*County Field Tours and Monsanto Field Day. D. Monks and D. Delaney
*Reniform Nematode Research Continues C. Burmester
*Defoliation Season Around the Corner. M. Patterson
*Nutrient Deficiencies in July and August. C. Mitchell
*Stinkbug Lifecycle Increases Threat. R. Smith
*2002 Cotton Calendar.  D. Monks

This year's cotton crop has been up and down since the start of the season.  Each area of the state has suffered for various reasons and some of the problems continue to affect the crop.  However, a crop that was only fair in mid-July has been upgraded towards average over the past few weeks.  There are a few areas of the state with excellent cotton but most is categorized as "fair to good".  Our potential looks good if August weather cooperates.

It is time to make preparations for visiting local farms at several county cotton tours.  Tours are being organized in Shelby, Tuscaloosa, and Lee/Macon counties by local county extension personnel.  These tours are generally well attended and provide an opportunity for producers, county agents, specialists, and others in the cotton industry to learn about the crop.  Areas of interest will include variety performance, insect decision-making, defoliation planning, and the current economic situation.

Another opportunity that we are afforded in August is a field day at the Alabama Agronomy Center in Loxley hosted by Monsanto.  The field day will be held on August 15 from 9 a.m. until 1 p.m. (includes lunch).  For more information and reservations, please call Marie at 251-964-6236.  The areas of interest include: Enhanced Roundup Ready Technology; Bollgard II; Mon 007; Alternative Refuge; Conservation Tillage; and Bio-Fuels.

Spots of severely stunted cotton erratically scattered, yellowing of upper leaves, poor root systems, compressed internodes, these are all symptoms cotton farmers found in scattered cotton fields this spring.  Most symptoms began appearing in early June when the weather finally began to warm-up. These symptoms were found in no-till and conventional tillage fields. These symptoms were found in fields that were treated with nematicides and those that were not. Some fields have seemed to improve over the last month while others have shown little improvement. The only common factor in all these fields is heavy populations of reniform nematodes.

Although we have been farming with these nematodes for several years, the exact reason(s) for the increased damage this season is unknown. It appears the nematodes were at very high levels at planting in some fields and the cold stress encountered in mid May could have lead to the severe damage.

Research by Auburn scientists into the control of reniform nematodes in cotton has been underway for several years. This season we have several field tests located across the state. These tests include: 1) testing of nematicide products applied at planting and through-out the growing season, 2) cotton variety screening trials in heavily infected fields, and 3) testing of rotational cropping systems.  Greenhouse and laboratory analysis of reniform nematode control is also being conducted.  These studies include: 1) screenings of winter cover crops to reduce nematodes, 2) screening of cotton varieties for tolerance, 3) nematicide degradation studies, and 4) soil microbial studies.

Farmers need to be aware of this nematode problem and identify possible problem fields. Soil nematode samples should be taken in these problem fields this fall.  Hopefully the research studies conducted this season will provide some new information on control practices we can use to combat the reniform nematode.

Cotton should be loading the bolls on right now.  Hopefully most fields have received adequate rainfall to develop normally.  Although cotton was delayed by cool weather and drought in the spring, many fields will be ready for harvest aid treatments by the second week of September.  Some newer products along with older standard materials are available this year.  LeafLess from Uniroyal is a liquid mixture of Harvade and thidiazuron (the active ingredient in Dropp and FreeFall).  LeafLess rates are 10 to 12 fluid ounces per acre and should be applied with 1 pint per acre crop oil concentrate.  This material provides cotton defoliation and regrowth control.  Adding ethephon (Prep, Boll’d, Superboll, etc.) at 1.33 pints per acre or higher will provide boll opening as well.  Aim is a fast acting material that provides some cotton defoliation and weed desiccation.  Crop oil concentrate should be added with Aim for optimum performance.

Regrowth control and boll opening can be obtained by adding thidiazuron and/or ethephon to Aim.   A mixture of Aim and Harvade with crop oil concentrate can provide good weed desiccation and cotton defoliation.  I expected to see significant leaf sticking with this mixture last year, but this was not the case.   The rate for Aim is .016 pounds active per acre and a new two pound per gallon formulation may be available this year.  Last year’s rates were 2/3 to 1 ounce of the 40 DF formulation; rates for the 2 EC formulation would be 1.0 to 1.6 fluid ounces per acre.  Def/Folex is still a good standard for defoliation without any regrowth or boll opening properties.  Mixtures of these products with thidiazuron or ethephon have long been standards in the harvest aid business.  Ginstar is a liquid version of Dropp, which contains diuron and a good adjuvant.  Ginstar at 6 fluid oz per acre alone has provided good defoliation and regrowth control.  Finish and CottonQuik provide moderate to good defoliation and boll opening alone.  Adding a product with thidiazuron (Dropp, FreeFall, and Ginstar) to these products will provide good defoliation, boll opening, and regrowth control in one mix.

Regardless of the product or products used, there are some general points that apply for optimum performance of all harvest aids:
1- all harvest aids work better in warm temperatures (> 80 F);
2- good coverage of the leaves and bolls is critical (that’s why sequential applications are usually better than single applications); and
3- cotton that’s ready to defoliate will always respond better than cotton that’s not ready.

