Lowndes – Echols Ag News

Control of Cowpeas

Cowpea Control (Prostko)

Every so often, I get a few inquiries about herbicides for the control of cowpea (Vigna unguiculata) (Figure 1). Unfortunately, cowpea (also known southern pea, black-eye pea, or crowder pea) can be a very difficult plant to control and not much research data is out there.  In preparing our UGA Weed Science graduate students for the upcoming 2019 National Weed Science Contest, I was able to collect some good data for various herbicides (Table 1).

In summary, the following herbicides could be used for the control of cowpea depending upon the planted crop:  PRE = Atrazine, Balance Flex (isoxaflutole), and Tricor (metribuzin); POST = Classic (chlorimuron), Engenia (dicamba), Enlist One (2,4-D), Envoke (trifloxysulfruon), Gramoxone (paraquat), Liberty (glufosinate), Osprey (mesosulfuron), Roundup (glyphosate), Sharpen (saflufenacil), and Stinger (clopyralid).

Figure 1.  Cowpea

Table 1.  Cowpea (‘Top Pick Pinkeye Purple’) control with PRE and POST herbicides, TyTy, Georgia, 2019.1

Herbicide Rate/A


Application Method


Test 1

Control (%)

Test 2

Control (%)

15 DAT3


20 DAT


14 DAT


Harness 7EC 22 PRE 0 0 0
Atrazine 4L 64 PRE 100 100 100
Diuron 4L 26 PRE 0 0 0
Valor SX 51WG 3 PRE 0 10 20
Pursuit 2SL 4 PRE 0 8 0
Balance Flexx 2SC 6 PRE 100 100 100
Callisto 4SC 3 PRE 60 65 0
Prowl H20 3.8ASC 48 PRE 0 5 0
Zidua 85WG 1 PRE 0 10 0
Dual Magnum 7.62EC 21 PRE 0 12 0
Spartan 4L 1 PRE 0 0 0
Tricor 4L 24 PRE 100 100 100
Enlist One 3.8SL 13 POST 95 95 100
Buctril 4EC 12 POST 50 70 30
Classic 25DG + COC4 0.5 POST 95 95 85
Select Max 0.97SC + NIS 25 POST 0 10 0
Stinger 3SL 8 POST 95 100 80
Engenia 5SL 6.4 POST 95 95 85
Fusilade DX 2EC + COC 12 POST 0 10 0
Resource 0.86EC + COC 4 POST 0 0 0
Reflex 2SL + NIS 12 POST 50 50 50
Liberty 2.34SL +

N-Pak AMS (2% v/v)

22 POST 100 93 85
Sandea 75DG + NIS 0.66 POST 40 25 30
Osprey 4.5DG + MSO 4.6 POST 70 88 85
Accent 75DG + COC 0.66 POST 65 75 60
Gramoxone 2SL + NIS 32 POST 100 95 90
Facet 75DG + MSO 16 POST 50 60 55
Sharpen 2.85SC + MSO 2.5 POST 95 92 80
Laudis 3.5SC + MSO 3.5 POST 65 68 60
Envoke 75DG + NIS 0.09 POST 85 88 90
Roundup PowerMax 5.5SL 22 POST 100 97 90

1Test 1: Planting Date = May 28; PRE = May 29; POST = June 13 (~8” tall cowpea).

2Test 2: Planting Date = June 17; PRE = June 18; POST = July 8 (~8” tall cowpea).

3DAT = days after POST treatment.

4COC = Agridex @ 1% v/v; NIS = Induce @ 0.25% v/v; MSO = MES 100 @ 1% v/v.

Slippery Algae in Turfgrass

Published on 06/13/19

Rain, overwatering can cause slippery algae to pop up in turfgrass lawns

By Clint Waltz for CAES News

Recent dry weather encouraged the use, and possible overuse, of irrigation systems. Followed by tropical conditions characterized by heavy rainfall and humidity, there have been reports of a jelly-like substance growing in turf.

