Viburnum Leaves Turning Brown
So why do viburnum leaves turn brown? In most cases, fungus is to blame. Below are the most common situations for browning in these plants:
Fungal spot or Anthracnose
Take a close look at your browning viburnum leaves. If they have irregular brown spots that are sunken and dry, they may have a fungal spot disease. The spots begin small but merge together and may appear red or gray. Among the most common causes for viburnum leaves turning brown or black are leaf spot diseases. Don’t panic. Leaf spot fungal diseases, as well as the fungal disease anthracnose, usually do not do lasting harm to your plants. Keeping leaves relatively dry is the key to preventing leaf spot diseases where leaves turn brown on viburnum. Do not use overhead irrigation and leave sufficient space between your plants for air to pass through. Rake up and burn the brown viburnum leaves that have fallen. If the brown leaves on viburnum are caused by leaf spot disease or anthracnose, you can treat the plants with fungicides available in commerce. For example, treat anthracnose by spraying the leaves with a copper fungicide.
Powdery or Downy Mildew
Mildew diseases can also be a reason leaves turn brown on viburnum species. Both powdery mildew and downy mildew can result in brown viburnum leaves as the foliage dies. You’ll see mildew diseases more often during times of humidity. Plants sited in shade suffer most from them. The tops of viburnum leaves infected by powdery mildew are covered with a powdery fungal growth. This usually happens in summer. Downy mildew causes light green spots mostly on the lower leaves. Leaves that die from these infections turn brown. If your leaves turn brown on viburnum because of mildew diseases, take steps to reduce water on them by using the same tips as for leaf spot diseases. You can also control mildew by spraying fungicides containing horticultural oil.
Rust
If the spots on your viburnum leaves are more rust-colored than brown, the plants may have a rust infection. This is also caused by various fungi. Viburnum leaves infected by rust will wither and die. This is a contagious disease, so you’ll want to destroy diseased plants in the spring before new growth starts.
Other reasons for leaf browning
Dog urine also causes viburnum leaves to brown. If you have a male dog that runs in your garden, this may explain the brown viburnum leaves.
