Gardening expert JJ gives advice about a poplar tree problem

Zelma Stoffberg of Onrus River writes: About six years ago, we planted a few Populus simonii trees on our property. They started off well but we noticed problems about three years ago.

The trees sprout well in spring but by December the underside of the foliage (right in the photo of the leaves) starts developing an orange-brown powder and this powder spreads throughout the garden. The upper surface of the leaves is covered in spots.

The leaves soon die and fall off. Our local nursery suggested we spray with Virikop, but this has not helped over the past two years. In summer, our trees look so sad and provide no shade at all.