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

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. (https://agr.wa.gov/departments/insectspests-and-weeds/insects/hornets/faq

Facts

• 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 https://agr.wa.gov/hornets.  (Be patient; the map loads slowly.) The map will be updated as additional reports are made.

Life cycle

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.

Management

• 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.

Resources

Asian giant hornet – A list of reliable resources related to this recent invader which includes a link to report a sighting in Oregon. http://agsci-labs.oregonstate.edu/vegnet/2020/05/05/asian-giant-hornet-pnw-info-sources/

“Don’t panic over Asian giant hornet” (KGW8 News: text and brief video; May 4, 2020)  – https://www.kgw.com/article/tech/science/environment/murder-hornet-spotted-in-washington/283-a9b560e3-e7fd-4a66-ac34-3015c2390aa0

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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.

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. (https://idtools.org/id/mollusc/factsheet.php?name=Deroceras 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.

Resources

“Winter Cutworm: A New Pest Threat in Oregon” – https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9139.pdf

 “Slugs and Snails in Oregon” (ODA) – https://agsci.oregonstate.edu/sites/agscid7/files/vlach-2016-odaguidemolluscs-forweb.pdf

“Snails and Slugs” – http://ipm.ucanr.edu/QT/snailsslugscard.html

 “Cornu aspersum” [The Brown Garden Snail, formerly Helix aspersa] – https://idtools.org/id/mollusc/factsheet.php?name=Cornu%20aspersum

 “Terrestrial Mollusc Tool” (USDA, University of Florida, & Lucidcentral: Incudes Fact Sheets with images; and a Glossary – https://idtools.org/id/mollusc/glossary.php

Natter’s Notes

Jean R. Natter, OSU Master Gardener

The Japanese Beetle (Popillia japonica) Eradication Project

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: https://www.japanesebeetlepdx.info/.

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).

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. (https://oregoninvasiveshotline.org/reports/detail/2670)

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. (https://oregoninvasiveshotline.org/reports/detail/2778)

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. (https://oregoninvasiveshotline.org/)  

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 https://extension.oregonstate.edu/ofpd.