Inquiries from Ask Extension

Jean R. Natter, OSU Master Gardener

Houdini fly in Multnomah County? (Multnomah County; 2021-04)

Q: We noticed these flies in our mason bee tubes. After some googling we think it might be a Houdini fly. Is this something that needs to be reported? Are there steps we need to take to help the bees?

Houdini fly.
The Houdini Fly, Cacoxenus indagator, was recently identified as an invasive pest in Oregon; it is a kleptoparasite from Europe which lays its eggs on the pollen cake meant for a Mason Bee, thereby starving the bee. (Client image; 2021-04)

A: Thank you for the excellent images of the Houdini Fly, Cacoxenus indagator, recently identified as a serious, exotic insect pest of Mason Bees.

Here’s a pest alert about the Houdini Fly with good images, plus suggestions for people who keep mason bees. See “Houdini Fly Found in Washington” –

This website provides additional details about protecting your Mason Bees:

Because the flies move slowly, you’ll be able to collect several samples to submit for ID. Refrigerate them in a small covered container until submitted. (Feel free to crush any extra flies you may discover later.) 

I suggest you report the flies to the Invasive Species Hotline; call 1-888-468-2337 or use their online form at

Overrun by little moths! (Lane County; 2021-05)

Q: The east-facing side of my Coburg, OR, home has hundreds of little moth-like bugs lighted on it. They started to appear in early April, when the weather started warming up. Can you tell me what they are, and how I can control their population?

A: The small insects are called Drain Flies, a Psychoda species. Other common names for them are Moth Flies and Filter Flies.

Drain Flies are most commonly found indoors near moist areas, such as sinks, wet-mops that have been wet for several days, or in damp basements. These flies are poor fliers and are often found near their source.

Potential sources outdoors include a nearby area that remains moist for an extended period. Places to investigate as a source include roof gutters clogged with debris, at the base of downspouts, a wet spot near a leaking spigot, moist compost, and/or dirty garbage cans.

Drain flies are considered to be nuisance pests because they don’t cause damage to people, their pets or belongings. The remedy is to locate and eliminate their source. No pesticides needed. A wet-dry shop-vac could help decrease the number of the adults but will do little as long as the moist breeding site remains.

White Egg Like Spots (Clackamas County; 2021-05)

Q: What are these white egg-like spots on my bush?

Azalea Bark Scale on branch of shrub.
Azalea Bark Scale are small white, sedentary, sucking pests which slowly drain the vitality of several shrubs, especially Azalea, Pieris (Andromeda), and Rhododendron. (Client image; 2021-05)

A: Azalea Bark Scale are small sucking insects which can cause their most common victims — Azalea, Pieris (Andromeda), and Rhododendron — to slowly decline over an extended period of time. (Certain other shrubs may also be affected, but far less often.)

You can physically attack those small beasts by rubbing them off with a toothbrush.

Then, because you’re very likely to miss the small, newly hatched larvae (youngsters), follow-up with a commercial Insecticidal Soap Spray, diluted according to label directions. Coat all surfaces of the stems and branches thoroughly, front and back, top and bottom. Then repeat the spray, as needed, through the following months.

Woolly aphids on Old Apple Tree (Multnomah County; 2021-05)

Q: Our old apple tree has wooly aphids, how can this be treated!

A: Woolly apple aphids, Eriosoma lanigerum, are impossible for home gardeners to eradicate. The reason? The main colony of woolly apple aphids are on the tree’s roots whereas only some move to the top growth every spring. The result of an infestation is a gradual decline in tree vigor. In spite of that, fruit yields are often large enough for a family’s use.

Our official Insect Management Handbook says “This aphid is considered a minor pest in the PNW. If colonies are found on trees, they can be physically removed. Many Geneva and Malling-Merton rootstocks are resistant.”

You can limit the damage somewhat by spraying commercial insecticidal soap, prepared according to label directions, directly on the woolly aphids you find on the bark, then repeat as need through the growing season. Other pesticides that might be considered are rated as “highly toxic to bees.”

No pesticides are available for soil treatment.

In commercial apple orchards, woolly apple aphids would be avoided by not planting susceptible kinds of apples. You might consider planting a new apple with one of the resistant rootstocks mentioned above.

