Here are 10 pests and diseases that can affect hydrangeas.
Tip
Insects on your hydrangea aren’t always bad, on the contrary.
double-check you identify the insects on your hydrangea before you take any steps to remove them.
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Powdery Mildew
This fungus is one of the most common diseases of hydrangeas.
It causes dusty or cottony splotches of white or gray powder on the leaves and stems of infected plants.
Later, the infected areas may turn purple.
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Powdery mildew is unsightly but it usually does not kill the plant.
However, it is important to limit the spread by pruning out infected plant parts.
If the infection is severe, apply a fungicide that is labeled to treat powdery mildew.
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The prime time for botrytis blight to occur and spread is in humid and cool weather.
It causes tan spots withreddish-brown haloson the leaves.
While it is usually not deadly, it weakens and plant and may defoliate it.
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If the problem persists, apply a fungicide that is labeled to treat the disease.
Phytophthora root rot often affects potted hydrangeas.
Root rot cannot be diagnosed without inspecting the roots of the plant.
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This, in return, attracts ants.
Wash off minor aphid populations with a garden hose.
If the infestation is severe, apply insecticidal soap.
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The larvae usually start with the smaller roots, and then move on to the bigger ones.
As a first step, trim off any infested foliage.
If the infestation persists, apply horticultural oil.
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Sometimes these insects also feed on flower petals, especially white ones.
Adult rose chafers are slightly 1/3 inch long and tan-colored.
They are mostly found in places with sandy soil.
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Spider mites mostly occur during hot, dry weather.
Keep your hydrangea well-watered during dry spells and wash off minor infestations with a garden hose.
Hydrangea Diseases and Pests.University of Connecticut.
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