Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Posts Tagged ‘peanut’

Plant Disease Info – September 2015

Posted by romeethredge on September 14, 2015

Plant disease has been a big problem this year and here’s some good  insight and recommendations from Dr. Bob Kemerait, UGA Plant Pathologist.

Soybean rust, so very quiet for much of the season, is now much more active in the southeastern United States.  For current finds of soybean rust, please see www.sbrusa.net.

 

Soybean rust has been found throughout Mississippi and Alabama. 

 

While we have found fewer “hits” in Georgia, as of last Friday we have found it in Decatur County and then rapidly in Colquitt County and now Burke County.  Given the general distribution in Alabama and the west-to-east distribution in Georgia, coupled with recent rains and cooler weather, I think the disease could quickly be found in any field in the state.

 

IMPORTANT to NOTE:  though the disease is finally spreading (and rapidly), we are seeing the SPREAD but the BUILD-UP is lagging behind.  That is, the disease is widely but thinly scattered at the moment.

 

With time, the disease will build until frost.  

 

Growers with soybeans that are full-seed/R6 or close to it are “safe”.  Soybean fields with pods where seeds still have weeks to develop until they fill the pod are at risk.

 

For growers who spray now, late in the season, even use of tebuconazole is likely to be of benefit. 

 

PEANUTS/White mold:  Cooler temperatures should begin to help subdue a disease that has been troublesome for many, but not all, this season.

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Peanut Disease Questions

Diseases are always a constraint to peanut production in the southeastern United States, but some diseases have been especially troublesome in 2015.  For reasons that are not clear, tomato spotted wilt has, for the third year in row, caused significant losses in some fields.  Unfortunately, there have even been a few fields considered to be at “reduced risk” where damage from the tomato spotted wilt virus has been severe.  Other diseases, especially stem rot (white mold) caused by Sclerotium rolfsii and Aspergillus crown rot caused by Aspergillus niger, have led to a continuous battle with the grower throughout the season in terms of fungicide programs and considerations for re-planting the crop earlier in the year.  I believe there have been at least two very important factors.  First, the season has been extremely warm; such favors the development of both white mold and Aspergillus crown rot.  Add in some periods of rainfall/moisture and it is the “perfect storm” for white mold.  Second, our huge acreage planted to peanut in 2015 is a certain indication that some of our peanut fields were planted on a short rotation, increasing the risk to diseases like stem rot/white mold and even Rhizoctonia limb rot and leaf spot.  The 2015 season will likely be remembered as one where more effective (and, of course, more costly) fungicide programs for management of white mold were needed.

Now in September,  we have four common questions with regards to disease management in peanut fields.

  •  With harvest in sight, how should I finish out my disease management program?

Answer:  The 2015 season has been very favorable for white mold and many growers have wisely continued to protect their crop from this disease beyond the traditional window between 60 and 105 days after planting.  However, cooler temperatures anticipated as we head into September should help to slow white mold.  Any grower who has four weeks or more to go until harvest, except those at low risk based upon Peanut Rx, should maintain a fungicide program at least for leaf spot diseases and perhaps for white mold.  Growers with three weeks to go until harvest and without a disease problem (white mold, leaf spot or other) can likely suspend their program unless a tropical storm or other system threatens that might delay harvest.  Growers with a significant disease problem may consider protecting the crop to within two weeks of projected harvest.   Fields with excessive levels of leaf spot or white mold demand special measures as harvest nears.  (Note:  in extreme cases, it may be impossible to do anything to slow the spread of disease once it is established.)  Where leaf spot is problematic in a field, growers may consider including the fungicides Alto (5 fl oz/A) or Topsin M (5 fl oz/A) + a pint of chlorothalonil to manage the disease.  Growers with white mold should consider continued use of a white mold fungicide, to include tebuconazole, until late in the season.

  • With diseases in the field, should I consider digging the crop early to avoid additional digging losses?

