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Chinese Privet at Sanford Stadium

With college football kicking  off this weekend,  I have a little history on the hedges at Sanford Stadium

By Doug Collins, Lee County Extension Coordinator

Among the privets, Chinese privet (Ligustrum sinense) is the outlaw of the family.  Brought into the United States just shy of a decade before the start of the American Civil War, this plant has escaped from cultivation and become a noxious weed.  It is spread by birds and is common along roadsides and in woods.  It can thrive in shade or full sun.  One variety of this species is sold as a landscape plant.  Other than that, it is generally considered a nuisance.  In our climate, it is pretty much an evergreen.  In colder climates, it is deciduous.

Chinese privet has one claim to fame in Georgia.  The famed hedges in the University of Georgia’s Sanford Stadium are composed of Chinese privet plants.  When Sanford Stadium was built in the 1920’s, the business manager of the athletic association had been impressed with the rose bushes in the Rose Bowl in Pasadena, California and wanted to have something similar in UGA’s new stadium.  Rose bushes were deemed not to be the best choice for the Athens climate, so Chinese privet was planted.  The privet was reportedIy trucked into Athens from Atlanta as the result of a last-minute decision and planted by workers with shovels and flashlights just hours before the stadium’s inaugural game against Yale. I have heard a story that a species other than Chinese privet was originally planted and the Chinese privet later invaded and pushed out the previously planted plants.  I have found no documentation supporting this legend.

The hedges were removed in 1996 to allow Sanford Stadium to be used as a soccer venue for the 1996 Summer Olympics.  Before they were removed, cuttings were taken to propagate new plants so that the hedges could be restored after the Olympics.  Enough new plants were propagated so that some could be sold.  A fellow county agent bought one of these plants.  I kidded him for paying good money for a noxious weed.

Row Crop Disease Update August 27

Dr. Bob  Kemerait gives a row crop disease update

  1. Soybeans: Asian soybean rust is still lightly scattered from Decatur County to Appling County, but has only been found so far in KUDZU.  Soybean rust is certainly not a major problem at the moment; however it could become so.  Management options are to protect the crop with a fungicide sometime between the R1 (early bloom) and R3 (early pod set) stages.  Such timings may correspond well with other disease and insect control measures.  Some “Cercospora leaf blight” is being reported; this disease causes much of the upper foliage to take on a “bronzed” cast and then leaves drop prematurely leaving the “bony” petioles like skeleton fingers to the sky.  Cercospora leaf blight also causes purple seed stain.  Fungicide applications at pod set (R3) can help manage this disease.
  2. Late-planted corn: Southern corn rust is now commonly observed on older corn across the Coastal Plain, corn that is too late for it to matter.  However, southern corn rust does pose a threat to younger corn and preventative protection with a fungicide is something to consider, especially as the crop approaches the tassel growth stage.  Also, I am receiving numerous reports of young corn affected by northern corn leaf spot (Bipolaris zeicola) which produces numerous, small-to-medium sized red/brown spots, sometimes with appearance of concentric rings.  Typically, corn is most severely affected by northern corn leaf spot early in the season and then grows out of it; however I cannot be sure that this will always be the case.  I have no data on fungicides for management of northern corn leaf spot, but as it is closely related to northern and southern corn leaf blights, I am confident that mixed mode of action products we already use will be helpful for the “spot” disease.  If a grower does spray, applications as early as V6-V8 would be appropriate. But again, I just don’t know if it matters.
  3. Cotton: I hear you.  And I feel your frustration.  We have three diseases of significant importance in the field right now.    Boll rot.  The rain and heavy vegetative growth we have seen this year has created perfect conditions for fungal boll rot.  We are seeing a lot of it.  We are not seeing a lot of bacterial boll rot, though some is certainly there.  Fungal boll rot is most severe in lower bolls deep in the canopy or where insect damage also occurs.  Fungicides are not an effective treatment; only opening the canopy up to increase airflow and reduce humidity can help reduce boll rot.  2.  Areolate Mildew.  First, Andrew S. and others, I didn’t make the name up.  Second, I know that there is great concern and I have heard growers complaining that there fungicide applications did not stop the disease.  Here are some thoughts.  For the second year in a row, Areolate mildew is early and widespread.  Areolate mildew can cause significant premature defoliation.  I do know that fungicides like Headline and Quadris and certainly Priaxor can slow the spread of the disease, though not necessarily stop it, especially when it is well established in a field.  It is not clear how much yield is at risk or that can be protected; but it is believed that significant premature defoliation is not a good thing, unless one is trying to open the canopy up to slow boll rot.  Here are my recommendations, though they have not been proven with any hard data.  If a grower is within 4 weeks of defoliating the crop anyway, save the money and don’t spray.  If the grower is more than 4 weeks of defoliating and the areolate mildew is not too severe (i.e. already causing significant leaf drop) then there may be a benefit to treating with a fungicide.  This may not stop the disease but will slow its development.  3.  Target Spot.  Target spot has been severe and widespread in this rainy season.  I believe well-timed fungicides have been helpful this year.  I don’t believe there is any benefit to a fungicide application after the 6th week of bloom.  Either there is too much disease already to stop it or there is not enough time for disease to develop.  In this season, a second fungicide application 2-3 weeks after the first application is something to consider.
  4. PEANUTS: Getting lots of questions these days about late-season peanut disease problems.  Just a few thoughts.    Three weeks to go until you dig the peanuts and little-or-no disease in the field?  I wouldn’t put out any more fungicides unless there is threat of a hurricane or tropical storm.  If three of more weeks out and on your last spray and you are seeing some leaf spot develop, applying a pint of chlorothalonil tank-mixed with 7.2 fl oz of  tebuconazole or 5.5 fl oz of Alto or 5 fl oz of Topsin or 2.5 fl oz of Domark.  If time for your last spray and very little leaf spot is present, then 1.5 pints of chlorothalonil may be all you need.

