Natter’s Notes

Japanese Beetle Eradication: Update

Jean R. Natter, OSU Master Gardener

No Japanese Beetle logo
(Image: Oregon Department of Agriculture)

Japanese beetle eradication: One year down, 4 to go.

Japanese beetles (JB) will remain front and center as important invasive pests in Washington County. The eradication effort began in 2017 and will extend through 2021. The Oregon Department of Agriculture’s (ODA) 2018 plans are progressing well for the continuing effort against these serious invasive pests of agriculture and home landscapes.

Few questions were submitted to the Washington County MG office during 2017 about JBs, so, ODA did an excellent job explaining the project to affected citizens and recruiting their cooperation. (I responded to just 2 client inquiries, both from far outside the quarantine area. One about the dying birch trees on Cooper Mountain where the client was concerned he “saw some of those bugs” and even “dug some out of the trunk.”)

News from ODA

“Using data from our 2017 trap detections and the resulting predicted JB trap catches for 2018, we have expanded our treatment area for next year in Washington County. As was the case in 2017, consent is needed from residents for ODA and our contractors to be able to enter the properties and treat with Acelepryn G. In January, residents within the treatment area will receive notice in the mail with details about the infestation, our plans for eradication, and consent forms to return to us. Consent can also be granted using our online form. Treatment is scheduled for April and May 2018. In addition to the treatments in Washington County, we also plan to treat [a] small area at Portland International Airport and a residential neighborhood in Oakland, OR, [Ed. Note: Douglas County] based on 2017 detections. These infestations are believed to be unrelated to the Washington County populations.”

ID Characteristics of the Japanese Beetle
(Image: Oregon Department of Agriculture)

ODA’s Proposed Response Plan for 2018

ODA’s 2018 Proposed Response Plan for Japanese beetle has been finalized and is now available. As previously announced, all known infested properties will be treated.

ODA’s directives about yard debris

ODA’s “newest alert about the quarantine” describes appropriate handling of potentially contaminated yard debris and contains a brief FAQ. (

Male Japanese beetles captured in a pheromone trap. Image adapted from Oregon Department of Agriculture
Male Japanese beetles captured in a pheromone trap.
(Image adapted from Oregon Department of Agriculture)

Informational Open Houses by ODA

ODA has scheduled two open house events for Cedar Mill and nearby neighborhood residents to have their questions answered about the JB eradication project:

– Tuesday, February 13 at Leedy Grange, 835 Saltzman Rd, 9:30am-12:30pm

– Monday, March 5 at Cedar Mill Community Library, 12505 NW Cornell Rd, 5:15pm-7:15pm

FAQ about the granular Acelepryn G

During 2017, a granular product was applied to turf areas of affected properties using a drop spreader. A detailed FAQ concerning Acelepryn G is at the Oregon Health Authority (

What to do if a JB is seen

“If you see the adult Japanese beetle within the treatment area then the Oregon Department of Agriculture advises that you dispose of them in a container of soapy water.

“If beetles are observed outside the treatment area please put the specimen in a container or bag and email or call ODA.”


– ODA news release 2017-12-14: “ODA makes plans for Japanese beetle battle part 2“ (

– ODA’s Japanese Beetle website, an overview of the infestation and its management, now with extensive updates. (

– “Japanese Beetle Treatment Map with Trap Placement” outlines the proposed 2018 quarantine area in blue while dots indicate individual traps. (

– “Current Suppression and Eradication Projects” contains succinct summaries of the green waste quarantine, the 2017 JB detections, and a list of links to JB resources at ODA. (

– Oregon Health Authority has an extensive FAQ fact about Acelepryn G, the granular insecticide used against JBs in Washington County.

(Click the link below for PDF containing the above text and all the images.)

Japanese Beetle Eradication: Update, PDF

Natter’s Notes

Slugs & Snails

Jean R. Natter, OSU Master Gardener

Snails and slugs. Ugh. Slime and holey leaves. Yuck. Oregon’s rainforests offer prime habitat where slimy pests thrive.

