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Alabama Cotton Shorts

April 13, 2020

April 13, 2020
 
Situation. Almost Time to GO, at least in the southern half. There’s an old saying which seems accurate: “Pecan trees never lie.” The meaning and application is that when pecans leaf out, it’s okay to plant cotton. The first weekend in April, pecans were green and shining from the southern part of Alabama to at least as far north as Lafayette.
 
Well, not so fast… Following Sunday’s (April 12) rain, most of the state will see temperatures dip into the 40s and even 30s for a few days, so there’s no need to rush planting. Maybe by the end of this week or the first of the following, producers in the central to southern portions of Alabama will commence.  (Brown)
Thrips Update. We recently ran the Thrips Infestation Predictor for Cotton (CottonTIP) that Dr. Smith wrote about in Cotton Shorts a few weeks ago (https://climate.ncsu.edu/cottonTIP). As you would expect, there was a big difference in the timing of thrips flights between the southern (earlier) and northern (later) parts of the state. In central/southern Alabama (below I-20, south of Birmingham),  cotton planted between April 1-21 are at the highest risk of thrips injury. Cotton planted along I-20, between Tuscaloosa and Anniston, should have peak pressure between April 13-21 and again between April 26-May 13 planting dates. In the TN Valley and Sand Mountain regions, May 6-16 and 26-31 planting dates have the highest thrips injury risk. Updating the model every couple of days before and after planting can give an idea of if supplemental foliar applications may be needed. We will continue to post updates here and on Twitter to keep you up-to-date on any changes.  (Graham and Smith)

True Armyworms. We have also gotten several calls about armyworms found in fields after burndown for cover crops or no-till across the state. This armyworm is almost assuredly the true armyworm. This species can be differentiated from fall armyworm by the black rings on around each proleg and the lack of inverted “Y” on its head capsule. It is not uncommon to find true armyworms feeding on grasses in the springtime, and they can sometimes reach treatment levels in wheat. Larvae left in fields that have been burned down will be looking for something to eat when cotton emerges. Although true armyworm is susceptible to Bt, larvae will not ingest enough protein to die before damaging cotton.

Scouting for true armyworm is best done in the morning, as larvae hide underneath plant stubble during the heat of the day. We do not have an official threshold for true armyworm, however we do not recommend planting into fields with larvae present. Much like with cutworms, applying a mid-rate of pyrethroid behind the planter may be the most economical way to manage this pest. Based on reports from the mid-south, we suspect true armyworms may be a problem for seedling corn and soybeans as well. Make sure to scout fields that aren’t in conventional tillage prior to planting to avoid any headaches with a pest that can easily be managed.

Please call if we (Scott 662-809-3368 or Ron 334-332-9501) can be of any help.  (Graham and Smith)
Extension Cotton / Row Crop Entomologists Dr. Scott Graham and Dr. Ron Smith. Dr. Graham joined the ACES / AU faculty on April 1, 2020.
Dr. Scott Graham, New Cotton / Row Crop Extension Entomologist at Auburn University. For the past 96 years, only four persons have served as an Extension Cotton Entomologist on campus at Auburn University. With respective starting dates, they are as follows:  Mr. John Ruffin, 1924; Dr. Walter Grimes, 1961; Dr. Roy Ledbetter, 1962; and Dr Ron Smith, 1972. And now comes Dr. Scott Graham.
 
It is with great pleasure that we welcomed Dr. Scott Graham to this position on April 1, 2020. Dr. Graham comes to us from AgBiTech Company, an Australian-based company that globally provides biological pest control products. A native of Mississippi, he received his B.S. and M.S. degrees in Entomology at Mississippi State under the guidance of Drs. Angus Cachot, Jeff Gore, and Don Cook, and completed his Ph.D. in Entomology at the University of Tennessee with Dr. Scott Stewart (Ph.D. Auburn University). Dr. Graham has been trained and mentored by four of the most highly regarded cotton and row crop entomologists in the South.
 
