Natter’s Notes
Jean R. Natter, OSU Master Gardener

As I write this in early September, fires are raging in much of Oregon and air quality ranges between unhealthy and hazardous due to nearby fires or at a distance by smoke plumes. //Unfortunately, due to turn around time for the metro MG Newsletter, you won’t receive this advice until long after it is the most useful. //But perhaps, during a future event, you’ll recall the most critical guidelines to help protect you and yours.

Perhaps the single best link for info is where there’s nearly endless info under the headings of Air Quality Information (AQI) & Health; Fires; Maps & Data; Education; International; and Resources. When the Home Page opens, click “Allow Location Access” to receive an air quality rating from the sensor closest to where you live.

Let’s review a number of other helpful links about smoke, health safety, and gardening.

The risks of particulate matter in smoke

“Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream. Of these, particles less than 2.5 micrometers in diameter. . . pose the greatest risk to health.” (

Note that only an N95 mask or respirator will protect your lungs from the smallest particles in wildfire smoke.

– Guidelines for working indoors or outdoors

Wait until the air quality reaches healthy levels to begin cleanup because disturbed ash particles can enter, and damage, your lungs.

– Ash disposal 

“Collected ash may be disposed of in the regular trash. Ash should be stored in plastic bags or other containers to prevent it from being stirred up. If you suspect hazardous waste, including asbestos, is present, contact your local hazardous waste authorities regarding appropriate disposal. Avoid washing ash into storm drains.” (

– What should I do about wildfire ash covering my yard and garden: “. . . a thin dusting of ash on plants (can still see the green color) isn’t likely to have long term effects on plant health before our fall rains wash it away, so no need to remove.

“Focus instead on clearing heavier amounts of ash from plants that you regularly come into contact through gardening activities, that are near windows, doors or air handling units, food producing plants, or plants that are of high value to you.

Don’t wash the ash down the storm drain. Instead direct the rinse water into low traffic grassy or ornamental areas (away from your fruit & veggie garden) which will act as a natural filter. Large amounts of ash can be gently swept into a pile, bagged in plastic sacks, sealed, and thrown away “

– Take precautions when wildfire ash lands on fruits and vegetables: “Avoid going outside to harvest while smoke lingers.” Rinse twice, once outdoors and again in the kitchen sink. If the produce is near a burned building, potential health-affecting toxins may be present. Peel produce like tomatoes, apples and root crops and strip the outer leaves of lettuces and other greens. For a more thorough cleaning, soak vegetables and fruits in a 10% white vinegar solution (one teaspoon vinegar to three cups water), which can lift soil particles off vegetables like kale, Swiss chard, savoy cabbage and fruit like peaches, apricots and nectarines.”

– Indoor Air Filtration: If you have central air conditioning, turn the control to “fan.” If you lack central air, consider a portable filter; the best kinds use HEPA filtration.

– Backyard Poultry in Fire-Affected Areas (UCCE; 2017): “In addition to all the destruction and inhalation of smoke associated with the recent fires in Northern California, one of the unfortunate legacies remaining are chemical contamination of land, soil and water. . . . Since backyard chickens are food animals with respect to egg and meat production, there is a risk that some of these substances may be ingested by chickens and deposited inside eggs which are then laid by the chickens. . . .  Unfortunately, there is limited scientific data on this issue. . . .”

At the time of this blog entry (2017), UCCE had several stringent recommendations concerning backyard poultry, including lab testing of the eggs. (

– Produce Safety After Urban Wildfire (UCCE; 2018): “Plant samples DO NOT show extensive contamination of produce exposed to wildfire smoke, and our findings suggest a low health risk from ingesting produce exposed to wildfire smoke.” (

– Safe Ash Clean-Up After a Fire: The greatest risk if from tiny invisible dust particles. Avoid cleaning up until air quality improves and it’s safe to be outdoors. (

– Fire Recovery Guide: What to do with your land after a wildfire.(California Native Plant Society; 2019;

– How to stay safe in a smoky pandemic: A Q&A.

Natter’s Notes

Jean R. Natter, OSU Master Gardener

As of early July 2020, there’s a new pest in town, and it goes by the name of Southern Pink Moth, alias Pyrausta inornatalis. The adult moth, found in SE Portland and submitted to the Oregon Department of Agriculture (ODA) was soon declared a new record for Oregon.

Less than two weeks later, a person from Milwaukie submitted an inquiry to Ask an Expert about a small pink moth resting on a salvia leaf in their garden. Its ID was soon verified as a Southern Pink Moth.

Adult Southern Pink Moth, Pyrausta inornatalis
The Southern Pink Moth, Pyrausta inornatalis, wingspan 13mm, was recently identified as a first record for Oregon. Host plants are annual and perennial Salvia species. (Image source:

Normal distribution of the Southern Pink Moth is across the southern states, and are most common in the southeast. On the west coast, only four other specimens have been documented, those from Southern California.