2nd Q: We’ve just tried some Safer Insecticidal soap and will reapply again tomorrow.
Last year the tree produced lots of apples, this year we see very few coming. Will these aphids harm surrounding plants?

2nd A: Woolly apple aphids are specific to apple trees. They won’t damage other plants.

It’s unlikely you’ll need to use insecticidal soap daily. Limit its use to when you see new aphids, then spray only the fresh white specks.

This year’s small crop may be a normal event because apple trees tend to “alternate bear.” That is, after they produce a huge crop, the following year they’ll produce a small crop.

But, there’s a simple trick to even out production one year to the next. It’s called thinning.

To thin, when the fruit is thumbnail-sized, remove the excess to a reasonable number. In general, the goal is to keep only one fruit per cluster. However, if what remains may be too heavy a load for the branch at harvest, remove even more of the as yet undeveloped fruits.

The result of thinning? Even though you’ll have fewer apples at harvest, they will be large for their kind and high quality.

ID what ate my dahlia? (Multnomah County; 2021-05)

My dahlia was about 8 inches tall and had a quick death, did some digging and found these little white worms around the stem looks like they ate it. What are they? What’s the best way to get rid of them?

A: Thank you for attaching the images. The 1st image (white larvae and wet soil) and the 3rd (rotted stem) are the most telling.

It’s very likely the stem rotted from excessively wet soil, then the larvae came in to clean up the debris. It’s also likely that the tuber is also rotted.

After dahlias begin growing in the spring, they do well with moderately moist soil.

See Dahlia Culture — 

Spring’s Earliest Pests: Aphids

Jean R. Natter, OSU Extension Service Master Gardener

After all we’ve been through this past year, what with the COVID pandemic and quarantine, gardeners are getting itchy about planting. I was, too, until the middle of March when night time temperatures dropped into the 20s in mid-March. I imagine it was even colder for many of you.

Even though my dreams of planting soon were dashed – tomatoes, peppers and eggplants need consistent night temps of 50 to 55F – my thoughts soon drifted to insect pests, then to their natural enemies.

The leaders of the potential pest parade will be various species of aphids, also several kinds of caterpillars, the latter specializing on crucifers (cabbage and kale crops), among them cabbage whites (Pieris rapae) and several species of cabbage worms. Unfortunately, various species of both kinds may be present throughout the growing season.

Oh, and let’s remember that slugs and snails are ever-present through the season.

So, let’s review a few things, including safe management.

We should begin with the preferred pest remedy: An alert gardener, ready to spring into action, who knows which natural enemies (NEs) are allies, and who acts promptly. Prompt action, aided by the numerous beneficial insects already present, means pesticides are often unnecessary.

Aphids are small, soft-bodied, pear-shaped pests that tend to cluster on new growth which they sometimes distort as they remove plant sap from plant parts. (If you have roses, you’ll likely see them there first.) Aphids may be almost any color, perhaps even spotted, banded, or striped. Most infest buds, flowers and new leaves, often distorting them which sometimes mimics disease.

Caterpillars, also called chewing worms, are the plant-munching larvae of various moths and butterflies. (More about caterpillars next month.)

Recall that pest control is a lot like mowing the grass; it requires repetition. You get to do it over, and over, and over, again. (sigh)
Always start with the safest methods
, namely search-and-destroy missions throughout the garden or ornamental planting. Reserve pesticides for those instances when the pests get out of hand. Always identify the pests and apply the appropriate product only to the hot spots of pest insurrections. Then, too, use pesticides strictly according to label directions.

As you likely know, aphids of one kind or another are present year-round locally. They’re perhaps the most common plant pest you’ll encounter. Aphids pierce plants with their hollow mouthparts to withdraw sugary fluids. Often, they’re undetected until leaves curl or the plant is coated with sticky honeydew (aphid excretions). Repeated sharp water sprays are often sufficient against aphids. Or increase your fire-power with a commercial insecticidal soap such as Safer’s, mixed according to label directions. For soap sprays to be effective, they must contact the pests. No home remedies, please; they may damage plant tissue.

Fortunately, you have lots of free help readily available among insects. Your skilled assistants (the NEs) are typically most active during the morning and late afternoon but hide during the heat of the day.

