Trees are living and breathing things and like all living things sometimes get sick. However, with the proper diagnosis, treatment and expert arborist advise, in a large number of cases we can bring them back to life. Quite often, homeowners are unaware that their trees are in fact diseased and infected. Below are common tree diseases found in Ontario.
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First identified in the Netherlands and often labeled as DED, this tree illness is caused by ascomycetes or sac fungi that have affected elm trees in both North America and Europe. Bark beetles are accomplices in the spread of destruction as these insects carry ascomycete spores in weakened elm. Sac fungi target the xylem or water vessels of elms, further weakening the tree. The situation finally becomes a gateway for other bark beetles to wreck elms in record time. Disease confirmation is done in laboratories as people can mistake DED for other tree diseases. However, black discoloration of white sapwood can be a helping indicator of DED. Prevention involves targeting beetles primarily by coating bark with methoxychlor or similar pesticides. Disposing of elms both dead and weak is also necessary.
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Credit: D. Gordon E. Robertson Creative Commons
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Native in both Korea and China, ALB, its shortened name, invades several trees like elm, maple, and ash. This beetle has long antennae and white dots surround its black exoskeleton. A distinct ALB-infected tree symptom is the existence of at least inch-deep "pencil" holes found in the infected tree bark. As the insect bores perforations in the tree, signs of infection include the presence of sawdust on branches. Consequently, the hardwood sap would leech out from the bores, another characteristic symptom. Other than these signs, ALB can also lay its eggs on tree barks, making depressions on tree surfaces. For preventive measures, inspectors set up quarantine areas for slowing the spread. Additional treatments include the application of chemicals and the removal of trees that have high infection potential.
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Shortened to EGM, the larval stage of these moths are the main harbingers of decimation in various shrubs and conifers. Larvae can cause outbreaks due to their insatiable appetite. This poses threats to North American forests because these organisms cause the increased susceptibility of hardwood to illnesses. The continuity of them feeding on leaves causes loss of foliage in trees. To identify its caterpillar stage, one should find features such as grey & yellow patterns, red & blue dots, and hairy bristles on its body. Cautionary actions involve reporting EGM eggs and larvae to agriculture authorities.
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This tree disease makes leaves, such as in maple trees, to be covered in spots of yellow and black, resembling tar. Caused by fungi from the genus Rhytisma, the illness is only cosmetic, which means that it only affects leaf surface and is no illness of life-and-death for an infected tree. However, leaf tar spots can enlarge over time, forming clusters. Since this is a disease involving fungal spores blown by the wind, avoiding the occurrence of tar spots in healthy trees needs to start with leaf disposal of affected ones during autumn. Burning, composting, or burying infected leaves is one way to eliminate and limit the presence of the fungi. Copper-containing fungicides for treatment is available but used rarely.
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It is often confusing to differentiate these pests since both make webs. Tent caterpillars thickly weave their webs on tree forks while fall webworms spurn webs that loosely envelope branches. The former thrives in spring while the latter lives during the summer or fall. Early detection is essential to avoid leaf loss. To prevent further pest proliferation, one should do practices like scouting for egg clusters and removing webs with sticks.
Tree disease control using pesticides is also another option, but it is important to consult first with authorities before deciding to kill pests chemically. |
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