Answer:  In the majority of cases, it is better to harvest the peanut crop as the appropriate maturity to insure good grades.  In many cases, achieving good grade is preferable to reducing some digging losses that result from weakened pegs.  Rarely do we encourage growers with tomato spotted wilt in the field to dig early.  Our most popular variety, ‘Georgia-06G’, seems to be more forgiving to end-of-season defoliation than earlier varieties were.  Though we want to maintain good leaf spot control throughout the season, the tolerance to yield loss Georgia-06G demonstrates when premature defoliation occurs further allows growers to keep the crop in the ground until suitable harvest.  Where white mold and especially CBR are problematic, digging a crop early may be necessary as both diseases can greatly increase digging losses.  If the diseases is contained, meaning that it is not continuing to spread in the field despite a number of individual plants which are affected, then I would suggest keeping the crop in the ground.  However, if either of these diseases is rampant and active in the field, then it may be necessary to dig the crop to avoid significant yield loss.

  • Why do I have so much white mold in the field and did I get ANYTHING from my fungicide program?

Answer:  I have been asked this question again and again, over and over this season.  First, here are a few things to remember.  The 2015 season has been very favorable for white mold, pushing all of our fungicide programs to the limits of performance.  No program, no matter how much you spend, can control all disease in a field.  I think 75% control may be all we can get sometimes.  Couple warm temperatures with dry conditions and our dryland fields are, well, you know what I mean.  Without rain or irrigation to wash the fungicides to the crown of the plant, performance and control are reduced.  Our huge peanut acreage must mean that some of our fields are on a short rotation.  Short rotation, hot temperatures and perhaps over-reliance on tebuconazole because of low peanut prices all add up to a white mold “field day”.

How do you know if your white mold program worked for you?  If you look out in a field and see a number of white mold “hits” you are likely to be disappointed.  However, if such “hits” are contained to a one, maybe two plants and do not extend in streaks down the field, then you can be confident that your program was engaged and fighting for you.  Also, if finding active white mold is difficult, then you can also be confident that your program was working for you.  Note, however, that managing underground white mold is especially difficult because of getting the fungicide to the target below the soil surface.  Underground white mold is difficult to control, even under the best of circumstances.  Control may be improved with timely irrigation or rainfall, or by spraying the crop at night.

  •  Is there anything I can do now to prepare for disease management in peanut next season?

Answer:  Yes, there are several things.  First, do your best to increase the number of years between peanut crops in a field.  Second, identify the diseases that have been most problematic in your field and work with your county agent to develop a comprehensive management plan to include choice of variety and fungicides.  Educate yourself on fungicides that are available now and those, such as Elatus, that will be available in 2015.  Lastly, consider taking nematode samples and preparing for nematode management in 2016 with resistant varieties (Tifguard and Georgia-14N).  Also, note that our current predictions are for a strong El Niño this winter, bringing increased rainfall and cooler temperatures.  Growers should anticipate how such will affect disease management in all of their crops to include delays in planting or in application of Telone II.

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Morningloy control in Peanut

Posted by romeethredge on August 28, 2015

We’ve been getting many questions lately about late-season morningglory control in peanut.  In most cases, it is too late in the year to apply herbicides.  Pre-harvest intervals (PHI) of peanut herbicides with POST activity on annual morningglory are as follows: Cadre = 90 days; Cobra = 45 days; Ultra Blazer = 75 days; 2,4-DB = 30-45 days.

 In Dr. Eric Prostko’s, UGA Weed Scientist, opinion, the best thing a grower can do for annual morningglory this late in the season is to apply a pre-harvest application of either Aim or ET (i.e. 7 days before digging).  Both herbicides will provide sufficient dessication of annual morningglory plants (except smallflower) to improve peanut vine flow through a digger with minimal effect on the peanuts . It is very important that the peanuts be dug in 7 days after treatment (or as soon as possible after that time).  If digging is delayed, the morningglory vines could start to recover/regrow especially after a rainfall event.  Specific recommendations for these herbicides can be found on page 502 of the 2015 UGA Pest Control Handbook.

Figure 1.  Annual morningglory response to Aim (5 DAT).

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Digging… Time… To evaluate

Posted by romeethredge on August 28, 2015

At peanut digging it’s a good time to evaluate field problems so that you can plan for the next time peanuts go in the field, as well as look at problems that may affect other crops in the rotation. Look for nematodes and diseases that have affected you.

