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Black spots on Holly leaves

Steps you can take for healthy Hollies

By: Sandy Feather 2014
Penn State Extension


Q. Our holly is getting black spots on the leaves. Then the leaves turn yellow and drop off. Can you tell us what causes this and what we can do to stop it?

A. The writer enclosed samples of the spotted and yellow leaves, as well as samples of the newer growth that showed no evidence of black spots or yellowing. The plant is an American holly, Ilex opaca. Although these plants are considered evergreen, they shed their older interior leaves annually in spring, just as needled evergreens shed their older interior needles in the fall. This usually happens in conjunction with new growth at the tips of the branches that remains green and healthy. While the sight of a beloved plant suddenly shedding leaves is alarming to the owner, as long as they are the older interior leaves, there is no need for concern.
 

Holly shrub
Blue Holly

There are a number of leaf spot diseases that can affect American holly, but they usually affect the older leaves that will be shed anyway. Tar spots on older leaves are considered by many plant pathologists to be secondary invaders that take advantage of senescing foliage. They are not thought to be damaging to overall plant health.

 


Steps you can take to maintain the health & vigor of American holly:

  • Rake up and destroy or dispose of infected leaves. This removes the causal organism from the site and can reduce the severity of spotting in the future.
  • Test the soil around your holly and fertilize and adjust soil pH according to the results. American holly grows best in well-drained, slightly acid soils with a preferred pH of 5.0-6.0.
  • Provide supplemental irrigation when we get into hot, dry summer weather. Irrigation is best applied at the base of plants, rather than overhead irrigation that wets the foliage.
  • Prune plants to allow for good air circulation within the plant and sun penetration into the interior. This allows the foliage to dry quickly after rain or heavy dews.

Holly leaf spot diseases are more common during wet spring weather, because tender new growth is more susceptible to infection than older, hardened off foliage. Fungicide applications are rarely warranted in the landscape.

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