leaves on puka
live on a semi-coastal section (within 500m of the sea) with well-drained
soil. I have planted puka around our section, but over the past
year most of them have succumbed to what I suspect is phytophthora.
The leaves turn yellow, droop and the tree appears to be rotting.
I have not overwatered or fertilised the trees. The age of the tree
does not seem to be important - some of them are several years old.
Most of our other plants are natives and they are very healthy and
symptoms do suggest root rot (phytophthora is the most common form),
but I recommend you do some further checking, as your soil sounds
relatively freedraining and root rot generally doesn't occur in
freely drained soil. Nor would I expect a lot of pukas of different
ages to succumb at the same time, unless there had been a flood
or significant waterlogging, which you would no doubt have been
Dig up one of the smaller
affected pukas and check out its roots. Healthy roots should be
white and firm all the way from the trunk out to the root tips,
with healthy branching side roots. Roots infected with root rot
will be at worst brown and soft, often with the outer tissue coming
away, leaving a thin central threadlike portion. Less affected roots
may have brown lesions or soft damp areas in them and the root tips
may be dying back.
If the roots are healthy,
the problem is probably from some other cause, perhaps drought,
frost, severe wind damage or damage to the base of the trunk from
collar rot, rats, possums or rabbits.
If you decide root rot
is the culprit, then I suggest you try to improve drainage around
the root system. One way is to plant on a raised mound so excess
water drains away quickly. You could also try treating the remaining
trees with the fungicide aliette, available as No Root-rot.
Gardener, Issue 182, 2005, Page 26
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.