By John Ashworth, CSU Extension – Denver Master Gardener since 2014
In the metro Denver area, Japanese Beetles (JB) are unfortunately here to stay. They have steadily spread from the southern fringes of the metro area to Denver and the surrounding suburbs. It’s not too soon to develop a plan of attack for JBs in this year’s garden. Start by understanding the life cycle of the Japanese beetle and how you can interrupt it to reduce the numbers in your yard. This image shows that life cycle.
CSU Extension has published this excellent fact sheet, which covers the life cycle, strategies for reducing infestations, plant choice, and routes for attacking grub and adult populations.
The adult female lays eggs in grassy areas in late last summer. The eggs then hatch into larvae, which feed on the grass roots until early fall, when they move deeper into the soil to overwinter.
In spring, the larvae move closer to the surface, feed on grass roots, pupate, and emerge as adults. Springtime is also when you can limit Japanese beetle numbers by taking proactive action. Let’s look at three options – biological controls, chemical options, and plant selection – to help reduce JB damage in the next few months.
JB grub. Credit: University of MN Extension
Biological Controls
In mid-May, as the grubs move closer to the surface, a mail-order biological control, grubGONE!, can be applied to the lawn. It contains a bacterium, Bacillus thuringiensis, which attacks the grubs before they morph into adults and emerge. Apply it with a regular fertilizer or grass seed spreader and then water thoroughly, following the manufacturer’s directions.
In the more rainy and humid eastern United States, many homeowners routinely apply “milky spore,” a bacterium that lives in the soil and attacks the Japanese beetle grubs as they move toward the surface in springtime. According to CSU, milky spore has not been shown to sizably reduce JB populations in our area, likely due to our arid, drier climate.
Chemical Options
There are several effective chemical insecticides that can be applied to grass in mid-summer. These are readily available and contain the chemicals imidaclopid, chlorantraniprole, or chlothianidin. Common tradenames for these insecticides are Scott’s GrubEx, Merit, Zenith, and Arena. These chemicals can provide effective grub control for two weeks to several months.
They’ll work best when applied to the soil shortly after Japanese beetle eggs are laid or after they have hatched. For most parts of metro Denver, this is late June to mid-July. The effectiveness of these chemicals drops if the application is delayed until August or September when the grubs are larger and more resistant.
CSU Extension recommends trichlorfon for late-season application. These insecticides are fast-acting and effective but degrade relatively quickly. They are sometimes used when large colonies of grubs are discovered in turf later in the summer.
Plant Selection Can Help
In spring, decide if you want to keep plants in your yard that are highly attractive to Japanese beetles, such as Virginia creeper, silver lace vine, linden trees, rose of Sharon, and hibiscus. Consider substituting less-attractive varieties. Valuable food and plants that adult beetles prefer (grapes, and roses in particular) can benefit from protection. See my earlier post to learn about plant substitutions that have worked in my yard and ways to protect plants from damage
Fine mesh netting protects basil from JB damage. Photo: John Ashworth
Later this Season
One way to reduce Japanese beetle populations next year is to reduce your grass watering in late July and early August when the female JBs are laying eggs. The females have difficulty laying eggs in drier soil so you will have fewer larvae in the fall and the following spring. Resume normal grass watering in late August and September.
Managing JB impact requires planning and persistence. Hopefully, this post will help you be successful!
By John Ashworth, CSU Extension – Denver Master Gardener since 2014
In the metro Denver area, Japanese beetles (JB) are unfortunately here to stay. They have steadily spread from the southern fringes of the metro area to Denver and the surrounding suburbs. To limit damage to trees and plants, it’s important to understand their one-year life cycle, learn to interrupt it, and work to reduce the population.
As this diagram shows, adult JB emerge from the soil in early summer. They’ll damage foliage, buds, and flowers of host plants for about two months. By late summer, females dig into moist areas of turf and deposit eggs near grass roots. Upon hatching, the larvae feed on grass roots until early fall. By late fall, the larvae move deeper into the soil and remain there until spring when they again move closer to the surface and pupate. This new generation of beetles emerges as adults in the early summer.
In mid-July you will start to see adult JB activity, such as skeletonized leaves or deformed buds. Since adults are easy to spot with the naked eye, the most effective strategy is to brush the insects into a jar of soapy water daily, ideally every morning and evening.
Researchers differ on the very best time of day to pick JB : CSU recommends mornings, when temperatures are cooler, while this research suggests that evenings are best because flying beetles find their meals by following the distress pheromones emitted by the plants. It is believed that picking beetles in the evening reduces overnight feeding. In the morning, beetles don’t know where to land!
