Hydrangea Diseases
| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Botrytis Blight |
Petals turn brown and fall. Leaf spots form,
especially where faded petals have fallen. Flower buds are killed
before opening. |
Botrytis cinerea |
Space plants to insure good air circulation.
Maintain low humidity. Avoid watering late in the day. Remove
crop debris. Apply a combination of chlorothalonil and mancozeb. |
| Cercospora Leaf Spot |
Brown to purplish-brown spots enlarge on the
leaves, causing them to yellow and fall. Cuttings may be killed. |
Cercospora |
Space plants to insure good air circulation.
Maintain low humidity. Avoid watering late in the day. Remove
crop debris. Apply azoxystrobin, copper, chlorothalonil, chlorothalonil
+ fenarimol, potassium bicarbonate, myclobutanil, copper + mancozeb
or mancozeb. |
| Powdery Mildew |
Yellow areas form on leaves. These may become
purplish. White, cottony fungal growth forms on the lower surface
of the leaf. |
Erysiphe polygoni |
Maintain low relative humidity at night. Apply
Ampelomyces, fenarimol,
iprodione, triadimefon, piperalin, or myclobutanil. |
| Virescence |
Flowers are green and may be stunted. Leafy shoots
grow from the flower parts. Plants decline and die. |
Phytoplasma |
Discard infected plants. Maintain good insect
control. |
| Viruses |
Leaves may be mottled, have yellow spotting,
dead flecks, line or ringspot patterns. Plants may be distorted
or have flower color breaking, or few flowers. |
Hydrangea ringspot, tomato ringspot, timpatiens
necrotic spot |
Plant virus-indexed cuttings. Maintain good insect
and mite control. Destroy infected plants. |
Fungicides mentioned above:
| COMMON NAME |
TRADE NAME |
| Ampelomyces quisqualis |
AQ 10 (biological control agent) |
| azoxystrobin |
Heritage |
| chlorothalonil |
Daconil 2787, PathGuard, Exotherm Termil |
| chlorothalonil + fenarimol |
TwoSome |
| copper |
Phyton, Camelot |
| copper + manozeb |
Junction |
| etridiazole + thiophanate methyl |
Banrot |
| fenarimol |
Rubigan |
| iprodione |
Chipco 26019 |
| mancozeb |
Dithane, FORE, Pentathlon |
| myclobutanil |
Systhane |
| piperalin |
Pipron |
| potassium bicarbonate |
Remedy |
| triadimefon |
Bayleton |
|
