Ben Hill County Ag

May Cotton Team Newsletter

Crop Progress and Assessing Plant Stands for Replanting
(Freeman)
As of April 29th, approximately 12 percent of Georgia’s cotton crop has been planted according to the
USDA NASS crop progress report. This is significantly ahead of our previous five year’s average of 7
percent. Although wet through most of the winter and spring, conditions in most parts of the state
have become dry, and much of our planted acres tend to be on our irrigated lands. These dry
conditions may be favorable for field work however, rainfall is needed if we are to have adequate soil
moisture to ensure proper stands on a lot of our dryland acres. Fortunately it looks like we will get
some much needed precipitation as the 10-day forecast shows high chances for rainfall for much of
our cotton growing regions of the state.
In a perfect world, we would only plant cotton during optimal conditions however, in the real world
cotton is often planted in harsh or sub-optimal conditions for a variety of reasons. It is important to
check and evaluate your cotton stands soon after emergence so that any decisions on replanting can
be made quickly as these decisions can become more difficult as more time passes. One of the first
things that needs evaluating is the overall plant population across the field. This can be recorded
several ways but a plants/ft average needs to be recorded from several/many different areas of the
field to get a good representative sample of the field’s plant population. The second part of the stand
assessment is noting the occurrence of 3’ or greater gaps between plants. A field may have a lower
than “optimal” plant population but if most of the plants are evenly spaced then very little if any yield
losses may occur. Fields with a high number of 3’ or greater gaps have a higher likelihood of lower
yield potential and delayed maturity.
When deciding if the current stand is adequate or if replanting will be needed considerations must
be taken for the extra costs or seed, fuel, labor, additional herbicides and insecticides as well as
hidden costs like the decrease in yield potential from a later planted crop. Other questions that
should be asked are: How uniform is the stand across the field? Should I replant the entire field or
only spots? If I replant only parts of the field, how will the difference in maturity affect me later in the
season with PGR management and defoliation?
The original preemerge herbicides should also be taken into account. If Warrant was used as a PRE,
replanting should be delayed for 14 days as long as tillage (strip till equipment) is done and 21 days
if no tillage is done to avoid serious injury to the replanted crop.

Herbicides and dusting in cotton can be a mighty challenge!
(Culpepper)
Herbicide injury and weed control are both challenging when dusting in cotton and the topic deserves
discussion.
The most effective approach to minimize cotton injury from preemergence (PRE) herbicides is to
place the cotton seed in moist soil where it can imbibe (absorb) clean water free of herbicides.
Next we need our cotton roots to “out run” the herbicide as the herbicide is moving down into the soil with
rainfall or irrigation. When placing cotton seed in dry soil and then applying a PRE herbicide, it is
likely impossible for water to get to the seed without being contaminated with the herbicide.
However no two herbicides pose the same challenge under these conditions; here are a few thoughts
with several products:

1. Reflex moves very effectively in water thus it is the product most likely to reach the seed at higher
concentrations. Although that is not beneficial for the cotton seed, it is very beneficial for weed
control as the product is activated more effectively with lower amounts of rainfall or irrigation than
other cotton herbicides. Additionally, our research has shown Reflex to sit on the soil for 17 days
before being activated and then still providing about 90% control of the pigweed emerging after
activation.

2. Warrant poses a unique challenge, if the encapsulation breaks down releasing the active ingredient
prior the cotton plant emerging then injury can be quite significant. It is the encapsulation of Warrant
that provides us the ability to use it “safely” PRE in cotton. Any time one is uncertain of cotton
emergence within 5 or 6 days of applying Warrant, one may want to consider other options. Ideally
Warrant needs around a half inch of rain for activation and our research has shown it to still be quite
effective on pigweed after sitting on the soil and waiting 11 days for activation.

3. Diuron will move down to the seed less aggressively than Reflex but if a heavy rain occurs within
a few days of dusting the cotton in and applying diuron, injury will be much greater than normal.

4. Brake likely poses the least damage potential to cotton in this environment but the herbicide may
not perform on weeds properly until a half inch or more of rainfall occurs.

Obviously, dusting cotton in and applying PRE herbicides is far from ideal. The next thought from
every grower is, of course, I just want apply herbicides after planting. This thought is extremely scary
when considering the monumental challenges our family farms face with herbicide resistance in
Palmer amaranth. If one does follow this path of not using PRE herbicides, there are several key
points to consider. First, there must be no weeds emerged when the cotton seed is placed in dry soil.
In theory, no additional weeds should emerge until it rains. Second, the first postemergence
herbicide application should occur as soon as the cotton is fully emerged (do not wait to see weeds
at 70 mph from the road); the treatment must kill emerged weeds (Palmer and spiderwort) and must
include residual herbicides. Third, a second postemergence herbicide application should be made 14
to 18 days later and again include a residual product. And finally and absolutely essential, is that the
layby application is made with hoods or a layby rig improving weed coverage and control while
minimizing cotton injury. The layby application should include conventional herbicide chemistry
such as diuron, Caparol or Cotoran; also include Envoke if help is needed with morningglory or
nutsedge.

