Weed of the month for July 2015 is Common Purslane

Purslane 

Biology: Common purslane (Portulaca oleracea L.) is a summer annual broadleaf weed (Fig. 1) that is commonly found in low maintenance turf swards (Fig. 2), turf seeded in summer (Fig. 3), next to sidewalks and driveways, and in mulched beds and gardens (Fig. 4).  Purslane is a succulent plant with a prostrate growth habit, and it is one of the most common weeds in the world, especially in vegetable production.  Purslane can reproduce by both seed and stem fragments.  A single plant can produce as many as 240,000 seeds in a single year (Zimmerman, 1970), and seeds can be viable for up to 40 years (Darlington and Steinbauer, 1961).  Severed stems are able to from adventitious roots, which allows the weed to regrow from stem or intact root fragments following cultivation (Miyanishi and Cavers, 1981).  Purslane has a unique way of conducting photosynthesis in that it is able to switch from C4 to crassulacean acid metabolism (CAM) in the presence of short days or drought stress (Proctor, 2013).  In short, CAM photosynthesis is advantageous in arid conditions because the plant closes its stomata during the day to reduce water loss and opens them at night to collect the carbon dioxide required for photosynthesis.  Additionally, purslane is an edible plant that can be found at farmers markets for use in crunchy salads or ethnic cuisine, and it can be cultivated for ornamental use (Fig. 5).

Fig. 1. Common purslane.

Fig. 2. Common purslane in thin turf.

Fig. 3. Arrows marking purslane seedlings.

Fig. 4. Common purslane is a common weed along sidewalks and in gardens and landscape beds.

Fig. 5. Ornamental purslane. "Toucan Hot Mix' shown.


Identification: A succulent broadleaf, purslane has fleshy, glabrous (smooth) leaves and stems.  Leaves are green with a red margin, lack a petiole, and are rounded at the tip.  Additionally, the leaves of purslane can be alternately arranged near the crown of the plant and become opposite or whorl-like towards the apex.  Stems are plump, red in color, and originate from a central point to from a rosette.  Prostrate spurge is a look-a-like weed to purslane (Fig. 6).  Prostrate spurge will have smaller leaves and stems and a more strictly opposite leaf arrangement that purslane.  Additionally, spurge, like milkweed, will exude a white sap when the stem is severed. Purslane has a yellow flower (Figs. 7 & 8) that is rarely seen and following pollination, its seed pods (Fig. 9) can hold many seeds (Fig. 10).

Fig. 6. Prostrate spurge (left) and common purslane (right).

Fig. 7. Common purslane flowering.

Fig. 8. Close-up of the common purslane flower.

Fig. 9. Following pollination and ovule fertilization, a seed pod encapsulates the seed.

Fig. 10. When the seed pod opens, many seeds (>20) per pod are spilled onto the ground.


Cultural control: Common purslane is generally not an issue in a healthy and well-established turf stand, but it can be found in thin or newly established areas.  Thus, cultural practices that improve the competitive ability of the existing turf and/or promote the establishment of a new stand are the best methods of purslane management, prevention, and control.

Biological control: The purslane sawfly (Schizocerella pilicornis) and the portulca leaf-mining weevil (Ceutorhynchus portulacea or Hypurus portulacea) can contribute to reducing purslane infestations, though total control may not be realistic.

Chemical control:Triclopyr, fluroxypyr, and dicamba are the most effective herbicides for postemergent purslane control in cool-season turf.  In addition to the herbicides already listed, metsulfuron or a combination of sulfentrazone and metsulfuron can be used in warm-season turf for postemergent purslane control.  For preemergent purslane control, spring applications of isoxaben or late-winter applications of simazine can be used in cool-season and warm-season turf, respectively.

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.

Quincy Law, Graduate Research Assistant, Purdue University

Aaron Patton, Turfgrass Extension Specialist, Purdue University

 
References:
  1. Darlington, H.T. and G.P. Steinbauer. 1961. The eighty-year period for Dr. Beal’s Seed Viability Experiment. American Journal of Botany 48:321-325.
  2. Miyanishi, K. and P.B. Cavers. 1981. Effects of hoeing and rototilling on some aspects of the population dynamics of pure stands of Portulaca oleracea L. (purslane). Weed Research 21:47-58.
  3. Proctor, Christopher. 2013. Biology and control of common purslane (Portulaca oleracea L.). Ph.D. Thesis, University of Nebraska-Lincoln.
  4. Zimmerman, C.A. 1970. The causes and characteristics of weediness in Portulaca oleracea L. Ph.D. Thesis, University of Michigan.
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What Was That? Flying Green June Beetles Will Get Your Attention

Green June beetles Cotinus nitida have been flying in many areas across the Midwest and although they are harmless, their sheer size can be very intimidating to folks who don’t recognize them. These large, attractive, emerald and copper colored beetles (Fig. 1) are one of several species of scarab beetles whose larvae are known as annual white grubs. Of the insects belonging to this group Green June Beetles may be one of the most interesting, not only because of their charisma, but also because of their peculiar biology and behavior.