If white mold is popping up in your field late in the season and is confined to individual plants scattered across the field, then you may want to mix tebuconazole with your last leaf spot spray.  If the disease is more severe, or you are really worried about it, then you might consider using 16  fl oz or Convoy rather than tebuconazole.

It is generally advisable to wait to dig the peanuts until they are “ready” based upon the hull-scrape test.  This is true even if there is significant tomato spotted wilt in the field or some white mold.  HOWEVER:  if there is significant defoliation from leaf spot or significant white mold in the field, it often best to dig the peanuts earlier than planned to avoid excessive digging losses.

Hog Show Time

It’s that time of the year for exhibitors to get their hogs for the Lowndes Area Market Hog Show. Entry deadline for the show is September 14th. The show will be held November 5th and 6th at 6:00 PM with the sale being November 7th at 7 PM. A change this year is showmanship will be on Monday night and weight classes being judged on Tuesday night  If you do not have a child involved in showing, try and come out and support these exhibitors at the show. Feel free to call the office 333-5185 if you are interested in showing or need your hog tagged.

UGA Cotton and Peanut Research Field Day

Cotton & Peanut Folks,

 

On Wednesday September 5th 2018 in Tifton, GA the UGA Cotton and Peanut Teams will be hosting 2018’s UGA Cotton & Peanut Research Field Day.  This annual event provides an excellent opportunity for anyone who is interested in learning more about our two most widely planted row crops here in Georgia.

 

We have planned a day which we hope will be both interesting and informative while allowing plenty of opportunities for the fellowship and fun we come to expect at a UGA Field Day in Tifton.

 

There is no cost to attend, we only ask that you RSVP if you plan to attend (just for a lunch headcount – call Mrs. Jeannie Evans at 229-386-3006 or email her at jevans12@uga.edu ).  The Georgia Cotton Commission and the Georgia Peanut Commission have graciously sponsored the field day’s lunch, in addition to continually providing the funding needed to support UGA’s research and education efforts.

 

For more details on speakers, locations and specific times be sure to take a look at the agenda (see attached).  The agenda, as well as maps for traveling to and from the research farms we’ll visit, can also be found at www.ugacotton.com .

