Ornamental cherry tree. Asked June 14, 2020, 3:17 PM EDT. Algae, lichens and moss often form green or grey, powdery or mossy, crusty growths on the stems, branches and trunks of trees and shrubs. The leaves either shrivel, turn brown and remain hanging on the tree throughout winter in the case of leaf scorch, or become yellowed, mottled and drop prematurely in the case of leaf spot. To avoid damaging an actively growing tree or shrub, apply these chemicals during the plant's winter dormant period. Copper sulfate and lime sulfur are toxic to humans, and lime sulfur is corrosive to painted surfaces. In fact, some 536 lichen species are associated with ash! Its beauty is more noticeable in winter, once the distractingly gorgeous autumn leaves have fallen. On fruit trees, the black leech like creatures are in fact green but covered with black slime. It's easy to mistake lichens as the cause of tree or branch death because they tend to grow on sick trees. Tree trunks, stumps, rocks, fences….they are all magically transformed. Although chemical sprays will kill lichen, there are no chemicals specifically approved for lichen control on tree and shrubs. Like many gardeners, I have been stubborn in trying to grow plants not native to their environment in order to achieve a certain effect. It affects pear, cherry and apple trees as well as some ornamental shrubs, hawthorns in particular. Lichen indicates slow growth and moisture. Like verdigris . The gum is coming from a hole in the bark of the tree. While this can worry gardeners, these growths are harmless, although may occasionally indicate a lack of vigour in the affected plant. Spraying is not recommended to control these … In fact, the reason they turn up is because a sick tree has a thin canopy and lets in the sun that makes lichens grow. The trunk below is a Japanese maple. All of this really underlines how crucial a single ancient tree can be for our varied lichen species. Some of these growths look like lichen and some like fungus. Look at the point where the gum is exuding from the tree. Below is a variety of lichen on an ornamental cherry tree. Cherry leaf scorch and leaf spot are diseases of Prunus spp. This is the Cherry Slug Sawfly (Caliroa cerasi) sometimes also called the Pear Slug Sawfly. All the earthy colours. caused by the pathogenic fungi Apiognomonia erythrostoma and Blumeriella jaapii. In both cases, they are probably indications of a problem rather than the cause of a problem. Look for wood debris (frass) mixed in and around the exuding gum. Harmful thick lichen growth on ornamental trees is an under recognized problem, I believe. Bark can become more alkaline with age, so species such as ash – which has a relatively high pH (alkalinity) of bark - are home to a lot of species. Before moving on to other causes of gummy cherry trees, let’s review the symptoms most associated with a peachtree borer infestation of flowering cherry.