Four photos show life cycle of Lady Beetle (Hippodamia convergens). Egg stage, larva stage, pupa stage, adult stage.
– Life cycle of Lady Beetle (Hippodamia convergens) (Source: A Pocket Guide to Common Natural Enemies [revised 2021]

Ladybugs (aka lady beetles) are the most colorful aphid killers. Most of these ¼-inch, glossy, hemispherical adults are red, often dotted with black. The ladybug’s elongated ¼-inch youngsters are quite different, resembling the tiniest of alligators. Their soft bodies are slate-gray or black with tufts of dull orange hairs. Both adult and child chomp on aphids. In time, even the aphids’ toes will be gone.

In spite of advertising hype promoting sales of ladybugs, realize that they typically leave for other bug-filled garden. But, if you are determined to purchase natural enemies, know that lacewings are more valuable

because their diet is more diverse. After lacewings decimate the aphids, they’ll switch to other small, soft-bodied pests including young caterpillars, various insect eggs, or even mites.

– Green Lacewing adult (Chrysoperla species) compared to fingertip. (Source: A Pocket Guide to Common Natural Enemies [revised 2021]

Hereabouts, lacewings are naturally present year-round. You’re most likely to see the fragile, 5/8-inch, filmy-green adults fluttering from shrubs at dusk. The larvae are the aphid eaters, though. Look for 3/16-inch tan or gray, soft-bodied creatures similar to ladybug larvae but with Jaws that resemble old-fashioned ice-tongs. Eggs are easy to recognize, they’re small, greenish-white, and mounted on hairlike stalks.

Worm-like larvae of certain flies also kill aphids. The largest larvae (Syrphid flies, aka flower flies) are about 1/4 inch long but are difficult to spot because of their greenish or grayish color whereas the tiny, almost dot-sized, orange fellows (Midges) are easy to spot because of their color. All such larvae search for lunch by blindly groping. Just as do lacewing larvae, fly larvae pierce aphids, drain them, then abandon the empty carcasses.

Tiny, non-stinging wasps kill aphids, too. After they insert an egg into an aphid, their larva dines inside the aphid as it gradually transforms into a bloated, papery shell. Some weeks later, an adult wasp exits through a circular hole created in the aphid’s empty exoskeleton.

Impatient folks who would rather fight than wait for NEs to break into action need to understand that water,plain, or doctored with insecticidal soap, kills aphids but is safe for most helpful insects. Commercial pesticides are useful for uncontrolled hotspots but most kill more NEs than pests. When a pesticide is needed, consult with a garden center, then always follow label directions precisely. Because sprays rely on contacting the aphids, act before the pests are protected within crinkled and distorted leaves.

Power-assisted blasts can help you gain control quickly.Forceful water sprays are appropriate for sturdy plants whereas gentler handling is better for plants with rather soft tissue, among them such as violas and leafy lettuces. Aphids are so soft and squishy that harsh water sprays will injure them such that they’re unlikely to return to the plant. But, because healthy, intact aphids can give live birth to an aphid every 20-30 minutes, you’ll need to repeat the spray anyway. With more potent products, the goal is to only spray enough to coat the pests.

Realize that plant damage is possible with all pesticides, including soaps.That’s especially true if the spray is applied on a sunny day or was inadvertently – or not — mixed at too strong a rate. It’s always wise to test the spray on a few plants, then check for damage several days later. Browned or burned plant tissue is obviously serious whereas soap smudges are merely unsightly.


  • Sustainable Gardening: The Oregon Master Gardener Handbook
  • Book: Pests of the Garden and Small Farm (ANR #3332; University of California)- Available at booksellers.
  • Book: Natural Enemies Handbook {ANR #3386; University of California)- Available at booksellers.

Coming next month: Cabbage Worms and Other Chewers

Natter’s Notes

Jean R. Natter, OSU Extension Service Master Gardener

Once again, the annual Gardeners’ Itch is surging. That’s in spite of the mid-February snow storm that likely afforded one last browse through catalogs, or possibly created a faint cloud of apprehension as you wondered why you bought so many seeds.

Start your project with new containers or thoroughly wash used ones. Just about anything will do as long as it’s at least two inches deep and has drainholes. Plastic containers are a good choice as they slow moisture loss. Consider multi-celled propagation trays; 6-packs you’ve saved from previous years; individual small pots; or use 4- or 5-inch pots as community pans, each one with a different kind of seed.

