	Terraclor, Defend, PCNB
piperalin	Pipron
thiophanate methyl + mancozeb	Duosan, Zyban
triadimefon	Bayleton
triforine	Triforine