Precious little info is available about this small pest. The only official details I was able to locate stated that the adult moth is about a half-inch long, with a wingspread of 13mm.  The forewings are reddish-pink, the hindwings fuscous (brownish gray) and fringed. In the southern states, the adults fly March to November. The larvae bore into salvia flowers and flower buds.

Comments on a garden forum described the larvae is small (about a half-inch), almost translucent, and marked with dark dots. The larvae bore into the base of salvia flowers and flower buds. (As a result, they can be classified as budworms, and will annoy gardeners just as much as do the familiar geranium- and petunia-budworms.) Each pupa is in a filmy cocoon attached to the plant.

Larva of Southern Pink Moth, aka Salvia Budworm, Pyrausta inornatalis on the base of a bud of a Salvia plant
Larva of the Southern Pink Moth, aka Salvia Budworm, Pyrausta inornatalis, is classified as a budworm because it has the nasty habit of boring into the base of Salvia flower buds and flowers. (Image source:

Bacillus thuringiensis (Bt) can be used effectively against budworms but timing is critical. One must apply Bt as soon as the first flower buds are damaged. Better yet, apply Bt as the eggs start to hatch such that Bt-coated tissue will be the caterpillars first bite. Unfortunately, Bt degrades quite rapidly when exposed to sunlight, so repeat applications may be needed. Fortunately, Bt targets caterpillars without damaging other insects.

A more direct control method is to check buds for tiny holes and then removing (or squishing) those that are infested.  Other times, the caterpillar will still be on the outside of the bud. Cold winters are believed to kill the pupae, with temperatures of 20F or less able to reduce the next season’s population.

No control guidelines have been issued by ODA or OSU as yet. But since this is a newly introduced species, ODA would be interested in any reports and locations so that they can map the spread of this species. Contact ODA at 503-986-4636.


The Canadian Entomologist” –

BugGuide: Images of adults, larvae and pupae –

Multiple images at “Butterflies and Moths of North America” – lg larva

Discover Life: Images adults (resting and pinned), also a distribution map –

BugGuide – image of adult

BugGuide – image of larva

Natter’s Notes

Jean R. Natter, OSU Master Gardener

Once again, herbicide damage rears its ugliness in home vegetable gardens. A recent new release from the Oregon Department of Agriculture (ODA) reported that clopyralid has been detected in composted manure (referred to as herbicide carryover) from McFarland’s and Deans Innovations. (See news report:

Then, too, it’s important for gardeners to avoid inadvertent drift from glyphosate (in RoundUp products) and 2,4-D (a broad-leaf herbicide).  

Potato plant with leaves showing yellowing from herbicide drift damage.
Fig 1 – Glyphosate drift during the growing season. Glyphosate damage to plants (here, potato) during the growing season affects the newest cells first, this because glyphosate moves with the sugars. Look for yellowing of the new tip growth and at the base of expanding leaves. Glyphosate is the active ingredient in RoundUp and certain other herbicides. (Client image; 2020-06)  2020-06 client

Herbicide carryover is sneaky, a wolf in sheep’s clothing. Some gardeners who add composted manure to their soil will be rudely surprised when they see their damaged vegetables. Here’s the deal: Several active ingredients in commercial products (clopyralid and aminopyralid) persist for a year if not actively composted during that time. It’s currently illegal to use such products in home gardens and landscapes. Their main use is agricultural, on grains and pastures. The rude encounter that may confront gardeners most often occurs from free manures shared by farmers who are unaware of what their pest companies applied to their pastures and grain fields.  The herbicide on the grains passes through the gut and exits intact even while the livestock are unaffected. Thus, no one suspects mayhem is possible. (Images-

The most sensitive plants

Of all the plants you might grow, tomatoes and grapes are super-sensitive to just a whiff of errant herbicide. Then, too people want to know if they can safely eat the produce. Well, it’s like this: That’s not something the producer tests for; most likely they’ll suggest you discard it.

Rules to garden by

Inadvertent herbicide damage from any cause may be fatal or temporary. Drift during application is another possibility both during fall clean-up and/or weed-killing forays during the growing season.

A.) The best guideline for managing weeds: Kill ‘em while they’re young. Make it your rule to pull it when you see it. In other words, don’t tell yourself you’ll get it later. (Don’t bother asking why I say that.)

B.) Remove it before it blooms. (Seeds are the next developmental stage!)

C.) Don’t contribute to the abundant Soil Seed Bank. If buds or flowers are present, don’t throw it down with the thought “I’ll pick it up later.”

Test composted manure before you apply it

Do a simple bioassay (in several pots) before the compost is added to the garden. Or, if you’ve already added it, do the bioassay in the garden plot before you plant.  (Easy instructions are at

Responsible use of herbicides avoids off-target damage

Forsythia plant showing narrow, stringy growth which is an indication of herbicide damage.
Fig 2 – Glyphosate, applied during the prior fall, usually as a clean-up spray. Sub-lethal doses of glyphosate are easily delivered to off-target plants via a light breeze and/or spray turbulence. Look for clusters of narrow (stringy) growth, such as here on forsythia, sometimes called witches’ brooms, at the nodes during the spring growth surge. On roses, differentiate from similar-appearing rose rosette. (Client image; 2020-06) //

Responsible use of herbicides will avoid inadvertent damage to off-target plants.

