Hello Ernest,

Thanks for writing in. Sorry to hear about the problems you're having with your forsythia. This year, we've had lots of problems due to the high heat coupled with the lack of rain which have really stressed our plants. It's possible that these have combined to stress your new forsythia.

In more detail, spots on forsythia leaves can be caused fungi and/or insect pests:

• Fungal infections: Small to large brown or black spots on the leaves are usually caused by fungi like Septoria and Alternaria. These spots are mainly an aesthetic issue, but they can lead to leaf distortion and drop-off. To treat, you can:
  • Remove and dispose of infected leaves (do not put in the compost, but discard in the trash so you don't risk contaminating your compost with the fungus)
  • Apply a fungicide, such as a copper-based fungicidal soap or a baking soda and soap mix
  • Ensure good airflow around the plant
  • Avoid overhead watering
  • Prune to open the canopy
  • Clean up fallen leaves and debris around the plant base - this is really important now that Fall has commenced and leaves are turning and dropping
  • Sterilize gardening tools, especially when working with diseased plants
• Four-lined plant bug: Small, round depressed spots that may be brown, black, or translucent on leaves. To treat bugs, you can remove them by hand. Also spray with Neem oil.

Good luck! Let us know if you have further questions

Lesley for DC Master Gardener team