This year white mold has been severe and any white mold program has been challenged and we see some in most all fields. Look to see how many hits of mold you had and if the mold was really running down the row, and then evaluate your fungicide spray program. The 2015 UGA Peanut Update has good sections on Disease and Nematode control by Dr. Kemerait, UGA Extension Plant Pathologist.

As peanuts are inverted we can look for underground mold which we sometimes don’t see from the topside. Usually dirt will stick to these affected peanuts and they will be sort of soft and we’ll see some of the white mycelium usually as well.

Here’s a good example of it.

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Another yield grabbing culprit is the Peanut Root Knot Nematode. We naturally have nitrogen producing nodules on the roots that are stuck to the sides of the roots but actual swellings are nematodes. Often the roots look bushy and hold more dirt, and if you look closely the pods have knots on them, too.

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Peanut Leaf Scorch

Posted by romeethredge on July 31, 2015

Peanut Leaf Scorch is showing up, but is nothing to be concerned about.

 Leptosphaerulina crassiaca is the causal organism of Peanut Leaf Scorch. We’re seeing some of this now. This was in a field of Tiftguard variety peanuts that were brought in to me today.  Dr Bob Kemerait, UGA Extension Plant Pathologist, says it causes some leaf symptoms but does not cause yield loss in peanut. Our normal fungicides used in peanut probably help with this as well.

 

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Ten Peanut Insect Questions

Posted by romeethredge on July 17, 2015

TEN PEANUT INSECT QUESTIONS and ANSWERS for 2015 Dr. Mark Abney, UGA Extension Entomologist

Q1. Lesser Cornstalk Borer (LCB) took me to the cleaners last year. What do I spray this year, what rate and how often?

  • Do you have any LCB now? If not, do not treat. 2014 was the worst LCB year in memory, and treating fields this year just because there was a problem last year is not a good strategy. Scout your peanuts!

Q2. Everybody is talking about Diamond (novaluron) & Prevathon (chlorantraniliprole) for LCB. Which one do I spray and how much?

  • Neither of these products is currently recommended by UGA Extension for LCB because there are not enough data. Nevertheless, both look promising. If you choose to use one of these products, consult the label for rates.

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Q3. How good is Dimilin (diflubenzuron) on lesser cornstalk borer?

  • Trial results are variable. It is not listed in the UGA Pest Control Handbook for LCB.  Dimilin is an insect growth regulator and it is not as hard on beneficials as Lorsban or other broad spectrum materials, and it will control foliage feeding caterpillars.

Q4. Can I apply liquid chlorpyrifos to my peanut for burrower bug and/or LCB?

  • NO.

Q5. Should I apply granular Lorsban for burrower bugs?

  • Do you consistently have burrower bug damage? If not, then NO. If yes, then you probably should; there are no other options for controlling this pest. Be sure to scout Lorsban treated fields for caterpillars and spider mites.

Q6. I hear they are catching burrower bugs in light traps this year. What does that mean?

  • No one really knows at this point. Burrower bugs are native to the US and feed on a lot more than peanut. We cannot predict if 2015 will be a bad year.

Q7. Spider mites killed me last year; do I need to be worried about spider mites in my peanuts in 2015?

  • You should be monitoring fields for pests including spider mites. Spider mite infestations usually start at field borders, especially those adjacent to dirt roads, and dry corners. Comite and Omite (same AI) are the only legitimate option(s) available. Early detection and good miticide coverage are essential to control.

  • Q8. When do I spray for three cornered alfalfa hopper?

  • There is no validated economic threshold. A threshold that was proposed in the early 2000’s in response to increasing TCAH populations on “Georgia Green” peanut is:

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This threshold is probably too low for current varieties. Work is being done now at UGA to determine thresholds for this pest.

Q9. What can I spray for TCAH?

  • Pyrethroids are pretty much it, but they will kill beneficial insects, and you will probably have more caterpillar pressure.

Q10. Should I spray these caterpillars in my peanuts?

  • PART I. Probably not, but since you are going to spray them anyway, please do not mess up. Pyrethroids are cheap, but they kill beneficials, and they do not kill all caterpillar species. There are plenty of good, selective caterpillar materials listed in the UGA Pest Management Handbook.

