Excerpts from the latest Peanut Pointers Newsletter (Various Authors):
- Weather & Climate Outlook – Pam Knox
- Disease Update – Bob Kemerait
- Runner-Type Average Maturity – Scott Monfort
- Insect Update – Mark Abney
- Spray Volume and Droplet Size Considerations – Simer Virk
- Irrigation Update – David Hall, Jason Mallard, and Wesley Porter
Weather & Climate Outlook – Pam Knox
The temperature in July has been generally slightly cooler than normal, with daytime temperatures
below normal (from clouds) and overnight temperatures warmer than normal due to the abundant
humidity we have experienced this month. This is also reflected in the wetter than normal rainfall for
most of Georgia in July, as several fronts have dropped into the state from the north, serving as a focus
of developing thunderstorms that have produced spotty rain across the region. Some areas have seen a
lot while other areas nearby have been mostly missed by the showers. Because of the rain, drought
conditions in most of the state have seen significant improvements, and these are likely to continue.
In August, the pattern looks similar to July, especially in the first two weeks. We will continue to see
periods of showery weather broken by occasional dry periods. Temperatures are expected to be hotter
than normal early in the month but should move back towards more seasonal conditions later in August.
Precipitation in the first two weeks is expected to be near normal but is expected to increase again near
the end of August, especially if the tropical season starts to ramp up. It will be scattered as we expect in
summer thunderstorms, and some areas will see more rainfall than others.
So far this year, the Atlantic tropics have been relatively quiet, with just three named storms and no
hurricanes so far. This has been due in large part to large plumes of Saharan dust that affect the vertical
temperature structure of the atmosphere and reduce thunderstorm development while cooling the sea
surface a little. Once these subside, we should start to see the tropical waves coming off of Africa grow
more quickly and turn into tropical storms and hurricanes as the peak part of the tropical season
approaches in mid-September. Of course, we don’t know where they will go, but the Southeast usually
gets the effects of several of them.
Longer-term, NOAA and others are continuing to predict the continuation of a triple-dip La Nina, which
is keeping the Eastern Pacific Ocean one of the few areas in the globe cooler than the long-term
average. This is expected to last through winter, which could mean another warmer and drier than
normal winter for at least parts of Georgia. Last year when this happened, it meant that some parts of
the state did not see frost until well into January, allowing some pests and diseases to overwinter well
into the year. This makes early treatment of potential problems, including in-furrow treatment,
something of special importance in 2023. However, that is a long way off yet, and ENSO predictions in
mid-summer are not always accurate for next winter, so you will need to keep an eye on this when it
comes closer to planning for the next growing season.
Disease Update – Bob Kemerait
August is a month that is critically important for disease and nematode management for peanuts grown
in Georgia. Heat, humidity, sporadic rainfall, days since planting, and growth of the peanut plants all put
the crop at high risk for diseases, especially white mold and leaf spot. The heat, humidity, rainfall, and
irrigation are near-perfect in August of 2022 for infection and development of fungal diseases. The
dense canopy of foliage that has developed in many fields traps moisture and humidity, thus prolonging
leaf wetness periods and increasing risk to diseases. The dense canopy of foliage also makes it more
difficult for fungicides applied to the leaves to reach the crown of the plant for protection against white
mold.
By this time of the season, much of the crop is between 90 and 100 days after planting, which is
sufficient time for leaf spot and white mold to become established in most, if not all, fields. Incidence of
disease is should be lower in well-rotated fields and/or in fields where appropriate and timely fungicide
programs have been deployed. Where crop rotation is short, or where there have been delays in
fungicide applications, or where the choice of fungicide could have been better, peanut growers may
find that August is the month to fight to find some way to re-gain control of disease in the field.
For disease management in August, I have five recommendations.
- Continue to scout fields to ensure that there are no surprises as far as the development of white mold or leaf spot.
- Recognize that even where there is good disease control in a field NOW, there is plenty of season left until harvest.