Figure 1. Adult Green June beetle feeding on a ripe peach


Adults typically emerge from the soil during July and heavily infested areas may appear to swarm with activity as the beetle fly about during the day. Adults feed on a variety of ripe fruits and vegetables and may also be attracted to the sap oozing from wounded trees. Emerging females secrete a milky fluid that attracts males to the soil surface for mating as shown in the accompanying video taken by Dr. Cliff Sadof (video 1).


Video 1. Adult Green June beetles in a mating swarm (Video by Cliff Sadof)

After mating, adult females dig burrows in the soil pushing up small mounds of soil in the process. They seem to prefer high organic matter soils and may be attracted to soils fertilized with compost or manure-based products. Groups of 10-30 eggs may be deposited into a compacted ball of soil, about the size of a golf ball, that the female creates. Several such egg masses may be present in a single burrow composed of several chambers.

After the eggs hatch, larvae (Fig. 2) begin feeding on organic matter by mining through the soil. This activity loosens the soil and may dislodge plant roots, sometime causing damage to turf. As the larvae develop, their burrows may reach 6-12 inches in depth. Soil displaced during this process is deposited at the soil surface creating mounds of soil that may attain 2-3 inches diameter (Fig. 3). On warm nights, especially following rain, larvae may emerge completely from their burrows, crawling considerable distances on their backs! (linked video 2) They have been known to end up on sidewalks and patios, or in garages and swimming pools!

Figure 2. Green June beetle larva can reach 2 inches in length

Figure 3. Mounds of soil formed by burrowing Green June beetle larvae
Video 2. Green June beetle larvae can cover significant distances crawling on their backs

Larval burrowing activity may be observed anytime from late summer through early spring as long as soil temperatures are sufficient and larvae usually pupate by mid-June.
The pupal stage lasts about 3 weeks and emerging adults must dig to the surface to start the cycle again.

If green June beetle damage becomes a concern, keep in mind that a large, showy, orange and black colored parasitic wasp, Scolia dubia (Fig. 4), is often able to keep this insect in check. Although the presence of these wasps (which may occur in small swarms) can sometimes alarm homeowners, they are relatively docile and don’t usually sting unless captured or otherwise provoked. In areas where these wasps are active, application of insecticides should be avoided because of the biological control services they provide.


Figure 4. The Scoliid wasp Scolia dubia parasitizes Green June beetle larvae
(Photo by Sharon Moorman)

Because green June beetle adults are attracted to high organic matter soils, thatch layers should be managed and kept at a minimum. Reduced use of compost topdressings and manure based-fertilizers may reduce the attractiveness of turf areas to egg-laying females.
If insecticides must be used, early instar grubs that are present in late July and early August are the best target because they are relatively easy to control. Any soil insecticide labeled for white grubs will be effective if the application is followed by enough irrigation to move the material into the thatch where the larvae are feeding.

Applications targeting later instar larvae should be left on the surface and not irrigated since these larvae come to the surface to feed at night. However, pre-treatment irrigation can encourage these larger larvae to come to the surface where the insecticide is deposited. Neonicotinoid insecticides are sometimes not effective for controlling late instar green June beetle larvae. Carbaryl (Sevin) or trichlorfon (Dylox) are recommended in such cases.

It should be noted that insecticides applications targeting late instar larvae will often result in larvae dying on the surface. Mortality of large numbers of these larvae may create a problematic stench when conditions are conducive – take my word on this.


by Doug Richmond, Associate Professor and Turfgrass Entomology Extension Specialist

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2015 Turf and Landscape Field Day a Success


On Tuesday, July 14, 2015 the Purdue Turf Program, the Purdue Green Industry Working Group and the Midwest Regional Turf Foundation successfully hosted the Turf and Landscape Field Day. Rubber boots were needed at this year’s field day due to all the recent rains and we even had to extract a couple of cars from our grass parking lot but the weather on field day was wonderful and the education, food, and exhibitors were top notch!

The Turf and Landscape Field Day is Indiana’s largest Green Industry field day. This was the second year with landscape research tours added. Specialists from four different departments in the College of Agriculture shared with Green Industry professionals their research findings, recommendations, as well as advice on troubleshooting problems.

