Hello - I have had 2 Grevillea Bronze Ramblers growing well in my garden for 2 years, but this winter (s hemisphere) they have both died off very suddenly. The die off has started at the stem and worked its way out to the tips of the branches - the leaves have gone a dark/ashy grey colour as the die off has proceeded. I have inspected the stems and seen no signs of pest entry, such as borers - any ideas?
I have had a rosmarinifolia type grevillea do a similar thing. Whole branches would dy off at the stem. I just kept cutting them off and throwing the affected branches in the bin. The dye off eventually stopped, and the bush looks healthy again (though a bit mishapen).
If you are on the coast where there has been some good solid rain for the last few months, it is probably root rot. Both of those Grevilleas hate wet feet.
Wrigley and Fagg "Australian Native Plants" report that die back can be caused by the Rhizoctonia (a fungus). Apparently, this can be controlled by an appropriate fungicide. Rhizoctonia is a fungus which has proved troublesome to a number of Australian plants. Its presence is noted by a dying out in the centre of otherwise healthy plants.
Phosphite (active ingredient in Yates Anti-Rot and Agri-Fos) is different from phosphate. I read some research studies about this, phosphite does not break down into phosphate except in tiny negligible quantities. So this anti-fungal will not harm grevilleas.
Alternating between phosphite and liquid sea kelp spray helps my newly planted grevilleas have a better chance of survival.
This post was edited by scorpionleather on Sun, Oct 19, 14 at 22:28
justcorreas
pos02
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