Recently, Pear Trellis Rust (Gymnosporangium sabinae) became the newest contributor to this hodge-podge-let’s-try-everything year. During 2016, the first case of pear trellis rust was reported in the northern section of the Willamette Valley, that on a Bartlett pear growing in Milwaukie, Clackamas County. (See “Pear Trellis Rust: First Report in Oregon” Metro MG Newsletter, January 2016; http://extension.oregonstate.edu/mg/metro/sites/default/files/dec_2016_mg_newsletter_12116.pdf). Then, in mid-September 2017, an inquiry about a pear leaf problem in Multnomah County was submitted to Ask an Expert. [Fig 1; Fig 2] Yes, it’s another fruiting pear tree infected with trellis rust. It seems that gardeners are beginning to recognize this newcomer.
“Symptoms [of trellis rust] on pear begin as yellowish-orange leaf spots early in the season. Young fruit and twigs can also be infected. Leaf spots can become bright reddish orange during the summer. By mid-summer, tiny black dots (pycnia) appear in the center of the leaf spots.” [Fig 3] By late summer, brown, blister-like swellings form on the lower leaf surface just beneath the leaf spots. This is followed by the development of acorn-shaped structures (aecia) with open, trellis-like sides that give this disease its common name. (Fig 4) Aeciospores produced within the aecia are wind-blown to susceptible juniper hosts where they can cause infections on young shoots. These spores are released from late summer until leaf drop.” (“Pear Trellis Rust, Gymnosporangium sabinae” (http://www.ladybug.uconn.edu/FactSheets/pear-trellis-rust_6_2329861430.pdf)
Signs on affected alternate host junipers are difficult to detect. During wet weather in spring, look for swollen areas on branches which exude orange jelly-like horns.
Differentiate Trellis Rust from Pacific Coast Pear Rust
Trellis Rust is quite different from the widespread Pacific Coast Pear Rust you’ve likely seen every spring on Amelanchier (shadbush; serviceberry) and pears.
Pacific Coast Pear Rust infects both Asian and European pears. And, as is common with rusts, it also has an alternate host. During spring, host incense cedars (Calocedrus decurrens) are recognized by the bright orange jelly-like globs on the foliage. On pears, the bright orange, powdery spores erupt on fruits, flowers, leaves, and twigs, often deforming them. [Fig 5; Fig 6] Management includes removing nearby hosts. A home-use spray is available for ornamental pears but not edible pears. (Keep current with the PNW Disease Management Handbook.)
Management strategies for trellis rust
Minimizing overhead irrigation might help reduce the number of infections. But you know how Oregon springs are. It rains! Cultural management may help decrease infection rates:
Collect and discard infected leaves.
If practical, remove juniper hosts from a 1000-ft radius. (The PNW Disease Handbook states “J. communis, J. horizontalis, and J. squamata are immune or highly resistant.”)
No chemical remedies are available for edible pears.
Master Gardeners as First Responders
When MGs see a plant affected by a disease or insect, we’re required to verify our tentative diagnosis before we suggest a remedy. So, here’s an important project for you: Help track the spread of Pear Trellis Rust.
If you suspect pear trellis rust while volunteering at the MG Offices or elsewhere in the metro counties, request images and/or samples. Take pictures and jot down a history with at least these few facts, if known: the name and age of the pear; when the client first detected the problem; also, in which town the tree grows. Next, email the images and history to me (firstname.lastname@example.org). After I verify your tentative diagnosis, I will notify both you and the pathologist.
Click the link below for a PDF containing the above text and all the images.
This has been an interesting year as far as plant problems go. The past winter was colder than usual; this spring was wetter than usual; this summer hotter and drier than usual; and, oh yes, we had a total solar eclipse (2017-08-21) even as I was writing this. Then, too, in spite of the plentiful rainfall this past winter and spring, established trees in forests and landscapes are dying from consecutive years of drought.
For the most part, causal agents of plant problems are abiotic, caused by naturally-occurring adverse environmental factors, also the garden’s care-takers, John and/or Jane Doe. So, when clients ask which disease afflicts their plants, we have a lot to consider. We need a detailed history of what occurred and when, including pre-plant preparations as well as follow-up maintenance.