1.) Follow all label directions, among them guidelines for personal protection.

2.) Never spray any pesticide(such as an herbicide or insecticide) if the temperature is, or will exceed, 80F that day.

3.) If you use herbicides, dedicate a sprayer for that purpose, marking it boldly to avoid accidents. In spite of a thorough cleaning of the sprayer and wand, a minute herbicide residue will damage ultra-sensitive plants, among them your tomatoes.

The Bottom Line: Be an aware gardener!


– “Gardeners often unaware of exposing tomatoes to herbicide” (

– Images of Herbicide carryover –

– “Landscape Plant Problems,” (MISC0194; WSU) A book in all metro MG Offices. See the section titled “Common Herbicide Damage.”

Natter’s’ Notes
By Jean R. Natter, OSU Master Gardener

Asian Giant Hornet on finger
Fig 1- An Asian giant hornet (Vespa mandarinia) resting on hand. (Photo: Takehiko Kusama; found in Niigata, Japan;

As is true with the introduction of numerous other invasive species, there is no real way to tell how the Asian giant hornets (AGH; Vespa mandarinia) arrived in the Pacific Northwest. Among the possibilities are via international container ships, imported products, travelers visiting the US, or people returning from another country. The hornets are native to temperate and tropical eastern Asia, including parts of Japan, China, India, and Sri Lanka. (


  • An adult is 1 1/4″ to 2″ long with a striped abdomen, orange head, and black eyes
  • AGH predators and are a potential serious threat to honeybees
  • AGH are ground-nesters, active from May to August
  • AGH has an annual colony, with cooperative care of the larvae by the workers.

Current distribution  

To learn where AGH have been sighted, see the map at  (Be patient; the map loads slowly.) The map will be updated as additional reports are made.

Life cycle

Fig 2
Dorsal view of an Asian giant hornet, Vespa mandarinia. (forestryimages – 5570920 Allan Smith-Pardo, Invasive Hornets, USDA APHIS PPQ,

AGH nests underground, often in abandoned rodent burrows. It’s an annual colony in which all, except the mated queens, die at the end of the season, August, in their native land. Metamorphosis is complete, with 4 life stages: Egg; larva; pupa, a non-feeding resting stage; and adult. The life cycle is about 40 days. The larvae are fed masticated prey by the workers. Adults are predators of many large-bodied insects such as grasshoppers and beetles. European honey bees (Apis mellifera) are very susceptible to attack.

In the spring, the overwintering queens locate a nest site and lay about 40 eggs. She rears the first generation which then takes over food gathering and larval care. The colony is aggressively defended throughout the season. In the fall, males wait at the entrance for the females, mate, then die.


  • This is definitely not an opportunity to be a hero. AGH’s half-inch long stingers can easily penetrate a traditional beekeeper’s suit. After your sighting is verified, let the pros do the heavy lifting.
  • Commercial traps for wasps and/or hornets won’t work because the holes are too small.

Critical cautions

  • AGH seldom sting humans but, when they do, the effect can be very serious.
  • Use extreme caution near Asian giant hornets. The venom is more toxic than local bees or wasps.
  • Beekeeping gear won’t protect you.
  • Persons allergic to bee or wasp stings should never approach an Asian giant hornet and/or its nest.
  • If you find an individual or colony, report it to your state Department of Agriculture immediately. (See the list of Resources.)

Opportunities for MGs

Well, as is common when a new invasive insect is reported, numerous “sightings” have been reported but only 2 verified. A newspaper in Louisiana even ran a story saying essentially “It’s not here.”

A prime opportunity for every Master Gardener is to share a research-based Teachable Moment with family, friends, and the public. One way is to provide a Pictorial ID of Look-a-Likes (at the end of this story) which compare sizes of insects which might be confused with AGH.


Asian giant hornet – A list of reliable resources related to this recent invader which includes a link to report a sighting in Oregon.

“Don’t panic over Asian giant hornet” (KGW8 News: text and brief video; May 4, 2020)  –

Natter’s Notes
Jean R. Natter, OSU Master Gardener

Ants! They’re players in perhaps one of the oldest good-news-bad-news stories ever.

The good news is that ants are valued for their beneficial activities. They add large quantities of spent plant and animal remains into the soil as they cultivate and aerate the soil. They also create channels for water and roots. They’re predators, too, and are members of nature’s clean-up crew, carting away debris that includes stray crumbs and dead insects.

The bad news is that ants sometimes get carried away. If they aerate the soil in and around a rootball excessively, water passes through the soil too rapidly to soak in, the plant wilts, and may die. Then, too, people take a dismal view of their uninvited excursions indoors when they trail across the floor, headed for wayward crumbs or the pet’s dish.