 

In summary, the field day will start at the Tifton Campus Conference Center (TCCC) in the North Parking Lot at 8 AM.  After a brief welcome, the trams will leave for the RDC Pivot at 8:15 AM.  After four stops around the RDC Pivot, we will drive to the UGA Ponder Farm to tour several trials and hear from more of our speakers.  We will finish up the outdoor program prior to lunch (which will be at the TCCC) and hear from our economists inside as well as representatives of UGA’s administration and the Georgia Cotton & Peanut Commissions.

 

We look forward to seeing you there.  Please feel free to share this email and invite anyone who may enjoy learning more about cotton and peanut production in Georgia.

 

See you Wednesday, September 5th in Tifton!

 

Jared Whitaker & Scott Monfort

(UGA Extension Cotton & Peanut Agronomists, respectively)

 

 

 

Jared Whitaker, Ph.D.

The University of Georgia

Cotton Extension Agronomist
2360 Rainwater Rd.

Tifton, GA 31793

 

229-938-2448

jared@uga.edu

 

Weed Science Update – August 21 (Prostko)

A couple of things you might find of interest:

1) A local crop consultant recently sent me this picture of prostrate globe amaranth (Gomphrena celosioides).  I have never seen this plant before and for the record, Dr. Mark “The Czar” Czarnota (UGA-Griffin Campus) identified it for me.  It is a member of the Amaranthaceae (pigweed) plant family.  For more general information about this weed, please refer to the following link: http://wssa.net/wp-content/uploads/Gomphrena-celosioides.pdf

2) Had a peanut grower ask me if 2,4-DB applied to large sicklepod plants would have any effect on seed production.  A quick review of the literature would suggest that 2,4-DB applications made at the initial flower to peak flower stages of growth will cause significant reductions in the number of sicklepod seed produced.  However, applications before or after that time have no effect on seed production (only initial flower and peak flower seed numbers were statisicially different than the NTC-none).

Distillers Grain Offers Supplementation Options For Beef Cattle Producers

Dr. Lawton Stewart gives recommendations on feeding distillers grain. Across most of Georgia, most producers have experiencing ample rain and plenty of forage, therefore, winter supplementation is far from their thoughts.  However, now is a great time to start planning ahead.  Typically, three large factors taken into consideration when selecting a supplement are convenience, cost, and nutrients supplied.  Often times, we combine the latter two and look at cost per unit of nutrient (e.g. $/lb of protein or energy).  Unfortunately, sometimes nutrients supplied are sacrificed to maximize convenience or low cost.

Over past two decades, ethanol production has increased, and in turn, the byproduct of this industry (distillers grains) has become more available.  The growing popularity of this feedstuff has led to extensive research evaluating distillers grains in beef cattle production.  In fact, several studies have been conducted at the University of Georgia in an effort to evaluate its value, as well as ways to utilize it in a convenient manner.  For the remainder of this article, the discussion will focus on dried distillers grains with solubles (DDGS) because this is the most common form utilized in Georgia.

 

Nutrient value and mineral considerations

A summary of the nutrient analysis of approximately 130 DDGS samples submitted to Cumberland Valley Analytical Services (Waynesboro, PA) from the Southeast is presented in Table 1.  This byproduct can be fed as a protein source to replace other more expensive sources such as soybean meal.  Distillers grains are also an excellent source of energy, often testing between 85 and 95% total digestible nutrients (TDN).  The form of energy also makes distillers grains attractive for grazing cattle.  Since the starch is removed, the energy derived from distillers grains is primarily digestible fiber and some fat.

The mineral content of distillers grains should also be taken into consideration.  Dried distillers grain is high in phosphorus (P) and sulfur (S), but low in calcium (Ca). Supplemental Ca should be provided to balance the high phosphorus levels to maintain a Ca:P ratio above 1.5:1. If this ratio stays low for extended periods of time, urinary calculi, or “water bellies” may occur.  Also, excessive P excretion can have negative impact on water sources increasing the risk of algal bloom.