Thrips Foliar Sprays (Roberts)

Thrips are consistent and predictable insect pests of seedling cotton in Georgia.  Preventive insecticides are recommended at planting to reduce thrips infestations and seedling injury.  Supplemental foliar insecticides are needed in some environments and applications should be based on scouting and thresholds.  The need for supplemental foliar insecticide is dependent upon the severity of thrips infestations, the at-plant insecticide used, and the rate of seedling growth.

At-plant insecticide options include in-furrow granule applications of aldicarb, in-furrow liquid applications of imidacloprid or acephate, and commercial seed treatments of imidacloprid, thiamethoxam, and acephate.  Imidacloprid seed treatment is the most common at-plant insecticide used.  Thrips control and residual activity is greater for in-furrow granules and liquids compared with the seed treatments.  We would expect 3-4 weeks activity with in-furrow options and 2+ weeks of activity with the imidacloprid seed treatment.

The Thrips Infestation Predictor for Cotton (TIPs) Tool uses planting date, temperature, precipitation, and knowledge of when and how intense thrips infestations will be to predict risk of thrips injury to cotton for specific geographic locations.  For many areas, the tool is predicting thrips infestations to be similar to those observed during 2017 and 2018 which were both relatively low pressure years.  The TIPs Tool can be found at the following link:

http://climate.ncsu.edu/CottonTIP.

Vigor or the rate of seedling growth influences seedling injury from thrips.  Thrips initially feed on the underside of cotyledons; damaged cotyledons will appear silvery on the lower surface of cotyledons.  The majority of thrips eggs are laid on the cotyledons and it takes about 5-6 days for an egg to hatch.  Once a terminal is present thrips will move to and feed on unfurled leaves in the terminal.  As the leaves unfurl and expand the characteristic crinkling and malformations become obvious.  A rapidly growing seedling may unfurl a true leaf every 3 days where as a seedling which is stressed may take 4-5 days to unfurl.  Again, thrips are feeding on the unfurled leaves so thrips feed for a more extended time on the same unfurled leaf of a stressed plant than a rapidly growing plant.  The same infestation of thrips will create more damage on a slow growing plant.

The decision to use a foliar insecticide to supplement at-plant insecticides for thrips control should be based on scouting.  Scout thrips by randomly pulling a seedling and “slapping” the seedling against a piece of paper or box to dislodge the thrips.  Do this on several plants and determine the average number of thrips per plant.  Be observant for immature thrips when making counts.  Immature thrips are wingless and crème colored.  Adult thrips are usually brownish or almost black in appearance and have wings (depends on species, tobacco thrips is the most common thrips species infesting cotton and adults will be dark brown or black).  The threshold for thrips is 2-3 thrips per plant with immatures present.  The presence of numerous immature thrips suggests that the at-plant insecticide is no longer providing acceptable control (i.e. thrips eggs laid on the plant, egg hatched, and immature thrips is surviving).  Foliar insecticide options include the systemic insecticides Orthene, Bidrin, and dimethoate.  Note that these products are systemic.  Pyrethroids will not provide acceptable control thrips in cotton.

Economic damage from thrips rarely occurs once seedling reach the 4-leaf stage and are growing rapidly.  It is important that we make thrips decisions early in the plants development.  Seedlings become more tolerant to thrips feeding in terms of yield potential with every true leaf it puts on.  1-leaf cotton is much more susceptible to yield loss than 3-leaf cotton.

 

Managing Nematodes in Your Cotton Crop: What you do now
affects everything you do later (Kemerait)
We had a very mild winter this year. Mild winters may be nice in reducing our power bill; however
extended periods of very cold soil temperatures are essential for reducing nematode populations in
the upcoming field season. I don’t believe we had enough cold weather this year and it could make
nematode problems more severe for our cotton farmers.
If plant-parasitic nematodes are likely to be a problem in a cotton field this season, then the grower
has a very brief window of opportunity to effectively manage this pest. Southern root-knot, reniform,
sting, and Columbia lance nematodes all damage our cotton crop in Georgia and, while growers may
not find management options convenient, protecting the crop from nematodes is an essential step to
protecting yield. Nematodes begin to affect the root system of the cotton crop very soon after
germination. If the developing taproot and root-system is not protected, then all other production
efforts throughout the remainder of the season are compromised as the damaged plants can never
fully recover.
There are important steps necessary to reduce the risk of nematodes to a cotton crop and to protect
the crop once the seed is planted. It is critical to remember that once the furrow is closed, nearly
every management decision has been made and the grower will have to “live with” the results
throughout the season and on to harvest.

