How to treat Lilly Pilly hedge with black spot?

AnnaH1

Hi there, 

Just wondering if anyone can help me diagnose the problem with my Lilly Pilly leaves.  The last 3 plants in the row have started rapidly developing black blotches on the leaves.

It doesn't seem to be Sooty Mould because the discolouration is within the leaves rather than on the surface, and I can't see any parasites.

The affected plants are at the bottom of the slope, and we have had a lot of rain, so I'm wondering whether being waterlogged could cause this?  

Many thanks,

Anna

EricL

Hello @AnnaH1 

Based on the appearance of the leaf and the conditions you describe, the symptoms are most consistent with a fungal leaf spot problem, sometimes referred to as “black spot.” This type of fungal disease is common in Lilly Pilly and other hedging plants, particularly in situations where leaves remain wet for prolonged periods. Being located at the bottom of a slope, your plants are more likely to experience waterlogging and reduced air circulation, both of which create an ideal environment for fungal development.

The blotches you are seeing within the leaf tissue, rather than on the surface, are characteristic of fungal infection. To manage this, it is advisable to remove heavily affected leaves and dispose of them in household rubbish rather than compost, as this reduces the risk of reinfection. Clearing away fallen leaf litter from around the base of the plants will also help reduce the fungal spore load in the surrounding soil. Improving airflow through light pruning and ensuring watering is directed to the base of the plant, rather than overhead, will assist in minimising leaf wetness and discouraging further spread. Checking soil moisture before watering is also beneficial, as over-saturation can stress the plant and increase susceptibility to disease.

For treatment, a broad-spectrum fungicide is recommended. Options such as Liquid Copper Fungicide, Eco-fungicide, or Yates Anti Rot Phosacid Systemic Fungicide can be applied to control fungal activity and act as a preventative measure against new infections. Each product should be applied strictly according to the manufacturer’s instructions.

This combined approach of plant hygiene and targeted fungicide application should assist in halting the progression of the disease and allow the plants to recover more effectively.

I also suggest having a look at this guide - How to diagnose and revive a sick lilly pilly by @Noelle.

Please remember to wear personal protection such as gloves, goggles and a mask when using these chemical sprays.

If you need further assistance, please let us know.

Eric