Sulfur tends to be high and can vary widely between ethanol plants and can be as high as 1%.  The total ration should remain below 0.4% S to avoid issues such as Polioencephalomalacia, or more commonly referred to Polio or “brainers”.

Typically, DDGS should be limited to 30-40% of the total intake to avoid any negative impacts of excessive minerals while utilizing the protein and energy available.

Potential for heat damage

Distillers grains is high in moisture directly after the distilling process and is typically dried down to make transportation and storage easier. If excess heat is applied during the drying process, the protein in DDGS can be heat-damaged and become bound protein.  This reduces its utilization by cattle.  This damage can easily be detected by visual inspection.  Properly dried DDGS will have a light golden color; however, as it becomes heat damaged, it will darken in color and have a distinctive burnt odor.  Figure 1 illustrates the visual difference in an undamaged and a heat damaged load of DDGS.  Analysis of load-A, golden in color, indicates 30.7% CP and 2.3% bound protein, while load-B, darker in color, is 26.9% CP and 9.9% bound protein.  The adjusted CP, or available protein, for load –A and –B is 28.4% and 17%, respectively.  This can create protein deficiencies if not taken into consideration when balancing a ration.

Utilizing DDG in a free-choice hot-mix

An on-farm trial was conducted in Northeast Georgia to develop a hot mix to allow producers to feed DDGS free choice but maintain intake to a safe level.  In this trial, weaned heifers were offered tall fescue hay (56% TDN and 10% CP) with DDGS.  At first, DDGS was offered free choice, however daily intake reached 12 lb/hd, twice the recommended level!  A premix containing salt, limestone, and trace mineral (Table 2) was formulated to limit intake of DDGS while balancing the mineral content.  This “hot mix” limited the intake of DDGS to approximately 40% of the daily dry matter intake for both developing heifers (7.8 lbs) and bred heifers (9.3 lb), and resulted in average daily gains of 1.95

lb for weaned heifers and 1.07 lb for bred heifers.  A hot mix is a supplement that contains an intake limiter and allows a producer to put out enough feed to last several days with intake remaining relatively constant across that time.  This results in a feed strategy that is more convenient than feeding on a daily basis.  This DDGS hot mix could easily be utilized for brood cows and bulls.  In fact, several producers have reported success stories from utilizing this strategy.

 

Despite limitations with sulfur, phosphorus, and fat, distillers grains offer producers an additional option for protein and energy supplementation when cost is not prohibitive.  Additional research has been conducted in Georgia evaluating distillers grains for developing bulls, stocker cattle, and finishing cattle.  For information on the results of these studies, or assistance developing beef cattle rations utilizing distillers grains, please contact your local Extension office (1-800-ASK-UGA-1; extension.uga.edu).  Additional information can be found in UGA Extension Bulletin 1482,Using Distillers Grains in Beef Cattle Diets.

Corn kernel Rot/ Ear Molds

  1. Harvest early (or at least “on-time”) – The longer corn sits in the field in our hot, humid environment with the ever-present chance of rain in the forecast, the worse these molds will get. Encourage growers to harvest as soon as corn is ready to minimize this risk.
  2. Set fans high – smaller kernels near the tip of the ear tend to have the greatest infection. Our best opportunity to “clean” the grain is to blow small and infected kernels out the back of the combine during harvest.
  3. Dry and cool grain quickly – A major condition of early harvest (at high moisture) is that growers will need to immediately dry grain down and practice sound grain storage (if they are storing it). Storing grain too wet and too warm will favor fungal growth and greater infection.                                                                 Author Reagan Noland

August Cotton Newsletter

Cotton Management Considerations for the Remainder of 2018 (Mark Freeman)

 

The 2018 Georgia cotton crop is extremely variable in maturity. Much of the state has had cotton blooming and setting fruit for weeks where as other parts of the state still has a large portion of the crop yet to bloom. There is no one size fits all approach to management of this crop and decisions should be made accordingly.