The preferred method to “get rid” of ants is to use a commercially formulated ant bait. The ants feed on the bait, then carry some back to the nest to share with the family. 

It’s critical to understand the meaning of “I want to get rid of ants; permanently” And they want it now! For the pest control professional, it’s we’ll stop them now, then we’ll return when they do.”

Here’s where Master Gardeners have a stellar opportunity to share a “teachable moment” during which they help a client, neighbor, or friend, understand the true outcome of managing house-invading ants. To be blunt, one can only stop the influx temporarily, until the next time. 

Too often, people will only spray the visible ants in hopes of stopping the invaders. Unfortunately, applying that spray wastes time, money, and effort. It only affects the visible ants, a mere 10 percent, or less, of the nest’s population.

Whenever people report they have “sugar ants,” it’s likely they have odorous house ants, Tapinoma sessile. They’re just an 1/8-inch, and dark brown to shiny black. A quick and-dirty method to quickly verify their ID is to squash one or two. Then, they emit a distinctive, unpleasant odor which has been variously described as rotten coconut or petroleum-like.

Fig 1. Odorous house ant, Tapinoma sessile, feeding at a liquid commercial ant bait such as Terro. Whitish objects are ant pupae, the life stage between larva and adult.
Fig 1. Odorous house ant, Tapinoma sessile, feeding at a liquid commercial ant bait such as Terro. The whitish objects are ant pupae, the life stage between larva and adult. (

Effective baits for odorous house ants include Terro (a borate-based liquid) and Combat (a gel with fipronil). I keep a 2-oz bottle of Terro on hand because odorous house ants are very persistent little fellows; they will return, repeatedly through the year. Common events that tend to trigger an invasion at my place include after heavy rains; following a serious cold spell; and during summer’s heat. Sometimes, I wonder if they’re just in the mood.

After bait is set out, monitor activity. Add fresh bait as long as the ants stream in. It may take weeks until the foragers stop feeding. If they’re still going strong after 3 weeks, try another bait, this time with a different active ingredient, perhaps hydramethylnon or indoxacarb.

Frankly, everyone must discard their fantasies about eradicating ants. The more accurate strategy, although it may be far less satisfying, is to make a plan to limit the indoor invaders.

Odorous house ants, Tapinoma sessile, are probably the most common house-invading ants across the country. They’re small, dark brown or black ants, 1/16- to 1/8-inch long, with the usual 3 body parts of an insect – head, thorax, and abdomen. The characters which define them as ants are a petiole (a narrow connection between the thorax and abdomen) and two elbowed antennae. The characteristic which differentiates them from other ants is that their single petiolar node is very small and hidden by the abdomen. Then, too, when they’re crushed, they smell bad. Some people say the rather penetrating odor is similar to petroleum or rotted coconut.

Illustration of odorous house ant, Tapinoma sessile; lateral view. A key identification character is the small petiolar node hidden by the anterior portion of the abdomen.

Fig 2. Odorous house ant, Tapinoma sessile; lateral view. A key identification character is the small petiolar node hidden by the anterior portion of the abdomen. (

An odorous ant colony is relatively small, to about 10,000 individuals, with multiple queens. Nests are usually outdoors just below the soil surface, underneath pavers, wood piles, or other debris. But nests may also be indoors, in a wall void or near warmth-emitting sources.

Odorous house ant populations enlarge by one of two methods: mating of winged reproductives or via budding of the colony. Budding occurs when a hundred or so workers transport several of the colony’s queens to a new site. With time, a series of closely related, cooperative colonies forms — a supercolony. No wonder we can’t eradicate ants!

Managing ants requires a multi-pronged approach.

1. Sanitation (clean up regularly), and store perishable foodstuffs in tight, rigid containers.

2. Caulk and seal cracks in the foundation or gaps where utilities enter structures.

3. Manage honeydew-producing insects on landscape plants: mealybugs, whiteflies, as well as both soft and cottony scales.

4. Use commercially-formulated ant baits, refreshing the bait as needed until the foragers stop coming, perhaps as long as 3 weeks.

5. Keep a supply of effective bait on hand to use the next time the ants return!

Ant baits act slowly because the foragers share with other ants within the colony. If a bait is ineffective after several weeks, switch to one with a different active ingredient.

Commercial baits are formulated such that the foragers will survive long enough after feeding that they have sufficient time to carry bait home to colony members. (Editor’s note: Recall that Master Gardeners do not suggest home remedies.) When it comes to odorous house ants, have bait at hand so that you can rapidly respond to their subsequent invasions.


Identification and habits of Key Ant Pests in the Pacific Northwest (

– “5 Most Common Ants in the Home”-– Ants:

– Odorous House Ant Identification Resources  –

– “Don’t Let Ants Come Over Uninvited: Pavement Ants and Odorous House Ants” –   Both ants are similar, about 1/8-inch long and a brown-black color. The main difference is that odorous ants have one petiolar node whereas pavement ants have 2. (See Figure 2, above.)