The jelly-like matter is Nostoc, a genus of cyanobacterium formerly classified as blue-green algae. The algae — commonly known as star jelly and witch’s butter, among other names — may appear suddenly in lawns and other turf areas in warm temperatures following a period of rain, and the algae can also be an indication of overwatering.

In turf, Nostoc generally emerges on a site where the grass is growing poorly due to severe compaction, overwatering or both. It does not cause the turf to decline or die, but it does colonize areas where it has favorable growing conditions and the grass was already thin.

Poor drainage and compacted soils create a favorable environment for Nostoc. It dries out when moisture or rainfall diminishes, but it has only gone into dormancy. With enough moisture, it will come back to “life.”

In its hydrated, gelatinous, green state, it can be a safety hazard because it’s slippery — so be careful walking on it.

However, when it dries out, it can restrict turfgrass growth. Nostoc dries into a black crust that can prevent stolons from rooting, or “tacking,” into the soil. This delays the growth and spread of turfgrass.

Nostoc can be difficult to control. To discourage its growth, encourage the growth of the grass. Algae is less of an issue with an actively growing turfgrass canopy.

The first step is to check the irrigation system to make sure it is watering properly (i.e., not too often or too much). The turfgrass species grown in Georgia perform better when grown on the slightly dry side, so scaling back irrigation and adjusting the irrigation schedule will benefit the grass and can discourage algae.

The second step is to improve the internal soil and surface drainage. Core aeration opens the soil, allows oxygen into the root system and reduces compaction.

Allow the soil surface to dry out, then break up the Nostoc “crust” by cutting the upper ¼- to ½-inch. Breaking the algae into pieces will encourage it to spread. This also permits the turfgrass stolons to root into thin areas and outcompete the Nostoc.

With proper irrigation and core aerification, the grass can cover, and eventually predominate, the area where the Nostoc was present.

For more information about turfgrass in Georgia, go to www.GeorgiaTurf.com.

Clint Waltz is a Cooperative Extension turf specialist with the University of Georgia College of Agricultural and Environmental Sciences.

App Helps Fruit Growers

Published on 06/18/19

App helps fruit growers in Eastern U.S. diagnose disease and insect problems

By Denise M Hatcher for CAES News

Walking through his peach orchard, a farmer notices something he has not seen before on the leaves of a few trees. He quickly pulls out his cell phone and accesses the MyIPM smartphone app.

Through a series of descriptions, audio and images, the free mobile app and tool can help users diagnose crop diseases, insect pests and disorders of fruit crops grown in the Eastern U.S., including apple, blackberry, blueberry, bunch grape, cherry, cranberry, peach, pear and strawberry.

The app was first developed by plant pathologists at Clemson University to give growers a “one-stop shop” to access all of the resources they might need for disease management, says Brett Blaauw, an assistant professor and peach specialist with the University of Georgia Department of Entomology. A couple of years later, two more apps were created: one focused on insect pests and another geared specifically for the Northeastern region of the U.S.

“When I came to UGA, I worked on merging the three separate apps into one master app, which included new tools, crops and functionality,” Blaauw said. “The single MyIPM app currently has nine crops with disease diagnostic tools and six crops for insect diagnostic tools.”

To date, the app has been downloaded more than 2,100 times. Designed to promote integrated pest management in commercial fruit crop production, one of Blaauw’s favorite aspects of the app is that it’s full of useful information for users of both Apple iOS and Android mobile operating systems.

“Not only is there a large list of chemistries that are labeled for each disease or insect pest, but users also have the ability to view high-resolution pictures to identify symptoms and signs of disease and insect injury,” he said. “With that said, my real favorite aspect is that the app is free.”

The app is continually being updated by leading Extension specialists at seven land-grant universities and the Southern IPM Center.

Feedback from users has been overwhelmingly positive. Of the users surveyed, 65% say that the app has helped them manage pests and 70% say that it has increased their knowledge of pests and IPM, according to Blaauw.

“Nearly everyone I talk to about the app is pleased with its functionality and ease of use,” he said.

The app has been downloaded to more than 70 different countries, including India, Mexico and Canada.