It is also okay to squish or stomp on JB, contrary to earlier belief.
Japanese beetle skeletonizing a rose leaf. Photo: Melissa Schreiner, Colorado State University, Bugwood.org
Protective Barriers
Small plants, like basil, can be protected by a fine mesh toule placed over a hoop. Find this material at fabric stores. Garden centers also carry mesh products which may be helpful for larger plants such as roses, grapes, and other JB targets.
Basil pot frame and basil pot covered in toule. Photo: John Ashworth
Insecticidal Options
Use water-soluble sprays on larger plants to either repel the beetles or kill them when they attack leaves or flowers. Neem-based sprays repel the beetles, but do not kill them, and need to be reapplied after rain or sprinkling.
Pyrethrin sprays work for short periods of time and can be used on most food crops.
Safe bio-based spray such as beetleGONE! and beetleJUS! contain the bacterium Bacillus thuringiensis (BT). The beetles ingest the BT as they eat the plant and die in 2-3 days. These options are mostly safe for bees, but are only effective for a few days. Apply when pollinators are not present.
Many commercial chemical sprays (imidacloprid, permethrin, etc.) that are sold as effective for JB elimination are, unfortunately, highly toxic to bees and other pollinators, should not be used around flowering plants, and should be used only sparingly on food crops.
Plant Selection Can Help
It is important to know what plant varieties the beetles find most attractive. Consider removing and avoid planting those that are JB magnets such as roses, Virginia creeper, silver lace vine, linden trees, rose of Sharon, crab apples, and hollyhocks.
I have found by growing heirloom Cantare bush beans instead of pole beans, I have eliminated the beetle population in that area of my yard.
I also have had success planting leadplant (Amorpha canescens), a native shrub with attractive flower spikes in May and June. Beetles congregate and mate on the flowers without damaging the plant, and I’m able to pick them off easily. Since the beetles are lured to the leadplant, the nearby hibiscus and basil suffer less damage.
JB traps attract beetles from neighboring yards and increase the problem rather than solve it. They are helpful in confirming the presence of JB and are effective only when an entire neighborhood uses them. If you wish to use a trap, hang it far from the plants you are trying to protect.
Late Summer
Adjust Lawn Watering
To help reduce next year’s JB population, reduce grass watering from late July to early August when they are laying eggs as females have difficulty laying eggs in drier soil. Resume normal grass watering in late August.
Fall and Winter
Grubs burrow deep into the soil in late fall and remain there until spring. No action is needed at this time.
Spring
Block Adults From Attacking
In mid-May grass can be treated with the mail order biological control grubGONE!, which contains BT. The BT attacks the grubs before they morph into adults.
Readily available chemical insecticides containing imidacloprid, chlorantraniliprole, or chlothianidin kill grubs in the soil and are effective when applied to the lawn in mid-May. Common trade names are Scott’s GrubEx, Merit, Zenith, and Arena.
Since JBs are very mobile, these treatments reduce the population at large but may not eliminate them from your yard.
Closing Thoughts
By employing these practices you can reduce JB damage in your yard. In a future post I’ll delve further into springtime actions you can take to minimize grub activity in the lawn.
By Linda McDonnell, CSU Extension – Denver County Master Gardener since 2013
June is my favorite month in the garden – from the explosion of colorful blooming perennials and the promise of the summer harvest to the comfortable temperatures – it just doesn’t get any better. We’re also coming off a month of record-setting moisture, which makes the landscape greener and lusher than usual.
Early June columbines, coral bells & tulip foliage. Photo: Linda McDonnell
Our May gardening calendar covered the season-long essentials of weeding, mulching, and watering. Refer to it for those tips. On this post, let’s look at ways to keep plants healthy, troubleshoot potential issues, and enjoy the garden.
Trees and Shrubs
Check apple, crabapple, mountain ash, and pear trees for fireblight, a bacterial disease that emerges in spring, especially when there’s been wet, warm weather. Look for curled, bent shoots with brown or black leaves, and limbs shaped like a shepherd’s hook. Learn how to properly treat fireblight here.
Fireblight on an apple tree. Photo: I, Paethon via Wikimedia Commons
Suckers are shoots that spring up from the base of the tree trunk or root system. Aspen, sumac, chokecherry, and plum trees are prone to suckering. Suckers can indicate the tree is stressed. Hand prune suckers where they attach to the trunk or root system. CSU reports Sucker Stopper RTU™ may help with control.