- It is nearly impossible to have “perfect” control of white mold. Initial infection for white mold is likely to occur from individual plants being infected by sclerotia in the soil close to the plant. From this initial infection, the disease can spread and burn along a row, resulting in significant yield loss. NO fungicide program will eliminate initial “dinner plate sized” hits of white mold in a field (though good crop rotation will do that). A GOOD fungicide program will stop the initial “hits” of white mold from burning down the row. If your program is not stopping the “burn”, then we need to figure out why. It could be the fungicide is not reaching the intended target. It could be the fungicide is applied too late or at the wrong rate. Or, it could be that a better fungicide could be used.
- There is significant interest in mixing SPECIFIC formulation of sulfur, remember that NOT ALL sulfur products are effective for management of leaf spot in peanut. It is my experience that sulfur in the right formulation mixed with the right product is similar to adding a pint of chlorothalonil. Adding sulfur to a fungicide for leaf spot control is not magic, but it can be a cost-effective way to improve leaf spot control.
- Better products and systemic products. I don’t look for any white mold products to be systemic, but some fungicides are better at fighting white mold than are others. Some leaf spot fungicides DO have limited systemic/curative activity against leaf spot diseases and these products can and should be used judiciously in the peanut fields
Runner-Type Average Maturity – Scott Monfort
AUNP 17: is a medium maturing peanut (140 to 145 days). Good peg strength, good level of TSWV,
white mold and leaf spot resistance
FloRunTM ‘331’: This is a medium- maturing peanut (140 to 150 days). Good level of TSWV resistance
Georgia-06G: Georgia-06G is a medium maturing peanut (140 to 145 days). Moderate Level of TSWV
and leafspot resistance
Georgia-09B: Georgia 09-B is a medium maturing peanut (135 to 140 days). Some peg strength issues.
Susceptible to leafspot.
Georgia-12Y: This is a medium-to-late maturing peanut (150 days +) — Good peg strength, high level of
TSWV, white mold and leaf spot resistance. Very susceptible to Rhizoctonia Limb Rot.
Georgia-16HO: is a medium maturing peanut (140-145 days). We have observed slightly higher
incidence of leaf spot late in the season. We have also observed some peg strength issues in wet
conditions.
Georgia-18RU: is a medium maturing peanut (140-145 days). We have observed slightly higher
incidence of leaf spot late in the season. This variety is more susceptible to TSWV and have seen some
issues with vines crashing because of TSWV and Diplodia.
Georgia-20VHO: is a medium maturing peanut (140-145 days). This is a new variety for most growers. It
is low growing variety. It has good level of TSWV resistance. The one negative for this variety is that we
have observed significant pod loss in wetter years.
Insect Update – Mark Abney
The peanut insect management talk in August will most likely revolve around foliage feeding caterpillars.
There are soybean loopers, velvetbean caterpillars, redneck peanut worms, a variety of armyworms,
corn earworm and tobacco budworm, and a few odd ball species out in the peanut patch this week. Just
the talk of caterpillars is enough for some growers to add an insecticide to their next fungicide spray.
Scouting and treating at threshold remains the best strategy for managing caterpillars.
Dimilin remains a very good choice for velvetbean caterpillar, but it is not effective against loopers even
with good coverage. Loopers tend to feed low in the canopy (especially at first). It is difficult to get
insecticides down in the canopy, and many control problems with loopers and “premium products” can
be linked to application and coverage issues.
Spray Volume and Droplet Size Considerations – Simer Virk
Timely and effective fungicide applications throughout the season are an important tool for growers to
manage and protect yield from diseases like white mold and leaf spot in peanut. While selection of a
good fungicide program is critical, it is also important to ensure that the application efficacy is
maximized through proper selection of spray parameters including spray volume and droplet size. The
type of nozzle selection to attain proper droplet size has also been one of the common questions from
the Extension agents and growers in the past as well as this year. Below are few considerations for spray
volume and droplet size selection to improve spray coverage and canopy penetration in peanut along
with some illustrations:
- Spray Volume: One of the most effective ways to improve fungicide application efficacy is by
using enough spray (water) volume. The images below show spray coverage for fungicide
applications made at three different spray volumes of 10, 15 and 20 GPA. It is obvious from the
images that 20 GPA provided the highest coverage followed by 15 and 10 GPA. It was also
noticed in these studies that the highest volume (20 GPA) also improved the coverage at the
middle of the canopy due to more volume penetrating through and into the peanut canopy. As
most fungicide labels have a minimum spray volume requirement (for ground applied) of 15
GPA to attain adequate coverage, so it is important to not use the spray volumes below the
minimum recommended since it can affect both fungicide coverage and efficacy.
