My Lawn Has Never Looked This Bad!
Tony Koski, Extension Turf Specialist

Winter desiccation (aka "freeze-drying); made worse because the thatch layer was a little
thick? Probably some rabbit activity, and maybe some cranberry girdler as well? That 
combination will kill grass in the best of lawns during a severe winter.

It seems like nearly every lawn up and down the Front Range has experienced some level of turf injury this spring – more than I can remember in my 30+ years at CSU. Many have been cared for by avowed lawn geeks (like Alison’s lawn, pictured here!). These folks are used to turf perfection, so are especially shocked, dismayed and embarrassed by the spots and patches that have appeared in their normally picture-perfect lawn. What has caused so many beautiful (in 2021, anyway) lawns to become so bad this spring that owners are reluctant to send me pictures of them? Pinning down the exact cause of the turf damage without visiting the lawn can be difficult, but if you are seeing dead patches in your lawn this spring it’s almost certainly one of the following problems. Lawns that were seeded or sodded in 2021 (especially later in the year) were more likely to be injured. If the lawn hasn’t greened up by this point in time – especially after the recent rain – then it’s almost certainly dead, with the solution being new sod or seeding (go here

for some videos on seeding and sodding lawns https://planttalk.colostate.edu/youtube-videos/lawn-videos/#reseed)

Winter Desiccation (freeze-drying)
This is probably the most common cause of lawn damage this spring, most likely to occur on areas of the lawn that were drought-stressed going into winter last fall.  Turf stressed by poor irrigation coverage in 2021 (broken/plugged/low/crooked heads, low pressure, bad spacing) was more susceptible to being damaged by the dry, cold, sunny, windy winter conditions we experienced this year. Lawns with thick layers of thatch also appear to be more likely to have been injured. Check spots that are dead now for irrigation coverage deficiencies – before re-seeding or sodding. You rarely can detect non-uniform water application by simply watching your sprinkler system (“It looks like water is going everywhere” you say…but it’s not going everywhere uniformly). Don’t blindly trust your “irrigation guy”/sprinkler company when they tell you that everything “looks fine”. To be certain about uniformity of water application, it has to be measured by a formal or informal irrigation audit (here’s a DIY method to help you identify dry spots in your lawn).

This turf died from winter desiccation. When you can see where the
irrigation heads are, you know there are irrigation coverage problems. The
dead areas in this lawn were drought-stressed LAST FALL - which resulted
in the turf succumbing to the severely dry and cold winter. The turf also 
survived around the young tree - because of winter watering of the tree.

Insect Feeding Damage

Feeding by cranberry girdler (https://csuhort.blogspot.com/2020/10/cranberry-

This lawn was weakened by cranberry girdler feeding
last fall (2021); the cold, dry, windy winter resulted in
the death of the stressed turf

girdler-rears-its-ugly-head.html) or white grubs (https://extension.colostate.edu/topic-areas/insects/billbugs-and-white-grubs-5-516/) last fall could have gone undetected and so weakened turf root systems that the turf more easily succumbed to winter desiccation. Dead turf that peels up easily from the soil surface was likely fed upon by these insects. If the lawn hasn’t greened up by now, it’s dead and the only alternatives are to seed or sod the affected areas.

Turfgrass mites damaged this lawn. Notice the
lack of mite injury in the neighboring lawn (top
of photo) which received winter watering.

Mite Feeding

Winter mite activity can kill large areas of turf, usually on lawns facing south or west. The damage caused by winter mites can look identical to winter desiccation injury: orange or brown grass (early death), changing to grey/silvery grass (dead for awhile). Mite-damaged turf will still be strongly rooted, distinguishing it from damage caused by root-feeding insects. Even when mites are actively feeding in lawns, they can be difficult to detect – so mite injury is often confused with other types of winter damage. The best control for mites is late winter/early spring irrigation, or a few good snowfalls or rainy spring weather. Since they aren’t insects, insecticides don’t provide great control of turfgrass mites.

