leaves on echium
Echium 'Cobalt Tower' has something wrong with its leaves.
Most seem to be dying off and others have funny tines on them. Can
sample you sent contained leaf miner caterpillars, the larvae of
small moths which lay their eggs on the leaves. On hatching, the
young caterpillars burrow into the leaf and create tunnels between
the upper and lower surface. At first you'll see long, relatively
clear, tunnels, but as damage gets worse these can merge into large
dead areas, as has happened to your echium.
Hold a badly affected
leaf up to the light and you should be able to spot the small caterpillars
wriggling around inside, nicely protected inside their tunnels.
I split one of the leaves open to reveal the caterpillars you see
Protected inside their
tunnels, leaf miners can be difficult to control. In the early stages
of attack you could remove damaged leaves but as your echium has
most of its leaves infested you'll need to spray with a systemic
insecticide such as Target or Rogor, which travels through the plant
cells to be ingested by the leaf miners as they feed. Follow the
label recommendations carefully, especially with regard to protecting
yourself when mixing and applying these sprays.
Gardener, Issue 169, 2005, Page 28
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.