My rhodies are
growing back from being trimmed down last year, but the leaves are
being chewed up and have brown spots on them. What kind of spray
is the best to keep rhodies bug free? Is there something natural
you can make?
brown spots sound very much like an attack of thrips, which are
very common on rhododendrons in New Zealand. If the leaves
are also silvery-looking, and the brown spots mainly on the underside,
then it does sound like thrips are the culprit.
I don't know of any effective
"natural" remedies, but any insecticidal spray which mentions thrips
should do the trick. Liquid diazinon or orthene both work
well. Make sure you spray the underside of the leaves and
into buds and any other nooks and crannies. Read the instructions
carefully to maintain safety and to protect bees. You may
also need to spray any neighbouring rhododendrons or camellias,
which also get thrips.
If the problem is not
thrips, then it could be a fungal problem. In that case a
fungicide or formulation such as Shield could be effective.
Make sure that your rhododendrons
are as happy as possible are they in the right spot? Is the
soil a nice acidic well-drained but moist humus? If not, you may
need to think about changing the site or soil to make sure your
plants are as strong and disease-resistant as possible.
by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor
of Resource Management.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH