Crabgrass is out in full force in 2016!

Why is crabgrass so bad this year?
Several factors contribute to a bad year for crabgrass.
  • Crabgrass is a warm-season grass meaning that it thrives in hot conditions with optimum growth in temperatures ranging from 88 to 95 °F. However, our primary lawn species in Indiana are cool-season grasses and they prefer cooler conditions and have optimum growth in temperatures ranging from 68 to 77 °F. Therefore, our warmer than average summer resulted in an environment that encouraged crabgrass growth and decreased the plant competition from our existing cool-season grass lawns. NOTE: One minor exception to this is that tall fescue lawns - the cool-season turfgrass species with the best heat tolerance – had less crabgrass than Kentucky bluegrass and perennial ryegrass lawns.
  • The preemergence herbicides (crabgrass preventers) that are applied in spring to prevent the emergence of crabgrass seedlings work only as long as they remain in the soil. Generally, these products last in the soil about 60-120 days depending on a number of factors (rate applied, ingredient, turf cover, temperature, moisture, etc.). They breakdown in the soil overtime due to microbial activity.  When soil temperatures are higher, as they were this year, the preemergence herbicides breakdown more quickly. Additionally, the adequate rainfall that we had this year kept the soil moist and the microbial populations high, which also assisted in the herbicide’s breakdown. As such, a hot, humid summer results in the herbicide lasting a shorter length of time and the crabgrass “breaking through”. NOTE: When we have wet springs, some preemergence herbicides breakdown more quickly in the saturated soils due to anaerobic breakdown in saturated soils. It is a myth that preemergence herbicides leach through soils. They do not. Instead they are strongly bound (adsorbed) to the soil (at the surface where the crabgrass seed lays).
  • This was a good summer for turf diseases. Read the recent update from Dr. Rick Latin on disease in 2016. Crabgrass is susceptible to some diseases including leaf spot, but is generally not susceptible to the lawn diseases that cause our turf to decline in hot, humid summers. As such, lawns suffered and crabgrass did not.
  • Many homeowners mow too low and as a result, crabgrass increases. Lawns mown at 3.0 inches or higher have far fewer crabgrass problems than lawns mown short. Therefore, raise that mower so that you’ll have less crabgrass in the future. BONUS: Lawns mown at a higher height need mown less frequently, have deeper roots, are healthier, and need less watering.
  • Lastly, crabgrass plants get pretty big by the end of the summer. One plant can cover an area as big as a pie plate. This makes the lawn look poor even when a preemergence herbicide was applied. Keep in mind that there are thousands of crabgrass seeds in the soil (millions in some lawns). Even when a preemergence herbicide controls 95% of the crabgrass plants in your lawn, it may still not appear to have worked that well in a year like this.

What to do next?
The good news is that the end is near. Crabgrass will get zapped with the first hard frost this fall and you can begin now to battle against it and keep it from being problematic next year. This fall you’ll want to
  • Fertilize your lawn (at least once, twice is better). Read more here. Fertilizing the lawn in the fall months will help increase turf density and allow the turf to be much more competitive with crabgrass the following year.
  • Seed thin areas of your lawn as soon as possible. Read more here.
  • Adjust your mowing height so that your lawn is cut at 3.0 to 4.0 inches tall to help prevent future crabgrass problems.
Should I attempt to treat the crabgrass now in September?
NO! This is a summer annual plant, meaning that it will die naturally soon with the first frost. Additionally, large crabgrass plants are very difficult to control with herbicides. Two herbicide applications are needed to kill large, tillered-plants. As such, it makes no sense to spray expensive, marginally effective applications on a plant that is about to die naturally.

More information about crabgrass:

Aaron Patton
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Lawn Diseases 2016

The summer of 2016 has been quite favorable for the development of an assortment of infectious diseases on residential turf.  The primary driver of all of this disease activity is the weather.  In the lower Midwest, the combination of elevated temperature and ample precipitation since the beginning August of has spawned outbreaks of brown patch, dollar spot, Pythium blight, leaf spot diseases, and the appearance of symptoms of summer patch and necrotic ring spot.  Although infection is almost entirely a function of temperature and moisture, there are other factors (addressed below) that may hasten the decline of turf once disease becomes established.

