On 06/01/2013 13:17, rbel wrote:

I wonder if anyone has encountered this problem and found a lasting
solution to it. We have two half standard bays which are excellent
but for the continuing presence of caterpillars which damage the
leaves, particularly new softer leaves.

The caterpillars are of the leaf roller type but as the leaves are too
rigid to roll they stick adjoining leaves together and, in the safety
of the leaf sandwich they munch the surface layers leaving large brown
or semi transparent patches.

I have also noticed the same caterpillars on one of our Choisya
shrubs.

It looks as though they are the larvae of the Carnation tortrix moth,
Cacoecimorpha pronubana, which is a problem as I cannot find any
readily available effective controls online.

If anyone has discovered anything that works. I have tried a
thiachloprid (which being a neonicotinoid I only use as a last resort)
but so far even drenching the bays with it has not solved the problem.



I am hoping here that you do not use your bay leaves for cullinary
purposes, since the best way of ridding your trees of this pest is a
systemic insecticide. Because the caterpillars are protected, any
contact insecticide you use will not have any effect. A systemic
insecticide will get into the sap of your tree, the insects will suck
the sap and die.

In truth, I am not aware of a caterpillar specifically dependant on
Laurus nobilus (Bay Tree), but even if you have misidentified your pest,
a systemic insecticide will rid your tree of both Bay Sucker and Scale
insects.

If you do use your bay leaves in the kitchen, I suggest you cut a stem
or several for drying, then apply the systemic drench.

Hope this helps.

--
Spider
from high ground in SE London
gardening on clay