Rabbit Injury

Look for rabbit pellets (aka "poop") in the brown spots
in your lawn as a sign of rabbit activity.

Rabbits feeding is often concentrated in small areas of the lawn. The persistent feeding and deposition of urine can kill small to large areas (depends on how many rabbits are in the yard) over the winter. Rabbits can be trapped and relocated (where legal; check with local animal control for the laws that apply where you live); applying the fertilizer Milorganite to your landscape (lawn and garden beds) can repel rabbits - if they have somewhere else to feed and live.

Rabbit activity can result in the death of large areas in the home lawn.

While it’s good to know what may have killed parts of your lawn – so that you can take measures to prevent the same thing from happening in the future – the “fix” is generally the same: repairing the dead areas by seeding or sodding (here and here, for how to do this).

Ascochyta Leaf Blight: Facts and Myths

Tony Koski, Extension Turf Specialist
Dept. of Horticulture and Landscape Architecture

The visible wheel tracks does NOT mean that mowing 

"tracked" the ALB fungus on to the lawn. Rather, the 
lawn was drought-/heat-stressed when it was mowed. 
The wilted grass leaves were killed by the weight of 
the mower - but the grass plant is still alive.

It's back, in full force, on Colorado's lawns. Cool, wet springs, like this year's, create perfect conditions for Ascochyta leaf blight (ALB) outbreaks. When the transition from spring to hot, dry summer conditions occurs as suddenly as how it happened this year, ALB becomes epidemic in lawns.

We've blogged about ALB a number of times, so there's no reason to repeat what you can read there (2013, 2015, 2016, 2017). Without re-hashing what was written in years past,  the most important takeaway: it's a problem of drought, heat stress, and lack of water (or a sign of an irrigation system problem); mowing the stressed turf often increases the injury. The good news is that the grass is NOT dead, but can be revived with sensible watering and by paying closer attention to future irrigation needs.

Some ALB facts:

• While it is a disease, ALB is really a problem of water - not enough, or not frequently enough. 
• ALB can affect bluegrass, fescue, and ryegrass lawns.
• Fungicide applications will NOT make it recover more quickly - so don't apply them (or don't pay for your lawn care company to apply them!)
• While an ALB outbreak looks terrible and the grass appears dead, this disease does NOT kill grass.
• An infected lawn will recover, though it may take 1-3 weeks for full recovery. Recovery rate depends on severity, species of grass, and how you water (not swampy, but consistent moisture).
• Light fertilization - if your lawns has not yet been fertilized this year - can help speed recovery.
• The ALB fungus does infect grass leaves through the mowed off tip of the leaf blade - but that doesn't mean you should stop mowing the lawn when disease is active (mowing doesn't spread the fungus, nor does it significantly increase the amount or severity of the disease). 

Some popular myths about ALB:

• Maybe you've read on the never-wrong internet that the ALB fungus is spread by mowers? Wrong! The wheel tracking often seen on ALB-affected lawns occurs because the lawn was mowed when it was drought- and/or heat-stressed. The weight of the mower crushes the wilted leaves under the wheels, leaving brown tracks a day or so later. Often there is no ALB disease IN the wheel tracks - but plenty of blighted turf between the wheel marks. 
• You will also find claims that lawn mowing equipment should be disinfected between lawns - or after you mow you own lawn. Wrong again! The fungal spores that can result in ALB are everywhere already. Disinfecting your mower with bleach solutions or Lysol will not prevent future ALB on your lawn, nor will it prevent its occurrence on lawns of other clients (if you own a lawn care or mowing business).
• You will also read on that you should throw grass clippings from lawns suffering an ALB outbreak into the trash, because leaving them on the lawn will make the problem worse - or will cause it to happen in the future. Again, there is no evidence to suggest this to be true. As before, the spores are EVERYWHERE already. Grass clippings can be safely composted or used as mulch in gardens (because the fungus causing the lawn disease doesn't affect vegetable or flower garden plants).