Natter’s Notes

Jean R. Natter, OSU Master Gardener

Many gardeners are trying to be environmentally sensitive in various ways, in particular, trying to conserve water use in the garden. Often, an in-ground sprinkler system (or hose-end device) is forsaken on behalf of soaker hoses or a drip sytem. Unfortunately, the entire project can go south in a hurry. Plants don’t thrive; some become puny, others wilt, and still others die.

Rather than explaining how to install a drip system, I’d rather discuss the guiding principles one must adhere to if the system is to be successful. In other words, if the gardener intends to obtain the abundant yield s/he expects. So, consider starting your first installation with a kit; it will contain all the needed parts and clear directions how to hook them up. Or, if you’re determined to dive in and set up everything from the start, you might want to obtain an instruction text or a manufacturer’s booklet, the latter often free at retail outlets, located with the irrigation supplies.

The important principles

Oh, yes. Here’s an overriding principle, whatever your method: On an individual dripline, always use component parts from the same brand because, unfortunately, one brand’s half-inch, etc., isn’t necessarily the same as another brand’s.

Disasters can be avoided by understanding a few basic principles, perhaps the most critical of which include the following:

– Output of an in-ground sprinkler system is gallons per minute.

– Output of a soaker or drip system is gallons per hour.

– Therefore, a drip system must run much longer than a sprinkler sytem to adequately supply plants.

– A drip system will put out uniform amounts of water per hour if pressure-compensated drippers are used.

– Further, it’s important that a drip line is on its own valve, not combined with sprinklers. To convert a sprinkler system to drip, all heads must be either changed to drip or capped off.

Soaker hoses

With soaker hoses, the output is inherent in the product. Output will be the same the length of the hose as long as it is on level ground and the water pressure is only sufficient to make the hose sweat. If a soaker hose sprays, the plants at the far end of the hose will receive less water than those at the beginning. Then, too, the hose may burst. (The exceptions are hoses which are designed to spray.)

Even though soaker hoses aren’t pressure-compensated, gardeners can gain that advantage from a commercially available plastic drip hose which has built-in pressure-compensated drippers at specified intervals. (Just make certain the intervals match the spacing for the plants at hand.)

Watering principles

These principles concern the plants and planting media:

– At sunrise, a plant’s root system should be fully moist and ready to meet the day. With elevated temperatures, stomates close; water uptake slows and may stop.

– Whenever you water, moisten the entire rootzone. In general, rootzones for seasonal vegetables and flowers go to 10- to 12-inches deep, trees and shrubs to 18 inches.

– As a vegetable ages from seedling to maturity, its root sytem gradually enlarges, both deep and wide. Irrigation frequency and duration must also increase. Similarly, with young trees, as the years go by, the number of drippers must increase, as must duration of irrigation.

– Water movement in soils (and container mixes) relies on pore size: The bigger the pores the better, and faster, the drainage.

The larger the soil pores, the more rapidly water moves. Sandy soil has large soil pores and must be watered frequently to maintain moisture within the rootzone. (It’s very similar with potting mixes.) In contrast, the small pores of clay limit water penetration; several on-off cycles may be required to moisten the roots and avoid surface runoff. Over all, the same amount of water is required for both kinds of soils.

Illustration showing water movement in soils: loamy sand, clay loam, and sand.
When water is applied as a point source, as in drip irrigation, it moves downward and laterally, according to the basic characteristics of the soil. Here, equal amounts of water were applied to each of the 3 points. Notice at the far right, what occurs when a “drainage layer” is added. Consider a layer of a different texture to be a “barrier.”
Illustration showing water movement through sand vs clay.

When water is applied as a point source, as in drip irrigation, it moves downward and laterally, according to the basic characteristics of the soil. In sandy soils and potting mixes, water moves downward in a narrow profile. The much smaller pores of clay soil results in a shallow but broad profile. Such profiles mean that more drippers are needed per unit area of sandy soil than in clay-based soils. (Source: “Drip Irrigation for the Yard and Garden”)

Questions and answers

Q: How long should I water?

A: Long enough to moisten the entire rootzone; on average to about a foot deep. To know for certain, go outdoors, stick a trowel in the soil or potting mix, and look.

Q: How often should I water?

A: Often enough to maintain moisture throughout the rootzone, thereby avoiding wilt. To know for certain, go outdoors, stick a trowel in the soil, and look.

 (A vegetable that wllts won’t be able to produce the abundant yields it could otherwise. This is true in spite of the plant’s apparent recovery after you dashed over to water it.)

Q: Is it true that a drip system is 90 to 95 percent efficient?

A: It might be that efficient; the answer is to moisten the entire root system but to avoid excessive runtimes such as 24 or 48 hours.

Fun for gardeners: Run a watering test.