Just how plants react to high temperatures depends upon numerous factors, among them the extent and duration of the heat; the relative humidity; wind conditions; soil moisture content; the kind of plant, its age, site, and general status before the heat hit. (Phew! That’s a lot to consider.) Sometimes leaves are only damaged superficially. Other times, tissues die. Tissue survival is most likely when the plant is fully hydrated well before the heat hits. If heat is predicted, water the night before or early morning, between 2 and 6 AM.
One good thing about the recent heat waves, the accompanying low humidity has helped limit common leaf diseases. Well, except for powdery mildew, the fungus that creates a whitish film on the leaf surface. If that’s the case, recall that most fungicides are preventive and must be applied at the very first sign of disease, long before the leaf is snowy white.
Accurately diagnosing heat damage relies, in part, upon how well you “read” the signs and symptoms. It’s a skill that requires time to develop. (You know the old saw: Practice, practice, practice.)
Let’s take a look at how heat damage may be expressed, especially on leaves, since that’s often the only thing a client submits for diagnosis.
Young dogwood (Cornus sp.), probably about 2 years old, in a commercial landscape. (Fig 1) Exposure to bright sunlight damaged superficial tissues, killed the chlorophyll (green), revealing the underlying anthocyanins (red pigments), resulting in a reddened sheen on only the most exposed leaves. The somewhat shaded leaves retain excellent green color.
Vine maple leaf with dry, brown edges, evidence of acute water shortage to the shrub. (Fig 2) Sudden heat exposure to a 19-year-old shrub damaged many leaves in a wide swath across the shrub. Affected leaves were tan and shriveled while others only had dry edges. Client wondered if the tree was at the end of its life span. The Ask an Expert response, said essentially this: It’s the recent heat. (Client image; 2017-08) Click image for larger view.
Hosta, exposed to sudden and extreme heat, accompanied by low humidity. (Fig 3) The most severely damaged tissue at the right edge of the leaf, outlined by a zone of white tissue, still retains normal color. This kind of damage can develop in susceptible plants even if they’re in full shade. (J.R. Natter; 2017-06-24)
Click link below for PDF with additional information and images:
Where but in a garden do summer hours pass so quickly? – Anonymous
Summer greetings! We hope your gardens are flourishing in these high summer months. July and August are good months to sit back, enjoy your garden, and of course spend some time wearing your volunteer hat as an OSU Master Gardener!
Phones are ringing! Questions are flying into the Master Gardener phone clinics via email, phone calls, and visitors to our offices. This is a great time to expand your knowledge, collaborating with other MGs as you research and advise gardeners regarding their gardening conundrums. Sign-up on CERVIS or contact a phone coordinator.
Farmer’s Markets are busy and vibrant with a bounty of summer vegetables and fruits, plus lots of inquiring minds seeking answers to their garden questions. Each market has its own special qualities. Discover those unique traits by volunteering at a few farmers markets new to you. Grab an open slot on CERVIS Don’t despair if market schedules appear full. Check back often as schedules change and openings arise throughout the summer. Let a clinic coordinator know you if you are willing to serve as a substitute for last minute cancellations at your favorite market.
Summer Farmer’s Markets: Beaverton – Gresham – Hillsdale – King – Lake Oswego – Lents – Milwaukie – Oregon City – Sherwood – Tigard
Oregon and County Fair FUN!
If you want a big dose of summer fun, sign-up for an MG Clinic table at one of the county fairs or the Oregon State Fair. Give sage (OSU proven), garden advice to fair visitors and take a bit of time, before and after your shift, to grab some shaved ice and check out the fair competitions whether it is honey products, the biggest homegrown fruits and veggies, or the best home brew or chocolate layer cake! Sign-up on CERVIS to grab a shift now! Admission passes and instructions provided to all fair volunteers.
Clackamas County Fair, August 15 – 19 (Tuesday – Saturday). MGs are in a prime location at the Clackamas County Fair with our clinic table right by the entertainment stage, lovely display garden and plant sale. Join-in! Sign-up on CERVIS or contact coordinator Jane Collier: email@example.com, 503-266-1191.