Pests & natives

Fig 1 – Newly hatched slugs, 1 day old. (J.R. Natter; 2010-10)

“Of the 29 species of slug [in Oregon], 15 are exotic.” (Resource #2.) Of those, the gray field slug is the scourge of home gardeners and commercial growers.

Slug lifetimes vary, from one to two years, according to the kind at hand. (Fig 1) But it’s a different story with snails. Brown Garden Snails (BGS) live to 4 years, Giant African Snails – they’re not here yet – 7 to 12 years.

Invasive Brown Garden Snails, Cornu aspersa were deliberately imported from Europe to California during the mid-1850s to be an upscale edible served in garlic-butter to moneyed goldminers. (Fig 2) Unfortunately for gardeners, snails escaped. Worse yet, when the market went bust, unsold stock was released. (More info at Pacific Northwest Nursery IPM:

The native Pacific Banded Snail, Monadenia fidelis, resembles BGS, but has different habits. It primarily inhabits wooded areas, and is seldom a garden pest. When you compare the brownish shells of BGS and Monadenia side-by-side, it’s easy to see that the pattern on BGS is somewhat tweedy whereas Monadenia is strongly banded. (Fig 3)

The Gray Field Slug, Deroceras reticulatum, also called the milky slug, has cloudy mucus. Although it’s a rather small slug, just 15 to 50 mm long – about ½- to 2-inches – it’s a

Fig 2 – Brown Garden Snails in the PNW often have very fragile shells., (J.R. Natter; 2012-05)

serious pest in both commercial agriculture (especially grass seed producers) and home gardens.

The European Red Slug, Arion rufus, is an accidental import from Europe. A showy one. When disturbed, it contracts into a bell-shaped blob.

Leopard Slugs, Limax maximus, are impressive because of their 4- to 8-inch length when extended. If you’ve ever found a mess of slime on a wall, window, or screen, likely this slug and an intimate buddy were the source. During their unique mating practices, the pair of slugs entwine around each other while suspended from a sturdy strand of mucus. (Explicit images at

Management of slugs and snails

– Natural slug predators exist, but are unlikely to limit populations as much as desired, especially if you plant from seed – seedlings are choice nibbles — or if your favorite plantings are leafy greens or hostas.

– Several different night-working, predaceous ground beetles labor on your behalf. Scaphinotus species, for one. (See

– Regularly scheduled search-and-destroy missions, either early day or late evening. Besides that, revenge feels good!

– Forget about sharp things. You know; stuff like DE, coffee grounds and/or crushed filbert shells. Slime has a purpose, one of which is protection. Plus, such barriers must remain dry. (See “Snail barriers” –

– If you use baits, the best time to apply them is before the snails and/or slugs mate and lay eggs. Some species do so in August, others during fall. Then, some repeat in March.

The future of management

Fig 3 – Differentiate between the native Monadenia fidelis (L) and the pest Brown Garden Snail, Cornu aspersa (R). (J.R. Natter; 2014-04)

As you may know, gardeners in Europe supplement the natural populations of soil-dwelling, slug-killing nematodes (Phasmarhabditis hermaphrodita) with commercially reared preparations of the same tiny beasts. (See  But, due to strict regulations, those nematodes can’t be exported elsewhere.

But wait. Help may be on the way. Rory McDonnell was hired by OSU about 2 years ago as the Invertebrate Crop Pest Specialist to help farmers manage pesky slugs and snails. (Yea! Gardeners will benefit, too.) He has since located a domestic strain of Phasmarhabditis hermaphrodita on the OSU campus. Just as with all potential biological control agents, requirements include extended testing and evaluation prior to formulation and release of a commercially available product.  (Keep your fingers crossed.)

McDonnell is also working with essential oils and novel attractants. Among the latter, an extract from cucumber slices looks particularly promising.

