How to treat black spot on Lilly Pilly?

[CarolynD]

    

I purchased my house last year and all along this wall the previous owners had planted Viburnum, which I noticed had black spot on the leaves. So, I tried spraying them with Liquid Copper but soon realised that the problem was very bad. So, we removed all the plants as well as all the mulch and dug a deep trench to remove the infected soil too. We left the trenches open all of last winter and spring and kept spraying with different kinds of fungicide to cover our bases. In November last year, we planted these new established Lilly Pilly trees. I have recently inspected them to find that they now also have black spots on their leaves. I have just sprayed with more liquid Copper but I'm at my wits end here now. Could someone please tell me that I'm over-reacting and/or help me with a solution? Thanks so much! 

[JacobZ]

Hi @CarolynD,

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

To me, your lilly pillies look relatively healthy, and if anything, they might have a couple of patches of sunburn from water sitting on their leaves and magnifying the UV rays.

Allow me to tag some of our experienced gardeners for their thoughts - @Noelle, @mich1972, @robchin, @mashthyme.

I would make sure any watering I am doing is aimed down at the base of the tree so it can get to the roots, where it is most effective. I'd also continue to monitor the spots for any changes but wouldn't worry a great deal at this point.

If you notice any changes in the coming weeks, please get back in touch so we can assist further.

Jacob

[CarolynD]

Hi Jacob,

Thanks so much for your response!

My concern is that these trees did not come with these black spots on the leaves - so it has developed in 6 months or so. The black spots are also only on certain trees - the areas where the fungus issue was the worst before I pulled up the entire garden. I think if it was the sun scorching water droplets (would be from the rain because these plants are only watered through retic) then it would be happening on all the trees don't you think?

I am concerned that if this is the same fungus infection then it could be contagious.

Thanks again for all your advice and help!

[JacobZ]

Hi @CarolynD,

There is some possibility that it is fungal, but it appears to be very isolated at this point. It doesn't immediately jump out as a fungal issue, but it is hard to tell. It does look like some cases of Myrtle Rust, although very isolated.

At this stage, I would be removing the effected leaves and thinning out plants to allow for better airflow. Make sure you use clean, sharp secateurs, and any of the plant that is removed is disposed of.

I would also suggest water is not applied to the leaves at this point as the moisture can exacerbate fungal issues.

If they are popping up in the same area as they were on the Viburnums that used to be there, then the soil is the constant variable. I would be looking at the soil as a possible cause.

Like with your Murrayas I would be suggesting you test the pH balance of the soil and maybe even consider removing and replacing it with fresh stuff.

You should also have a look through @Noelle's article on How to diagnose and revive a sick lilly for some further information and guidance.

Let me know what you think.

Jacob

[CarolynD]

Hi Jacob,

Thank you again for all your thoughts!

I have already replaced all the soil to the depth of about 60-70cm. Given that the other pH tests I did were very alkaline, I could apply the liquid sulphur to lower it here too?

I really hope that it's not still a fungus issue. Should I still apply liquid copper just in case?

[EricL]

Hello @CarolynD 

Please make sure to follow the application instructions for the liquid sulphur. Over application of the liquid sulphur can be bad for lilly pillies as well. In regards to the liquid copper, I see no harm spraying your lilly pillies with this fungicide as it can be used as a preventative. Please make sure to follow application instructions.

Please make sure to wear personal protection such as gloves, goggles and a mask when spraying your plants.

If you need further assistance, please let us know.

Eric

[AlanM52]

Hi @CarolynD,

I will start with a short story 🙂

I purchased a pair of then in 2010.

  

March this year and prepping for pruning.

Everytime I walk through there I smile and feel good - why is that?

That is the first time ever I planted a pair and both have survived.

Generally they have been healthy but I did notice about six years ago that something was eating the leaves -  Aphids - and there were also blacks spots.

Since then and depending on Aphid activity.

they get sprayed with this.

The black spots are not always there but if the are they disappear.

Not sure what the connection is.. there is clue hiding somewhere?

With regard to all the work you did with infected soil etc.

We gave up trying to grow five tomato plants in a box!

Did all the recommended things soil change etc. and even had a Tangi heater running under black plastic.

Could not get rid of the Fusarium Wilt spores in the soil, something not right?

A few years ago a friend of the missus gave her some tomato plants so we planted them in the same box which produced lovely tomatoes. Must be the supplier we always used (because the mother-in-law went there lol) which was just a house growing in the back yard and selling out front. Could it be there are nurseries out there where you get free spores with the plants you buy?

Cheers

[CarolynD]

Thanks for your input, Alan! Great story

I'll definitely look out for aphids. I do have that spray already because I get aphids on my mock orange plants too.

Enjoy your lovely tomatoes!