Very often on trees and branches of woody fruit species, as well as other ornamental trees and shrubs, lichens phenomenon is noticed.
Lichens occur in almost all kinds of fruit trees, especially plums, walnuts, apples and pears, in extensive or abandoned orchards. Lichens are made up of two or more different organisms living together, algae (green or blue-green algae) and fungus (Ascomycota). They live in symbiosis, from which both of these organisms have a common benefit. Algae through photosynthesis create organic matter, and mushrooms procure water and mineral nutrients, so that they complement each other. Lichens are not pests or parasites on farm plants, but their appearance may indirectly harm plants because they can reduce the potential of the plant life or vigor, but also can be suitable habitat for the settlement of certain pests.
There are more than 15,000 species of lichens, and science puts them as a very good bioindicators and indicators of puritiy of farming habitat and environment. They never grow where the air is polluted and where are the remains of toxic substances. Their appearance on fruit trees is the best sign of good environmental and farming conditions in the orchard. Usually they occur in older fruit trees, and if they start to grow on young trees, it's a sign that the fruit trees are in weaker condition, or that they're weakened by various factors of unfavorable environment. Lichens never occur in orchards with regular fungicide protection, because most fungicides, those based on copper, quite well suppress them. List of cooper fungicides for every fruit tree you can find in Agrivi farm management system.
Almost all fruit trees have lichens on their bark and mature orchards can contain many species. They are indicators of pollution and monitoring the changes in the spread of lichens is important for understanding how our environment is changing. Suppression management of lichens include late winter treatment and treatments at the beginning of the fruits growing season with cooper fungicides.