Turf species:  Not all turf species are susceptible to all diseases. 
In general, Kentucky bluegrass (KBG) is less prone to brown patch , dollar spot, gray leaf spot, and Pythium blight—but very susceptible to root diseases such as necrotic ring spot and summer patch.  Root pathogens are present in all soils, and infect turf as soil temperatures increase beyond 60F.  With ample moisture, infection will continue through summer.  Plants are killed outright in some instances, but in most cases, KBG can tolerate some infection.  However, during periods of environmental stress, infection-impaired plants cannot survive, and characteristic dead patches or rings or frog-eyes appear. 

After the droughty years of 2009-2012, many of us turned to turf type tall (TTF) fescue to better tolerate periods of dry weather.   The summers of 2015 and 2016 have revealed the weakness of these grasses in terms of susceptibility to gray leaf spot and brown patch.  They are not susceptible to root diseases-and that is an important reason for favoring this type of grass. 

This was not a good year for perennial ryegrass (PRG)!  Its only redeeming feature is that PRG is not susceptible to the root diseases.  We are learning that even the so-called “gray leaf spot resistant” cultivars will suffer during prolonged periods of favorable weather.

Fertility:  Nitrogen status will influence disease severity.
Some pathogens are favored by nitrogen levels that approach excess, others thrive when nitrogen levels are low.  I usually recommend a little (0.2 lb/M) supplemental N in early summer, when the fall-applied reserves have been used.  This helps keep plants growing through summer and helps recovery from red thread, dollar spot and actually can prevent serious rust outbreaks.  However, this practice can be risky on PRG and TTF because brown patch is favored by lush growth promoted by nitrogen.  Also, from my experience, supplemental N (0.25 – 0.50 lb/N) during summer can help mask the effects of summer patch and necrotic ring spot (on KBG only).  Again this can be risky because some leaf spot diseases (NOT gray leaf spot) flourish when leaf and shoot growth are stimulated by N.   Pythium blight, a disease that strikes when temperatures exceed 90F during the day and 70F during the night is also favored by high nitrogen nutrition.  This year seems to have been one where we are  “damned if we do and damned if we don’t” with regard to nitrogen fertility.

Irrigation:  Timing and amount.
We cannot define the best time to irrigate in all different scenarios, but we do know the worst time—early evening hours (6:00 pm - 9:00 pm).  Irrigation at this time adds to the period during which leaves are wet.  An increase in leaf wetness by a few hours can mean the difference between a severe outbreak and the appearance of some mild symptoms. It is difficult to generalize about the amount of water to apply.  However, from a disease prevention perspective, deep infrequent watering is better than light frequent irrigation.

Growth stage:  Pitfalls of over-seeding during disease-favorable weather
We tend to think about repairing damaged stands of turf in late August through September. Seedlings and juvenile plants are most susceptible to infection.  Normally, the risk of infection is acceptable because weather changes to a pattern that favors turf growth more than fungal growth.  Not this year. 

Fungicides:  Timing is everything (almost)
Fungicides are valuable chemical tools to help avoid or mitigate turf damage.  Granular products are available with multiple active ingredients to protect against a variety of diseases.  However, they work best when applied preventatively, or before symptoms appear.  Having said that, I am convinced that modern fungicides can be used to control dollar spot, brown patch, red thread, and rust--even after symptoms appear (but certainly long before the lawn is wiped out).   Leaf spot diseases (including gray leaf spot) are best controlled before symptoms show. When symptoms become apparent to most observers, infection is way beyond the stage of a “mild” infection.  Most of these fungi reside in the turf or thatch or soil, so the same areas of turf will be prone to outbreaks each year.  The weather will determine if a severe outbreak materializes. This year the weather favored disease.
The most difficult “fungicide” decisions involve the root diseases on KBG.  Fungicides can be effective, but they must be applied in late spring, often before there are any symptoms at all.  (We know that fungicides are NOT effective against root diseases once the patches and/or rings are in full form).  So, it is important to understand the disease history of the site before considering a fungicide option.  Caution--because fungicides do not move down to the roots through the leaves inside the plant, fungicides must be washed off leaves (into thatch/soil) for any chance of success.  Getting the right amount of chemical to the right place at the right time is not easy , and this difficulty further complicates decisions to use fungicides for controlling root diseases on residential turf.