  • PART II. The threshold for foliage feeding caterpillars in peanut is 4-8 larvae per row ft. Use the lower end (4) on smaller or stressed peanuts and the upper end (8) on healthy, vigorously growing plants.

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Peanut Weeds

Posted by romeethredge on July 1, 2015

Dr. Eric Prostko, UGA extension weed scientist, gives a good Peanut weed control update, below.

1) Cobra or Ultra Blazer applications should be avoided if possible when the peanut plants are in the R5 (beginning seed) to R6 (full seed) stage of growth (Figure 1).   Results from a 9 location study conducted in 2005-2006 indicated that Cobra applied at this time could cause a significant peanut yield loss (~5%).

Figure 1. Peanut Stages of Growth.

2) Nearly all 2,4-DB labels limit the official number of applications that can be made in peanut to 2.  Results from trials conducted in 1997 indicated that peanut plants (Florunner and GK-7) were tolerant of multiple applications (1, 2, or 3) of 2,4-DB.  Research is currently underway in 2015 to confirm these older results using GA-06G.  Check out Figure 2 for a list of how much and when 2,4-DB can be applied according to current labels.

Figure 2.  Summary of 2,4-DB labels for use in peanuts.

3) On more than 1 occasion this year, growers have accidently applied 2,4-D amine rather than 2,4-DB to peanut plants.  Fortunately, we have a good idea what could happen to peanut yields when this occurs (not that bad depending upon rate and peanut stage of growth).  Check out the following UGA Extension publication:

http://extension.uga.edu/publications/files/pdf/C%201036_1.PDF

“Not a rocket scientist for sure but I am thinking that is a great idea to read and check the label (or at least look at it) of any pesticide jug before dumping it into a spray tank.  As my father once told me, fast and ready sets the pace but slow and steady wins the race!”

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Potato Leafhoppers in Peanut

Posted by romeethredge on June 26, 2015

Potato leafhoppers, not to be confused with Three cornered alfalfa hoppers. sometimes cause leaf damage in peanuts. They feed on the leaf and cause the V shaped yellowing.  A treatable situation has been reported in our area. They usually start on a field border and go out into the field in an area, so good scouting is needed to spot them.

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Here’s Dr. Mark Abney’s, UGA Extension Entomologist, report about them.

“As I walked through my test plots and a few commercial peanut fields this week I noticed that we are starting to see some potato leafhoppers and very early hopper burn. Also there was some heavy leafhopper pressure in at least one field in southwest GA this week. We need to be observant as we scout fields in the coming weeks. Low level leafhopper infestations are very easily overlooked, and scouting from the truck will almost guarantee that you will not see them until the hopper burn is bad.

Hopper burn will appear as yellowing of the tips of the leaves. This yellowing can be very dramatic when infestations are heavy. It is worth mentioning that hopper burn will not immediately go away once the insects stop feeding. This means you should confirm that potato leafhoppers are still active in a field with hopper burn before making an insecticide application. Scouts should be aware that leafhopper infestations often begin at the edges of fields and spread from there. Be sure not to overlook edges as you walk your fields.Potato leafhopper adult.

There are no validated economic thresholds for potato leafhoppers. The presence of adults and nymphs in the field means that reproduction is happening, and populations are likely to grow. We do not want to be too aggressive with this pest, especially in hot dry conditions where insecticide sprays could trigger secondary pest outbreaks. Nevertheless, we do want to prevent severe hopper burn.”

 See Dr. Abney’s post on 27 May 2015 for more info.

Hopper burn on peanut caused by potato leafhopper.

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Peanut Growth Stages

Posted by romeethredge on June 26, 2015

We often talk growth stages in crops but in peanuts we don’t very much.  We say they’re blooming or pegging or putting on pods. Here are the “official” reproductive stages in peanut. This will be good so we can talk a little more precisely to know where we are agronomically in peanut growth and development.

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Lesser Cornstalk Borer Control Options

Posted by romeethredge on June 19, 2015

We have new possible options in lesser cornstalk borer (LCB) control in peanut. This was a terrible pest in dryland peanuts last year and is turning up again this year in some fields.