While people will always claim that "it can't be water", it ALWAYS is. When you can see where the sprinkler heads are in a lawn affected by ALB, that should be a sure indicator that it is a watering issue. Read the previous blogs listed above for suggestions on getting a lawn back to health after an ALB outbreak.

Looking Forward to Fall Gardening

Posted by Sarah Schweig, Broomfield County Extension

With the relentlessly hot weather lately, this post is devoted to gardening in that magical time that’s just around the corner - daytime temperatures are less severe, nights are cool, the soil has been warming all season, and (hopefully) we receive some rainfall. Early fall is a great time for establishing many plants, and a particularly pleasant time to be in the garden. At the top of my list are moving around some perennials, getting spring bulbs in the ground, and doing some much needed overseeding of the lawn. We’ve still got some time before these fall gardening tasks, but now is the time to prepare!

Planting Perennials
A window of opportunity for perennials opens once the hottest temperatures of the summer have subsided. If you stroll your favorite garden center around this time, the inventory may be low, but the prices usually are, too. It’s also a good time to divide and transplant many perennials. For overcrowded or overgrown plants, dividing every few years can support plant health. A general rule of thumb is not to divide plants when they are in bloom. For fall division, focus on plants that bloom from spring to early summer. Whether new plantings, transplants, or divisions, allow 4-6 weeks for plants to establish in their new homes before the ground freezes.
 
What to do now
Take some time to assess your spaces and plants while your garden is still in its full glory. Do you see overcrowding? Gaps in the landscape? These are your targets for division and transplanting. If (like me) you're just not feeling your original design anymore, that's also a good reason to change things up.


Fall-Planted Bulbs
What’s better than a gift you give your future self to open when you most need it? Enter crocus, squill, daffodils, and all the other hardy bulbs and corms that provide the first flush of spring color. On the Front Range, the ideal time to plant spring-blooming bulbs is late September into October. If planted after this window, roots may not have time to establish before the ground freezes, which is key to survival into the next season. If planted too early, the shoots may begin to develop this year. This takes valuable energy away from root establishment, which similarly reduces chances of success in the spring.

What to do now

Shop! For the reasons above, it’s important not to be hasty with planting, but you’ll find many bulbs have been bought up by the ideal planting time. If you buy bulbs before it’s time to plant, store them in a dry location out of direct sunlight with good air circulation (net bags work well for this).

Seeding Cool Season Grasses
Whether you’re overseeding a few bare spots or planning an overhaul, you can seed cool season grasses like fescue, bluegrass, and ryegrass into the fall. Cool season grasses can even be seeded now, though higher temperatures mean even more diligence (and water) will be needed to maintain the moist conditions needed for seed germination and seedling survival. 

What to do now
Remember you’ll need to complete some pre-planting steps like choosing your seed, killing existing vegetation if needed, raking away debris, and aerating to prepare the seed beds.
 
Set yourself up for success by first asking why new grass is needed. Is the current grass species appropriate for your site and needs? Are irrigation issues contributing? Make adjustments now to avoid repeating the process next year.
 

Garden Problem Tour

By Sherie Caffey, Horticulture Agent, CSU Extension-Pueblo County

   This summer, COVID-19 has the Extension office in Pueblo closed down, so I have been working from home. This has given me a chance to look around at things going on in my yard and garden that I haven’t had time to pay attention to in previous years. Of course there is a lot going right, but here is a little tour of the issues I have found this year. Maybe you have some of the same issues, and I can offer some suggestions on what you can do to remedy them.

   I have several trees in my yard that were here when I moved in. While doing some much needed trimming earlier this year, I noticed one of my American Elms had a very black trunk and branches. Upon further inspection, I noticed small brown and white structures in the cracks of the bark that looked similar to mealy bugs. What I have is a pretty bad case of European Elm Scale. The black color on the trunk and branches is black mold and is commonly associated with scale infections. There aren’t many control mechanisms that work well, but if you have Elm Scale you can see your options here: https://planttalk.colostate.edu/topics/insects-diseases/1400-24-european-elm-scale/. For me, this tree is not in a great place and runs into my power lines so I won’t be sad to lose it and therefore probably won’t treat it. If my neighbors or myself had other American Elms it could spread to this might be more of an issue.

