Managing bindweed in the garden

by Vicky Barney

Before I found it in my garden, I thought field bindweed (Convolvulus arvensis var. linearifoliu) was a rather pretty plant.  It looks like a morning glory (in the Convolvulus family), growing along the ground or as a vine, and producing pretty white or pink flowers.  But unlike Morning glory, it grows extremely quickly, takes over gardens and lawns, returns year after year, and is nearly impossible to eradicate. 

Field bindweed can be distinguished from morning glory by its arrowhead shaped leaves and its ability to grow in nearly any environment – in yards, along roads, in pastures.  One plant will grow an extensive underground root system that may travel 10 feet deep and contain a 2-3 year food supply.  It will produce up to 300 seeds that stay viable in the soil for 40 years.  And it cannot be dug out easily - the stems are fragile and any root piece left in the soil will produce a new plant.

Field Bindweed

Because of the tenacity and invasive nature of this non-native, the Colorado Noxious Weed Act has identified field bindweed as a “List C” species, which means local government may require it be contained, eradicated, or suppressed.  It may never be completely eradicated in our gardens, but it can be contained and suppressed if we are consistent with healthy gardening practices.

Vigilance – Look for bindweed when weeding or after introducing new soil or new plants into your yard. (My bindweed arrived in the soil of a nursery grown shrub.) Young seedlings can be removed if roots are dug several inches below the soil.   Established plants should be cut or pulled at the surface as soon as possible, stressing the plant and slowing its growth.

Mulch – Bindweed grows best in sunshine.  Mulching regularly will discourage growth.

Healthy Soil – Improving the nutrient balance of your soil will discourage most weeds.  A soil test will determine the necessary steps to soil health specific to your yard. (https://webdoc.agsci.colostate.edu/soiltestinglab/soilsample_horticulture.pdf)

For large dry land infestations of field bindweed, a biological control is available.  CSU’s Plant Talk 1493 has more details on using the bindweed mite. (https://planttalk.colostate.edu/topics/insects-diseases/1493-bindweed-mites/)

CSU’s Plant Talk: Controlling Bindweed (https://planttalk.colostate.edu/topics/weeds-cultural-problems/2104-controlling-bindweed/) includes a discussion of using herbicides.  Like the controls listed above, this method requires several years of vigilance.  It also requires careful application to minimize damage to surrounding life.  It is not an option for those of us cultivating wildlife friendly yards.

Perseverance and healthy gardening practices will discourage nuisance weeds like field bindweed.  Fortunately, these same routines will keep our gardens flourishing.

Vicky Barney gardens for wildlife and is a member of the Master Gardener Class of 2011.

The Rise of Spruce Beetle in the Colorado Mountains

by Emily Jack-Scott (Garfield County Master Gardener Apprentice)

The spruce beetle (Dendroctonus rufipennis) is currently the leading insect responsible for killing trees in Colorado, having usurped mountain pine beetle in 2012 (2017 Report, CSFS). These bark beetles have swept through hundreds of thousands of acres of forested lands in the Colorado Rockies in recent years. Since 2000, close to 2 million acres have been impacted across Colorado. Counties most heavily impacted between 1996-2018 include Hinsdale, Mineral, Saguache, Gunnison, Conejos, and Rio Grande; each experiencing hundreds of thousands of affected acres. (2018 Report, CSFS)

Figure 1 Tree mortality in Colorado caused by mountain pine beetle vs. spruce beetle. Spruce beetle overtook pine beetle as the lead insect pest in 2012. Credit: 2017 Report on the Health of Colorado's Forests (CSFS)

Spruce bark beetles are a native species, endemic to the Rocky Mountains. In Colorado, the beetles favor high alpine (above 9,000’) Engelmann spruce, but will also attack Colorado blue spruce and Norway spruce, and at lower elevations. At usual low endemic levels the beetles target dead trees, from windfall events or the like. But once they rise to epidemic levels they will attack live trees, initially favoring larger diameter trees (over 16” diameter), progressively targeting smaller spruces down to 3” diameter. Larvae overwinter under the bark of infested trees, emerging as adults and flying to new host trees between May and July the following year. Once they find a new host, adults chew through a host tree’s bark to tunnel around in the tree’s cambium and outer-most sapwood just beneath the bark, creating elaborate tunneling patterns known as galleries. It is in these galleries that they will lay their eggs, which will hatch into larvae in the fall and start the life cycle over again (2018 Report, CSFS; CSFS Quick Guide).