Here’s a photo of one in a peanut field this week sent to me by Luke Johnson.

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Some preliminary testing in Grady County by Dr. Abney, UGA Entomologist and Brian Hayes, County Agent shows promise for a couple of products.

Here’s comments from Grady county Agent Brian Hayes, “The only product that we at UGA currently recommend for control of LCB is granular Lorsban, but a trial we had with Dr. Mark Abney (UGA peanut entomologist) last year here in Grady County showed a couple of very promising products.”

Go to Brian’s Blog for more test plot results and info.

More studies are being put in this year including one field recommended by Consultant Mark Mitchell in Decatur county. Scouting for this and all pests of peanut is very important.

Two of the products that show early promise are Prevathon and Diamond. Both are labeled for peanut and Prevathon recently got an additional label update.

Here’s some info from the recent label for Prevathon, one of the products in this study. .

“Apply PREVATHON® at 14 – 20 fluid ounces per acre (0.047 – 0.067 lb ai/acre) as a foliar spray for lesser cornstalk borer infestations later in the peanut growing season. Foliar applications should be made in sufficient water volume to achieve thorough coverage of peanut foliage and the soil area around the peanut main stem and growing limbs.

Applications of PREVATHON® by conventional foliar application methods should be followed with an overhead irrigation of 0.5 – 1.0 inches of water within 24 – 48 hours after application to enhance contact with lesser cornstalk borer larvae.

 PREVATHON® may also be applied through overhead sprinkler irrigation systems,

Peanut fields with a history of lesser cornstalk borer populations should be scouted weekly and PREVATHON® application made early when adult moths are active and laying eggs and when larvae are just beginning to hatch.
Apply when populations reach local established treatment thresholds to prevent crop damage.”

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Peanut Calcium

Posted by romeethredge on June 8, 2015

“The More Things Change…

The more they stay the same !” says Dr. Glen Harris, UGA Extension Soil Scientist, who gives us this report.  When we switched from growing small-seeded Georgia Green to large-seeded Georgia 06G we really thought we would need to increase our gypsum or calcium recommendations.  But after years of research we concluded that the recommendations didn’t need to change.

You can still use a pegging soil sample ( 3 inches deep, next to the peanut row soon after emergence) and if you have at least 500 lb/a of soil test calcium AND if your calcium to potassium ratio is 3:1 or better, than you don’t need to apply gypsum.  If you do not meet EITHER of these requirements then you need to apply 1000 lb/a gypsum at early bloom.  Also, all peanuts grown for seed should automatically receive this gypsum application regardless of soil test calcium levels.

There are a number  of different gypsum or landplaster fertilizers currently available. Chemically they are all calcium sulfate and the good news is that we have tested these too and they are all comparable as far as providing calcium to the pegging zone of a peanut.  Probably the most commonly one used now is technically called Flue Gas Desulfurized or FGD gypsum and is a byproduct of scrbbing sulfur gas out of smokestacks at coal burning power plants.  I call this “smokestack” gypsum although a lot of growers refer to it as “synethetic” gypsum.  There is also the old ‘wet bulk” phosphogypsum(a by-product of the phosphorous fertilizer production) and the naturally mined USG 500 among others.

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The lime method can also be used to provide calcium to the pegging zone of peanut but a few things : 1) this method should really only be used when you also need a soil pH adjustment, otherwise use gypsum if you need calcium, 2) both dolomitic or calcitic lime can be used.  Some people think you HAVE to use calcitic but this is not true, (dolomitic gives you Magnesium as well) and 3) the lime method does not work as well as gypsum under dryland conditions during years of normal rainfall.  We have good replicated field data to support this too.

We have also been testing putting calcium chloride though the pivot at peak pod fill (60-90 days after planting).  This method has a fit when you are on the borderline of needing some calcium. The benefits are you can apply this yourself and you do not have to run over the vines.  One disadvantage compared to gypsum or lime is that this method with not build your soil test calcium levels basically at all.”

Posted in Fertilization, Peanuts | Tagged: , | Leave a Comment »

 
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