Each gardener must determine for his/her own soil runtime and frequency for their own soil. And realize that it varies among containers, raised beds, and inground plantings. Run the drip system for an hour, stop for an hour, then check the soil with a trowel. How deep and wide did the water go?


– How-to booklets from suppliers available at retail outlets with drip irrigation supplies

– “Drip Irrigation for Every Landscape and All Climates” by R. Kourik (2nd edition; Metamorphic Press)

– “Drip Irrigation in the Home Landscape” – University of California; 2015

– “Drip Irrigation for the Yard and Garden” R. Troy Peters, Ph.D. WSU

Natter’s Notes

By Jean R. Natter, OSU Master Gardener

The Winter Cutworm, Noctua pronuba, was officially identified by Oregon Department of Agriculture (ODA) as an invasive pest in Oregon during 2012. Even so, the metro Master Gardener offices had been receiving complaints about their activity since 2001.

Plants were nibbled and/or destroyed from fall through the winter. At first, most folks assumed the damage was due to slugs and snails. However, the mutilation was different than the shredded tissue left behind by slugs and snails. Seedlings were toppled; emerging bulbs lost their heads and sometimes flower buds; and hostas lost leaf tips or had gaping holes. At my place, the pests would climb my 3- to 4-foot tall delphiniums to eat the flower bud at the tip of the stalk, sometimes settling down for a snooze.  To accurately identify the culprits, MGs in the offices had to activate their Master Gardener CSI mode.

The Winter Cutworm, Noctua pronuba

As you likely recall, caterpillars (Order Lepidoptera) have complete metamorphosis, with 4 life stages.  After the adults mate, the female lays several hundred eggs in a large tidy patch, most often covering, or nearly so, the surface of a leaf. The larvae (youngsters) hatch in 2 to 4 weeks. These caterpillars have different habits than most you are familiar with because they feed at night, whenever the temperature exceeds 40F, from fall through winter.

Perhaps the most effective treatment strategy is to go outdoors about 10 pm or so, with a cup of soapy water and tongs or a pair of gloves. As you trek through your plantings keep any eye out for caterpillars chomping at your expense. They may be anywhere from ¾ to 1.5 inches long, the size depending on their age. They’re often aligned with the edge of a leaf, or out-of-sight among the leaves. Hand pick and drop into the cup.

During the day, the larvae hide just under the soil surface, typically quite close to the stem of the victimized plant. Disrupting a bit of soil often reveals their hiding place.

The caterpillars of the Winter Cutworm (Noctua pronuba, aka the Large Yellow Underwing) appear bright green after they have molted; the color will gradually change to the various browns within hours. Source:

Fun for gardeners

This spring, as you prepare your garden, it’s very likely you’ll find a number of Lepidoptera pupae in the soil. Rearing the pupa is the best way to determine the parent moth’s identity.

To rear pupae, place in clear container with a porous lid, such as paper toweling secured with a rubber band. Set the container somewhere you’ll see it, but not in the sun, then wait for the adults to emerge.

The Gray Garden Slug

Slugs, especially gray garden slugs (Deroceras reticulatum) thrive throughout the northwest, feeding in gardens, greenhouses, roadsides and fields. They’re omnivores which feed on live plant material and much more, including mushrooms, dead slugs, earthworms. They have the ability to detect predatory carabid beetles through the use of olfactory cues. And, because slugs are hermaphrodites, reproduction is by cross-fertilization which may occur year-round when conditions are favorable. Mating occurs mainly at night with each animal capable of laying approximately 60-75 eggs (4 mm each) in a clutch, totaling about 700 eggs per year per slug. Each slug may live a year or two. ( reticulatum)

The Gray Garden Slug (Deroceras reticulum) is perhaps the most damaging slug in local gardens. Damage often avoids (stringy) leaf veins. Source: reticulatum

Fun for gardeners

If you happen upon a clutch of slug eggs – they’re transparent and either round or tear-drop shape – scoop them up with a bit of surrounding soil, put them in a clear container with a porous lid, and wait.


“Winter Cutworm: A New Pest Threat in Oregon” –

 “Slugs and Snails in Oregon” (ODA) –

“Snails and Slugs” –

 “Cornu aspersum” [The Brown Garden Snail, formerly Helix aspersa] –

 “Terrestrial Mollusc Tool” (USDA, University of Florida, & Lucidcentral: Incudes Fact Sheets with images; and a Glossary –

Natter’s Notes

Jean R. Natter, OSU Master Gardener

The Japanese Beetle (Popillia japonica) Eradication Project

Because Japanese beetles (Popillia japonica) typically feed in groups, they can decimate their host plants in short order. Roses are a particular favorite. (Image downloaded 2017-02-06:

The Japanese Beetle (Popillia japonica) Eradication Project of the Oregon Department of Agriculture (ODA) issued its most recent update in late 2019.

Overall, 95% of you [within the quarantine boundary] consented to treatment this year. With your help we treated 8,500 residences, 6 schools, 8 parks, 3 shopping centers, and 1 golf course. This came out to roughly 3,000 acres.