Washington County Fair, July 27 – 30 (Thursday – Sunday). Nestled right next to the demonstration gardens is the perfect location for the MG clinic. This area of the fairgrounds owes its planning and attractive appearance to the Washington County Master Gardeners and is a popular stop for fairgoers. Yes, MGs have bragging rights for this beautiful feature of the fair grounds. Come see it! Sign up on CERVIS or contact Margery Brunello: firstname.lastname@example.org or 973-699-2304
Oregon State Fair, September 1-2. For the ultimate fair experience, take a quick jaunt to Salem for the Oregon State Fair. Master Gardeners from around the state host the OSU Extension Master Gardener Clinic. Our Metro MG program does the honors on Friday and Saturday, September 1st and 2nd. Don’t miss this festive state celebration! Sign-up on CERVIS or email Jordis Yost, email@example.com and ask for a morning, afternoon, or evening shift on Friday, or Saturday.
When logging into CERVIS for the first time, enter your email and click on “Don’t Know password/ Reset password” to get a temporary password.
Please only sign up for events that you know that you can attend. If you need to cancel an event, please contact the clinic coordinator for a list of other volunteers interested in serving as substitutes. It is your responsibility to find a backup.
Master Gardeners Advise Program
An engaged and thoughtful group of 40 Master Gardeners convened on Tuesday, June 6th for a Metro Master Gardener Advisory meeting. Using the 2014-2019 Metro Master Gardener Strategic Plan as a prompt, participants broke into three groups for a brainstorming session, offering suggestions and recommendations for the program moving toward the future. Lively discussion ensued, with the compilation of many thoughtful and insightful suggestions. Program staff greatly value the input and creative ideas. These suggestions will be further explored via upcoming Master Gardener Liaison Meetings.
Master Gardener Liaison Meetings are open to all Metro Master Gardener volunteers. Upcoming meetings:
Tuesday, August 8 10am to 12noon, Washington Co. (location TBA)
Tuesday, October 10 10am to 12noon, Clackamas Co. (location TBA)
Tuesday, December 12 10am to 12noon, Multnomah Co. (location TBA)
There will also be a special meeting to explore the use of technology in the Master Gardener Program following the August 8th Liaison Meeting. The technology meeting will be from 1:00pm to 3:00pm. Look for an email invitation to the Liaison Meetings in the next couple of weeks (RSVPs required for all meetings), with details on specific locations which will rotate among the three counties.
Hands-on in Demonstration Gardens Summer is a glorious time for hands-on learning in any of our ‘Partner’ demonstration gardens. Each garden offers unique active, relevant, learning opportunities. Contact a coordinator and dig in!
Beautiful, historic gardens. Consider spending time this summer in a beautiful, garden – dispensing reliable gardening information.
It is a very special year at Washington Park International Rose Test Garden. Sign-up for a shift as the garden celebrates its Centennial year!
The Pittock Mansion is another lovely and historic setting in which to share your garden knowledge.
Sign-up for a shift via CERVIS or contact the clinic coordinators.
Log Your Hours
Thank you for your passion, energy and volunteer service educating the gardening public. We want to be sure to have a record of all your efforts. Here is the link you need for the forms to log your volunteer hours. Choose from a PDF or Excel form. All hours due by October 1, 2017. http://extension.oregonstate.edu/mg/metro/forms
Save the Date! Saturday, October 28th FALL RECERTIFICATION!
Our annual Master Gardener Fall Recertification Training is scheduled for Saturday, October 28th, 8:00am to 3:30pm, at Clackamas Community College. This annual event is a daylong continuing education opportunity. Earn 6 hours of continuing education/recertification credit by attending.
A great line-up of speakers is forming. This year’s presenters all bring their wealth of experience from their work with OSU Extension Service. They will offer a wide range of topics to enrich the knowledge base of Master Gardeners. They are Joy Jones, Sam Chan, Brooke Edwards and our very own Weston Miller.
The Fall Recertification day also gives us the opportunity to congratulate the new class of trainees as they step up to Veteran status after completing their volunteer requirements. We will present trainees with their OSU Extension Service Master Gardener badges and a big shout out for successfully completing the program.