Figure 2 Tree mortality caused by spruce beetle. Credit: USDA Forest Service, Region 6, State and Private Forestry, Forest Health Protection. Source: William M. Ciesla collection; Fort Collins, Colorado.

What to look for:

Signs include the small dark brown beetles or white creamy larvae themselves. Symptoms include frass (insect poop, appearing as a fine sawdust from boring activity) collecting in the furrows of bark along the trunk, thin streamers of sap running down the trunk, visible small holes in the trunk with or without pitch tubes (see Figure 3), increased woodpecker activity, and/or the yellowing and eventual dropping of needles. Unlike pines attacked by mountain pine beetle the needles do not turn a vibrant red before falling off. Rather they fade to a sickly green before drying out entirely and falling off over time (CSFS Quick Guide).

Figure 3 Pitch tubes Credit:  USDA Forest Service

Spruce beetle is not confined to forested areas, and therefore should be on the radar of gardeners and landscapers in the mountains. Spruce beetle can sometimes favor trees in landscaped and urban settings, which may be under additional pressures and adverse growing conditions. Other factors that can make trees more at risk are drought stress, recent fires, increasingly mild winter low temperatures, and abundance of spruce in an area (Spruce Beetle UAF).

The Colorado mountains have not only experienced these stressors in recent years, but most recently incurred historic avalanches during the 2019 winter. These avalanches resulted in the disturbance, uprooting, and death of countless spruce, serving as magnets for spruce beetles. This will likely increase spruce beetle pressure in forests and yards of the high mountains that were otherwise minimally impacted over the last few decades (see map below of recent spruce beetle activity in Colorado). 

What you can do:

Options for prevention are limited. Pyrethroid insecticides can be sprayed on tree trunks during flight windows (May-July), and very new research is confirming that certain formulations of MCH[S1] [EJ2]  pheromone packets (namely MCH-AKB) has efficacy deflecting beetle attacks. These pheromone packets release a scent that sends a false signal to beetles that a tree of forest stand has already been infested by spruce beetles, so new beetles pass over such trees (Hansen et al. 2019). Once trees have been attacked, they should be felled and either completely removed from a location (including chips and slash), or should be cut and stacked in an area with full sun and covered completely with clear plastic. (Spruce Beetle, CSFS)

Sources

2017 Report on the Health of Colorado’s Forests. Colorado State Forest Service.

https://csfs.colostate.edu/media/sites/22/2018/01/2017_ForestHealthReport_FINAL.pdf

2018 Report on the Health of Colorado’s Forests. Colorado State Forest Service. https://csfs.colostate.edu/media/sites/22/2019/03/FINAL-307714_ForestRpt-2018-www.pdf

CSFS Quick Guide – Spruce Beetle FM-2014-1. https://csfs.colostate.edu/media/sites/22/2014/02/Spruce-Beetle-QuickGuide-FM2014-1.pdf

Hansen, E.M., Munson, A.S., Wakarchuk, D., Blackford, D.C., Graves, A.D., Stephens, S. and Moan, J.E., 2019. Advances in Semiochemical Repellents to Mitigate Host Mortality From the Spruce Beetle (Coleoptera: Curculionidae). Journal of economic entomology.

Spruce Beetle – Trees/Forests at Risk. University of Alaska Fairbanks. http://sprucebeetle.open.uaf.edu/2-module-2/

Spruce Beetle. Colorado State Forest Service. https://csfs.colostate.edu/forest-management/common-forest-insects-diseases/spruce-bark-beetle/

Despite beetle threat, Aspen-area avy debris to remain. Aspen Times. July 2, 2019. https://www.aspentimes.com/news/despite-beetle-threat-aspen-area-avy-debris-to-remain/

Noxious weed look alikes – don’t pull the wrong plant!

by Irene Shonle

It is heartening to see so many people being committed stewards of their land who are working to eradicate the noxious weeds on their property.  Thank you to everyone who is participating!  A word of caution -  it is possible to be a little too enthusiastic. This happens when someone pulls or treats the wrong plant – a plant that has the misfortune of looking like a noxious weed. These look-alike plants are often native, and can provide good habitat for pollinators, or at the very least, will occupy space that otherwise could be invaded by a noxious weed, so it’s best to learn how to distinguish which is which.

