PEAR TRELLIS RUST
Girdling root on tree
(800)724-6680
www.owentree.com
Girdling root on tree
CONTACT OWEN TREE AT:
(800)724-6680
Pear trellis rust was introduced into the western United States in the 1990’s and has now made its way east to Michigan. Sadly, it is firmly established throughout much of the metro Detroit area. This foreign disease causes serious damage to fruiting pear trees in its native Europe, and here it is causing devastating damage to flowering pears in our landscapes.
Pear trellis rust is caused by a fungus, Gymnosporangium sabinae, and is similar to our native cedar-apple rust. Both develop on new leaves and fruit. As infection progresses, yellowish-brown spots appear on pear leaves and fruit. By summer’s end these spots have grown and turned to unsightly bright orange-black deformed areas. The fungus then produces fruiting bodies on the undersides of leaves and on the fruit. Not really distinguishable from the leaf spot with our native rust disease, the fruiting bodies of pear trellis rust may best be described as conspicuous orange blobs that split-open to release the seed-like spores.
Also in common with our native rust disease, pear trellis rust requires two alternate hosts to complete its life cycle. Many species of juniper are the alternate host. The infection forms on the stems of junipers, developing into spindle-shaped woody galls. The galls typically do not seriously injure junipers and are only noticeable during a short period of time in the spring.  When they are releasing spores, the galls on juniper plants develop orange jelly-like “horns”. These spores are then carried by the wind to flowering pear trees where infection of the pear leaves will occur.
Not only is pear trellis rust an unattractive disease, it injures trees. This is the most important difference between cedar-apple rust and pear trellis rust. Infection from pear trellis rust can be so heavy as to cause pear trees to almost totally defoliate by mid-summer. Defoliation stresses the tree, but pears will replace some of the lost leaves. While this means pear trellis rust may not be fatal, the pear will be unsightly for most of the growing season and have little landscape value. In addition, pear trellis rust will infect and kill twig tissue causing indented areas called cankers. Once twig cankers are formed there is little that can be done to prevent serious infection of the new leaves and fruit.
Treatment options for pear trellis rust are limited. Pruning galls from junipers in early spring before they release spores will reduce new infections. Fungicide sprays are effective, but only on the leaves. Once cankers have developed in the twigs, fungicide sprays are ineffective in preserving good appearance through the summer. Sadly, ornamental pear may be off of our list of useful and beautiful landscape trees.
There is no way to prevent pear trellis rust spores from finding your pear tree. The only option is to prevent the spores from infecting the leaves of your flowering pear. For clients with ornamental pear trees, we recommend two applications of fungicide in the spring to limit leaf infection. At this time, this is the only way to prevent the disease from developing untreatable cankers. Monitoring and removing galls on juniper, or possibly removing the juniper itself, is important around valuable ornamental pear trees.
tree service in Lake Orion, MI
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Owen Tree Service provides tree, lawn, and landscape services to the following cities and towns:
Genesee County, Michigan:
Burton
Davison
Flushing
Goodrich
Linden
Otisville
Clio
Fenton
Gaines
Grand Blanc
Montrose
Otter Lake
Flint
Genesee
Lennon
Mt Morris
Swartz Creek
Lapeer County, Michigan:
Almont
Brown City
Columbiaville
Imlay City
Metamora
Peck
Attica
Clifford
Dryden
Lapeer
North Branch
Sandusky
Hadley
Mayville
Otter Lake
Silverwood
Macomb County, Michigan:
Armada
Clinton Twp
Grosse Pointe
Macomb
New Haven
St Clair Shores
Centerline
Detroit
Grosse Pointe Farms
Ray
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Chesterfield
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Grosse Pointe Shores
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Romeo
Utica
Clinton
Fraser
Grosse Pointe Woods
Mt Clemens
Roseville
Warren
Harrison Twp
New Baltimore
Shelby Twp
Washington
Oakland County, Michigan:
Auburn Hills
Bloomfield Village
Ferndale
Orion
South Lyon
Berkley
Clarkston
Franklin
Madison Heights
Ortonville
Southfield
Beverly Hills
Clawson
Hazel Park
Milford
Oxford
Troy
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Commerce Twp
Highland
Novi
Pleasant Ridge
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Birmingham
Davisburg
Holly
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Pontiac
Waterford
Bloomfield
Detroit
Huntington Woods
Oakland
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Bloomfield Hills
Farmington
Lake Orion
Oakland Twp
Rochester Hills
White Lake
Farmington Hills
Lathrup Village
Orchard Lake
Royal Oak
Wixom
St. Clair County, Michigan:
Algonac
Casco
East China
Harbor Beach
Lexington
Peck
Allenton
Clay
Emmett
Harsens Island
Marine City
Port Huron
Berlin
Clyde
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Jeddo
Marysville
Richmond
Brockway
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Kimball
Memphis
Sandusky
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Lakeport
North Street
St Clair
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