Blaauw is currently working on adding a section on beneficial insects to help growers identify “good bugs” using the app. He hopes to see the app expanded to include more crops.

For more information on the MyIPM app, visit https://apps.bugwood.org/apps/myipmseries/.

Michele Hatcher is the editor of the Hexapod Herald, the newsletter of the University of Georgia Department of Entomology.

Turf Grass News

Turfgrass Blog: 2019 Edition

Clint Waltz, Ph.D.

University of Georgia Turfgrass Specialist

June 10, 2019


With the recent dry weather encouraging the use, and possible overuse, of irrigation systems then the recent tropical conditions – rainfall and humidity – I have had several pictures and questions about a jelly-like substance growing in the turf.  The jelly-like “stuff” is a Nostoc algae, a genus of cyanobacterium formerly classified as blue-green algae.  It has multiple common names like star jelly, witch’s butter, and others.  Under warm temperatures Nostoc may appear suddenly in lawns, and other turf areas, following a period of rain and can be an indication of overwatering.  In turf, it is generally on a site where the grass is growing poorly due to severe compaction, overwatering, or both.  It does not cause turf decline or death; it colonizes areas where it has favorable growing conditions and the grass was already thin.  Poor drainage and compacted soils create a favorable environment for Nostoc.  It will dry-out if the water or rainfall diminishes but it has only gone into dormancy.  With enough moisture, it will come back to “life”.


In its hydrated, gelatinous, green state it can be a safety hazard.  It is slippery.  Be careful walking on it.  However, when it dries-out it can become restrictive to turfgrass growth.  Nostoc dries into a black crust that can prevent stolons from rooting, or “tacking”, into the soil, delaying turfgrass growth and spread.


Nostoc can be difficult to control.  To discourage its growth, encourage the growth of the grass.  Algae is less of an issue with an actively growing turfgrass canopy.  The first step is to check the irrigation system to make sure it is watering properly (i.e. not too regular or too much).  The turfgrass species we grow in Georgia perform better when grown on the slightly dry side, so scaling back the irrigation and adjusting the irrigation schedule will benefit the grass and can discourage the algae.


Improve internal soil and surface drainage.  Core aeration opens the soil, allows oxygen into the root system, and reduces compaction.  While allowing the soil surface to dry-out then breaking up the Nostoc “crust” by scarifying the upper ¼- to ½-inch can break the algae into pieces and encourage its spread, it also permits the turfgrass stolons to root into thin areas and outcompete the Nostoc.  With proper irrigation and core aerification the grass can cover and eventually predominate the area where the Nostoc was present.



Summer Heat

Published on 05/23/19

Spring season brings summer heat to Georgia

By Clint Thompson for CAES News

Georgia temperatures are rising, and the weather is only going to get hotter with little rain in the forecast. That’s not good news for Georgia’s cotton producers who are in the middle of planting this year’s crop, says Jared Whitaker, University of Georgia Cooperative Extension cotton agronomist.

According to the UGA Weather Network at www.georgiaweather.net, temperatures eclipsed 90 degrees Fahrenheit in most of south Georgia this past weekend and are expected to reach 100 F by the middle of next week.

“Cotton is going to be the most sensitive crop to these types of conditions just because of the relatively poor vigor of cotton seedlings compared to other crops Georgia producers plant,” Whitaker said. “Cotton seed is very small and conditions need to be near perfect for several days after planting to ensure we get a suitable stand. When soils dry and temperatures rise, it becomes increasingly difficult for producers, especially in nonirrigated fields.”

Whitaker says that an informal survey he conducted last week revealed that around 50% of the state’s farmable fields had been planted. Progress was a little further along than usual because of good planting conditions in late April. Also, producers are trying to minimize their risk from losses that could occur at harvest by planting some cotton earlier than usual.

He is concerned that poor conditions could delay planting to the point that yields are affected.

“We really need to have a good stand established before the end of the first week of June to ensure that we have enough time to make an entire crop,” Whitaker said. Growers need rainfall within the next couple of weeks to get this crop started in the right direction.