Dr. Graham’s Ph.D. research involved field and laboratory evaluations of the thrips-lygus cotton trait under development by Monsanto, now Bayer. He is extremely well qualified and has the skills and personality to continue the great tradition of cotton / row crop entomologists that have served at Auburn University for almost a century. His responsibilities include cotton, soybeans, and peanuts.
 
Dr. Graham’s contact info:  email scottg@auburn.edu; mobile 662 809-3368.
Dirt Cheap Weed Control. Cotton commodity prices have plummeted over the last weeks and are now at or well below the cost of production. Looking for ways to survive, some growers are thinking about a “dirt cheap” way to manage this crop. In such situations, chemicals and fertilizers are typically among the first inputs to reduce. I don’t oppose cutting back, but I am concerned that overly reducing weed control efforts could seriously affect future operations. Weeds are persistent problems and cannot walk or fly away from a field or farm. One year of sloppy pigweed management can result in significant expense for clean up over the next 3 to 5 years.
 
I’ve had a few calls with growers requesting a “dirt cheap” weed control plan for cotton and peanut. Here are my thoughts about maintaining sufficient weed control but not at a higher costs.
 
Burndown:  
For marestail fields, Roundup + Sharpen 1oz/A.
For no-till or conventional till cotton fields, Roundup + Valor 2 oz.
For generic glyphosate, add NIS surfactant at 0.5 gallon per 100 gallons of spray solution.
 
PRE (from 3 days before planting to 3 days after planting):
For pigweed and grassy fields, Warrant 3 pt/A.
For fields general broadleaf weeds like pigweed, sicklepod, morningglory, teaweed, etc., Cotoran 2 pt/A.
For heavy pigweed and grass pressure, Reflex 8 oz + Warrant 2 pt/A is a great choice.
For PRE herbicide activation, a 0.5 inch rainfall is needed for activation.
Add 2 pt of Gramoxone if weeds have emerged at planting.
 
For pigweed fields:
1st POST over the top of cotton (at 20 to 25 days after planting):  Roundup PM 32 oz + Xtendimax / Engenia (Xtend Cotton) or Enlist One (for Enlist Cotton only) + Warrant 2.5 pt or Dual Magnum 16 oz or Outlook 13 oz or generic version of Group 15 herbicides. Timing is absolutely critical. Treatments should made when weeds are less than 3 to 4 inches tall. As soon as pigweed can be seen on the ground, get your sprayer ready and spray them.
 
Follow-up Post or Layby:  If 1st POST applications for pigweed were made in a timely manner and if residual herbicides from Group 15 (Warrant, Dual, Outlook or generics of these herbicides) have been activated by rainfall, then apply Valor 3 oz or Cotoran 2 pt/A about 2 to 3 weeks later using a layby, hooded, or post-direct sprayer. Cotton needs to be at least 10 to 12 inches tall to minimize crop damage. Use a coarse droplet nozzle if possible. If some pigweed survived 1st POST, spot spray Liberty or a generic glufosinate and then follow with the layby, hooded, or post-directed treatment. Two generic glufosinate products Scout from Valent and Interline from UPL performed equally to Liberty in trials last year. Liquid AMS has shown promise in enhancing the control of large sicklepod and pigweed with Liberty (glufosinate).  
 
The game plan is simple. Try to start clean, spray everything timely, and use plenty of cheap residual herbicides in PRE, 1st POST and Layby applications. Try to avoid a 2nd POST broadcast over-the-top using more expensive POST herbicides. If we don’t run out of rain and if growing conditions remain mostly normal, I am hoping to get through in-season weed management within $30 per acre. Don’t forget to cut off pigweed seedheads before picking cotton!!! Pigweed produces too many seeds per female plant -- we cannot ignore them.
 