 

With much of our crop planted late due to the rainfall in late May and June, we must remember that the window for blooms to become harvestable bolls is compressed compared to a full season crop. It is important during that early bloom period to minimize stress to the crop in order to retain as much lower node fruit as possible as the cotton does not have time to compensate for losses early on. Remember that the best way to manage vegetative growth is by having high early season fruit retention. This limits the amount of available carbohydrates that the plant can use towards vegetative growth later in the season. PGRs should also be used to limit vegetative growth and enhance lower node retention.

 

When should we terminate our PGR applications? Research conducted at UGA and other parts of the country suggest that PGR applications should cease when cotton reaches 5 nodes above white flower. In theory a late season mepiquat application could stop further vegetative growth and divert carbohydrates and resources to boll production, but research has shown that there is no benefit to cotton yields, plant heights, fiber quality, or regrowth potential after defoliation.

 

One more note on PGRs, with the widespread rain across the state, the issue of rainfastness has been a concern when applying mepiquat. The rain free period after mepiquat chloride application is 8 hours. Although tank mixtures with an adjuvant are not necessary, their use may aid in plant uptake and help shorten that rain free window. Another option is Pentia (mepiquat pentaborate). Pentia requires a rain free period of two hours after application and that can be reduced to one hour when Pentia is tank mixed with an adjuvant.

 

If irrigation water is available, all steps should be taken to ensure that the crop does not encounter drought stress when adequate rainfall has not occurred. This is especially true for the first six weeks following first bloom as this is the period of peak water demand. Irrigation scheduling has been a topic of conversation and research for the past few years and several quality cotton irrigation scheduling methods exist which use soil moisture sensor technology. However, if a grower does not intend to utilize one of these methods they are encouraged to follow the UGA Checkbook irrigation schedule which can be found on page 132 of the 2018 UGA Cotton Production Guide. One thing to note when using this method is that rainfall or irrigation amounts do not “carry over” to the next week. For example, if water demand for a particular week was 2’’/week and you receive 3”, that extra inch does not affect the amount of water required for the following week.

 

 

Insects (Phillip Roberts)

 

Silverleaf whitefly (SLWF) adults have been observed in low numbers in cotton in some areas during the past week to ten days.  To date very few immature whiteflies have been observed in cotton.  We are not aware of any field which has exceeded threshold for SLWF.  Most reports include observations of individuals or a few adults when searching plants for corn earworm.  However, the presence of SLWF in a field is worth noting and management of all insect pests must consider the presence of SLWF.  All efforts should be made to minimize the need to treat SLWF with insecticide.

Management Considerations:

  1. Scout for the presence of SLWF adults.  It is important to know if SLWF is present!
  2. Conserve beneficial insects, do not apply insecticides for any pests unless thresholds are exceeded (beneficial insects will also suppress corn earworm).
  3. If SLWF is present in a field, avoid use of insecticides for other pests which are prone to flare SLWF.
  4. Scout fields frequently for adults and immatures once fields are infested with SLWF.
  5. Be timely with SLWF insecticides when thresholds are exceeded (many learned in 2017 that it is difficult to play catchup with SLWF).
  6. Be very aware of SLWF infestations in hairy leaf varieties and late planted cotton, these are high risk fields.

There is no question that agents, scouts, consultants, and growers are looking more closely for SLWF this year based on the problems we had in 2017.  Historically if we see SLWF in cotton during the month of July we should anticipate problems with SLWF, especially on late planted fields, and manage appropriately.  Infestations do not come close to where we were a year ago.  In 2017 treatable populations first occurred during the last week of June and many acres were treated in July; so we are in a much better situation this year compared to last.  It will be important that all fields are monitored closely for SLWF and hopefully proper proactive management can minimize damage and the need for SLWF insecticides.  Your County Agent has additional information on management and scouting of SLWF in cotton.