   The next problem I saw in my yard was in my lawn. It looked really great earlier in the year, but with the extremely hot weather we have been seeing in Pueblo I’ve been seeing some brown spots appearing. There are many potential causes of brown spots in lawns, but by far the most common cause is a lack of water due to poor irrigation coverage. I’m sure this is the problem that I am seeing, but to be sure I will be performing a simple at home lawn irrigation audit. To do this, set out identical containers in different spots in your lawn (brown spots and green spots) and run your system. You can measure the amount of water in each container to see if the brown spots are getting less water. To read more about brown spots in lawns click here: https://planttalk.colostate.edu/topics/lawns/1553-brown-spots-lawn/#:~:text=1553%20%E2%80%93%20Brown%20Spots%20in%20the,to%20maintain%20a%20healthy%20lawn.

   Next, I checked out my vegetable garden and noticed my zucchini plant had leaves that looked white and powdery. This is a common fungus you might see on cucurbits, called powdery mildew. It’s caused most often by poor air circulation and too much shade. Shade is definitely my problem. Neem and horticultural oils can be used on existing infections, but can damage plants if used improperly so always read the label and check out this link for extra information: https://planttalk.colostate.edu/topics/vegetables/1833-powdery-mildew-vegetables/. I’ve made my first application of Neem oil and am hoping for good results.

   Also in my vegetable garden, I noticed some of the tomatoes were getting cracks and indentions. This can be caused by inconsistent watering. The plants get a bit dry, and then suddenly get a bunch of water, and the fruit basically outgrows its skin and cracks. I think I will try to be better about the watering schedule, and also add some grass clippings or straw as mulch to stabilize the soil moisture. I know a lot of people have various problems with tomatoes. This fact sheet is amazing for narrowing down the problem: https://extension.colostate.edu/topic-areas/yard-garden/recognizing-tomato-problems-2-949/.

   So that’s a tour through the yard and garden issues I am having. I hope someone will see one of my shortcomings and be helped by it!

Be Careful with Crabgrass Pre-Emergent Herbicides

Tony Koski, Extension Turf Specialist

Pre-emergent herbicide injury on a Kentucky bluegrass
home lawn. The herbicide was on a fertilizer carrier, thus
the darker appearance where a higher-than-recommended
rate was applied.

Among the mostly widely used lawn weed control products, pre-emergent herbicides (aka “crabgrass preventers") are generally very safe to use on most turf species. Safe, that is, if applied at the correct rate. Using a spreader without adjusting its setting to apply the correct rate, applying the product with a spreader that isn’t operating properly (plugged, skipping, etc.), applying with excessive overlap, or thinking that “more is better” can cause unintended damage to the desirable turf. In the past few weeks we've seen a greater than normal number of pre-emergent herbicide "oops" on home lawns.

New root growth suppressed by a 

misapplication of a pre-emergent herbicide,

displaying the symptomatic root clubbing.

Pre-emergent herbicides “prevent” annual weeds like crabgrass and foxtail from becoming a problem by killing very young, germinating seeds and seedlings; they don’t sterilize the soil, and they don’t kill seeds in the soil. These herbicides kill the young crabgrass, foxtail, and barnyardgrass seedling by stopping root formation – so the tiny plant can’t take up water and dies from drought stress. The crabgrass preventers used most often on home lawns (by lawn care companies, as well as in do-it-yourself products sold to the homeowner) include pendimethalin (Scotts crabgrass prevention products), prodiamine (sold as Barricade; also in Ferti-Lome, Monterey, Bonide, and Pennington home lawn care products), and dithiopyr (sold as Dimension; also in some Ferti-Lome, Hi-Yield, Bonide, and Pennington homeowner products).

Note the root clubbing (red arrows)
on shallower roots: deeper
roots (green oval) are more normal
in appearance because they are
growing beneath the pre-emergent
herbicide layer.

