I also had 2 grevilleas which died. They were Grevillea'Poorinda Beauty' and Grevillea 'Yamba Sunshine'. These were attacked by a sap sucker variety and thrips. They went from healthy florishing plants to dead within 5 days. I treated them with rogur which saved them a couple of times, but in the end it didnt.

I have other varietys of grevilleas in the garden that are growing really well. All of the grevilleas are less than a year old.

Does anyone have any ideas re the mould and how to prevent my healthy grevilleas from being attacked ie companion plants?

I live in Mackay, QLD.

You would do well to get as much airflow through the plants, so a prune may be in order.

if so that is commonly caused by scale insect and/or mealy bugs, and they are commonly bought to the plant by ants. mealy bugs easy spot they are little whitish furry bugs around near the growing tip, scale look like hard little pimply lumps also around near the growing tip.

if it is the above you need to control the ants first then make a white oil solution (homemade is easy) and spray the infected area with that after the heat of the sun.

it has been very dry of late that is when ants become more prevelant, also with your callistemon problem because of the dry (low humidity) could it be spider mite? if so they are easy to control just introduce some mist watering around the foliage area to increase humidity keeping a bucket of water under each plant will also help the humidity.

in both cases if the problem is too bad a prune up to remove all infected tip end wouldn't be out of the question, just be sure to destroy the prunings don't compost them or hold them on site.

len