If you’ll use individual peat pellets, pre-soak well prior to seeding. Then set them side-by-side, one pellet touching the next, thereby increasing moisture retention a bit. After the seeds sprout and begin to develop roots, the pellets will dry rapidly. You might consider a multi-cell tray with individual units the perfect size to hold just one pellet.

The method using individual peat pots is similar. Pre-soak the pots, fill with seeding mix, plant the seeds, then water to settle the mix. But when you transplant to the garden, strip off the peat pot to allow the roots unhindered access to the garden soil.

Fill your containers with a sterile, fine textured growing medium. Do it the easy way with a commercially-packaged seed-starting mix because they’re formulated to drain well in shallow pots. A bonus: The mix is sterile, that is, as long as you don’t set the filled pots on the ground.

Instead of scooping potting mix to fill the pots, use a professional trick to ensure the media remains light and airy, two qualities which guarantee good-sized air spaces that, in turn, allow excellent drainage.

To do so:

a. Set your containers in a group, the sides touching each other.

b. Slightly moisten the media: Add hot water and toss gently to combine, until the media is barely moist throughout.

c. Pour the barely moist media into the containers.

d. Level off excess media with the side of your hand. 

e. Pick up each container and gently tap it onto a hard surface 3 times from a height of 4 inches.

f. Lightly tamp the surface of the media in each container, just enough to level the surface.  (An excellent “tamping tool” is the bottom of another container that matches the available surface area.)

Sow your seeds on the surface of the mix.  Drop one or two seeds onto the surface of each of the smallest units.  If you’re using 4-inch pots, sparsely sprinkle about 20 seeds over the surface. With still larger containers such as a nursery flat, first create shallow rows, then seed. 

Cover the seeds with moist media, the depth to match the diameter of the seed.  Large seeds – such as beans, corn, radish, and squash – are best sown directly into the garden but, for these, wait until the soil is warm enough for rapid germination. Corn and basil planted early will fail.

Water each container thoroughly by setting it in water. Remove when the surface glistens with moisture, allow to drain, and set in a bright, moderately warm place. Alternately, group the pots in a nursery flat and use a gentle spray, moving it back and forth, to thoroughly moisten the media.

Create a mini-greenhouse, of sorts, for your seeds by slipping its pot into a clear container of some sort.  Match the “greenhouse” to the size of your project.  Use what you have at hand, perhaps a clear plastic bag which rests on bamboo sticks to allow head room; or clear plastic storage boxes such as those for shoes and sweaters.

Set the ‘greenhouse’ in a warm but not sunny place. If needed, lift the cover briefly to vent excess moisture that accumulates on the insider.

Spindly seedlings result due to inadequate light at a window, (Client image; March 2017)

Seedlings require bright light! As soon as the seeds sprout, the main challenge is to provide enough light to develop sturdy seedlings.  Sunny windowsills rarely provide adequate bright light for seedlings.

Some folks use a commercial light stand but you can substitute a 2-tube fluorescent fixture suspended 2 inches above a workbench holding the plants. Suspend the fixture on chain so that you can adjust the height as the plants grow. My old-school strategy of one cool white and one warm white tube works well. The plantlets will thrive with 16 hours of light a day.

Seedlings will also benefit from a slightly lower temperature at this stage. On average, daytime temps of 65 to 70°F and nighttime temps of 55 to 60°F are adequate. Then, too, if seedling roots dry out, they die! Watering from the bottom is a gentle method, but dump the excess within 20 minutes.

Seedlings also require fertilizer! Begin fertilizing when the cotyledons ( seedling leaves) are flat out. Use fertilizer-enriched water at half-strength for every other irrigation. And always transplant seedlings, either to a larger pot or to the garden, when the first set of true leaves expand.

Always transplant seedlings when the first set of true leaves expand. But recall that you’ll need to harden off the seedlings prior to planting outdoors. Hardening off means to prepare tender, indoor-grown plants for a harsher life outdoors. (See “Sustainable Gardening.”)

And finally, be aware of the potentially unhappy side of gardening: Herbicide carryover in manure compost. And that’s true whatever the source, free or commercial. I recently responded to an Ask Extension inquiry from a gardener whose vegetables were affected during 2020. (See resource list for online links.)