“We’re always a week away from a drought,” Whitaker said. “And that’s certainly the case this year.”

The last substantial rainfall was recorded during the weekend of May 10 through May 12. Three days of rain yielded 1.5 inches in Tifton, Georgia; 0.81 inches in Alma, Georgia; 1.2 inches in Griffin, Georgia; and 1.52 inches in Vienna, Georgia.

But since much of the state’s crops are grown in south Georgia’s sandy soils, any moisture that region receives is soaked up quickly.

UGA Extension peanut agronomist Scott Monfort says that approximately 65% of Georgia’s peanut crop has been planted. But like the state’s cotton farmers, Georgia’s peanut producers will need to monitor their crop’swater needs during this extremely hot and dry period.

“To have high temperatures this early is pretty tough. It means these plants are going to go through heat stress earlier than normal this year and farmers are going to have stay on top of it as far as irrigating,” Monfort said. “While we normally wouldn’t irrigate this early, we might have to start if we lose too much moisture.”

Growers also need to be careful planting in fields with marginal moisture.

Summer doesn’t officially begin until June 21. Pam Knox, UGA Extension agricultural climatologist, believes that temperatures in June, July and August will depend largely on how much rainfall Georgia gets.

“There is not much correlation between early season heat waves and the rest of the summer. However, if it stays dry, then hotter-than-normal conditions are likelier just because all of the sun’s heat goes to warming the air instead of evaporating water from the soil and plants,” she said.

For more information about what weather to expect this summer, read Knox’s climate outlook on her blog at https://t.uga.edu/4YB.

Clint Thompson is a news editor with the University of Georgia College of Agricultural and Environmental Sciences based in Tifton.

Some Georgia Lawns “Greening Up” Faster Than Others

While many warm-season turfgrass species have shown signs of significant green-up, some grasses and locations still have an appearance of being dormant or slowly transitioning.

To date, the average 4-inch soil temperature for the entire month of April on the University of Georgia campus in Griffin, Georgia — fairly central for the state — is 64.1 degrees Fahrenheit. In general, this is warm enough to get green growth, but it is barely warm enough to stimulate root growth or initiate new growth from rhizomes buried within the upper couple inches of the soil for Bermuda grass and zoysia grass.

Understanding the growth characteristics of Georgia’s warm-season species and considering recent environmental factors, it is not surprising that most grasses appear green while others seem slow to green up. The “slower” grasses, or locations within the landscape, could be delayed by other influences.

If grass is growing in an area on the north side of a building, in a low area that retains more water, in a wet spot in the landscape, where the ground is shaded or geographically north of Griffin, it may be a little slower to green up. Water is a good buffer of heat, meaning that it takes more of the sun’s energy to warm the soil to the same temperature than if the soil were dry. Wet areas will green up more slowly than drier areas.

Considering the amount of rain the state has received since last summer, all Georgia soils likely have good to excellent moisture content. Also, a thin area may be slower to cover, or appear green, because the soil temperatures for initiating new shoots from rhizomes will take more time. It takes more time for warmth to move through the soil and trigger new growth than it takes for the new shoot to reach the soil surface.

Warm-season grasses have changed substantially over the past two to three weeks. Likewise, the next two to three weeks should encourage growth and green-up.

They say “patience is a virtue,” and a little green grass seems to cause us to be less virtuous. Be patient and stay with the program. Georgia’s warm-season turfgrass species should be growing strong shortly.

For more turfgrass information from UGA Cooperative Extension, go to www.georgiaturf.com.

Clint Waltz is a Cooperative Extension turf specialist with the University of Georgia College of Agricultural and Environmental Sciences.

Choosing Tomato Varieties (4-H Tomato Sale Going on Now)

By Jake Price

The desire for fresh homegrown tomatoes is probably the main reason homeowners have gardens.  Most plants are planted in late March and April, or when they are available at the garden centers.  Each spring, many homeowners run into problems with their plants.

