Hedging and hedges – Cypress hedge die-back

Over the past couple of years, cypress hedges have become increasingly prone to a mysterious die back, and there have been no obvious factors causing the problem. It now appears that trimming the hedges in the autumn months (predominantly October) has a significant linkage with the occurrence of foliage dieback in Leyland cypress, and watering hedges that experienced progressive dieback does seem to help deliver increased hedge recovery in some cases.

If the die back manifests as yellowing shoots in summer - many of which will be brown and dead by late summer and on clipped hedges the dieback looks very pronounced, with the lower part of the hedge being more severely affected than the top – you almost certainly have aphid infestation, and you can confirm this if a black powdery coating of sooty mould develops on the stems and foliage. The greyish brown aphids which cause the problem are active from May to November, sucking sap from the stems. Despite the aphids being quite large, they are extremely difficult to see. To deal with the problem, spray in early summer at the first sign of an attack to prevent damage occurring. Suitable products contain imidacloprid or bifenthrin. Because it is difficult to spray large hedges, some damage will inevitably occur and recovery is likely to be a slow process.

Other significant reasons for die back are honey fungus and physiological causes such as aftercare problems, dry soil, dense planting of the hedge or excessive shoot pruning.

Hedge gardening cypress photograph by Ingorr, used under a creative commons attribution licence

 

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