Illegal in Oregon

Oh, yes. Forget about pitting decollate snails, Rumina decollata, against pest snails and slugs. These predators are legal only in the 7 southern most counties of California. Simply put: Decollates are illegal in Oregon.


  1. “Snails and Slugs”- Practical advice for day-to-day management:
  2. “Slugs and Snails in Oregon” (J. Vlach, Oregon Dept. of Agriculture): Helps identify Oregon’s commonly encountered slugs and snails; prints well if set up with 2 pages per sheet.
  3. “Slug Portal” – All-in-one resource about slugs in Oregon. Lots for slime devotees to learn there, including identification, the life of a slug; monitoring; management; research; and more. Go to
  4. “Terrestrial Mollusc Tool” – In-depth identification tool for enthusiasts.:

(Click the link below for PDF containing the above text and all the images.)

Snails and Slugs PDF

Natter’s Notes

Rose stem girdler, a new pest of caneberries & roses

Jean R. Natter, OSU Master Gardener

As insects go, rose stem borers, Agrilus cuprescens, (Fig 1) are small metallic beetles in the Family Buprestidae, about a 1/4-inch long when mature. This imported European species attacks two favorite garden plants: Roses and caneberries. Their larvae bore into the stems, eventually girdling them. The growth beyond that point wilts and dies. (Figs 2 & 3)

The older name, Agrilus aurichalceus, is still used in various resources. Other common names include bronze cane borer, cane fruit borer, and raspberry borer.

Facts about borers

Before we delve into further details, we need to understand that all insects that bore into plants behave similarly. For rose stem borers, it’s essentially this:

  1. Stressed plants release volatiles (e.g.: ethanol) to attract the pests.
  2. The borers find the host by following a scent emitted by the plant.
  3. The beetles “taste” the plant and, if it’s suitable for attack – adequately stressed – release aggregation pheromones which attract more of their kin.
  4. After sufficient beetles have arrived, they release a “de-aggregation” pheromone which essentially says “Back off, dude.”

5.The beetles lay eggs on the canes. The larvae hatch and immediately bore into cambium where they feed in a spiral pattern, girdling the stem.

  1. The stem develops a gall (a slight enlargement); the growth beyond the girdle dies.
  2. The 4th instar larvae overwinter in the stem.
  3. Adults emerge about mid-May, mate, and lay eggs singly on canes.
  4. Repeat from #5 the next season.


“Flatheaded borers are larvae of a remarkable group of beetles known as buprestids or metallic wood boring beetles, so named for their luminous, metallic exoskeletons. While the adults levy no particular offense other than to nibble a few leaves, their youngsters are real trouble makers and some of the most devastating pests of woody plants.” (

Here in the northwest, we’re already familiar with another small invasive buprestid, the Bronze Birch Borer (Agrilus anxius). They inflict serious damage and, often kill, stressed birch trees by girdling them, thereby disrupting the flow of the phloem and xylem. (Details at “Bronze Birch Borer” –

Host plants

As you might suspect, hosts of rose stem borers include roses, but also certain other members of the rose family, among them caneberries commonly grown in home gardens, including both raspberry (red and black) and blackberry. Affected roses may be wild or cultivated kinds.


Affected canes develop a gall (enlargement) at the feeding site which dries, weakens and may break. Fruit production may decrease. Caneberry plants with normally lush growth may die. (Figs 4-6)


Management of rose stem girdler in Oregon is currently limited to cultural methods.  Plant in well-drained soil and provide adequate water and fertilizer to avoid plant stress. When telltale enlargements are seen on the canes, remove them by pruning below the damage, then destroy the prunings.

MGs as First Responders

Here’s an important project for you: Help track the spread of Rose Stem Girdler in caneberries and roses.

If you suspect such a diagnosis while volunteering as an MG, or in your own berry patch or rose bed, get images and/or samples. Jot down a history with at least a few known facts, among them the cultivar name of the plants; when the damage was first detected; also, in which town the plants are growing. The most useful images to verify a diagnosis are the entire plant; a view of the affected cane(s); and a cut-away of the affected section.