Prune spring flowering shrubs now to control their size/shape, remove dead wood, increase air circulation, and improve flowering next year. Find tips here.
Vegetables and Herbs
CSU’s Grow & Give program is a way to share your harvest with the community. Consider signing up to donate excess produce on the Grow & Give website. You’ll also find excellent growing tips and insect/disease help on the site.
If you’re growing in containers, remember that they dry out quickly. Check daily as temperatures rise. Mulch will help retain moisture.
For the best flavor, remove flower buds from culinary herbs.
It’s hard to pluck lovely chive blooms! Photo: Pitsch from Pixabay
Perennials and Spring Flowering Bulbs
When flowers fade, snip tulip and daffodil flower stems at the base. Leave the foliage until it yellows and goes limp. As it dies back it’ll provide valuable nutrients to the bulb which will help with next year’s flower production. Apply bulb food now too. If you already pulled the foliage, you could still add fertilizer.
Deadheading, or removing flowers that have finished blooming is a matter of personal preference. Deadheaders cite encouraging re-flowering, creating a tidier landscape, and reducing unwanted reseeding as motivators. Others prefer a more natural appearance that provides food and shelter for birds and other animals, reseeds freely, and features interesting seed heads. Many gardeners deadhead some, but not all plants.
If you deadhead perennials, consider the plant’s growth habit when pruning. For example, cut the flower stem about ¼” above the next set of leaves or an emerging bud on upright clumping perennials such as echinacea. Shear mounding plants – such as catmint, golden storksbill, and cranesbill geranium – down to about three inches. This is quick and easy. They’ll look scruffy but rebound quickly.
Ornamental grasses and most climbing roses bloom once a season so deadhead for aesthetics or to remove diseased foliage.
Shear golden storksbill to get more flowers & contain size. Photo: Linda McDonnell
To keep mid to late season blooming perennials from flopping, reduce their height by 25-30% in early to mid-June before flower buds emerge. This Chelsea Chop promotes side branching, creates shorter, stockier plants, and delays flowering by a week or two. Good candidates include soft stemmed, clumping plants such as New England aster, chrysanthemum, and false dragonhead.
Manage Unwelcomed Visitors
Creeping bellflower (Campanula rapunculoides) is prolific in Denver. Treat it as a weed. Unlike other campanula species, it’s a fast growing, sharp elbowed invasive that will choke out any plant in its way. It has heart-shaped leaves at its base, which become narrower as they move up the stalk, and green to reddish stems. Mature plants have stubborn, deep, white fibrous roots. Left unchecked it can reach three feet tall and produce nodding light blue bell-shaped flowers on one side of the stem. Control by digging out the roots and removing new growth as it pops up. If you’re plagued with this thuggish plant, this handout from Wisconsin Extension is a must read.
You’ll regret letting creeping bellflower get this big! Photo: Linda McDonnell
Aphids are back. These soft bodied, green, tan, or orange sesame seed shaped insects are relatively harmless to shade trees and ornamental plants. They suck on tender young foliage and mark foliage with a sticky honeydew secretion. Lady beetles, green lacewings and parasitic wasps feast on aphids. A strong stream of water may be enough to dislodge aphids without compromising biodiversity. Insecticidal soaps can also be effective.
Rabbits are cute but can be destructive to plants and turf. Find tips for creating barriers and using safe repellants here.
Japanese beetles will emerge from the ground in late June or early July. Get ready to pick and drown or stomp them. Review CSU’s report for details and watch for our July JB post for helpful tips.
by Gail Leidigh, Colorado State University – Denver Master Gardener since 2021
I recently had the opportunity to catch up with Karim, Denver Extension’s new Horticulture Agent, to chat about insects, his thoughts on Colorado, and what he’s been up to in his new job. I hope you enjoy this interesting conversation!
Karim & bees
Hi Karim, it is so nice to meet you! Can you tell me a little bit about yourself?
For as long as I can remember, I’ve been turning over rocks, inspecting plants, and investigating every nook and cranny in search of arthropods. I sincerely love entomology and horticulture, and I hope to use my knowledge of these interrelated fields to create programs that not only get the people of Denver excited about horticulture but also have a positive and long-lasting impact on its flora and fauna.
I’ve worked for a garden center, a state park, and a landscaping company. Regarding entomology, I’ve worked for the Smithsonian’s National Museum of Natural History for nearly a decade. This ranged from taxonomic research with the USDA-ARS, to working as an animal husbandry technician in the Insect Zoo/Butterfly Pavilion. The latter involved quite a bit of outreach, engaging museum patrons daily.