Scout All Cotton For Corn Earworm

Bt cotton technologies have allowed cotton growers to significantly reduce insecticide inputs for caterpillar pests.  However Bt cotton is not and has never been immune to corn earworm (CEW).  Since commercialization of Bt cotton, a percentage of Bt cotton grown in Georgia has required supplemental treatment of CEW with foliar insecticide in most years.  Introduction of 2-gene Bt cottons significantly reduced the need for CEW sprays compared with the original single gene Bt cotton.  The industry is beginning to transition to 3-gene Bt cottons which will improve efficacy against CEW compared with 2-gene Bt cottons.

In recent years susceptibility of CEW to Bt cotton has significantly declined in parts of the US (especially in the Midsouth and North Carolina).  Only a small percentage of 2-gene Bt cotton has required supplemental treatment for CEW in Georgia during recent years so we have not observed this decline in efficacy in the field (or have we?); this is due in part to low corn earworm infestations in cotton.  However we did see a slight increase in CEW insecticide applications during 2017.

UGA researchers have seen reduced field efficacy in Bt corn in Georgia.  We have also seen reduced efficacy of the original Bt toxin in bioassays for CEW collected in Georgia.  Basically what is happening is CEW is/has developed resistance to the Cry1Ac gene.  If the original Bt gene is no longer providing control of CEW, our 2-gene Bt cottons (Bollgard 2, WideStrike, and TwinLink) will be relying on a single gene and overall efficacy will be reduced.  There is variability in performance of Bt cotton technologies.  The chart to the right illustrates relative efficacy of commercially available Bt technologies.  Note that all Bt technologies continue to provide excellent control of tobacco budworm!

 

Bottom line is that all Bt cotton must be scouted on a regular basis and growers must be prepared to act accordingly if thresholds are exceeded.  When scouting pay close attention to blooms, bolls with stuck bloom tags, and small bolls.  When corn earworm escapes occur in Bt cotton they are usually observed near or just below the uppermost white bloom.  The threshold for CEW in Bt cotton is when 8 larvae ¼ inch or greater are found per 100 plants.  We recommend scouts search the top 12 inches of plants and one bloom, one bloom tagged boll, and one small boll per plant.  Remember that larvae must hatch and feed on the plant to ingest the Bt.  However if larvae reach ¼ inch in length survival is likely.  React in a timely manner with supplemental foliar sprays if thresholds are exceeded.  Coverage and penetration of the canopy with insecticides will be important as escaped CEW will be down in the canopy. Only spray other pests (i.e. stink bugs) based on thorough scouting and appropriate thresholds.  Conservation of beneficial insects such as bigeyed bugs will reduce the risk of CEW issues.

 

Diseases (Bob Kemerait)

 

August is a Critical Month for This Year’s Target Spot Control and Next Year’s Nematode, Fusarium Wilt and Bacterial Blight Control

One of the most important components of disease and nematode control in the cotton crop is “timeliness”.  “Timeliness” means deploying the best management tactic to fight diseases and nematodes before these foes become well-established or before the opportunity to use a tactic has passed.  August is a very important time in the cotton season to both be timely for possible fungicide applications this season and for preparation for next season.

Foliar Diseases.  As of the fist of August, there are four foliar diseases active in some, but certainly not all, cotton fields in Georgia.  These include bacterial blight, caused by Xanthomonas citri pv. malvacearum, Stemphylium leaf spot, caused by the fungus Stemphylium solani, target spot, caused by the fungus Corynespora cassiicola, and areolate mildew, caused by the fungus Ramularia spp.

There is little that can be done to manage bacterial blight at this time in the season, other than to note if it has occurred in your fields and which varieties have been affected.  Because of weather during the summer of 2018, even varieties which have shown some level of resistance to bacterial blight in the past have been affected this year.  However, now is the time that growers should note the level of bacterial blight in their crop and begin to make decisions as to variety selection for 2019.  Growers have an increasing number of “bacterial blight resistant” varieties from which to choose.

 

Photo Greg Slaughter

Stemphylium leaf spot is characterized by numerous small spots with dark purple/brown margins and often times gray, papery centers.  This disease occurs when the cotton plant is deficient in potassium; potassium deficiencies may exist because of poor soil fertility, perhaps from leaching, or during periods of drought where potassium is not taken up into the plant.  Stempylium leaf spot is managed by insuring proper levels of potassium in the plant; fungicides are not an effective management tool.