Misapplication due to poor technique (excessive overlap), using a faulty spreader, and intentional or unintentional application at excessive rates can damage desirable turf by stopping or stunting root production in the spring – when these products are typically applied AND when the grass plant is forming its root system. Damaged roots can’t take up water effectively, resulting in turf that is very drought sensitive. Severely damaged plants die – often in spots in the lawn where there was excessive overlap (as in the photos) – leaving brown strips or spots.

Diagnosing this injury can be tricky. Plants on the border of the dead turf will often display stunted root systems – with roots showing little or no branching and a distinctive “clubbing” at the end of the stunted roots. Because pre-emergent herbicides aren’t very water soluble and tend to remain near the surface of the lawn, deeper roots (maybe only an inch or so deeper; see photo) may grow more normally and not display the clubbing seen on roots growing near the surface. Above-ground, the turf may appear dead or severely thinned in stripes that follow application/overlap patterns. As the turf thins, new leaves formed by the surviving grass plants will be wider/more coarse due to the lack of crowding by adjacent plants (the more dense a turf is, the finer the leaf blades will be). The herbicide-stressed turf may also be more susceptible to diseases like leaf spot and dollar spot.

More subtle above-ground symptoms of
pre-emergent herbicide injury on a Kentucky
bluegrass lawn.

Pre-emergent herbicides can last a long time in the soil (4-6 months) – a good thing for providing season-long weed control. That long residual is a bad thing, however, when a pre-emergent causes turf death from over-application – and the residual effect can be even longer because of the very high rates of application that have killed the grass. This makes it difficult to repair areas by overseeding into them – because the herbicide will kill the young seedlings as they germinate. Creeping grasses (bluegrass, the more rhizomatous tall fescue cultivars, bermudagrass) will grow into the killed areas slowly over the summer. Repair by overseeding may have to wait until fall, when the herbicide has been degraded by soil microbes and other degradation forces in the soil. Worth trying, however, is core cultivation/aeration of the affected areas, followed by overseeding with perennial ryegrass. The seed will germinate below the herbicide “layer” on the surface and has a good chance of surviving and masking the damaged turf.

The take-home message? All herbicides have the potential to harm non-target turf, so always follow the label instructions and apply the product using good technique and well-maintained, properly-calibrated equipment.

Crabgrass is Here - Finally!

Tony Koski, Extension Turf Specialist

Seedling crabgrass (May 22) in Fort Collins.
Notice the young plants are coming up in a dead
plant (a weed "cadaver") from last year. This is
why it's important to encourage healthy grass
growth in weedy lawns in the fall - to break the
cycle of seed germination the following year.

The up and down spring – periods of above normal heat and below normal cold spells – has delayed crabgrass seed germination by about 2 weeks. That’s a good thing if you were a little late putting out your crabgrass pre-emergence herbicide (aka crabgrass preventer).

But now that crabgrass HAS germinated, control efforts (if you want to control crabgrass and its warm-season weedy cousins – foxtail and barnyardgrass) should be focused on post-emergence herbicide products. Once you can see these annual grassy weed seedlings, it is too late to use a pre-emergence product.

As with any landscape pest, it is absolutely essential that you accurately identify the pest in question before purchasing and applying the control product. It makes no sense – environmentally, financially, and for your precious time – to apply a product that won’t work because you haven’t correctly identified the pest.

This is not crabgrass! Crabgrass and other seedling
grassy weeds are still very small now. This is a
clump of tall fescue - which will not be killed by
crabgrass control products containing quinclorac.

For example, crabgrass and the other just-germinating warm season grassy weeds are still very tiny now. If you have large, fast-growing, “ugly” (coarse, clumpy, wide-bladed) grass growing in your lawn NOW it is NOT crabgrass – which means that none of the herbicides labeled for control of crabgrass will eliminate these unsightly, undesirable grasses. We have blogged previously about grasses that people mistakenly refer to as “crabgrass”. These unattractive, perennial grasses can’t be controlled with either the pre- or post-emergence crabgrass control products.