For fields without pigweed:
1st POST over the top (at 20-25 days after planting):  Roundup PM 32 oz + Warrant 2.5 pt/Dual Magnum 16 oz/Outlook 13 oz/or a generic of these herbicides. Add liquid AMS to enhance control of large broadleaf weeds and nutsedge. Use 2 oz of Staple LX if morning glory and nutsedge have been problematic in the past. After 2 to 3 weeks, if fields remain mostly clean and cotton is over 12 inches tall, apply Valor 3 oz or Cotoran 2 pt/A in a hooded, post-direct, or layby sprayer. If some weeds survived 1st POST, spray Roundup again to finish them up. Spot spray pigweed or morning glory with Liberty. Then follow with the hooded, post-directed, or layby application.  (Li)
Dr. Ron Smith, Auburn University. Bugwood.org
Grasshopper: Sporadic Pest of Seedling Cotton. Grasshoppers have been a sporadic pest of seedling cotton for a dozen or more years. This problem emerged with the conversion to reduced tillage systems. Certain seasons seem to be worse than others. Overwintering populations are influenced by environmental conditions, and rainfall is likely more important than temperature. Dry winters are favorable for grasshopper population since they overwinter as eggs in the soil. Grasshopper problems are sporadic and almost always associated with reduced tillage fields.

The primary grasshopper that damages cotton is the differential species which also overwinters as eggs in the soil. Eggs hatch from late March throughout April, May, and June as soil temperatures rise and spring rains occur. The first nymph to leave the egg pod makes a tunnel from the pod to the soil surface through which the succeeding nymphs emerge. Nymphs feed and grow for 35 to 50 days before becoming adults which can then fly. The nymphs or immatures can only jump. Their development proceeds most rapidly when the weather is warm but not too wet. Mature grasshoppers mate and continue feeding on plants. About 2 weeks later, females begin to deposit clusters of eggs in the soil. Soil particles are glued together around the eggs to form a protective pod. Each pod may have 25 to 150 eggs. Most grasshopper species only complete one generation per year.

In fields with historical grasshopper problems, growers may want to take a more preventative approach by adding a grasshopper insecticide to their burn down herbicide. Since not all grasshoppers emerge from the egg stage at the same time, a long residual IGR (insect growth regulator) insecticide could also be utilized. Dimlin has proven to be a good management tool for grasshoppers. It has extended residual that provides good control of immature grasshoppers but will not control adults.

There are no established thresholds for grasshoppers in cotton and will likely never be since their feeding habits are so unpredictable. Some fields and some years may have grasshopper damage while other fields and years have the same level of grasshoppers but no damage. Preventative insecticide applications for grasshoppers are a judgment call. When grasshoppers are observed and cotton is in the susceptible stage, treatments can be based on the risk level that an individual grower is willing to take.

Grasshopper problems are greater in lighter soils or soils with higher sand content. Damage often occurs in the same fields or farms from year to year. As stated, grasshopper damage is unpredictable but can potentially threaten a stand. Grasshoppers may feed on foliage, but most economic damage occurs when grasshoppers feed on the main stem of emerging (in the crook or cracking stage) seedlings. In some cases, grasshoppers may completely sever the stem, but more often they will chew partially through the stem weakening the plant which will falls over at the feeding site.
 
Most all cotton insecticides will control immature grasshoppers when applied at a low labelled rate. Later into the spring, adult grasshoppers are very difficult to control with any insecticide, even at a high labelled rate. Acephate (Orthene) at 0.6 lb. active per acre has proven to be the most effective grower treatment for adult grasshoppers.  (Graham and Smith)
This issue contributors:
Dr. Scott Graham, Extension Entomologist
Dr. Steve Li, Extension Weed Scientist
Dr. Ron Smith, Professor Emeritus, Extension Entomologist
Dr. Steve M. Brown, Extension Agronomist  (Editor) typos and other mistakes are mine 

About the Alabama Cotton Shorts Newsletter
Alabama Cotton Shorts is a newsletter designed to keep cotton producers in the know. From planting dates to crop inputs—there are many factors to consider. The Alabama Cooperative Extension System is dedicated to providing science- and research-based information, derived from field experience and observations. A team of Extension specialists are working to provide Alabama farmers with timely information throughout the growing and harvest seasons.

By subscribing to the newsletter you will receive pest updates, weed management suggestions, market updates, industry news, and other information. Specialists are making field observations and reporting their findings in hopes of helping producers make more informed choices in the field.

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