Pests and Diseases of Holly Trees

Holly trees are a beautiful addition to your landscape, providing visual interest throughout the year. While they are generally quite hardy and disease resistant, Holly trees do occasionally suffer the effects of pests and diseases. Here are some common holly tree ailments, and what you can do to fix them.

Diseases

  • Tar Spot, also called Holly Leaf Spot, is a fungal disease that causes small yellow spots on the leaves of your holly. Eventually the spots turn reddish brown and sometimes black. The infected areas drop out, leaving holes in the leaves. Defoliation will occur if the disease is left unchecked. Gather up and destroy any infected leaves.
  • Botryosphaeria Canker, also called Bot Canker, is another fungal disease common in holly.  Symptoms are sunken lesions on stems and brown decay under the bark. Left untreated, branches will begin to die off. Quick attention is key if bot canker affects your holly tree. Pruning out infected branches should take care of the problem.
  • Chlorosis, or Iron Chlorosis, causes light-green or yellowish leaves with darker-green veins. It is caused by high pH levels in the soil, leading to iron deficiency in the plant. This problem can be remedied by correcting the pH of the soil by using acidifying fertilizers. Avoid planting holly near concrete surfaces, as this is often a trigger for chlorosis.
  • Spine Spot causes small gray spots with purple margins on the leaves of your holly bush. It is caused by the spines of one leaf puncturing an adjacent leaf, creating tiny holes. This generally happens because of windy conditions. To prevent this, try shielding your holly from the wind, holly tree pruning to remove branches to close to one anoter or moving your holly to a more protected location.

Pests

  • Holly Leaf Miners are flies that lay their eggs under the surface of the leaves. The larvae then hatch and feed, causing yellow or brown squiggly blotches on the leaf. The best way to remedy this is to hand-pick the leaves and destroy them.
  • Scale causes little brown bumps on the underside of leaves, as well as reduced vigor in the plant.  At the first sign of scale, leaves can be scraped by hand to rid them of scale inscects. If the infestation is severe, you may need to spray with horticultural oil or pesticide.
  • Mites are tiny pests that can resemble small spiders. You may see the bugs on your holly, or you may just notice the resulting damage: discolored leaves, which will die off if the mites are left untreated. You can spray your holly with a soap solution to get rid of the mites. Be sure to repeat the application in a week or so, to catch any newly hatched mites.

Of course, preventing these issues in the first place is ideal, and can be achieved with good holly tree care. Be sure to maintain good soil and water conditions and fertilize regularly for happy, healthy holly trees.

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