{"id":1039,"date":"2018-06-01T17:43:17","date_gmt":"2018-06-01T17:43:17","guid":{"rendered":"http:\/\/blogs.oregonstate.edu\/mgmetro\/?p=1039"},"modified":"2018-06-26T19:55:05","modified_gmt":"2018-06-26T19:55:05","slug":"pear-trees-rust-times-2","status":"publish","type":"post","link":"https:\/\/blogs.oregonstate.edu\/mgmetro\/2018\/06\/01\/pear-trees-rust-times-2\/","title":{"rendered":"Pear Trees: Rust, times 2"},"content":{"rendered":"

Natter\u2019s Notes <\/strong><\/h1>\n

Pear Trees: Rust, times 2<\/strong><\/h1>\n

Jean R. Natter, OSU Master Gardener
\n<\/strong><\/h3>\n

Pear trees are having a rough time of it this spring. It seems that this year supplied\u00a0 the perfect conditions for rust on pears. So, let\u2019s compare and contrast\u00a0 the two important rust diseases of pears in Oregon. Recall that cedar-apple rust is not<\/u> an issue in our region.<\/p>\n

Seven different Gymnosporangium<\/em> species cause rusts on members of the rose family in Oregon. For this discussion, let\u2019s differentiate between Pacific Coast Pear Rust (G. libocedri<\/em>) and Trellis Pear Rust (G. sabinae<\/em>).<\/p>\n

Most rust fungi have two different hosts: the primary host\u00a0 — in this case, pear– on which growth and yield may be severely affected and a secondary host which typically displays subtle effects. With both diseases, pear trees exhibit brilliant orange spores on affected tissues, spores which readily rub off.<\/p>\n

\n \"Numerous<\/a>\n
Numerous powdery, bright orange spores are present on leaves, twigs, blossoms, and fruits in Pacific Coast Pear Rust, as shown here and in Trellis Pear Rust. (Client image; Lincoln County; 2012-05)<\/figcaption>\n <\/figure>\n

Pacific Coast Pear Rust<\/strong> is a well-established disease in the northwest and, this spring, is on a spree infecting leaves, twigs, blossoms, and newly set fruit. All ages of trees are affected, from venerable specimens to newly planted saplings. Incense cedar is the alternate host.<\/p>\n

Trellis rust, aka European Pear Rust<\/strong>, was found in western Oregon in 2016. It\u2019s considered well -established in western Washington, coastal British Columbia and Contra Costa County, CA. Known infections in Oregon are in Benton, Marion, and Clackamas Counties. Junipers are the alternate hosts.<\/p>\n

\n \"Trellis<\/a>\n
Trellis Pear Rust, also called European Pear Rust, on back surface of leaf. (Client image; Multnomah County; 2017-09)<\/figcaption>\n <\/figure>\n

Differentiating between these two rust diseases<\/strong> of pear relies on careful examination of symptoms on submitted sample(s) and images. Both rusts sport bright orange, powdery spores on pears. A diagnostic symptom for the trellis variety is an \u201cacorn-like\u201d eruption on the backs of leaves later in the season.<\/p>\n

Be certain to ask about potential alternate hosts nearby. \u00a0Both alternate hosts of these pear rusts ooze orange gel during wet spring weather. Off-season, affected junipers have subtle, elongated galls while incense cedars may develop \u00a0a more obvious symptom, witches\u2019 broom(s). (http:\/\/www.missouribotanicalgarden.org\/gardens-gardening\/your-garden\/help-for-the-home-gardener\/advice-tips-resources\/pests-and-problems\/diseases\/witches-broom.aspx<\/a>)<\/p>\n

Management choices are limited<\/strong> for home gardeners who fear for their fruit crop.<\/p>\n

– Sanitation<\/strong> \u2013The common advice to collect and discard affected parts is unlikely to limit rust unless alternate hosts are removed.<\/p>\n

– Resistant varieties<\/strong> \u2013 Growing resistant varieties is commonly suggested for disease management for backyard trees. In pear rust, both Asian and European kinds are affected. \u2018Bartlett\u2019 is usually less affected while \u2018Winter Nellis\u2019 is severely affected. Resistant varieties aren\u2019t listed for trellis rust.<\/p>\n

The PNW Disease Handbook states \u201cEliminating either host [primary or secondary] is the only practical cultural control.\u201d For Pacific Coast Rust the PNW says \u201cRemove alternate hosts around the orchard.\u201d (It also states that, spores from the gel on incense cedar can be blown 6 for 10 miles.) The advice is more specific for trellis rust: \u201cRemove all junipers within 1000 feet.\u201d<\/p>\n

– No home-use chemicals <\/strong>are listed for either rust. So, the gardener\u2019s next predicament is to locate a company which sprays fruit trees. Clients will need to research local companies that spray landscape trees. (I found that company websites usually offer a link to \u201ccontact us\u201d while some list a phone number. You\u2019ve heard it before: Let your fingers do the walking.)<\/p>\n

Resources <\/strong><\/p>\n

Pear Trellis Rust <\/strong><\/p>\n

–\u00a0 Pear, primary host – https:\/\/pnwhandbooks.org\/plantdisease\/host-disease\/pear-pyrus-spp-trellis-rust-european-pear-rust<\/a><\/p>\n

– Juniper, secondary (alternate) host- https:\/\/pnwhandbooks.org\/plantdisease\/host-disease\/juniper-juniperus-spp-pear-trellis-rust<\/a><\/p>\n

Pacific Coast Pear Rust <\/strong><\/p>\n

–\u00a0 Pear, primary host – https:\/\/pnwhandbooks.org\/plantdisease\/host-disease\/pear-pyrus-spp-pacific-coast-pear-rust<\/a><\/p>\n

– Incense cedar, secondary (alternate) host- https:\/\/pnwhandbooks.org\/plantdisease\/host-disease\/juniper-juniperus-spp-pear-trellis-rust<\/a><\/p>\n

(Click the link below for PDF containing the above text and all the images.<\/strong><\/p>\n

Pear Trees: Rust, times 2 – PDF<\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Natter\u2019s Notes Pear Trees: Rust, times 2 Jean R. Natter, OSU Master Gardener Pear trees are having a rough time of it this spring. It seems that this year supplied\u00a0 the perfect conditions for rust on pears. So, let\u2019s compare and contrast\u00a0 the two important rust diseases of pears in Oregon. Recall that cedar-apple rust… Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":8248,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1179565],"tags":[],"class_list":["post-1039","post","type-post","status-publish","format-standard","hentry","category-natters-notes"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/posts\/1039","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/users\/8248"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/comments?post=1039"}],"version-history":[{"count":3,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/posts\/1039\/revisions"}],"predecessor-version":[{"id":1045,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/posts\/1039\/revisions\/1045"}],"wp:attachment":[{"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/media?parent=1039"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/categories?post=1039"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.oregonstate.edu\/mgmetro\/wp-json\/wp\/v2\/tags?post=1039"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}