Step 1. Practice good crop rotation to reduce parasitic nematode populations in a field. Peanut is an
excellent rotation crop for cotton as peanut is not a host for the reniform, Columbia lance, or southern
root-know nematodes. Corn is not a host for the reniform nematode. Soybean is a host for the
southern root-knot and reniform nematodes; however if a grower planted a “nematode-resistant”
variety in the previous season, then the impact of the nematodes on the future cotton crop should be
reduced.

Step 2. Take soil samples, optimally in the fall of the previous cropping season, to assess both the
types of nematodes and population size in a field. To be able to make the best management decisions,
it is important to know not only which kinds of nematodes are in a field, but also how many of them
are there. Growers could take samples now that soil temperatures have risen; however nematode
counts may still be deceptively low and misleading as far as best management options.

Step 3. Consider planting a root-knot nematode resistant variety, such as DP 1747 B2RF, Phytogen
480 or Phytogen 580. These varieties are not resistant to reniform, sting or Columbia lance
nematodes; however they can have a tremendous impact when planted where southern root-knot
nematode is a problem. Planting one of these resistant varieties in a field infested with root-knot
nematodes will accomplish two things. First, damage from root-knot nematodes will be minimal, if
it occurs at all. No nematicides are needed. Second, the root-knot nematodes will be unable to build
in the field, so populations will be lower for the next cotton crop.

Step 4. If a grower chooses not to plant a root-knot nematode resistant variety, either because he
preferred another, susceptible, variety or because reniform, sting or Columbia lance nematodes were
the problem in the field, then he must consider using a nematicides to protect the crop. To make the
most informed decision about which nematicides to use, the grower should have some idea about the
size of the nematode population in the field. This is best accomplished with results from fall
nematode counts. Samples taken in the spring before planting, but after soils warm, could give some
information if nematodes are found in the sample. However if nematodes are not found in the sample
then this may simply be because they have not yet built to a detectable level following the colder
winter months.
Where parasitic nematodes are well-above “threshold” levels, there is no nematicides that can
perform as effectively as Telone II (3 gal/A). Telone II is a fumigant that must be applied when the
soil is neither too wet or too dry. Typically Telone II is applied 7 to 14 days ahead of planting;
however when soil conditions are right and heavy rain is not expected within 3-4 days following
planting, Telone II can be applied at the same time as the seed is planted.
In fields where Telone II will not be used, or where nematodes are at a “moderate threat”, growers
should consider using AgLogic (5-7 lb/A) or Velum Total (14-18 fl oz/A). Both products protect the
cotton crop against nematodes and thrips. Though results from nematicide trials are notoriously
variable, I am comfortable with the recommendation that Velum Total (16-18 fl oz/A) is gernally
equivalent in performance to AgLogic (5 lb/A). Where pressure from nematodes is severe, it is my
observation that AgLogic (7 lb/A) offers greater protection than does Velum Total. But, of course,
that additional protection comes at a cost.

Seed treatment nematicides, to include AVICTA Complete Cotton, COPeO Prime, Bio ST, Nemastrike
all are convenient tactics for managing nematodes; however they may not be enough. I have
significant data for AVICTA Complete Cotton and COPeO Prime and an increasing volume of data for
BIO ST. I have limited data for Nemastrike. Seed treatment nematicides are most appropriate for
low levels of nematodes in a field. As populations of nematodes increase, the benefit of the seed
treatments, as compared to Telone II, AgLogic, or Velum Total, is lost. Also, performance of some
seed treatment nematicides in Georgia may not match that reported in advertisements.
I do not have data to show the value of combining use of a seed treatment nematicide with either
Velum Total or AgLogic; however I generally do not think any additional benefit in yield will offset
the added cost of the combination treatment.
Once the furrow is closed, growers have only one additional treatment option and that is either
Vydate-CLV or RETURN XL as a foliar-applied nematicide at approximately the 5th to 7th true leaf
stage. This treatment should be in addition to an earlier nematicides treatment and not as a “stand
alone” treatment. Results with Vydate-CLV have been mixed, but it seems most promising where
reniform nematodes are a problem.