Alabama Cotton Picksack

• Alabama Cotton Field Expo........................D. Monks, D. Delaney
• State of the State............................................D. Monks, C. Burmester, D. Delaney
• Managing Nutsedge in Cotton.....................M. Patterson
• Sidedressing Nutrients Other Than N.......C. Mitchell
• Plant Bugs.........................................................R. Smith
• Controlling Growth With Mepiquat..........D. Monks, D. Delaney
• Cotton Calendar.............................................D. Monks, D. Delaney
   

The 1998 Alabama Cotton Field Expo will be held on August 20 at the Tennessee Valley Substation in Belle Mina. This year?s expo is supported by the Alabama Cotton Commission and producer checkoff funds and will feature cotton research in many areas, equipment from local dealers, and information from basic chemical, fertilizer companies and local distributors. There will be guest speakers on three different tours and a special speaker following lunch. Experiment station tours will begin at 8:00 a.m. and will continue until lunch. Lunch will be provided and there is no registration fee. Following lunch, the day will continue with stops on local farms demonstrating the latest in cotton production. Please make plans to attend and watch for further information.

As of May 22, the entire state was in dire need of rainfall. The cotton crop ranged from seeds that were "dusted in" and were waiting on rain to small plants with 4+ true leaves. The cotton in the central and southern counties that has consistently looked the healthiest was planted following a strip till implement and conservation tillage. We have a reasonable stand in many fields and older cotton is growing well with the warm temperatures. Thrips have been heavy and many producers are treating to reduce the damage. Producers should continue to monitor their fields closely for thrips, plant bugs (at squaring), and growth stage (especially for Roundup Ready cotton). We need rain.

Nutsedge is becoming more of a problem in Alabama cotton fields. This weed is more common in the sandy coastal plain soils of South Alabama, but is increasing in cotton fields in the Tennessee Valley. Yellow and purple are the two species which cause the most problems in our row crops. These weeds are perennials which reproduce mostly by the spread of underground tubers. Yellow nutsedge is usually larger than purple and lighter green in color. The leaf tip of yellow nutsedge narrows to a needle-like point while the leaf tip of purple nutsedge is more often shaped like the bow of a boat. Purple nutsedge is usually harder to control than yellow from a herbicide susceptibility standpoint. Several herbicides that have activity on yellow nutsedge will not control purple nutsedge.

Preplant herbicide options for nutsedge (both yellow and purple) control in cotton is limited to Zorial. If you have a severe nutsedge problem, then incorporating one-half rate of Zorial and following with the other half rate preemergence will help. Staple herbicide has soil residual activity on both nutsedge species, although the full effect of this treatment may not be noticed until the following year. The arsenical herbicides MSMA and DSMA are still some of the most effective treatments for both nutsedge species. Two applications of MSMA or DSMA post-directed will help beat back a heavy nutsedge infestation. If yellow nutsedge is a problem, then a mixture of Dual plus MSMA will provide burndown and residual activity. Roundup Ultra in Roundup Ready cotton or in hooded sprayers has activity on both nutsedge species. Two applications of Roundup Ultra at the quart rate will probably be needed. Nutsedge is not tolerant of shade, so anything that encourages canopy closure will help control nutsedge.

On deep, sandy soils and sandy soils with a known traffic pan or tillage pan, about 20 pounds per acre of sulfate-S (ammonium sulfate, ammonium thio-sulfate, sulfate of potash magnesium) should be included as a side-dress if none was applied at planting. This is mainly a concern in southeastern Alabama.

Research on very sandy soils under irrigation in Georgia has suggested that sidedressing potassium (K) can boost yields and quality. Most Alabama soils have enough clay in the topsoil or subsoils to retain K applied preplant. Alabama research has shown that the best way to apply K to cotton is broadcast preplant. Don't depend on foliar K to correct a deficiency late in the season.

Sidedressing Nitrogen on Cotton (a poem)

How should N be applied to a crop?
It doesn't matter at all.
If it's not too soon when the plant starts to bloom
And adequate rain starts to fall.

It can be broadcast or dribbled or
inserted with a dibble,
Or knifed down the middle of the row
It can be handed or banded or flown on as demanded.
If it's there when the crop starts to grow.

Those who irrigate like to fertigate.
This spreads it out for the season.
But those who wait until it's too late
Find foliar is not a good reason.

Anhydrous is cheap but dangerous to keep,
But just as effective on the crop.
Applied close to the side could mean root-a-cide,
But in the middle it's never a flop.

With lots of nodes and a heavy boll load
And an excellent growing condition,
Foliar N is good towards the end
When you're in the proper position.

Following thrips, the second potentially economic insect on cotton in 1998 will likely be plant bugs. The May-June weather and planting dates will have a major impact on plant bug numbers and damage. In making treatment decisions, it is more important to quantify the pinhead square loss than the actual numbers of plant bugs present. Treatment decisions should be made differently for Bollgard than conventional varieties. On Bollgard cotton, growers may go after plant bugs more aggressively during the early square period in June. We would like to set 80 to 100% of the early squares on Bollgard varieties. On conventional varieties, growers cannot afford to treat for plant bugs and destroy beneficials during the June tobacco budworm moth flight. A lack of beneficials during this flight can result in high early season inputs or excessive early square loss to budworms. Therefore, growers should work with a plant bug threshold as low as 50% square set on conventional varieties. This is especially true for areas of the state south of the Tennessee Valley. Some plant bug insecticides are more selective (soft) against beneficial insects than others. All will suppress beneficials to some degree. In general, the soft insecticides are more effective on immature plant bugs than adults. In June, most plant bugs in fields are the migrating adults, while later in July or August in-field generations of primarily immatures may be present.

Cotton grown under high moisture and nutrients can produce excess vegetation called "rank" growth. Rank cotton often results in boll rot, increased insect pressure, and decreased picking efficiency and lint quality. Mepiquat chloride has been used to regulate growth by reducing excessive vegetative production resulting in shorter plants. The shorter plants allow more air movement and sunlight penetration, reducing boll rot and increasing the light reaching the lower leaves. Fruit retention can be higher on lower fruiting branches, resulting in increased earliness. The effect on final yield can be variable.

Mepiquat chloride acts to reduce gibberellic acid production, a plant hormone necessary for cell growth and expansion. Treated plants are often shorter and greener compared to non-treated plants. This is a result of smaller, thicker leaves on the mepiquat-treated plants. Producers have different approaches for beginning mepiquat chloride applications. Regardless of the timing, the results will depend on mepiquat chloride concentration in the plant. For this reason, larger plants with more vegetation will have a higher dilution rate and require higher application rates for similar effects compared to smaller plants.

Note:  The satellite updates will be transmitted at 12:30 PM on the listed days and can be viewed using coordinates:  Galaxy 4, transponder 10 (except for Sept. 2- TBD).  Each update will feature Extension cotton specialists covering the latest pertinent topics affecting Alabama producers.  We apologize to those of you who tuned in for the May transmittal. The times were inadvertently changed prior to air-time.

You can access cotton and other row crop information through our website at:
http://www.aces.edu/department/cotton/index.html

As always, if we can be of service at the Alabama Cooperative Extension System, please do not hesitate to call or visit your local county Extension office.
 

Alabama Cotton Picksack Newsletter Reference: PSK-6-98; D. Monks and C. Burmester, Editors

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