I obtained a bachelor’s in biochemistry from Virginia Tech, and I recently received my master’s degree in entomology from the University of Hawai’i.
What do you think of Colorado so far?
Winter is different, things like galls on trees are easier to see. There are lots more native plants in Colorado, and it is much more ecologically stable. Hawaii has many introduced bio-controls from farmers trying to control pests and other introduced plants. There have been lots of failures, with unintended consequences of those introductions.
Many invasives also arrived in Hawaii accidentally too, on infested plant material, or via ship traffic. As I’m sure you know, having an understanding of natives/invasives can be a double-edged sword. Whenever I hiked in Hawaii, I was saddened at the abundance of invasives and the scarcity of natives. In contrast, non-horticulturalists would just see greenery and be happy.
But even on the Colorado hikes I took this winter, I was continuously delighted at the abundance of native plants, birds, insects, fungi, etc. This state presents such diverse and beautiful wildlife and landscapes. I can’t even imagine how much more I’ll see as things warm up!
I hear that you have some unique pets – can you tell me a little bit about them?
There are three total organisms: two tarantulas, a female named Winona Spider, and a male named Aragog, as well as a colony of cockroaches that I feed to them. At the moment, Winona Spider has escaped from her cage, and hopefully will be found soon! Tarantulas are blind and have extremely sensitive hairs on their body that allow them to sense things, and they build silk webs on the ground that further allow them to sense vibrations and other things. I would also like to get a pet scorpion at some point.
Besides their fascinating biology, I enjoy having tarantulas as pets because they’re like me for two reasons: they’re very low maintenance and extremely solitary. While I am an introvert, I become an extrovert for this job which I am very passionate about.
Winona Spider has been found! Photo: Karim Gharbi
What was the topic of your master’s thesis?
I researched the use of essential oils to control western flower thrips, which are among the most insecticide-resistant insects in the world. It turns out that essential oils have the same chemical mechanism as pesticides and so thrips are still resistant. Thrips are destructive, hide in tiny areas, and are vectors for things such as the tomato spotted wilt virus.
What is your favorite insect?
Parasitic wasps, because within this group there are so many survival mechanisms such as viruses or multiparasitism. Many of the wasps encountered in our gardens have co-evolved with a group of viruses that are their partners in controlling horticultural pests. These viruses gestate in special cells of the wasp mother’s ovaries, restricting themselves from attacking other tissue. Once the mother finds a suitable host, she injects the virus along with her eggs. The virus then gets to work attacking the host immune system, making that unfortunate insect a more suitable host for her young. The wasps are so dependent upon these viruses that the host immune system will kill them in the absence of their associated viruses.
Another fascinating behavior that some parasitic wasps engage in is hyperparasitism. There are parasitic wasps of parasitic wasps. And parasitic wasps of those parasitic wasps. Talk about karma.
What do you consider to be the difference between a beneficial and non-beneficial insect?
It is a grey area, but for a gardening habitat, non-beneficial pests would be herbivores, sap suckers, invasives, and predators that disrupt the ecology.
Is it okay to kill wasp nests? What is the best way to handle wasps?
You don’t have to worry about them, they don’t cause harm, and they prevent some vegetable diseases. If possible, it is just best to avoid them when you can.
What do you think about bee houses that have become so popular?
Colorado has 900 species of native bees – they are better pollinators – and bee houses are great habitats for native, solitary bees like leafcutter bees. You can also create habitats by drilling holes in stumps or pieces of wood. Undisturbed patches of bare soil are another great habitat for solitary pollinators like sweat bees.
There was a big increase in black widow spiders seen around the Denver area last summer – do you have any ideas why?
I’ve received this question several times and have not found a definite answer. I may launch a research project into the increased population so that I can provide a clear answer to the people of Denver.
Right now we know that the main factors driving black widow populations are habitat availability and prey availability. Black widows prefer to nest in dark, dry, undisturbed areas. This includes flowerpots, concrete blocks, piles of wood/bricks, water meters, electrical boxes, crawl spaces, and other similar habitats at ground level (e.g. holes in yards dug by dogs).
Controlling black widows hinges upon habitat reduction; reducing the prevalence of the aforementioned sites will reduce black widow populations. Black widows and their eggs can be killed by smashing, vacuuming, or using a pesticide.
Garden centers have many broad spectrum pesticide sprays that are used for black widows. There are no pesticides that only attack black widows, but you may find a spider-killer spray. Broadcasting pesticides over an entire lawn to control black widows will not be effective and will create an undue hazard to the environment, humans, and pets.