Photo Jason Brock

 

Target spot became evident in southwestern Georgia in the latter part of July and is likely present in many fields across the Coastal Plain of the state.  Target spot can develop quickly and is most common in good-growing cotton with high yield potential.  Extended periods of leaf wetness, where the foliage in the interior of the canopy remains wet well into the later morning hours, create perfect conditions for rapid development of target spot and premature defoliation from it.  Fungicides are an important management tool for target spot, though use does not always result in increased yields.  From our research, effective use of fungicides should be considered between the first and sixth week of bloom where the third week of bloom is typically the most critical time of management.  Scouting before use of fungicides to determine if the disease is present help to ensure that an application is warranted.  Priaxor is currently the most effective fungicide for control of target spot, though Headline, Quadris and others are also effective.

Areolate mildew was especially severe in 2017 and there are reports that the disease is back in 2018 if a few fields.  Areolate mildew has historically been confined to southeastern Georgia east of I-75; however it can be found elsewhere as well.  Typically arriving too late in the season to cause any damage (in fact, late-season defoliation may be a benefit), use of fungicides had often not been warranted.  However, in severe cases, the same fungicides used to control target spot are also effective in the management of areolate mildew.  Growers within three weeks of defoliating their cotton need not worry about managing areolate mildew.  Where areolate mildew occurs in a crop with anticipated defoliation a month or more away, and weather is favorable for continued development and spread of the disease, then use of a fungicide may be beneficial to protect yield.  Unfortunately, we have very little data at this point with which to refine our recommendations for management of areolate mildew.

 

It is too late to protect our 2018 cotton crop from plant-parasitic nematodes of Fusarium wilt; however now is the time that symptoms become very evident in the field.  Where stunting, poor growth and even dying plants are found in areas of a field, growers should take measures to determine 1) is it caused by nematodes?, 2) if so, what kind of nematodes, and 3) is Fusarium wilt also involved.  Detection and identification now will help growers to make best variety selection and possible use of nematicides in 2019.

 

Important Dates:

 

Field Days:

 

Midville – Southeast Research and Education Center – August 15th

Tifton – Cotton and Peanut Field Day – September 5th

 

For more information on any of the discussed topics please contact your local UGA Extension Agent.

Reductions in Grass Control in 2018? (Prostko)

Getting plenty of calls about perceived reductions in grass control after applications of ACC-ase inhibiting herbicides, such as Select (clethodim) or Poast (sethoxydim), have been applied.  Some folks first reaction to this “lack” of control is that we suddenly have widespread ACC-ase resistance.  When its comes to the issue of resistance, I will never say never.  But, before traveling down that bumpy road, I would like for you and your growers to consider the following:

1) Currently, only 2 grass species have been “officially” confirmed to have evolved ACC-ase resistance in Georgia including large crabgrass and Italian ryegrass. Scientific confirmation of herbicide resistance takes lots of time, manpower, and greenhouse space.

2) Labeled heights for optimum control of various common grasses with Select, including crabgrass, Texas panicum crowfootgrass, and goosegrass, are 2″- 6″.  

3) The following is some data illustrating the effect of Select rate and timing on the control of goosegrass.  Please note that goosegrass control was reduced by 16-23%, depending upon rate, when applied at the 4-6 tiller stage of growth.

Figure 1.  Goosegrass control with Select applied at different rates and timings.

4) If Cadre (imazapic) was applied prior to the grass herbicide application, it is very likely that grass control will be reduced.   Research has shown that Cadre can reduce the photosynthetic rate of goosegrass which then reduces the sensitivity of the ACC-ase enzyme to clethodim (Burke and Wilcut.  2003.  Physiological basis for antagonism of clethodim by imazapic on goosegrass.  Pesticide Biochemistry & Physiology) 

5) At this time of the year, peanut plants are kinda tall (> 12″).  Thus, any grass plants peaking out of the top of the peanut canopy are not likely to be adequately controlled due to size and coverage issues.