Two newer, good tasting, disease resistant varieties are currently being sold by the Lowndes 4-H club to support the camping program.   The two varieties are Red Bounty and Bella Rosa which both have resistance to Tomato Spotted Wilt Virus. Call 333-5185 for more information.  Plants are $1.00 each while supplies last.

Tomatoes are susceptible to a lot of diseases.  Once infected, it is too late to stop most diseases from killing or limiting the production of the plant.   Tomatoes come in all shapes, colors, and sizes.   A few cultural practices and planting varieties that are resistant to disease can make for a more productive tomato harvest.

When selecting your plants look for varieties that have a lot of letters next to the name.  This means that plants have a built in resistance to disease.   An example would be a popular variety called Celebrity VFFNTA Hybrid.  The letters stand for the following:

V = Verticillium Wilt
F = Fusarium Wilt
FF = Fusarium Wilt race 1 and 2
N = Nematode
T = Tobacco Mosaic Virus
A = Alternaria (Early Blight)
TSWV = Tomato Spotted Wilt

Tomatoes are classified as determinate which means most of the fruit ripens over a short period of time, and indeterminant, which means that fruit will continually be produced.  Determinant varieties produce a lot of tomatoes early and once the tomatoes have been harvested the plants can be removed.                                                                                                   Popular determinant varieties include:  Bush Celebrity VFFNTA Hybrid, Bush Early Girl VFFNT Hybrid, Celebrity VFFNTA Hybrid, and Mountain Spring VFF Hybrid.  Popular indeterminant varieties are:  Early Girl VFF Hybrid, Better Boy VFN Hybrid, Big Boy Hybrid, and Beefmaster VFN Hybrid.

Cherry tomato varieties are: Jolly Hybrid, Sweet Baby Girl Hybrid, and Super Sweet 100 Hybrid.  Of course there are many more to choose from.  Cultural practices will also prevent problems.

Tomatoes like a well-drained high organic matter soil and a pH between 6.2 and 6.8.  I would recommend you have a soil test done for your garden and follow any recommendations.  A soil test can correct any pH problems.                                                                                 Tomatoes frequently have a problem with a condition called “Blossom End Rot”.  This is when the bottom of the tomato turns black.  Blossom end rot is caused by a calcium deficiency in the fruit and is made worse when soil conditions fluctuate between wet and dry.                                                                                                                                                       Additions of dolomitic lime, which raises pH and contains calcium and Magnesium, can help prevent the problem.   If your soil pH is optimal, but your calcium is low, apply gypsum at 1 pound per 100 square feet.  Foliar applications of calcium can help provide a temporary fix if the problem is not excessive.                                           Mulching around your tomato plants reduces soil moisture fluctuations and keeps the weed pressure down.  Layers of newspaper can be placed around plants and mulch can be added on top to further prevent weeds.  Pine straw, bark, leaves, or most any type of mulch will be ok.

Selecting disease resistant varieties, mulching, and following your soil test results should make your tomato season more productive.  For more information on tomatoes and varieties visit this website:  https://secure.caes.uga.edu/extension/publications/files/pdf/B%201271_5.PDF

Don’t skip soil testing this spring

Published on 03/08/19

Don’t skip soil testing this spring

By Jason Lessl for CAES News

This spring, gardeners planning vegetable gardens — or even a major renovation of your ornamental beds — should take the opportunity to test their soil before they put plants in the ground.

One of the most fundamental, but often overlooked, aspects to any successful vegetable garden, flower bed, landscape or lawn is good, fertile soil. Getting your soil tested by a laboratory is the best and most accurate way to assess your nutrient and pH levels, which are vital components of maintaining your soil. The University of Georgia Soil, Plant and Water Lab offers such services.

When you send a soil sample to a lab, you will receive a detailed report of soil-nutrient levels along with crop-based recommendations on how to fix any potential deficiencies. The steps required to submit a soil sample are simple and can be achieved using a few commonly found household items. You can start by contacting your local county UGA Cooperative Extension office to acquire soil bags and to get information on how to submit samples. Find your county office by visiting extension.uga.edu/county-offices.html or calling 1-800-ASK-UGA1.