What to use NOW for young/seedling crabgrass, foxtail, and barnyardgrass? The following products are available in the garden product aisle at big-box and hardware stores, and at better nurseries and garden centers. What they all have in common is the ingredient “quinclorac” (and all contain herbicides for broadleaf weed control as well, like 2,4-D, dicamba, MCPP, etc.). Quinclorac provides excellent control of the most common summer annual grassy weeds: crabgrass, foxtail, and barnyardgrass in bluegrass, ryegrass, and fescue lawns.

Bayer Advanced Lawn Weed & Crabgrass Killer (quinclorac, 2,4-D, dicamba)
Ferti-Lome Weed Out with Crabgrass Killer (quinclorac, 2,4-D, dicamba)
Monterey Crab-E-Rad Plus (quinclorac, 2,4-D, dicamba)
Ortho Weed B Gon Max plus Crabgrass Control (quinclorac, 2,4-D, dicamba)
Roundup for Lawns - Northern Lawns (make sure it’s the Roundup FOR LAWNS!; quinclorac, dicamba, MCPA, sulfentrazone)
Spectracide Weed Stop For Lawns Plus Crabgrass Killer (quinclorac, dicamba, 2,4-D, sulfentrazone)

Crabgrass and its cousins are much easier to
control now - when they are small plants- than
in a couple of months when they have grown to a
plant of this size. Large crabgrass plants are very
difficult to kill.

It’s much easier to control crabgrass and its cousins this time of the year, when they are small. These grasses grow larger very quickly as we get sustained warm/hot temperatures. Large crabgrass plants are much more difficult to kill.

Make sure that you are spraying the right product for the weed in question! If you need help with the identification of weedy grasses – or any weed – in your lawn, you can bring a sample to your county Extension office. Or email me a high resolution photo of the grass (tony.koski@colostate.edu). 

We've blogged about crabgrass and other weedy grasses before...go here and here to see more photos of crabgrass and other weedy grasses, with hints on how to identify and control them.

And, as always, read the label for any pesticide you use and follow all instructions to ensure effective weed control and to avoid injury to your lawn or other non-target plants in your landscape.

Gardening for Drought Conditions

Here in Western Colorado we only got ½ of our average moisture last year and we are not doing any better this year.  Although the North and East portion of the state has gotten more moisture, since waters from Western Colorado are piped over the divide to Eastern Colorado, we all win if we can use our water sparingly.

http://droughtmonitor.unl.edu/

 

Drought Intensities

·               None: No Drought

·               D0: Abnormally Dry

·               D1: Moderate Drought

·               D2: Severe Drought

·               D3: Extreme Drought

·               D4: Exceptional Drought

Concerns with drought are saving trees since they are much more permanent and provide so many benefits from shade to reduction of crime and about 100 more reasons to have trees.  Water for the trees.   https://digitalcommons.usu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1013&context=cwel_extension

 Often we see people retrofit their landscape to xeriscape (dry scape or low water landscapes)but they forget about the needs of the trees   http://extension.colostate.edu/topic-areas/yard-garden/xeriscaping-retrofit-your-yard-7-234/

Xeriscape does NOT have to mean cactus and succulents, but we love ours at the TRA Mesa County Extension Office, Photo by Susan L. Carter

And certainly there are certain situations where we need grass like ballfields areas for pets etc…  But we can minimize the amount of lawn and water features that are not necessary.

If starting a new landscape, use the principals of xeriscape. http://planttalk.colostate.edu/topics/water-wise-xeriscape/1901-xeriscape-basics/

Note I did not say ZERO scape, there is no such thing and rockscapes are very hot and increase cooling needs of your home and business thus using more water. Use plants that require less water like native plants suited to your elevation and area are great choices.  http://planttalk.colostate.edu/topics/trees-shrubs-vines/1710-native-plants/

Studying Plants on the Grand Mesa, Photo By Susan L. Carter

And consider that sometimes we have areas that are naturally wetter such as drainages or seeps, so install plants that like more moisture in those situations.  We call that Right Plant, Right Place. 