- Droplet Size: Size of the spray droplets is another important consideration for maximizing the
effectiveness of fungicide application. The images below show coverage obtained at three
different droplet sizes (medium, very coarse and ultra coarse) for the spray volume of 15 GPA.
Again, it can be seen that smaller droplets provided better and more uniform coverage while the
larger droplets, especially ultra coarse, had less and non-uniform spray distribution. It was also
noticed that the larger droplets were unable to penetrate the peanut canopy resulting in
considerably reduced coverage at the middle of the canopy. Selecting nozzles that can produce
medium to coarse droplets at the nominal operating pressure(s) is recommended to attain
adequate coverage and maximize application efficacy.
Irrigation Update – David Hall, Jason Mallard, and Wesley Porter
June was very hot and dry and provided some challenges, while it turned wet in certain areas of the
state. While, some areas have gotten rainfall, others have remained dry. The last week of July turned
hot and dry again. If peanuts were planted during the late-April or Early-May time frame they are at or
just moving out of peak water usage and some of the rains has helped to keep the water requirements
satisfied. However, don’t forget that over-irrigating peanuts can cause yield reductions so be careful
when deciding when to apply irrigation especially if it has been as wet as it has been in some areas
lately. A good soil water balance model or soil moisture sensors can really aid in building confidence on
when to apply those few small events to prevent yield loss, and when not to apply those events for the
same reason.
For weekly peanut water requirements, please refer to the graph below (the UGA Checkbook). Keep in
mind that these requirements are for peanuts that were planted between mid-April and mid-May and
that they are for both irrigation and rainfall. This graph should give you a good idea on where we stand
for the month of August. Most growers that planted in this time frame will reach peak water use during
the month of August and then the daily water use will slowly start to decline. DO NOT get behind on
irrigation as the weather can just as easily become hot and dry over the month of August. If you fall
behind with hot and dry weather it is difficult to catch up with irrigation only during peak demand. For
those of you using a soil moisture sensor or Irrigator Pro as your irrigation scheduling method, they will
definitely let you know if you get behind on irrigating and it will be a difficult challenge to get that soil
moisture back up with irrigation alone, especially with the deeper depths.
One point to keep in mind about using Irrigator Pro, especially if you’re a new user and this is your first
year running it, if you planted in the mid-April – mid-May window, you will hit the “R3 – Drying Out”
growth stage during the month of August, if you haven’t already. According to the crop model, this growth stage will occur at roughly 95 DAP. You will notice that the app will tell you to stop irrigating for
about a week. This is to intentionally withhold water once a maximum fruit load occurs on the plant and
to stress the peanut plants so that it will stop flowering and allocate resources to maturing the peanuts
that are already on the plant. So, if you see this occur and feel like your field is getting dry, don’t panic
its part of the model and how the soil moisture needs to be handled to ensure the plant reacts
appropriately physiologically.
Additionally, with the high amounts of rainfall over the past month it has been very difficult to get
sprayers into the fields, thus, many growers may be considering chemigation. Chemigation through
pivots may not be for everyone but with possible disease and insect pressure and many acres to cover,
this practice may prove timesaving and effective. Especially with above and below ground white mold
appearing in many areas this year. The hot, humid, and wet environments are the perfect recipe for
disease issues. Remember, read the label to ensure the pesticide is approved for chemigation. Also, run
the pivot at 100 percent to apply the least amount of water while chemigating. If your system can not
apply 0.1” or less per revolution, chemigation is not recommended. Remember the goal of chemigation
is to apply chemical to the foliage of the plant, not the soil. This also means that a chemigation event
cannot accurately and validly be counted as an irrigation application. It is also very important to know
that your pivot is apply uniformly before considering injecting anything through it for application. So, if
you have not had a recent uniformity test performed on the system we strongly discourage the usage of
chemigation or fertigation.
If you have further questions about irrigation requirements, chemigation or fertigation reach out to your
local UGA County Extension Agent.