you please tell me what is causing this damage on my trees and roses?
It is killing off parts of the branches. I had an idea it was cicadas,
but don't they develop below ground?
damage to the twigs was caused when an adult female cicada laid
her eggs in that typical herringbone pattern which causes long scars
to develop in the branch. The eggs take many months to hatch, during
which time they are kept nice and moist, protected within the branch
tissues. When they eventually hatch, the nymphs wriggle free, fall
to the ground and work their way down cracks in the soil until they
are well below ground where they feed on sap from tree roots. By
this time the original damage caused in laying the eggs has weakened
twigs and branches to the point where they often break off under
their own weight or in wind.
Some of the most serious
cicada damage I've seen was in an orchard planted close to native
bush where branches on the apple and pear trees were so weakened
they collapsed under the weight of even a light load of fruit.
Cicada nymphs spend many
months in the soil before they reappear above ground and moult into
the chirruping insect whose raucous chorus is such a familiar late
summer sound in many parts of the country.
Adult cicadas only live
for a month or two, during which time they mate, the female lays
its eggs and the cycle starts over again.
Overseas, one species
of cicada is known to spend up to 17 years underground as a nymph,
but New Zealand species have a much shorter life cycle.
very little you can do to prevent cicada damage apart from pruning
out damaged branches when you spot them.
Gardener, Issue 176, 2005, Page 34
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.