Natter’s Notes

Jean R. Natter, OSU Master Gardener

In case you haven’t been outdoors recently, you need to know weeds are growing in spite of the soggy soil from all the recent abundant, rainfall. So, let’s review a few strategic management strategies for successful weed control in gardens and landscapes. As you may know, the PNW Weed Management Handbook (see resource list) has a thorough overview of the subject.

Annual weeds are classified as warm-season or cool-season plants, with each kind genetically destined to germinate (sprout) in the appropriate season, then survive for a year or somewhat less. The same categories are assigned to perennial weeds but these are considerably more long-lived, persisting for 3 or more years.

As a result, gardeners must be vigilant year-round.  

Several key principles limit weed populations in gardens and landscapes, among them these:

– Kill weeds when they’re young; ten fingers are always at hand.

– Don’t allow weeds to set seed.

– Annual weeds will die when cut just below the crown.  Use a knife, or any one of various hoes – standard garden hoe, diamond hoe, or a scuffle hoe.

– Perennials will re-grow when cut off, even if covered with mulch  Vigorous kinds will make it through a lasagna garden; and may lift landscape fabric and/or polyethylene sheeting. 

– To kill perennial weeds, you must starve the roots; to do so, remove all green growth every week for as long as it takes, very likely several years.

– Herbicides are rarely a “once-and-done” remedy.

Gardeners can make good use of creating a “stale seedbed” before planting a flower or vegetable bed, or even a lawn. The reason?  Hundreds of dormant seeds — termed the “Soil seed bank” – have been deposited in the soil during years and years of poorly managed, or unmanaged, weeds. Whenever soil is disturbed, some of those seeds are brought near the surface where they germinate because they are exposed to light, also appropriate temperatures and moisture.  

Start a stale seedbed a month or so prior to the desired planting date, thereby allowing for a cycle or two removing weed seedlings.  Do everything needed to prepare the planting bed: dig; remove obstructions and weeds; amend the bed; level the soil; then moisten the soil to settle it and allow for germination.  As soon as a good stand of young weeds about inch tall is present, destroy them using your preferred method: hand, hoe, flamer or, if you must, herbicide. 

The earlier a stale seedbed is started, the more germination cycles possible, the fewer weeds will be present to steal water and light from the desired crop.  Next, seed or transplant your veggies or flowers with minimal disruption of the soil, and deal with any seedling weeds promptly.

With perennial weeds, choose among these destructive techniques:

1. Dig it out; repeat as needed.

2. Cut it off; repeat as needed.

3. Herbicides are effective if the right kind is used according to label directions; repeat as needed for re-growth and/or use #1 and #2, above.

Tools to help limit weeds:

– Hands

– Hoes

– Herbicides, organic or synthetic: Contact products kill only top growth (fine for annual and seedling weeds); systemic products translocate (move) into other plant parts, sometimes into roots.

– Mulch, with the understanding that new weeds, in the form of seeds, will continue to arrive via clothing; muddy boots; new plants; birds; hitchhikers on mowers; or may be blown in.

– Flamer

Some trees are known to put up root suckers after they are cut down, among them are such broadleaf trees as ash, aspen, cottonwood, flowering cherry and poplar.  Conifers won’t re-sprout, even if the roots remain in the ground.

To limit root sprouting after a broadleaf tree is removed:

– Cut down the tree as soon as the new leaves have fully expanded in spring. 

(Principle: The tree used most of its reserves for new foliage, thus the stump/roots will put up fewer sprouts than if the tree is removed later in the season.)

– Immediately after the tree is cut off, paint a 2-inch-wide band of the other edge of the cut surface with an herbicide such as triclopyr or 2,4-D, following label directions.

– Remove new shoots as soon as they’re seen:

       – The more often new greenery is removed, the better the chances of decreasing the roots’ reserves; once a week is a good plan.

       – The longer new growth remains, the more reserves it sends to the roots, thereby extending the battle. 

– Be persistent and you will win; pause for a season and you lose.


– Sustainable Gardening (your MG Handbook)

– Weeds and Your Garden:;sequence=1

– PNW Weed Management Handbook: Online at  

– PNW Weed image gallery (from the 2010 Weed Handbook): Organized by common name, each weed with 1 to 3 images: seedling, flower and/or mature.