This year we trapped 7,749 Japanese beetles in the Cedar mill area. The overall number of beetles trapped in 2019 was a 56% reduction from the previous year. There was a 65% reduction in the number of beetles trapped within the 2018 treatment boundary as a result of the 2018 granular treatment and 2019 foliar treatment. We saw a 75% decrease within the boundaries of the supplementary foliar treatment.

In order to eradicate this pest, we will continue our treatment next season. We are thrilled with our success, and will be more aggressive with our approach next year while we have the upper hand. We are currently planning a larger treatment boundary for the 2020 eradication and will update everyone soon with the new map. We thank you all for your continued support with helping Oregon eradicate Japanese beetle.  It wouldn’t be possible without all of you!

We would also like to introduce the 2020 Japanese beetle team: Ashley Toland (Eradication Entomologist), Jessica Rendon (Japanese Beetle Eradication Specialist), and Austin Johnson (Japanese Beetle Outreach Coordinator). 

For more information on the Japanese beetle eradication project please visit our website:

New exotic Agrilus species beetle on twinberry in Portland

During 2019, a new exotic beetle was reported by the Oregon Forest Pest Detector (OFPD) program.

In May, an OFPD program graduate submitted a report to the Oregon Invasive Species Hotline after finding D-shaped exit holes and a green insect on a twinberry in her yard in southeast Portland. She recognized the signs as characteristic of insects in the genus Agrilus, which includes the bronze birch borer (A. anxius) and the deadly forest pest, emerald ash borer (A. planipennis).

Evidence of new exotic beetles (Agrilus cyanescens) attacking twinberry, a native honeysuckle, were found by citizen scientists in their Portland, OR, gardens during 2019. Fortunately, the beetles are not expected to become serious economic pests. But if you see the characteristic damage, report it to Invasive Species. (Image Camden, New Jersey, 2019:

The green insect she found was later identified as Agrilus cyanescens, an exotic beetle that has been established in the eastern U.S. since the 1920s, but this is the first detection in the Pacific Northwest. (

Then, in early August 2019, another OFPD graduate submitted a report to the Oregon Invasive Species Hotline after she noticed similar damage to a twinberry in her yard in northeast Portland. This was also later confirmed to also be Agrilus cyanescens. (

Known host plants in U.S. and Europe include those in the genus Lonicera (honeysuckles) including the native plant, twinberry (Lonicera involucrata Richardson). The Oregon Department of Agriculture does not believe Agrilus cyanescens will be an economic, ecological, or horticultural pest.

But, if you do notice any signs or symptoms of Agrilus cyanescens (branch dieback; 2 mm. D-shaped exit holes; serpentine-shaped galleries beneath the bark; and metallic green beetles feeding on leaves in April-May), we encourage you to submit a report. (  

The OFPD program trains volunteers to monitor for and report potential infestations of invasive forest pests. Thank you to these two Oregon Forest Pest Detector graduates for being on the lookout and submitting reports to the Oregon Invasive Species Hotline!  Details about the OFPD training program of citizen scientists are at

By Jean R. Natter

Group and water containers

In an emergency, as in you were caught off guard, realize that container-grown plants are more sensitive to cold than the same kind of plants in the ground. It’s because roots are more sensitive to cold than top growth. Root are essentially exposed when in pots but are protected by the large soil mass in the ground.

The first things that need attention are container-grown plants. Set them pot-to-pot tight, in a sheltered place, then throw frost-blanket or an old blanket over the group. You can protect hanging baskets similarly, by setting each one on an up-turned pot or bucket. Then, too, a large cardboard box will shelter an individual specimen nicely. Such emergency covers can protect against several degrees of cold.

But don’t use plastic sheeting unless you prop it above the plants. The reason? When the freeze arrives, any plant tissue touching the plastic will die.

If you have sufficient time to think ahead, make certain all the containers are well-watered, even those you’re unable to move because of their size or weight. Even though it may be hard to believe, moist growing media is less likely to freeze than if it’s dry. (That’s true for all plants, whether in a container or the ground.)

And if you forget to set the plants in a sheltered site, you may still be able to protect them if you act just before dawn, the time when the lowest temperature occurs

The effects of a freeze

Frozen plant tissue turns dark and becomes soft to mushy. The reason, in most cases, is that ice crystals form inside the plant cells during a freeze and, then, perforated the cell walls. If you see minor freeze damage on a treasured plant early in the day, you may be able to limit potentially serious damage by shading the damaged area from direct sunlight. With shade, the intracellular ice crystals thaw slowly and will be less likely to rupture cell walls than if they thawed rapidly.

