How to treat black spits on leaves of Sweet Viburnum?

[crackers0075]

Hi, last year I got these mysterious black spots on the leaves. Could never find any bugs etc. I cut off as many leaves as I could leaving the plants almost dead. Of the past few months they have grown really well. But alas these black spots are back. Can anyone help with how to treat this and stop it happening again. 

 

 

[JacobZ]

Hi @crackers0075,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

It looks like your viburnum could be dealing with a fungal issue, possibly anthracnose. Anthracnose is a fungal disease that often appears on viburnums as black or dark brown spots on the leaves, and it fits well with what you can see, particularly in the second image. It thrives in warm, humid conditions and spreads easily when leaves stay wet.

The first step in managing anthracnose is to remove and dispose of affected leaves as soon as you notice them. Avoid putting these leaves in compost, as that can allow the spores to spread further. It’s also a good idea to clean up any fallen leaves from around the base of the plant. Pruning lightly to open up the canopy will improve airflow and help the foliage dry out more quickly after rain or watering.

Watering practices play a big role in prevention. Try to water at the base of the shrub rather than overhead, as wet leaves provide the perfect environment for the fungus to grow. Watering in the morning is also better than in the evening, since it gives the leaves time to dry before night.

If the disease is persistent, you can use a fungicide such as Yates Liquid Copper Fungicide. Repeating treatments during the wetter months can help keep anthracnose under control.

With better airflow, mindful watering, and, if necessary, the use of fungicide, you should be able to manage anthracnose and keep your sweet viburnum healthy and thriving.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[crackers0075]

Gday JacobZ,

I have cut as many of the leaves off as I could find. The only thing is it’s mainly at the outside leaves, and we haven’t really had any humid weather yet in Melbourne. I will get the Yates stuff. Whilst pruning I found this little black bug only 2 on the entire lot of bushes, and some very minor affids. But it’s really annoying. 

 

 

 

[JacobZ]

Hi @crackers0075,

If it were insect-related, I would expect to see more of an infestation than just a couple of bugs. In saying this, it is still worth keeping an eye out for insects as we can't entirely rule them out.

I still think the issue is likely fungal.

What does the soil and the base of the plant look like?

Considering that you had the same issue last year, I think your soil could also play a part because the fungal pathogen causing the disease can survive on contaminated crop debris and in the soil, where it can remain viable for several years.

Alongside the above-mentioned approach, it is likely going to be worthwhile to replant your viburnum in some fresh soil. If there are fungal pathogens present in the soil, this would prevent them from returning and if not, your viburnums would get some fresh soil full of nutrients to help bounce back.

Let me know what you think.

Jacob

[crackers0075]

Hi Jacob,

The base of the plants/soil has sugar cane mulch covering it.  They have grown really well since last Spring, most probably more than doubling in size.  Re planting is not really an option.

[JacobZ]

Hi @crackers0075,

If it's not an option, then I wouldn't worry about it.

If you keep removing the affected leaves, treat the symptoms when they arise and continue to take good care of them, they should be ok.

Seeing them from further back, they look pretty healthy to me.

Jacob