When leaves don't look quite right and begin developing strange symptoms late in the season, the first things most growers think about are nutrient deficiencies.   A rusty red color to older leaves must be magnesium deficiency.   Yellowing in the plant top must be a sulfur deficiency.  Any other strange leaf symptom must be some micronutrient deficiency.  The fact is that at this time of year, a healthy cotton crop will rarely suddenly develop symptoms of a severe nutrient deficiency.   Deficiencies that may develop are usually associated with sulfur (early July), potassium (August), and nitrogen.  Here is a run down of some nutrient deficiencies that have been encountered in late-season cotton.

Sulfur deficiencies are almost always on deep sandy soils or where wet weather or soil conditions prevent deep rooting.  Most Alabama subsoils contain abundant sulfate-sulfur that plants can use.  Extremely wet weather or traffic pans or both can prevent deep rooting.  Sulfur can be tied up in a cover crop just like nitrogen but once it begins decomposing, the sulfur is released to the cotton crop.  Therefore, sulfur deficiencies are usually brief and occur in late June and early July.  Applying a foliar or soil sulfate-sulfur source can quickly green up a sulfur deficient crop.

Most cotton growers are particularly aware of potassium deficiencies because of all the attention it has received over the past decade.  Symptoms don't usually show up until the crop is at peak boll set.  That's when the crop needs the most potassium and the roots are starting to cut out.  Potassium naturally migrates from the leaves to the developing bolls.  Severe deficiencies will cause premature defoliation and severe yield loss.  Deficiencies are rare on old cotton fields that have been well fertilized in the past but may be common when cotton follows a pasture, hay, or silage crop.  Grasses are very efficient at getting soil potassium.  Cotton is not.  Applying soil or foliar potassium once symptoms appear is probably a waste of time and money.

Magnesium deficiencies get blamed for a lot of discoloration in the lower leaves at this time of year.  An actual deficiency is rare.  Older leaves may change color as they mature and die.  Insect injury, foliar diseases, and the weather can also affect leaf color.

Nitrogen deficiency may occur in late season, especially in a heavy boll-set situation.  Applying foliar urea can help if the cotton plant is still growing and not under moisture stress.  However, much too often I've seen desperate growers use expensive foliar-applied fertilizer in a vain attempt to salvage a poor crop.

Micronutrient deficiencies are almost never seen in cotton at this time of year in Alabama.  There has never been a documented case of cotton responding to zinc fertilization as a plant nutrient in Alabama.  Manganese and/or iron deficiencies have been associated mainly with cotton on highly calcareous soils of the Black Belt or on poorly drained Flatwood-type soils near the Gulf Coast where cotton is rarely grown.  Most producers routinely fertilize with boron either as soil applied or as a foliar spray.  This is the ONLY micronutrient that has produced a yield response in cotton in Alabama.  Responses are less than 1 field in 5 and the yield increase due to boron is usually less than 5%.

Strange leaf coloration at this time of year is usually physiological (related to cotton maturity or weather) or caused by insects or diseases.  Sometimes leaf spot disease can be related to stress especially potassium deficiency but this is not always the case.  Late season foliar or soil fertilization may help the grower sleep better at night knowing he did something, but chances are it is only adding to the cost of the crop, without adding to the value.

Many cotton producers in Alabama accept too much stink bug damage when it can be easily and inexpensively avoided. Growers need to be more conscious of thresholds when treating for stinkbugs. It takes about 30 to 35 days for the stinkbug to develop into an adult, and the adults can live for two months. The most accurate method for detecting stinkbugs is by slicing quarter-sized bolls. A boll of this size still is soft and is most preferred by the stinkbug. The reason for slicing bolls is that not all bolls with outside damage also will have internal damage. On the other hand, some bolls that appear to have internal stink bug damage will show no evidence of damage on the outside. The stinkbug is one of the most inexpensive cotton insect pests to treat, with controls costing $3.50 to $4 per acre. Phosphate insecticides are most effective on stinkbugs. Pyrethroids do an adequate job, with about 80 percent control of the Southern green stinkbug.

Date                          Event                                                             Contact
Aug. 1-4                  ALFA Commodity Conf., Huntsville                ALFA
Aug. 6                      Shelby Co. Cotton Tour                                  R. Colquitt,
                                                                                                       H. Dorough
Aug. 8                      Tenn. Valley Cotton Tour, TV Substation        C. Burmester, CA*
Aug. 14                    Tuscaloosa Co. Cotton Tour                           M. Mobley, CA*
Aug. 15                    Monsanto Field Day, Loxley                           D. Monks,
                                                                                                         Monsanto Rep.
Aug. 29                    East AL Cotton Tour                                      Jeff Clary
*CA- county agent.  Note: Cotton scouting schools will begin at 8:30 AM.

If you are interested in weekly updates for the state’s cotton crop, there are several sources for that information. The DTN terminal at your local supply dealer has a category called "Local Information". The state agricultural statistics reporting service has a website update at:

www.nass.usda.gov/weather/cpcurr/al-crop-weather

If you are receiving this newsletter via e-mail, please visit our website for additional cotton information at:

http://www.acesag.auburn.edu/dept/

Updates are sent each Monday morning to these services and DD60s are updated at the end of each week.  These updates will begin at the start of the planting season or soon thereafter.

Reference Number: PSK-7/8-02, D. Monks and C. Burmester, editors