golden totara is covered in tiny white insects. The tree is probably
20 or more years old and I've not noticed the problem before. Are
they harmful and, if so, what can we do about them? It would be
difficult to spray such a large tree.
sample you sent had a quite a severe infestation of scale insects,
which feed by sucking sap. Scale can cause quite serious growth
problems to some plants but totara are tough and should be able
to tolerate a few patches of scale. It's likely the scale are in
scattered populations, probably mostly in the lower, sheltered parts
of the tree and that the upper branches, which are more exposed
to the elements, will not be affected.
An easy way to reduce
a scale population like this is to lightly prune back the infested
shoots. Don't cut them hard back, just remove those shoots with
scale and dispose of them in the rubbish or burn them.
Alternatively, or as
well as pruning, you could apply an oil spray, which kills by covering
scales' skin with oil, blocking the breathing pores. Spraying oils
like Eco Oil, Clear White Oil, and Conqueror are safe and easy to
use. Ideally, spray on a cloudy day and try to avoid getting spray
on nearby leafy plants as the oil can damage tender new spring foliage.
Ensure thorough coverage, especially under the leaves where most
Gardener, Issue 204, 2006, Page 38
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.