Here is a recent video I did for our area on ideas to save water. Water Landscape Drought Go to the Pro Tip:  https://youtu.be/GK8M4vZC9a0

And some quick bullet points of what is in the video as well as additional tips.

•  Turn off your sprinklers before there is runoff.  Runoff lets us know the soil is a “field Capacity”, can hold no more water, and may deprive the roots of oxygen thus suffocating your plants.
• Make sure you are not irrigating hardscapes such as patios, driveways and sidewalks.
• Use a long skinny screwdriver or soil moisture to check moisture at 6” or deeper depth to determine if you need to water.
• Water at night.  And don’t set it and forget it; I’m talking about your irrigation clock.  Watering needs peak in July.  Then start to reduce irrigation to slow plants down for fall.  They will acclimate better to winter and be healthier.
• Never water everyday unless you just installed seed or sod.  Then water daily for the first month and start switching to less frequent deeper soaks to get roots deeper.  If you have to water daily to keep plants alive then something else is wrong like improper irrigation system setup or soil issues.  See our LISA, Landscape Irrigation Self Audit Website, and ask your local Agent if they have a kit you can check out.  http://extension.colostate.edu/topic-areas/yard-garden/lawn-irrigation-self-audit-lisa/
• Turf will get a blue tinge or footprints will stay in the lawn when it needs water.
• Group plants with similar watering needs together.  This is called Hydrozoning.
• Watering During Drought Factsheet:

http://extension.colostate.edu/topic-areas/yard-garden/watering-a-home-landscape-during-drought-7-240-2/

You can create beautiful landscapes using low water plants it your choices are much larger than just cactus, although they can be beautiful too. 

Yellowhorn Tree and other Xeric Plants at Mesa County CSUE TRA office

And remember when first planting, even a cactus needs water to get established.  So be a savvy water-er and check your plants and soil before you water and we will all benefit.  Enjoy where we live, it’s a drier state. 

By Susan Carter, Horticulture Agent, CSUE Tri River Area.

Lawn Winterkill: Lessons from 2016-'17

Tony Koski' Extension Turf Specialist

It’s been a dry fall and early winter throughout most of Colorado – in spite of the recent snow (that’s rapidly disappearing as I write this today). Little precipitation, combined with windy, sunny, and warm days, is a pretty good recipe for some winter turf injury (aka “winterkill”). Throw in some alternating extreme cold with the warm days and things get potentially worse for turf, trees, and shrubs in our landscapes. But not all “winterkill” is the same when it comes to turf. Here are some examples from the spring of 2017 (these were all in April/May) to illustrate that point.

Winter injury from drought – enhanced by VERY thick thatch in this bluegrass lawn. Note that the green turf is where water was supplied by a gutter downspout, runoff from the driveway (plus the concrete acts as a “mulch” for turf growing alongside it), and runoff from the neighbor’s gravel-covered plastic.

This lawn had been sodded in early 2016 and was perfectly green and healthy going into the winter of

Dead area is where home construction had been "staged",
resulting in extreme soil compaction before sodding.

2016. It had been handwatered religiously throughout 2016, was mowed the correct height, and was otherwise perfectly cared for. The problem was the soil under the sod. The dead area was where home construction was “staged”: lumber, roofing, tile, other building supplies were dropped off – along with concentrated, heavy, constant traffic. The soil was not tilled sufficiently prior to sodding, so almost no rooting occurred following sodding. The constant handwatering in 2016 kept it alive and looking perfect, but the lack of rooting during the winter resulted in winter desiccation and sod death in spring 2017.

Sod had not rooted into the compacted soil, which
lead to winter kill in spring 2017.

Winter mite injury

This lawn suffered from turfgrass mite feeding in the late winter and early spring. Mite feeding and reproduction is favored by dry conditions. Drought-stressed turf is often killed by mite feeding in the spring if numbers are high enough and no snowcover or spring rains occur – and if winter watering isn’t performed at least a few times during the winter.