Some of the most common mistaken identities up here are:

• Golden banner/yellow toadflax,
• Pineapple weed/scentless chamomile,
• Cutleaf daisy/oxeye daisy 
• Fireweed/purple loosestrife.

Golden banner is a native plant – it blooms in the spring, and has solid yellow flowers, and three-lobed (trifoliate) leaves. Yellow toadflax blooms in the second half of summer with two-tone yellow flowers with a darker throat, and has strap-shaped leaves.

Golden banner

Yellow toadflax

Pineapple weed, while an introduced plant, is not on the noxious weed list. It is, however, having a very good year, and can be easily controlled by hoeing or pulling.  It has ferny leaves that, when crushed, smell like pineapple. The whole plant only gets to 6-8” tall at the most. It develops small yellow buttons, but never white ‘petals’ (ray flowers). Scentless chamomile also has ferny leaves, but they have no odor (the plant names give good ID clues). It gets up to 3’ tall, and has hundreds of white flowers.

Pineapple weed

Scentless chamomile

Cutleaf daisy is a native plant with small white flowers and finely cut leaves that could look a little ferny. It can (and has been) mistaken for pineapple weed, scentless chamomile and oxeye daisy. The flowers on the native bloom in the spring, and the foliage has no smell. The whole plant is no taller than about 4” tall. Oxeye daisy blooms mid-summer, and has much larger flowers, as well as broader leaves with teeth (not ferny). The plant grows 1’-3’ tall.

Cut-leaf daisy and penstemon

Oxeye daisy

Fireweed is a native plant with 4 pink petals. It blooms mid-summer to fall. The leaves are alternate, and the plant can grow up to 4’ tall. Purple loosestrife is not known to be up at this elevation, but people have frequently pulled out fireweed by mistake. Loosestrife has opposite leaves (or even whorled – meaning that four leaves come out of the stalk at the same place). It has 5-7 purple petals and can grow up to 8’ tall. 

Fireweed

Loosestrife

Finally, we have many wonderful native thistles, and it’s easier to just learn to recognize our two common noxious thistles, Canada thistle and musk thistle, rather than all of the native thistles. Musk thistle has large, solitary purple flowers with a formidable row of teeth under the flower. The leaves have a whitish edge. Canada thistle usually forms thickets due to the root system, and has clusters of small purple flowers.  See below table for a quick reference to distinguishing these plants.

Native plant	Bloom	Leaves	Noxious weed	Bloom	Leaves
Golden Banner	Solid yellow, spring	Three-parted	Yellow toadflax	Two-toned with a darker throat, Mid-late summer	Strap-shaped
(Pineapple weed – not native, but not noxious)	Just a yellow button, spring-mid summer	Ferny, smells of pineapple	Scentless chamomile	White flowers, Mid-late summer	Ferny, odorless
Cutleaf daisy	Small white flower, spring	Finely cut, a little ferny	Oxeye daisy	Large, white, blooms	Small teeth on leaves
Fireweed	4-petals, pink, mid-late summer	Alternate leaves	Purple loosestrife	5-7 pink petals, mid-late summer	Square stem, 4 or more leaves come out of same place on stalk (whorled)
Native thistles	Varies – white, pink, brownish	Varies – usually very white on underside	Noxious thistles (especially Canada and Musk)	Purple-pink	Varies

For more information and pictures, we have a brochure online: https://gilpin.extension.colostate.edu/wp-content/uploads/sites/29/2016/09/Noxious-weed-look-alikes.pdf.