In an urban area like Denver, habitat availability is high but does not fluctuate to the extent that it would be driving the population explosion we are experiencing. So prey availability is probably the causative factor. But black widows consume a diversity of prey (ants, cockroaches, crickets, etc.) and each prey population is influenced by its own set of factors.
Readers may enjoy this fun video about the mating habits of black widow spiders:
What are your projects or plans for this summer?
I am researching whether cutting plants back in late fall vs. early spring impacts pollinator/beneficial insect overwintering success. Colorado gardeners often ask us this and unfortunately, there is a gap in the scientific literature.
I am partnering with our county’s amazing 4-H agent, Jenia Hooper, on a series of youth entomology programs at local rec centers, high schools, and churches. I bring pinned insect collections to showcase the diversity of Colorado and how it relates to horticulture. I also often bring my tarantula (if I can find her!) and roach colony and do a feeding for the kids. Then we go on an insect safari, walking around a greenspace and talking about the various insects/plants/wildlife we observe.
I’m also serving as a presenter for Denver Parks & Recreation’s Sustainable Landscaping course and Denver Botanic Garden’s Beginning Market Farmers class. I’m happy to talk to anyone/group about anything horticulture related, so long as they can tolerate my entomological tangents!
What would be your number one suggestion for a yard that is hospitable to beneficial insects?
Less turf grass, more native plants, variety, and diversity.
Are 10-lined June beetles a “good” or “bad” (non-beneficial) insect? We see many of them here seasonally.
They are harmless but do feed on foliage or roots. They are in the same family as scarabs and like Japanese beetles, you can go ahead and kill them, squish them, or I like to feed them to spiders.
Do you have places we can follow you for more insect content?
Posted onOctober 15, 2021|Comments Off on Denver Master Gardeners Look Back at the Growing Season – Part 2
Compiled by Linda McDonnell, Denver Master Gardener since 2013
Welcome back to part two of our garden season recaps. We hope you enjoy this look at the wins, challenges, and surprises from Denver Master Gardeners. If you missed part one, you’ll find it here.
HUMMINGBIRD BANQUETBarb Pitner, Denver Master Gardener since 2012
Can you find the hummingbird? Photo: Barb Pittner
This season’s goal was to create a garden to attract and feed hummingbirds. I started by removing a twelve-foot-wide circle of lawn with a two-foot-wide circle or “bullseye” in the center. The soil of this center area was prepped with compost into which four scarlet sage vines (Salvia coccinea) were planted around a four-foot-high decorative tower.
The remainder of the full-sun, brightly colored pollinator garden was filled with containers, which encircled the scarlet sage and descended in height from the center.
The tall scarlet sage vines were surrounded by containers of vibrantly colored ‘Giant’ zinnias alternating with containers of crocosmia varieties including ‘George Davidson’ (yellow), ‘Lucifer’ (deep red-orange), ‘Emily McKenzie’ (red-orange-maroon with a yellow eye). Cypress vines (Ipomoea quamoclit) were added to the crocosmia displays.
The outer ring of the garden was made up of smaller containers, brimming with lower growing annuals such as marigolds, blue Victoria salvia, red calibrachia, and red-yellow lantana.
Daily watering, regular feeding, and deadheading insured constant blooms from July to September. In addition to hummingbirds, the garden was regularly visited by native, honey, and bumble bees. All have been kept in good supply of nectar and pollen.
WINTER-SOWN BAPTISIA Susan Tamulonis, Denver Master Gardener since 2018
Baptisia plants (center) in August. Photo: Susan Tamulonis
Last December I was given thirty-eight Baptisia seeds (Baptisia spp; variety unknown, aka wild or false indigo) from a neighbor. This gift launched a multi-season challenge to nurture, document, and transform the seeds into healthy plants. Baptisia is in the Fabaceae (bean) family and requires cold temperatures to germinate – perfect timing for this project.
The dense, hard-coated seeds were treated to two boiling water baths and then soaked for two more days. The seeds were then planted in “mini-greenhouses,” constructed from milk jugs (one 1-gallon and two ½-gallons). The uncapped containers were cut in half horizontally and drainage holes were poked in the bottom. Seeds were sown in the base of the containers, lightly covered with soil, and watered. The top portion of the containers were replaced, creating dome-like planters. The containers were placed in a shady outdoor spot immediately after planting and were regularly checked for moisture and good drainage.
