I have two Macadamia trees in my New Zealand garden near Wellington.
One is a Beaumont and the other is a Nutty Glen, both planted about
five years ago.
The site is well sheltered from strong winds, and both are growing
well. The ground is over an ancient river bed, and is well drained.
The Beaumont has this year produced a few racemes of flowers.
New leaves are healthy looking, and deep green, but older leaves are
yellow between the veins, and develop brown/purple marks, which dry
up, and fall off.
Is this a sign of a virus/bacteria attack, or a pH or soil deficiency
of some kind?
Any advice would be appreciated.