6) Before dropping the R-bomb, please double-check use rates, stages of growth, adjuvants, rain-free periods, and field history.  The threat of herbicide resistance is definitely real but it does not happen in one night.

Row Crop Disease Update August 10, 2018

Dr. Bob Kemerait gives row crop disease update:

DISEASES of PEANUT:  White mold and leaf spot aren’t breaking lose in every peanut field in Georgia, BUT hot temperatures, high humidity and frequent rains have created near-perfect conditions for the development, spread and, sometimes, explosion of these diseases.  Growers need to stay on a good fungicide program, tightening spray intervals where disease is becoming problematic and/or where there is concern if the crops have received enough drying time after a fungicide was applied.

FOUR COTTON DISEASES:  Target spot, areolate mildew, Stemphylium leaf spot, and bacterial blight.

What a season it has become when target spot and areolate mildew are causing greater angst than bacterial blight.

 

EASY STUFF:

 

  1.  Bacterial blight is present and is affecting yield in some fields.  Susceptible varieties will get this disease and losses may occur.  THERE IS NOTHING TO BE DONE ABOUT IT NOW. However, growers should note the varieties where they find it and determine at the end of the season if the disease became severe enough to avoid planting those varieties again.
  2. Stemphylium leaf spot is present as well.  Stemphylium leaf spot is caused by a deficiency in potassium in the plant.  Dr. Glen Harris is our soil fertility expert; I believe he would agree that excessive rains could have leached potassium this year.  Fungicides ARE NOT a solution for Stemphylium leaf spot; Dr. Harris has the best information about managing potassium.

 

HARD STUFF:

 

  1.  Target spot and areolate mildew are present in a number of fields this year.
  2. At times, target spot and areaolate mildew appear late enough in the season that the defoliation resulting from these diseases does not affect yield and use of fungicides is not needed.
  3. The question for both diseases is not, “Can we protect the cotton in this field with a fungicides?” but rather, “Should we protect the cotton in this field with a fungicide?”
  4. We have very very little data on areolate mildew, but from what I do have, I am confident that we can easily control this disease using strobilurin products like Headline or Quadris, or mixed products like Priaxor or Elatus.  Proline may work as well but I don’t have data.
  5. Though we can control areaolate mildew, does it make us any more yield than if we didn’t control it?  When conditions are favorable, areolate mildew can rapidly defoliate a cotton crop.  If a grower is withing 3-to-4 weeks of defoliating anyway, I would NOT use a fungicide.  If the crop still had 4 or more weeks to go, I would consider weather, yield potential, how much disease is in the field and then decide to spray or not.
  6. If areolate mildew, or target spot, is already well-established in the field (i.e. causing significant defoliation, then there is little hope that a fungicide will help.
  7. Target spot is a significant concern this year and is widespread.  Not every cotton grower in the state needed to spray a fungicide for target spot, but I encourage growers to carefully consider their options.
  8. Target spot is of particular concern this year because a) the wet and warm conditions are perfect for an explosion of the disease, b) the disease has been found early in many fields, and c) the price of cotton makes protection 100-250 lbs lint/acre attractive.
  9. I believe the best window of opportunity for managing target spot is from the first week of bloom to the sixth week of bloom.
  10. A little target spot in a crop (meaning scattered spots on lower leaves and no defoliation) during the first week of bloom and favorable weather IS a concern, as it would be at the third week as well.  A “little target spot” at the 4th-6th week of bloom is much less of a concern.
  11. When a fungicide program begins as early as the first week of bloom because of the disease situation; a second application may be beneficial two-to three weeks later.  I don’t envision an application, follow-up or otherwise, after the 6th week.
  12. It will be quite difficult to control (impossible?) target spot if there is already significant defoliation in the field before an application is made.  If 25-30% of the leaves are already gone, a fungicide likely won’t work.
  13. THE  THREE MOST IMPORTANT POINTS TO MANAGE TARGET SPOT, in order of importance, are 1.  TIMING  2.  COVERAGE  3.  SELECTION of FUNGICIDE.