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Rose leaf damage pest unmasked...
Dear
Martin...
I have an old ‘New Dawn’ rose
(probably planted in the early 1960s) that for the last two years
has suffered from what I believe to be ‘rose
sawfly’. They are tiny caterpillar like grubs that
leave the leaves as dry skeletons. Last year it seemed to get the
whole rose – but later in the season a new flush of leaves
appeared.
I garden organically and don’t
usually spray my roses at all as I rarely see greenfly etc. I
have tried to pick up as much of the debris around the base as
possible.
You advice would be much
appreciated.
Best wishes,
Jane
Martin says...
Dear Jane
Many thanks for your recent enquiry regarding rose sawfly. It certainly sounds like the rose slug sawfly (Endelmomyia aethiops) is responsible for the damage caused to the leaves, as this little pest is also know as the rose slugworm or rose skeletonizer!
The grubs – yellow/green in colour and resembling tiny slugs - feed on leaf tissues and eventually reduce the leaves to a skeleton. This damage normally occurs between May and September and although the plant does not normally suffer too much, the remains of the leaves don’t add to the general garden appearance.
Preventing this pest from devouring the leaves is relatively easy. The larvae over winter in cocoons in the soil so some careful winter cultivation should expose them to both weather conditions and predators – or you can collect and dispose of them. Any larvae which escape this winter clean-up will emerge in May and June after a pupation stage and begin to lay eggs on leaf edges. Spraying with organic insecticides such as Derris or Natural Pest Control as soon as the larvae are spotted, and applying a follow-up spray a week later, should do the trick. Make sure you spray the young larvae as more mature caterpillars may be able to fight off the sprays listed above!
Hopefully this information will help keep the foliage on your roses intact and best of luck with your gardening this year! Martin
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