When to soil test?

Soils can be tested any time during the year, although it is typically best to take samples in the fall or winter. This is the time of year when most plants are dormant and the soil is most accessible. If pH adjustments are necessary, it is also the best time to apply amendments, as it can take several months for them to take effect. Lime (to raise pH) and sulfur (to lower pH) react slowly and should be mixed with the soil at least two to three months before planting.

How often do I test my soil?

For intensely cultivated soils including vegetable gardens, an annual soil test is recommended. Otherwise, for lawns and ornamental areas, sampling should be done every two to three years after initially establishing medium to high fertility levels and the appropriate pH.

Steps in soil sampling

Recommendations on when and how to apply nutrients are only as good as the soil sample submitted for analysis. To obtain a representative soil sample, the following steps are useful:

  • Map out the entire property. This will help in record keeping and ensure that the soil sample is representative of the entire area. Divide areas so that each soil sample represents one general plant type. For example, take separate soil samples for vegetable gardens, blueberry bushes, ornamentals, fruit trees, lawns, etc. If you have specific problem spots, sample those areas separately as well.
  • Use clean sampling tools and containers to avoid contaminating the soil sample. Collect samples with any digging tool you have available (hand trowel, shovel, soil probe, etc.).
  • Slightly damp soil is the easiest to work with. Clear the ground surface of grass, thatch or mulch. Push your tool to a depth of 6 inches for cultivated areas or 4 inches for lawn areas. Push the handle forward in the soil to make an opening, then cut a thin slice of soil of uniform thickness from the side of the opening, extending from the top of the ground to the depth of the cut. Repeat this process in a zigzag pattern across your defined area, collecting eight to twelve samples to mix together. For trees, take soil samples from six to eight spots around and below the leaf canopy. Take about a pint (around 2 cups) of the mixed soil (after removing large rocks, mulch, sticks and roots) and fill the UGA soil sample bag. Be sure to label the sample clearly on the bag. If the samples are wet, spread the soil out over clean paper and let them air dry. You also can take your samples to your local Extension office for submission. Once the lab has received your soil, it will take two to three business days to get your report.


For more information about when or how to test your soil, visit aesl.ces.uga.edu or call 1-800-ASK-UGA1 to contact your local UGA Extension office.

Farm Business Education Conference

UGA CAES, Extension partner with SBDC to host Farm Business Education Conference

By Clint Thompson for CAES News

The University of Georgia College of Agricultural and Environmental Sciences and UGA Cooperative Extension are partnering with the UGA Small Business Development Center to host a Farm Business Education Conference on Wednesday, Feb. 27 at the UGA Tifton Campus Conference Center.

The purpose of the conference is to help farmers learn more about the business aspect of farming. Industry experts will conduct sessions on value-added agricultural ventures and other topics relevant to growers.

“UGA Cooperative Extension is excited to once again be partnering with the UGA Small Business Development Center (SBDC). Each of us brings unique expertise and advice that together will result in better information for our clientele,” said Laura Perry Johnson, associate dean for UGA Extension.

Attendees will learn how to develop a business plan for their farming operation, including plans for effectively passing the business over to the next generation. Agricultural lenders will be on hand to offer tips on how to successfully obtain operating lines, real estate and farm loans and working capital funding. Certified human resource professionals will discuss how to manage employees of farms.

“When you think about farming, people understand there’s a product that’s being produced, but there’s a business side to farming too. Our goal is to assist new and existing farmers in understanding what is required to have a profitable season or assist with understanding new requirements that are coming down. The goal is to help educate on the business side of farming,” said Rob Martin, a business consultant with the UGA SBDC.

Martin, along with Sarah Cook from the Georgia Department of Agriculture, will conduct a session, “From Seed to Shelf,” where they will offer strategies for selling products in local, regional and national markets. Attendees also will have the opportunity to learn about food and production safety with different commodities.