More than any time in the past 10 years, weather during the summer of 2016 has favored outbreaks of so many turf diseases.  Mercifully, fall is approaching and we can begin the process of repairing damaged lawns.  We should also take note of diseases that caused problems this year and the factors that influence their outbreaks. To be sure, when such weather patterns return in the future, the same disease threats will revisit our lawns!

For further information on turf diseases, visit our website at
or, use your favorite browser to search “Purdue Turfgrass Disease Profiles”.

Rick Latin, Ph.D.
Professor of Plant Pathology
Purdue University

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Turf and Landscape Field Day on July 12, 2016

On Tuesday, July 12, 2016 the Purdue Turf Program and the Midwest Regional Turf Foundation will host the Turf and Landscape Field Day. The Turf and Landscape Field Day is Indiana’s largest green industry field day. This will be the third year with landscape research tours added. Specialists from four different departments in the College of Agriculture will share their findings and recommendations to Green Industry professionals. We invite you to join us. Attendees will receive education (with CCHs in categories 2, 3a, 3b, 6, and RT), listen to research updates, receive product updates from exhibitors, and also network with others in the Green Industry.

The field day will feature about 40 exhibitors representing companies from around the region ranging the gamut from equipment, seed, fertilizers, pesticides, landscape plants, hardscape and more. Last year approximately 525 attendees from Indiana and all its surrounding states attended to learn more about Purdue’s latest green industry research. Attendees came from a variety of backgrounds including business owners, managers and staff of wholesale and retail nurseries, landscape management firms, greenhouse growers, golf course superintendents and staff, lawn care companies, grounds maintenance departments, landscape design and installation firms, garden centers, consulting firms, educational institutions, suppliers and more!

This year’s field day will have three morning research tours and four afternoon tours including a field trip to Purdue's New Ackerman-Allen Golf Course. We will have sixteen different speakers at the field day including Purdue faculty/staff from Botany and Plant Pathology, Entomology, Horticulture and Landscape Architecture, and Forestry and Natural Resources.

YOU CAN STILL REGISTER ONLINE for this July 12 event until midnight, July 8 at the onsite price
THOSE WISHING TO REGISTER AFTER July 8 should register onsite at the field day at 8:00 am.
Register on-line, US mail, scan/email attachment, fax or call. 
Exhibitor Registration PDF
Brochure and Attendee Registration PDF
Register On-line (NEW registration system)

We look forward to seeing you this year at the Purdue Turf Field Day!  If you have any questions please contact Tammy Goodale at 765-494-8039 or

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Weed of the month for August 2015 is Field Paspalum

Field Paspalum  

Biology: Field paspalum (Paspalum laeve Michx.) is a warm-season perennial weed with short rhizomes similar to dallisgrass (Paspalum dilatatum Poir.). Much of the below Weed of the Month entry comes from research conducted in Indiana on how to control Field Paspalum. That research was published in 2012. Reicher, Z.J., A.J. Patton, and D.V. Weisenberger. 2012. Suppression of field paspalum in Kentucky bluegrass with mesotrione. [Online]. Appl. Turfgrass Sci. doi:10.1094/ATS-2012-0626-01-RS.