In April, to allow for more light, the top half of the containers were removed; germination began in May. By mid-June, seedlings were four to five inches tall with three sets of leaves. It was now time to plant them in full sun. In August, the seeds yielded seventeen healthy plants for a 58% germination rate.
And here’s where the story takes a turn…I returned from a fall vacation to find the young plants were mowed down by a hungry visitor, likely a rabbit. So while the winter-sowing process was successful, the plants didn’t survive!
A FUN & BENEFICIAL SURPRISE Jodi Torpey, Denver Master Gardener since 2005
Photo: Jodi Torpey
My biggest gardening success this season gave new meaning to the old saying about keeping one’s ear close to the ground. That’s because I grew an ear in a container of radishes.
Although I didn’t set out to grow a body part in my garden, I was delighted to see this flesh-colored, earlike growth pop up among the radishes during this year’s cool, wet spring. My “ear” was most likely a type of cup fungus belonging to the genus Peziza. These fungi are real bodies – the fruiting bodies – of cup fungi that usually live underground but can grow above ground in mulch or compost when conditions are right.
While they don’t all look like ears, they’re all good for gardens because they break down organic matter to make nutrients available to plants. An ear growing in that container turned out to be a real fun guy.
A TREE WORTH WAITING FOR! Lori Williams, Denver Master Gardener since 2016
Photo: Lori Williams
After a four-year delay in planting any tree, finally this summer a long-awaited, lovely peach tree found a home in our yard. It came with baby peaches all over, but we popped most off so the energy would go to the roots. The only decent gladiolus I planted this year were around the new peach tree – and we enjoyed nine very tasty peaches in mid-August. Highlight of our summer!
NATIVE POLLINATOR GARDEN: YEAR TWO Ann Winslow, Denver Master Gardener since 2019
A mass of chocolate flowers Photo: Ann Winslow
Last year, I shared my adventure creating a pollinator garden using native plants on this blog. You’ll find the posts here and here. This year, I’ve watched and recorded what has flourished and what has struggled – maybe because of weather, where the plant was sited, and in some cases, for reasons I can’t tell.
One big success was chocolate flower (Berlandiera lyrata). At one end of the garden, three plants became massive, merging into one enormous display, which will be divided in the Spring. They have been abuzz with native pollinators since June. Just what I hoped for!
In contrast, wine cups (Callirhoe involucrata) has struggled. It’s possible that the heavy spring rains caused it to grow leggy, splay out on the ground, and have few blooms. I’m cutting back the long, dead stems now as I see it’s getting new growth in the center.
Always something to learn. Every year is a new adventure in gardening.
Many thanks to the Denver Master Gardeners who allowed us to peak into their gardens, learn from their experiences, and be inspired by their results.
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Posted onSeptember 6, 2020|Comments Off on Cicadas, Courtship and Weather Whiplash
Dog Day Cicada (Tibicen dorsatus, T. dealbatus) photo by BugGuide.Net
Cicadas have been serenading the front range nightly since mid-July and typically continue their concerts until fall. Heard but rarely seen, Colorado’s 26 cicada species are abundant and generally harmless to plants, trees, and shrubs.
The distinctive, repetitive, buzzing (some might even say whiney) sound is the male cicada’s way of attracting females for mating. It is a hard to miss “love language” – measured by a Vanderbilt University audiologist at 85-88 decibels – comparable to a motorcycle or subway at 25 feet.
Colorado’s cicadas are not the headline-grabbing seventeen-year periodic cicadas found in the eastern and northern parts of the United States. In our region, cicadas in the immature nymph stage live underground for 3-5 years, feeding on fluids from plant roots. Once the heat-loving adult emerges from the soil, they will live only 4-6 more weeks. The life cycle is detailed in this CSU publication.
Just as the finishing touches were being made to this post, Colorado is expected to break two early September weather records within a 72-hour time span. Temperatures will tumble from 101 degrees to lows in the high 20’s, with possible measurable snow. Seasonal temperatures should return to normal the following day.
While this abrupt weather whiplash may effect heat-loving adult cicadas, the more critical and long-lasting impact will be to plants, trees, and shrubs. For help with frost protection, check out this CSU publication.
Here’s hoping Mother Nature has a change of heart!
Written by Linda McDonnell, Colorado Master Gardener since 2012
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Recently a report on the discovery of the large, native Asian hornet (Vespa mandarinia) in Washington state and British Columbia went viral. The New York Times dubbed it the “murder hornet” because of its striking appearance and size (about 2″ in length, wingspan of 3″), assumed threat to the honeybee population and quarter inch stinger to inject venom into humans.