– Weeds and other unwanted plants (text and images)

Natter’s Notes

Jean R. Natter, OSU Master Gardener

Early in 2020, a new pest of mason bee, Cacoxenus indagator, was identified in Washington State for the first time. It’s often referred to as the Houdini Fly because of the unique way it escapes from the mason bee’s nesting cell. It’s also nicknamed the Red Devil due to its large red eyes, or just Devil Fly. It’s presence in Oregon is suspected to but not yet verified.

Fig 1 – houdini fly, BugGuide

The arrival of the Houdini fly is suspected to be an unfortunate example of moving bees without carefully inspecting them and their nests prior to the move. “In New York, the first two records were in 2011, although it may have arrived there earlier. It had presumably come there from Europe, probably someone moving an unclean nest block,” said Josh Vlach, from the Oregon Department of Agriculture during an interview by Andony Melathopolous during PolliNation Podcast #154 (2020).

What damage does the fly cause?

“The flies don’t actually attack the bees; they’re kleptoparasites,” continued Vlach.  “The fly is in the same group as Drosophila fruit flies that fly around a bowl of over-ripe fruit.” They closely resemble their fruit fly cousins – about the same size, with large red eyes, but otherwise a dull brown color. They move rather sluggishly, and are often seen near the entry to a nesting tunnel.

After the mother bee leaves the nesting tunnel, the Houdini fly enters the tube, lays eggs on the pollen ball, then quickly exits. After the nesting cell is closed by the mother mason bee, the fly larvae hatch and eat the pollen ball. As a result, the mason bee larva starves.

Fig 2 – Cacoxenus indagator

 How to recognize an infestation

Telltale signs of these kleptoparasitic flies are sticky clusters of small white maggots in a nest cell. The bee larva is dead or missing. [Note: Kleptoparasite may be spelled with a “c” as in cleptoparasite.] But beware! Another pest, a parasitoid, produces a similar cluster of small white larvae.

Be aware of a look-alike infestation by tiny wasps

Unfortunately, to the untrained eye, the white larvae of Monodontomerus wasps could be mistaken for Houdini fly maggots. These small black wasps – sometimes referred to as ‘Mono’ wasps – are much more active than adult Houdini flies. The adult wasps erratically flit about. They’re parasitoids which lay multiple eggs in a single mason bee larva. However, the end point is the same as with the Houdini flies: Dead mason bees.

Management suggestions for Houdini flies (WSDA Pest Alert)

–  Harvest mason bee cocoons – Open mason bee nesting materials before they emerge in the spring and destroy Houdini fly maggots.

– Control adult mason bee emergence – If you cannot open nesting materials, place your nesting materials in a fine mesh bag and close tightly. As the bees emerge, release the mason bees daily and kill any Houdini flies.

– Only use nesting materials that allow you to open, inspect, and harvest cocoons. Visual inspections can greatly reduce Houdini fly populations. (Ed. note: Kill the larvae on sight.]

– Before purchasing mason bees, ask the provider how they harvested and whether they inspected the cocoons for Houdini fly.

Only purchase pest-free mason bee cocoons.

A few final words

– WSDA suggests: “Please do not unnecessarily move bee blocks or boxes around.”

– If you’re having sizeable losses of healthy mason bee cocoons, seriously consider modifying your materials, methods, and procedures.

– A viable alternative to using clustered artificial housing for native bees is a healthy environment with modest-sized patches of suitable flowering plants that provide a year-round succession of bloom

– Perhaps the best habitats for native bees are patches of bare soil, along with naturally-occurring tubes, among them spent plant stems and old holes from boring beetles, all in a pesticide-free location.


– PolliNation transcript #154 – An interview with Josh Vlach, ODA. (

– “Parasitoids and Cleptos”- [Caution: “. . .artificial bee nests and hotels may be preferentially used by introduced bee species and native wasps, rather than native bees]

– Video: Houdini fly, a kleptoparasite of Osmia –

– Video: Life cycle of Montodontomerus wasp – 

– “How to Manage the Blue Orchard Bee”- An overview.

– “Orchard Mason Bee” (10-Minute University) — Orchard Mason Bees (

 – Pest Alert WSDA//  Houdini fly found in Washington; images and 2 videos:

Video: How does Cacoxenus escape?; Video:Devil fly on nesting tubes. “The accompanying fauna of Osmia cornuta and Osmiarufa” – Pests of Osmia in Europe, with images –

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.)