A Cautionary Tale
Every year, if Asiatic hemlock adelgid is present, my hemlock trees are spread with horticultural oil or insecticidal soap to suffocate that sucking insect, which looks like tiny pieces of white cotton. It’s an exotic pest without native predators, and kills only hemlocks. No other, more toxic pesticide is necessary. Often the flowering plum will be included in the spraying if it has scale, another sucking, but native, insect. Two of my many hemlocks died, however, in spite of the spraying, a great loss because they were giant ones, over 90 Ft. tall. We miss their profound shade and beautiful grandeur.
The company made excuses, but I became suspicious when I realized that the man who did the spraying applied the pesticide from only one side of the trees, never walking around them. This year I hired another tree care company. A new arborist came who walked around my property looking at leaves and stems to check on the health of all the shrubs and trees. He pointed out that the flowering plum did not have any scale because a tiny insect predator was present, the green lacewing fly, a gossamer, fairy-like do-gooder that eats damaging insects such as scale and aphids. He had noticed an almost microscopic egg of the lacewing on the underside of a leaf, and so he did not spray the plum. He showed me a lacewing on a rosebush as well, and a bed of aphid- free roses as a result.