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Medium_image0516 Why are my mature Yukkas leaves all turning yellow/brown

we have a small backyard in Kellyville (NorWest Sydney), clay based soil, with a large number of lovely mature Yukkas established around the yard perimeter. They have always been healthy but all of a sudden the leaves are all going yellow and then brown.
Any suggestions/advice please.
Rgds. Tony

Submitted: 02:24PM, 09 May 2014
Answer: Hi Tony,
From the photo you kindly sent, the leaves have certainly yellowed dramatically. Could this have been happening for a little while now as they are very advanced plants and the yellowing appears to have started with the lower leaves and progressed upwards. I am not sure if just fertilising at this stage is going to improve the health of the plants that have advanced to this point.

It would also be worthwhile checking the plants to see if there are any sap sucking insects present. Infestation of thrip, mealy bug and scale can have a devastating effect on plants resulting in yellowing and browing of the leaves. If any of these pests are present, they will need to be controlled by spraying either with a contact insecticide such as PestOil or a systemic insecticide such as Yates Baythroid Lawn & Garden Insecticide.

Yucca can also be susceptible to fungal disease. If this is the case, Rose Shield, which contains a systemic fungicide will help to control these fungal problems.

Drainage is another important factor to consider. Perhaps for some reason the moisture level that your plants have been used to receiving has now changed. It would be worthwhile checking out.

To help your plants to recover, we would suggest regular applications of a seaweed solution. When the plants show signs of recovery, you can then start to add nutrients by applying an organic fertiliser called Uplift Organic Liquid Fertiliser.

Answered: 04:31PM, 21 May 2014


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