Its just root rot - Feb 22, 2012
We have had so much rain this summer many of the drought tolerant species you may have planted during the drought are dropping dead. The rain and heat creates humidity which causes many drought loving plants to get root rot. This fungus disease rots the root system so your plant can't take up water. It's ironic because your plant dies from lack of water. A green healthy looking plant will turn yellow one day and be dead the next. Unfortunatley there is often little you can do because by the time you notice the plant is sick it's too late!
If you do notice one of your plants is starting to turn yellow then you may need to put it on life support. Take a sample of the foliage to your local nursery. I may be a deciduous plant that is just preparing to drop it's leaves during autumn. Plants that are more susceptable to root rot include, Hebes, Pittosporums, Grevilleas, Proteas and Lavenders to name a few.
You will need to cut any sick plants back by at least 50%. There is no time for no mucking around, this is life or death stuff. The plants root system has rotted so there is no way that the roots that are still alive can pump water to keep the entire plant alive. Pruning the plant back hard may be its only chance for survival. There is a product available called Yates Anti Rot. This is a systemic fungicide that can be sprayed over the foliage and used as a soil drench. It kills the fungus in the soil. Next water your plant weekly with a seaweed solution. This will encourage new roots to grow.
Tim Pickles is a CNP horticulturist and director of Tim's Garden Centre 2 Queen St Campbelltown.