For more information on thistles, see this brochure: https://www.larimer.org/sites/default/files/uploads/2017/finaltg2nded.pdf

Or here: https://gilpin.extension.colostate.edu/programs/natu/native-thistle/

Irene Shonle is the CSU Extension Agent and Director in Gilpin County

Mosquitoes Already??

by Barbara Sanders

Even though we have had a crazy wet, cold, snowy, late Spring, the mosquitoes are out buzzing our ears and are procreating en masse. You may even be seeing their larvae wiggling in standing water.

Mosquitoes spread diseases by biting a disease-infected animal or bird and them moving to another for more food. Zika virus is spread by the Aedes species which doesn’t live in Colorado. West Nile virus spreads by the mosquitoes of the Culex species which feed from the evenings until morning. They carry the virus after feeding on infected birds. The symptoms of a bite from a mosquito with WNV for humans may be mild but it is best to consult with a health care provider. Horses, however, are in more danger and should be vaccinated by a veterinarian.

First line of defense is to remove all standing water! After every rain! Buckets, pots, saucers, bird baths. And check any other standing water frequently for the wiggling larvae.  Also, the mosquitoes like dark shrubbery. You could trim back a bit or use a spray. More on that in a bit.

There are several ways to protect ourselves from mosquito bites. Repellents come in many formulations. The synthetic repellent called deet is the most studied and used for over 40 years. The plant derived repellents containing citronella and other essential oils are as effective as deet but must be applied more often. Products containing permethrin as the active ingredient (an insecticide having some repellent properties) may be applied to clothing but not to skin. There are also devices using ultraviolet light, CO2, or an attractant. I call them “Bug zappers”, not terribly effective and they also kill a lot of beneficial insects.

Recommended products to kill the mosquitoes can be divided into two main groups: Larvicides and Adulticides. The first, Larvicides, eliminate the larvae before they emerge from the water as adults. These work on bird baths, ponds, water features, stock tanks and areas of standing water. The safest contain Bacillus thuringiensis israelensis known as Bti: Aquabac, Vectobac (which can be mixed in a sprayer), Mosquito Dunks, and Mosquito Bits (which can be broadcast). I love the dunks because they are easily found in stores and online. They are safe around pets, children, fish and birds.

Adulticides kill the adult mosquitoes. They are not very long lived but work well before an outdoor function in the evening and in the dark shrubbery where the mosquitoes will rest between bites. Look for products containing Permethrin: Safer Mosquito control, Raid Yard Guard, Ortho Outdoor Insect Fogger, and others. 

More questions may be answered by visiting the website https://extension.colostate.edu/mosquito-management/.  The website has a wealth of information as we are thawing out and are in our yards and gardens.

Barbara Sanders, Colorado Master Gardener since 1998.

Master Gardener Activities Farmers Market

by Ed Powers
I have been a Master Gardener for more than 9 years, 4 in Michigan and 5 in Colorado.  Master Gardeners are usually sponsored by a state university and the local County.  We are connected to a major agricultural university; in our case it is Colorado State University. I have worked many activities in those years in both states, although I have enjoyed Colorado the most.  Of all those activities, ones that I have enjoyed the most are the activities we perform at the Farmers Market. 

Master Gardeners at Evergreen Farmers Market assisting individuals

Farmers Markets have been around for centuries. Originally, they were found in many smaller farming communities for farmers to sell their produce to the local town’s people.  Things have changed over the years as larger grocery stores replaced these markets. For a period of time the farmer’s markets disappeared, but recently they have made a resurgence, in part because of a public desire for naturally and locally grown food.  Now, not only do we find produce but also clothing, cooked food and beverages, plants and many other things.

Farmers Markets have become a great place for Master Gardeners to help local individuals garden successfully.  

Markets are usually weekly and happen during the growing seasons. The Master Gardeners arrive at these farmers markets, set up a canopy, and are assigned a place to display gardening information about the local area.  While we set up topics to discuss at each of our weekly markets, most of the time individuals come in to discuss challenges within their gardening efforts.

It is a pleasure to use our own knowledge when answering their questions, and of course we do enjoy discussing gardening.  Also, we share other resources with them such as the CSU garden notes and fact sheets, and remind guests that they are welcome to email in questions they may have. We also work with younger gardeners, encouraging them to continue their gardening effort. This just a great time as we really enjoy assisting people.