Camellia flower with frost damage

Camellia sasanqua, a winter-flowering shrub with flower damage from freezing temperatures several days prior. The damaged tissue is somewhat brown and appears moist; the petals flop. (J.R. Natter; Dec 6, 2009)

Some generalizations

  • Get ahead of the game by adding several inches of mulch on the soil around cold-sensitive plants.
  • In general, recently installed plants, even if a kind that’s normally hardy, are more likely to be frost-damaged than those planted a year or more previously.
  • If a shrub or tree is seriously damaged during a freeze event, wait to remove damaged wood until after new growth begins in the spring. Then, cut at least an inch below the dead section. In the meantime, the damaged parts will provide a small amount of frost protection to the plant.
  • If a hard frost, extended or not, is predicted, move sensitive plants into a shed or garage for the duration. Water, if needed, during their stay. (One year, several of my plants were still in good condition after 10 days in an attached garage with only one small window.)
  • If a hard frost, extended or not, is predicted, move sensitive plants into a shed or garage for the duration. Water, if needed, during their stay. (One year, several of my plants were still in good condition after 10 days in an attached garage with only one small window.)


Winter Injury of Landscape Plants in the Pacific Northwest: (PNW Plant Disease Handbook;

Abiotic Disorders of Landscape Plants (A copy of this book is in each metro MG office; pages 133-138 and 175-176.)

The following two Natter’s Notes have many images of cold damage but, unfortunately, are old enough that some of the listed references no longer exist:

Natter’s Notes: “Cold Damage – Lessons from the Garden” (In metro Mg Newsletter, January 2011. pages 4-5)

Natter’s Notes: “December’s Cold Damage to Plants” (In metro Mg Newsletter, February 2010, pages 8-9)

Freezing winter weather takes toll on home landscape plants: OSU eNews, (Reprinted in metro Mg Newsletter, February 2010, page 10)

Western Red Cedars Dying

Jean R. Natter, OSU Extension Master Gardener

Failing trees have been a persistent topic in MG Clinics and on the online Ask an Expert service during the past 6 or 7 years. Overall, it’s been an issue of continuing higher than normal temperatures combined with less than normal rainfall. Then, too, few homeowners realize that the continuing heat and drought affects their landscape trees in spite of being watered with the lawn sprinklers.

Fig 1 (right): Western red cedar, Thuja plicata, with thinning crowns most likely due to climate changes and continuing drought. (“Why is My Tree Dying? – Western Redcedar (Thuja plicata)” – April 2019;

In order for trees to thrive, they should be irrigated separately from grass, with at least one watering to about 10 inches deep to the soil below the canopy every 3 weeks during our dry season. Indications of a water deficit is revealed by multiple signs and symptoms, among them wilted leaves; leaves with curled and/or dry edges; early fall color; leaf yellowing and early leaf drop.

Foresters have been puzzled by problems with Western Red Cedar (Thuja plicata) which normally do well on moist sites. The most recent thought is that these trees are finally succumbing to stress from many successive years of heat and drought stress.

Several recent Ask an Expert responses have noted “We are getting many reports of western redcedars dying this year, and the consensus seems to be that the combination of extreme heat and drought experienced since around 2013 through last summer is an important factor. Although this summer was mild, it often takes a year or so for a tree to show any signs of distress from drought.”

Another expert, in a response to a different client, said it this way: “Western redcedar are dying in some areas due to a complex of climate stress and other issues, with no clear primary agent of mortality.”

Two Western Red Cedars at the Oregon State University campus

Fig 2 (right): Two healthy Western red cedars (Thuja plicata) on the Oregon State University campus, southeast of Fairbanks Hall. ( OSU Landscape Plants;

In general, the foresters responding through Ask an Expert are including a link to a publication released in April 2019: “Why is My Tree Dying? – Western Redcedar (Thuja plicata)” which, in summary, states:

Top-dieback, branch mortality, crown thinning and whole-tree mortality in all ages of western redcedar has [sic] been observed recently at lower elevations in the Willamette Valley and beyond. Although it is common to see ‘spiked’ or dead tops in older western redcedar, usually there are living lateral branches and a functional crown. No single factor has been identified in these more recent die offs, but a combination of poor or unsustainable growing conditions may be to blame. Redcedar may simply be growing in areas or within microclimates outside of their preferred range or areas that are no longer sustainable for long-term growth under current climate conditions.

Then, too, it suggests that alternate species for red cedar on generally dry sites include incense cedar, sequoia, and big leaf maple; on more moist sites which don’t dry out in the summer, western white pine, maple, alder, ash, or cottonwood.


– Abiotic Disorders of Landscape Plants” (#3420 UCANR); pages 51-59. A copy is in each of the metro MG offices.

“Thuja plicata (Western Red Cedar)” outlines a basic description of this native conifer (50-70 feet, or more) which thrives in sun to part shade on moist soils, with numerous images of a healthy tree.

– “Why is My Tree Dying? – Western Redcedar (Thuja plicata)” – April 2019 –

– “Pruning Drought Stressed Shade Trees” encourages caution to remove as little wood as possible from a stressed tree, in part because it already has limited reserves, with precious little remaining to “spend” on otherwise unneeded wound repair.