The common thread here? Water! Turf, trees, shrubs, and other landscape plants may not be growing and thus USING much water during the winter. But when it’s dry, windy, sunny, and humidity is low, our landscape plants are LOSING water. When we don’t receive enough snow to provide periods of snow cover during the winter, and plants aren’t mulched (like turf!), are young and not fully established, or have poorly developed root systems, winter watering can be essential for preventing winter injury or death.

When weather allows (above freezing for a day or two), run a hose and sprinkler out to the drier parts of your landscape (especially south- and west-facing parts of your landscape), to new sod, trees, and shrubs, and to areas where you have experienced winter injury in the past (perhaps from turf mites). Apply enough water to moisten the crowns of the turf plants and to get some water into the root zone of new trees and shrubs. The goal isn’t deep watering, but rather to prevent desiccation of crowns and young root systems.

Ascochyta Leaf Blight on Lawns – 2017 Version

Mowing drought-stressed lawns can make
Ascochyta worse. Notice no disease at top
of photo - shadier and no drought stress here!

Tony Koski
Extension Turf Specialist

The appearance of Ascochyta Leaf Blight has become an annual springtime event on lawns in Colorado. We have written about Ascochyta before: see our 2013, 2015 and 2016 blogs on this lawn disease. For more detailed information on Ascochyta in lawns, read those blogs because I’m not going to repeat everything that we've already written about it.

What I do want to talk about is WHY the Ascochyta disease appeared so suddenly over the last week. We’ve been inundated with calls, emails and texts with a common theme: “My lawn was perfectly green, and now you should see it! What happened?”. The explanation of why – that the disease is incited by drought stress –  doesn’t make sense to people because it appeared after the very wet (2 plus inches of water) snowy/rainy storm that came on May 16-18. That abundance of moisture (here’s what people DON’T remember) was preceded by two WEEKS of above-normal temperatures and very dry weather (red flag weather, if you recall?). And while everyone who has seen this happen to their lawns claims they were watering, I saw a lot of drought-stressed turf in the week before the storm. All it takes to turn Ascochyta on is a day or two of drought stress and heat during the spring – which this graph clearly shows was probable in home lawns this May. Those who REALLY were watering their lawns (or have shady lawns, or north exposure lawns) are not seeing Ascochyta. 

Much of first half of May was warmer (red line) than average (green line).And there was almost no precipitation May 1-16. This is a perfect "recipe"for Ascochyta on lawns that aren't irrigated enough during warm springs.The disease cycle began BEFORE the wet storm, with the symptoms appearing immediately after the storm. The moisture came a couple of days too late!

Here are some pics of what we’ve seen the past week.

In these 2 photos, there is less/no Ascochyta in parts of the lawn that are shaded or receiving a little more water from gutter downspouts. Ascochyta is turned on by heat and drought stress in the spring

Some quick bullets on the disease (go here for more details):

• As bad as it looks, it isn’t dead!

• Affected turf will take 1-3 weeks to recover, depending on severity and turf species.

• It is NOT spread by mowing equipment – so there is no need to sanitize your mower.

• Fungicides are NOT EFFECTIVE for preventing or curing the disease – so don’t apply them!

• Adjust watering (and fix sprinkler coverage issues) to maintain consistent soil moisture, but not so that it is swampy (which will slow down recovery).

• This appears to be a disease that occurs when cool weather turns into hot weather (hence a spring disease), so it will pretty much disappear as we become consistently warm in the summer.

Ascochyta doesn't kill the grass plant. You will see new growth
under the dead leaves almost immediately following an outbreak
of this disease. Recovery can take 1-3 weeks, depending on
severity and grass species.

While you can see mowing patterns with Ascochyta, mowing and the mower
doesn't spread the fungus. The mowing is an additional stress when turf is
heat and drought-stressed - so the Ascochyta and mower stress combine to
cause the browning of the turf.