Identification: Field paspalum is a wide-bladed (3-10 mm wide), warm-season perennial turfgrass that becomes easily visible in mid-summer. It can have either dark green or yellow green foliage. It is found in cool-season and warm-season turf. It has a short rhizomes near the soil surface but spreads primarily by seed. Although these species have short rhizomes, they effectively are a bunch-type plant and form scattered clumps of grass in the landscape.  

Field paspalum and dallisgrass can be distinguished from one another by a few characteristics although they are more similar than different. The range of adaptation is different with field paspalum distributed into farther north than dallisgrass. Field paspalum can be found in Kansas, Missouri, Illinois, Indiana, Ohio, Pennsylvania, and Maryland whereas dallisgrass is less commonly distributed in those areas (Fig. 1). Leaf sheath, leaf blades, and rhizomes of the two species are similar (Fig. 2). Both species have terminal panicles with racemosely arranged branches of similar number and length (Fig. 3). Dallisgrass can be distinguished from field paspalum by the spikelets in pairs appearing to be in four rows on dallisgrass compared to two in field paspalum (Fig. 3). Additionally, dallisgrass has long, silky hairs on the spikelets while field paspalum is glabrous (Fig. 3). Dallisgrass also has a 5- or 7-veined glume while field paspalum has a 3-nerved upper glume with veins at the margins (Fig. 3).

Fig. 1.

Fig. 2.

Fig. 3.

Cultural control: Reduce soil compaction and promote practices that increase turf density. The most effective way to control these weeds is to dig up the clumps in the turf with a shovel.

Biological control: None known.

Chemical control: Another option is spot treatment with the nonselective herbicide glyphosate (Roundup and others). At least two glyphosate applications are needed. Apply when the plant first greens up in the spring (late April or May), and again when regrowth appears. Multiple follow-up applications may be required. You can also spray dallisgrass and field paspalum in October before they turn off color and enter winter dormancy. Use a 1-2% spray solution (1.3-2.6 fl oz of glyphosate/gal of water).

Obviously, glyphosate is going to kill some of the desirable grass and could leave big, brown spots in the turf so spot apply the herbicide only to the weed and not to the turf, if possible. You can even use a paintbrush, sponge, or foam applicator to apply the glyphosate only to the weed to help reduce the risk of injuring the desirable turf.

In Kentucky bluegrass, fine fescue, tall fescue, or perennial ryegrass lawns, three applications of mesotrione (Tenacity) at 5 oz/A spaced with a two-week application interval should reduce dallisgrass and field paspalum by 75 percent or more. Start making these applications in June. In tall fescue, two applications of fluazifop (Fusilade II) at 5-6 oz/A at three- to four-week intervals starting in late-April and September will suppress field paspalum and dallisgrass. Adding triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A to fluazifop will improve turfgrass safety. Do not use on seedling tall fescue less than four weeks old.

Tribute TOTAL (thiencarbazone + foramsulfuron + halosulfuron) at 3.2 oz/A also is effective at controlling dallisgrass in bermudagrass and zoysiagrass turf when making multiple applications in later summer and early fall before winter dormancy, and a subsequent follow-up application in spring.

In zoysiagrass, two applications of fluazifop (Fusilade II) at 3-4 oz/A at three- to four-week intervals during the summer will suppress field paspalum and dallisgrass. Adding triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A to fluazifop will improve turfgrass safety.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist, Purdue University
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New Turf Disease Publications

Turfgrass Disease Profiles: Root Knot Nematode

This publication describes the root knot nematode life cycle, and how to identify and manage them in turf. Free download at: 

Turfgrass Disease Profiles: Spring Dead Spot

Spring dead spot (SDS) is the most serious disease of bermudagrass. It is a root disease that kills individual plants, thins turf stands, and increases vulnerability to weed infestation. This publication describes the symptoms of SDS and suggests ways to control it. Free download at:

Bermudagrass spring dead spot.

