The most common problem with cotoneasters is mites. These pests suck plant juices causing the leaves to look speckled and in severe cases brown and fall off. These are a common problem during hot dry summers.

What is killing my cotoneaster?

Aphid - Aphids are spindly-legged, pear-shaped insects little bigger than the head of a pin. They suck sap from leaves and stems, causing cotoneaster foliage to curl, pucker, and turn yellow, while reducing the plant's vigor. Also called "plant lice," these pests attack tender branches and flower clusters.

How do you rejuvenate cotoneaster?

The most practical 'cure' is to cut all dead patches to the ground. In many cases this means cutting the whole hedge to the ground. It sounds drastic, but cotoneasters respond quite well to drastic pruning. A new hedge will grow back within a few years as long as the roots are healthy.