Dr. Whitney Cranshaw, Colorado State University’s Entomologist and Extension Specialist, offers a constructive look at the Asian hornet and cautions us to look past the dramatic, attention-grabbing headlines.
Cranshaw notes the following:
Traps and controls have been developed in Asia and can be adapted for use in the very small outbreak in Washington and British Columbia.
While some insects relocate to new areas via packing materials, wood or other carriers, this hornet does not hitchhike well. Given that, to reach Colorado, it would need to navigate difficult terrain from Washington. This is considered unlikely.
The insect is a woodland species which lives in low altitude, moist environments. It is not likely to thrive or adapt to the semi-arid Rocky Mountain region. If it did get transported here, it is doubtful it would survive.
It is a generalist predator and honeybees are just one of its many predatory targets. Whether the giant Asian hornet will pose any greater threat to honeybees than existing predators remains to be seen. But it is possible that colonies in the wasp’s preferred woodland areas could be the most vulnerable honeybees.
Cranshaw and other entomologists caution that “Murder wasp” is an unwarranted, fear-inducing name. While imposing and unique for its appearance, the Asian hornet’s potential impact needs to be kept in perspective and is not expected to live up to the recent hype.
Whoa! Look at this critter hanging out on Asclepias curassvica ‘Silky Mix’ milkweed, an annual milkweed I’m growing in planters. For perspective, the leaves in the photo are about 5.5″ long and 1.5″ wide at the longest point. While new-to-me, Milkweed Longhorn Beetle or Red Milkweed Beetle (Tetraopes femoratus) is relatively common and found throughout Colorado.
All milkweed longhorns feed and develop only on milkweeds (Asclepias spp), some feed only on one species, while others are not as particular. This visitor showed no interest in the nearby native milkweed, Asclepias tuberosa.
It hung out on a stem for several days, did little obvious damage to the foliage or flowers and moved only slightly. They can often be seen mating on the plant, although I only saw a solitary beetle.
The female milkweed beetle lays eggs at the root crown. The larvae, called roundheaded borers, will tunnel into the root system and later emerge as adults which live about a month. According to Dr. Whitney Cranshaw of Colorado State University, longhorn beetles rarely cause serious damage to plants.
Milkweed longhorns make a squeaking sound, especially if held (I don’t know this from experience). It is believed this is a warning noise. “Purring” has also been reported as a mating call.
The distinctive color is a result of feeding on the alkaloid toxins which are contained in the milkweed sap. This is the same defensive toxin found in monarch butterflies. The flashy color screams “danger” to predators.
If you are growing milkweed, keep your eye out for these colorful, over-sized beetles.
After a few wild weather days in my garden, yesterday morning I was out assessing hail damage to my new perennial bed and dahlias when I spotted a metallic bronze and turquoise body perching on one of the unshredded dahlia leaves. For a moment I marveled at the size of the beetle–much larger than I expected–and then the color and pattern. So lovely and kind of mesmerizing. And then it hit me. I’ve been heeding the warning of the onslaught of the Japanese beetle (Popillia japonica) but had yet to see one with my own eyes. Frankly, I couldn’t remember what they looked like or where they like to hang out, except that they are badbadbad.
Image via McKenna Hynes
I managed to snag two fairly mediocre photos and then took a quick swipe at it into a bowl of soapy water AND MISSED! It seemed to vanish into thin air! It had been sitting and sunning NOT nibbling on the luscious leaf unto which it perched for seemingly ever, and the moment I gave it a little nudge to its sudsy impending doom, it disappeared. Cursing, bewildered, picking, and digging madly, no dice.
Meanwhile, my wife is watching this ridiculous mission at six in the morning from the front stoop with her first cup of coffee and casual observance of just another peculiar garden act (she literally has footage of me scrambling to plant “just one more” seedling well after dark with a headlamp affixed to my noggin). She is curious, patient, surely entertained, and finally asks what I’m doing.
I explained to her the grave danger our flora faces and that the invaders have arrived. I showed her a photo of the insatiable beast to formally introduce the target. I did my best to order her into the cause. There are bowls of soapy water conveniently located throughout the premises, I flag to her with my best flight attendant gestures. She is charged with taking immediate action, and regular surveillance of all the beds. The alarms are sounding!