Next, email the images and history to me ( After I verify your tentative diagnosis, I will notify both you and the entomologist. And, yes, continue to keep your eyes peeled for this new invasive pest, the rose stem girdler in the future.


Be cautious while researching rose stem borers. Several insects have similar common names which can lead you astray. (It may be risky to trust information that uses only a common name for the pest.) What you can tell clients, with confidence, about the rose stem girdler is that management is currently limited to removing and discarding (or burning, where allowed) the galled cane(s).

PNW Insect Handbook contains a brief entry. Chemicals aren’t currently listed for use in Oregon. (

– “Rose Stem Girdler, Agrilus cuprescens”: A useful one-stop resource concerning the beetle’s life cycle and damage to raspberries. The suggested pesticides are for use in Utah, not Oregon. (

Garden Insects of North America; Whitney Cranshaw; 2004; pages 476-477; a copy is in each of the metro MG offices.

– “Gnarly Roses – Rose Stem Girdler” (

Damage to cane berry foliage by adult rose stem girdlers.
Fig 1 – Damage to cane berry foliage by adult rose stem girdlers, Agrilus cuprescens, is typically minor. (Whitney Cranshaw, Colorado State University,
Larvae of rose stem girdlers, Agrilus cuprescens, weaken the cane which may then break.
Fig 2 – Larvae of rose stem girdlers, Agrilus cuprescens, weaken the cane which may then break. (James W. Amrine Jr., West Virginia University,
Photo of Robin Rosetta, OSU, teaching workshop about Boring Pests of Nursery Stock
Fig 3 – Robin Rosetta, Entomologist, NWREC, during a workshop about Boring Pests of Nursery Stock, 2017-10-13.

Click the link below for PDF containing the above text and all the images.

Rose Stem Girdler PDF

Natter’s Notes:
Pear Trellis Rust, a new disease

Jean R. Natter, OSU Master Gardener

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; 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” (

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:

  1. Collect and discard infected leaves.
  2. 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.”)
  3. 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 ( After I verify your tentative diagnosis, I will notify both you and the pathologist.

Image of Pear trellis rust
Fig 1: Pear trellis rust (Gymnosporangium sabinae) on the top leaf surface of edible pear tree; Multnomah County, OR. (Client image; 2017-09)

Fig 2: Pear trellis rust (Gymnosporangium sabinae) on the reverse of a leaf from an edible pear tree; Multnomah County, OR. (Client image; 2017-09)

Pear trellis rust
Fig 3: Pycnia (the black dots) of pear trellis rust on the upper leaf surface are involved in development of infectious structures on the underside. Bartlett pear tree; Milwaukie, Clackamas County, OR. (R. Frick-Wright; 2017-09)

Click the link below for a PDF containing the above text and all the images.

Pear Trellis Rust PDF


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Natter’s Notes: Heat Stress

Jean R. Natter, OSU Master Gardener

September 2017

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.

Signs of heat stress on dogwood leaves
Fig 1 – Superficial heat damage to dogwood leaves (Cornus sp.) which killed the green pigments near the leaf surface, thereby revealing the underlying red pigments. (J.R. Natter; 2017-08

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.

Vine maple leaves suffering from heat stress
Fig 2 – Vine maple leaves, damaged by heat and sunlight. Owner asked if the 19-year-old tree had a disease. Another vine maple, planted at the same time, was fine. (Client image submitted to Ask an Expert; 2017-08)

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)

Heat Stress on Hosta plant
Fig 3 – Hosta leaf, damaged in less than a day, by searing heat and low humidity that dried the tissue so rapidly it retained its normal color. The crisp, dry zone at the periphery is separated from healthy tissue by a narrow white zone. (J.R. Natter; 2017-06)

Click link below for PDF with additional information and images:

2017-09 Heat stress_Natter’s_Notes