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Monitoring and Managing Caterpillars

Doug Richmond
Associate Professor and Entomology Extension Specialist
Department of Entomology
Purdue University

Caterpillars are the larvae of moths and butterflies and several common species are capable of damaging turfgrass. This publication will help you detect and identify the most common caterpillars associated with turfgrass.

Armyworms are the immature stage (larva/caterpillar) of the several widely distributed moth species. Species most often associated with turfgrass include the common armyworm Mythimna unipuncta (Fig. 1) and fall armyworm Spodoptera frugiperda (Fig. 2) These insects are better known as pests of agricultural crops, but they sometimes infest turfgrass, especially in areas that border agricultural fields or unmanaged areas such as ditches or fencerows. Outbreaks in turf tend to be patchy and sporadic, but sometimes occur on a larger scale. As their name implies, armyworms may occur en masse and can migrate across large areas of turf, cutting it down to crown level as they go. Because they often go unnoticed while they are small, turf may seem to disappear almost overnight once these insects reach a larger size. Small patches of brown and overall ragged appearing turf are more typical symptoms. Fortunately, unless the turf is severely stressed by drought, it generally recovers well with irrigation or rainfall and adequate fertility.

Figure 1.  Common armyworm with lengthwise brown, yellow and white stripes. 

Figure 2.  Fall armyworm with lengthwise stripes and inverted Y-shape on head (J. Obermeyer photo).

Cutworms are also the immature stage (larva/caterpillar) of several moth species, but only two species are typically associated with turfgrass. The black cutworm Agrotis ipsilon (Fig. 3) is primarily a pest of closely mowed, golf course turf where it creates unsightly pock-marks or depressions in highly manicured playing surfaces. Black cutworm damage interferes with play and can be a serious nuisance to golfers, especially with regard to their “short game”. The bronze cutworm Nephelodes minians (Fig. 4) is a more sporadic pest of lawns and low maintenance turf. Bronze cutworm has a penchant for feeding on turf under the cover of snow and damage from this insect is often unnoticed until after the snow melts and turf begins to green-up. Damage rarely occurs after mid-June.

Figure 3.  Black cutworm caterpillar and damage on bentgrass. 

Figure 4.  Bronze cutworm caterpillar with alternating dark and light lengthwise stripes.

Sod webworms
Sod webworms are the immature stage (larva/caterpillar) of several small buff-colored moths that are common during the summer months. The moths are easily observed as they fly from the turf when disturbed, only to light again several yards away where they typically align themselves lengthwise along a blade of grass. They roll their wings close around the body when at rest and they possess an elongated snout that gives their heads a conical appearance. Adults do not feed, but mate and drop their eggs into the turf canopy during the evening. Larvae (Fig. 5) overwinter in silken tunnels and emerge in the spring to feed on grass stems crowns and leaves. Damage usually occurs in sunny areas and may appear as irregular, brown patches that take on a thin or ragged appearance during the summer. On short-cut golf course turf, overwintered larvae may attract attention due to their habit of knitting together small pieces of debris or topdressing material over the entrances to their burrows. Two to three generations of sod webworms may occur each season.

Figure 5.  Sod webworm caterpillar with rows of dark, square spots.

Early detection of an insect infestation can be accomplished using a systematic approach that combines broad scale, coarse inspection of general turf appearance with fine scale inspection of individual plants or plant parts. If turf appears discolored or thin upon coarse inspection, examine suspect areas more closely by looking for feeding scars and tattered foliage. Probe the margins of damaged patches of turf by scratching through the thatch and looking for movement. Green fecal pellets also may be present and can be a good indicator for the presence of caterpillars.
The use of a disclosing solution (1 tablespoon of JoyÒ Ultra, DawnÒ Ultra or IvoryÒ Clear liquid dishwashing detergent in 1 gal. of water per 1 square yard of turf) poured over the surface of infested turf will encourage caterpillars to come to the surface where they can be collected and identified (do not use PalmoliveÒ as it may burn the turf). It is important to keep in mind that some caterpillars are only active at night and may be challenging to find during the day.
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