Fortunately, this is not a new issue in our area. We covered the arrival of the Japanese Beetle in 2018 and continue to reference the fact sheet from CSU to prepare you for the onslaught. According to the Colorado Department of Agriculture, the Metro Area has a high population level of the Japanese beetles comparatively to the rest of the state, due to water usage and higher moisture levels in residential areas. The Japanese beetle doesn’t love our dry arid climates but thrives in our commercially and privately maintained lawns and gardens that use external sources of water to imitate a moist and humid environment for the beetle to thrive.
Integrated pest management strategies can help prevent the Japanese beetle from settling into your garden area, including picking them off individually, reducing water in turf areas where they lay eggs and their larvae grow big and strong and demolish your lawn, selecting less appetizing foliage, and even getting chickens or ducks! Also, Party with a Parasite presents the Tachinidfly, a parasite that lays their eggs on a living host– a la JB–which hatch quickly and get to feeding. Cue: Bye Bye Beetle, Bye Bye. I’m not sure how to recruit this insect to the yard but will refrain from swatting at this time, just in case. Please use caution, good judgment, and safety when reaching for chemical management strategies by using only according to the label, and educating yourself on possible collateral damages; what else might be impacted by the use of this product?
I’ve been checking each plant several times since yesterday morning and have not seen another invader. My wife, on the other hand, casually mentioned last night that she saw one. It was so pretty. Was it in the Dahlias?! Yeah. Did you plunk it into the soapy bowl??? No.
Sigggghhhhh. My attempts at recruiting more defenders are plighted. New strategies underway.
By McKenna Hynes
Apprentice Colorado Master Gardener since January 2019
Mosquitoes seek me out in a crowd, leaving behind swollen, ridiculously itchy welts. They seem to ignore everyone around me. Admittedly, this is an annoyance and not a serious medical condition. However, nearly a billion people are affected by mosquito-borne diseases worldwide, so controlling mosquitoes is a serious and much researched topic.
There are definitely ways to lessen the chance of being the mosquito’s victim and a few popular beliefs which are not widely supported by research.
The scented geranium (Pelargonium citrosum, “Van Leenii”) has become known as “The Mosquito Plant.” Unfortunately, repeated studies have proven that the plant has no mosquito repellent properties, either in plant form or when the leaves are crushed to release the volatile oils. While the leaves have a lemon scent, they do not deter mosquitoes. Grow this scented geranium to enjoy it, not for bug protection.
Likewise, fragrant plants such as rosemary, catnip, lemon thyme, eucalyptus and peppermint will not repel mosquitoes. According to Colorado State University, although widely touted for repellant abilities, there is no reliable data to support that these plants or the oils released when the leaves are dried will repel mosquitoes.
The volatile compound from the citronella grass (a hard to find tropical plant) does have satisfactory mosquito properties, discussed below. But it can’t be stressed enough: simply growing any plant in the landscape won’t deter mosquitoes.
So what is effective?
Eliminate standing water. Stagnant standing water is an invitation for the female mosquito to lay her eggs. She can breed in as little as one teaspoon of water. The egg-to-adult stage takes just four days. With one human bite, the mosquito extracts enough protein (our blood) to lay up to three hundred eggs. Yikes.
Check drip trays, gutters and downspouts frequently. Birdbaths and water features are big breeding grounds. Change the water often (twice a week is recommended) or use a bubbler to keep the water moving.
Mosquito dunks, a larvicide which is harmless to organisms other than mosquitoes, can be added to ponds to kill mosquito larvae. Rain barrels should be installed with a protective cover and spigot.
Encourage beneficial visitors. Spiders and other insects feed on mosquitoes so avoid or limit the use of insecticides. Bug zappers which indiscriminately target the “good guys” have been shown to have little effect on mosquitoes, too.
DEET repellent. Skin lotions and sprays containing DEET, a highly effective chemical compound, have been used since the1950’s and are often combined with citronella oil. While not without its detractors, DEET offers relief to many. Apply it on top of sun protectant and not under clothing. Always wash it off when you go inside.
Dress defensively. Mosquitoes won’t bite through clothing. Closed shoes, socks, long sleeves and long pants do help. Clothing treated with permethrin also offers some benefit.
Burn citronella candles.The smoke or vapor from citronella candles provide some protection in the immediate area, such as a patio.
Create air movement. Mosquitoes dislike moving air so a fan on a porch or patio will discourage visits.
I’ve not had the first bite of 2019 yet and by practicing some of these tips, I’m trying to reduce the bumps and lumps left behind by these buzzing nuisances. Here’s hoping…
References:
Mosquito Management.Drs. Frank Peairs and Whitney Cranshaw, Colorado State University
Denver Gardeners 