It was a great opportunity for those attending to receive education, research updates, product updates and also a great opportunity to network with their colleagues and exhibitors in the Green Industry. The field day featured 41 exhibitors representing companies from around the region ranging the gamut from equipment, seed, fertilizers, pesticides, landscape plants, hardscape and more. The 489 attendees where mostly from Indiana and all its surrounding states but many national representatives were also there from various companies 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 provided three morning research tours and three afternoon tours including a popular weed garden tour, discussion on water conservation, and a tour of landscape/tree research at the Meigs Farm.

Nineteen different speakers were at the field day including Purdue faculty/staff from Botany and Plant Pathology, Entomology, Horticulture and Landscape Architecture, and Forestry and Natural Resources. This year’s field day was once again a success and continues to be a leading provider of information and education among the Midwest turf professionals and the Green Industry. Mark your calendars for next year’s Turf and Landscape Field Day, July 12, 2016.

Thank you all for coming!

Aaron Patton, Turf Extension Specialist

Kyle Daniel. Landscape and Nursery Extension Specialist













 
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Look Out for Herbicide Resistant Weeds in Turf

Herbicide resistance can be defined as the acquired ability of a weed population to survive an herbicide application that previously was known to control the population. The number of herbicide resistant weeds has been rapidly increasing in agriculture in recent years. Currently, 459 unique cases of herbicide resistant weeds exist globally, with 246 species (143 dicots and 103 monocots) and with resistance to 22 of the 25 known herbicide sites of action including resistance to 157 different herbicides are known (weedscience.org).

In a recent article by Scott McElroy in Golf Course Management where he reviewed herbicide resistance among turf weeds, he stated that “the development of herbicide-resistant weeds will be one of the great challenges for golf course superintendents and other turf managers in the 21st century.” Further he added that herbicide resistance among turf weeds is not a “potential problem” but a current problem. This is best illustrated by the recent identification of an annual bluegrass (Poa annua L.) population in Alabama that was found to be resistant to Revolver (foramsulfuron), Monument (trifloxysulfuron), Image (imazaquin) and Velocity (bispyribac)(McElroy, 2013). We also have glyphosate, dinitroaniline (preemergence herbicides), and triazine (simazine and atrazine) herbicide resistance among other annual bluegrass populations.

While annual bluegrass is obviously a wide-spread and problematic weed in turf, herbicide resistance is not limited to just annual bluegrass and not just limited to golf courses. Goosegrass, marestail (horseweed), and smooth crabgrass are among other weeds that were identified as herbicide resistant and still other weeds like ground ivy are known to be “tolerant” of herbicides with as much as 3x rates being needed to achieve control of some populations.

Do we have any of these resistant weeds in turf in Indiana? Yes, but fortunately not very many at this time.
  • Quinclorac (Drive XLR8 and others) resistance exists in smooth crabgrass found on a golf course driving range tee in central Indiana. The quinclorac resistant smooth crabgrass in Indiana was unresponsive to quinclorac applications by the golf course superintendent at label recommended rates (Drive 75DF at 0.75 lb ai/A) as well as a 3x label rate of quinclorac (Drive 75DF at 2.25 lb ai/A). We quantified the resistance of this population in the greenhouse to be resistant to quinclorac rates of 80x or more.  
  • A population of buckhorn plantain was discovered in central Indiana at a location that had received more than 30 years of herbicide applications with 2,4-D containing products. We assessed the level of resistance of that population and found that it required about 16x the label rate of 2,4-D to produce the same amount of injury as a susceptible population. We were able to find an alternative herbicide that worked to control the buckhorn plantain at this site, but at a cost of $100/A rather than the $15/A it previously cost to control buckhorn plantain with a 2,4-D containing herbicide at this site.
  • We are also currently evaluating a population of suspected herbicide tolerant/resistant ground ivy. 
2,4-D resistant buckhorn plantain.