“Each of these partners are part of Public Service and Outreach for the University of Georgia. We come together, pooling our resources; the UGA SBDC as the business side, Extension with their extensive knowledge of the industry and specific products, as well as the College of Agricultural and Environmental Sciences. We will bring that information together to provide opportunities for people to learn,” Martin said.

Conference attendance cost is $49 and includes lunch. The conference will begin at 7:30 a.m. and conclude at 4 p.m. Those interested in attending should preregister at www.georgiasbdc.org/georgia-farm-business-education-conference.

For more information about UGA Extension, see extension.uga.edu.

Yellow Nutsedge/Cadre Resistance

By Eric Prostko: In September 2017, after doing some preliminary screening (Figure 1), we collected yellow nutsedge tubers from a peanut field that were a strong suspect for resistance to Cadre (imazapic).  We sent the tubers to BASF for further greenhouse testing and just got back the results.  Unfortunately, it looks like this population of nutsedge has developed resistance to Cadre (Figures 2 and 3).  On the positive side, it does not appear to have developed cross-resistance to Sandea/Permit (halosulfuron).  In order to protect the grower’s privacy, I would prefer not to reveal the exact location of this field at this time.

Assuming adequate funding is obtained , I will be working very closely with our new teaching/research weed scientist on the main campus in Athens, Dr. Nick Basinger, to further investigate this issue.  Dr. Basinger recently replaced Dr. Bill Vencill.  If you are already aware of or become aware of peanut fields where Cadre has been used for yellow nutsedge control with less than optimum results, please let us know so that tubers can be collected from the field.   At this point in time though, I believe that this discovery of resistance is most likely an isolated case.

Here are a few things to consider in regards to this issue, especially how it compares to the herbicide-resistant Palmer amaranth problems that we have been dealing with since 2004:

1) At this point in time, only 1 case of herbicide-resistance in yellow nutsedge has been officially confirmed world-wide.   In 2013-2014, researchers from Arkansas confirmed halosulfuron resistance in a yellow nutsedge population collected from a rice field.  For comparison, 61 cases of herbicide resistance in Palmer amaranth have been confirmed.

2) In Georgia, Cadre was first commercialized for use in peanut in 1996 so it took more than 20 years for this resistance to occur in yellow nutsedge.  It took roughly 3-4 years for glyphosate resistance to evolve in Palmer amaranth after the introduction of RR soybeans (1996) and RR cotton (1997).

3) The GA problem site is a dryland field where peanuts were grown for 5 continuous years and Cadre was used every year (for economic reasons).  This is atypical of the normal crop rotation sequences used by most Georgia peanut growers.  Unlike glyphosate, Liberty and PPO herbicides, Cadre is not applied to fields on a yearly basis.

4) Yellow nutsedge can produce a large amount of seed but seed is not the primary propagation mechanism.  Some research has shown that <1% of yellow nutsedge seeds can develop into viable seedlings.  Seed is the only propagation mechanism for Palmer amaranth.

5) The primary mechanism of  yellow nutsedge propagation is through tubers.  In Georgia, a single yellow nutsedge plant, growing without competition in a bareground area, produced 700 tubers after 6 months of growth.

6) The primary mechanism of yellow nutsedge tuber dispersion in fields is through normal field operations such as tillage/disking and equipment movement (i.e. human action).

7) Foraging and soil disturbance from feral hogs has been reported to promote the long-term population maintenance of yellow nutsedge.

8) There could be also be some slight dispersion from waterfowl that prefer yellow nutsedge tubers as a food source (i.e. ducks, geese).  However, a recently published study from Missouri reported that no intact nutsedge tubers were recovered from mallard ducks in 8 feeding trials.  In these same feeding trials, 26% of Palmer amaranth seeds were viable after feeding.

Figure 1.  Cadre and Sandea field screen on suspect resistant yellow nutsedge population in Georgia, 2017.
Figure 2.  Suspect resistant yellow nutsedge population treated with Cadre 2AS @ 32 oz/A (8X rate), 21 DAT.
Figure 3.  Susceptible yellow nutsedge population (left) and suspect resistant population (right) treated with various rates of Cadre 2AS – 28 DAT