If you suspect you have a herbicide resistant weed, please contact me (ajpatton@purdue.edu)

10 things YOU should know about herbicide resistant weeds
  1. Herbicide resistant weeds are in turf and not just crop fields
  2. It is the tough to control weeds that are often developing resistance
  3. Few new herbicides coming to market to help control resistant weeds
  4. We aren’t currently doing a good job rotating the mode of action for herbicides/PGRs
  5. Preemergence herbicides are a tool to help control resistant weeds but they may not be labeled for sites with resistant weeds
  6. Preemergence herbicides don’t always help to control the weed (example: perennial weeds)
  7. Cultural practices only help so much to reduce weed populations
  8. Resistant weeds will spread by mowing, aerification, pollination, etc.
  9. Low herbicide rates – to save $ - increase resistance development rate
  10. Turf injury from herbicides may need to be tolerated to control resistant weeds
Bottom line is this:
  • Resistant weeds are a problem now, but luckily we don’t have too many in Midwest turf yet.
  • Turf managers will need to increase their knowledge of herbicide mode of action and increase their rotation of these various herbicide modes of action in the future to prevent weed resistance from developing just as they currently rotate fungicide mode of action in order to reduce the likelihood of developing fungicide resistance.
  • For more information on this topic, I suggest you read a helpful publication on preventing and managing herbicide resistant weeds by my colleague Dr. Jay McCurdy at Mississippi State University linked here.
  • If you suspect you have an herbicide resistant weed, please contact me (ajpatton@purdue.edu).
Dr. Aaron Patton
Turfgrass Extension Specialist

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What’s Next in the Forecast?


June 2015 was the wettest month on record in Indiana, Illinois, and Ohio, but I don’t have to tell you that if you live in one of these states as you’ve experienced it firsthand.


But what’s next? Here are some predictions of what we might face weather-wise in the upcoming weeks and months.

Precipitation:
Despite our wet period now, the models suggest that Indiana’s summer will have average precipitation. The “EC” in these July, August, September maps highlight that our summer has an equal chance (EC) of being wet or dry and an equal chance of being colder or warmer than average which is a prediction of being an average summer. See this link for a more detailed explanation.





Temperature:
Our temperatures have been below average for the first six months of the year.


The models suggest that Indiana’s summer will have slightly below average to average temperature. The “EC” in these July, August, September maps highlight that our summer has an equal chance (EC) of being colder or warmer than average. The “B” 33 means there is a 33% chance of us being below average in July, August, and September. See this link for a more detailed explanation.


What does all this mean? Possibly it means a good summer for cool-season turf in Indiana and another year of difficulty (cool spring, average to cooler than average summer) for warm-season grasses. If the end of the summer ends up being cooler than average, turf managers will need to adjust their normal practices slightly. For example, possibly seeding a week or two earlier than normal – much like we did in 2014. If August and September are cooler than average, we should seed cool-season grasses the whole month of August and into early September rather than waiting for our typical mid-August to mid-September window.

We obviously can’t predict the weather but some speculation can be helpful as we seek to prepare for what’s next.

Aaron Patton, Turfgrass Extension Specialist
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Wet Weather Makes a Great Environment for Yellow Nutsedge

Yellow nutsedge is a troublesome, difficult-to-control turf weed. Information on its identification is available in a recent weed of the month blog posting. Wet, summertime conditions like we are now having favor its growth and development. Understanding this plant’s biology will help in determining the best control methods. Two Purdue publications are also available to help answer questions on the best way to control this weed. The professional publication also addressed the identification and control of other sedge species problematic in turf.


Yellow Nutsedge Control (AY-19-W) | PDF (for homeowners)
Sedge Control for Turf Professionals (AY-338-W) | PDF (turf professionals)

Yellow nutsedge


Aaron Patton, Turfgrass Extension Specialist
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White Grub Season is Here

This is the time of year when annual white grubs begin to infest turfgrass and, in the Midwest, we are blessed with an assortment of different annual white grub species. This group of insects produces one generation each year with the adults becoming active by early June. Adults lay eggs in turf and 1st instar larvae are usually present and feeding in the root zone by early July. By early August, 2nd instar larvae are usually present and 3rd instar larvae may be present by the end of August. Most damage to turf is associated with feeding by 3rd instar larvae and this is the overwintering stage. In some cases, especially where European chafer is present, damage may also occur the following spring.

Management of white grubs should be based on previous history as well as the functional and aesthetic characteristics of the site. On high maintenance turf, tolerance for damage may be low and a preventive white grub management approach may be warranted. Conversely, minor damage to low maintenance turf may require no remediation at all aside from adequate moisture and fertility to help the turf recover. The chart below represents the relative efficacy of all white grub insecticides labeled for use in turf in relation to application timing.

The chart is intended to help turfgrass managers understand the insecticide choices available to them and help them make the best white grub control decisions at any given point in the growing season. Insecticide products that do not contain one of the active ingredients (chemical names) listed on this chart will not usually provide good grub control. Keep in mind that the active ingredients listed on the left side of the chart may be formulated and distributed under various trade names aside from those listed on the right. As always, remember to read and follow directions on the label of any insecticide product.



Doug Richmond
Associate Professor and Turfgrass Entomology Extension Specialist
drichmond@purdue.edu

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