Specialists Speaking - July 2008
July’s Goal — A Big Boll Load
What a contrast in weather conditions for southeast Missouri. In 10 days, we went from cool and wet to hot and dry. Not only did the temperatures warm up into the 90s, but the wind was also a factor in drying out the fields.
I have seen cotton with and without the wheat planted in the middles, and there is a big difference. The cotton without protection is tattered with some sandblasting being reported. This cotton is more desiccated than the protected cotton. There is also a notable height increase in the protected cotton.
We have gone from plenty of moisture to conditions with center pivots being used to keep the plants from drying out. The good news is that we are really piling up the heat units at this stage. We have already had almost as many heat units for the first two weeks of June than for the entire month of May. The bad news is that we have had high night temperatures to offset some of the gain in metabolites.
The plants do not recover as well with these night temperatures.
While our growing season has not been the most desirable, it hasn’t been all bad. Last year, even under drought conditions, we still produced our second best Missouri yield at 968 pounds per acre.
Under more favorable climatic conditions, we produced 1,054 pounds per acre in 2004. Irrigation and insect control will be the most important considerations in keeping this crop on target for the remainder of the season.
July is a critical month for many management decisions in cotton in the Deep South. Layby application of herbicides, N applications, controlling growth with growth regulators and irrigating to set a good boll load are all part of needed management decisions.
Rainfall has been very erratic with some areas having adequate rainfall and nearby areas remaining dry. Producers will have to scout each field to determine the needs of the crop due to the spotty rains.
The increase in acreage of corn and wheat has also brought an increase in the numbers of stinkbugs and foliage-feeding insects. It will be very important to scout fields that are near corn as it is drying down.
Stinkbugs will be moving out of the corn into cotton fields. Stinkbugs feeding can result in boll shed at an early stage or boll damage that can reduce picked yield by almost 100 percent.
Likewise, those fields that typically have had high hardlock damage can be sprayed with fungicides during bloom on a two-week schedule to reduce the amount of hardlock.
Headline has a label for controlling hardlock but will also reduce foliar diseases in those fields that have a history of early defoliation and hardlock.
As with all treatments that you have not tried and are skeptical about whether they will work, split fields with and without treatments to see if they are of benefit in your operation.
July will be a busy month for Georgia cotton producers as they manage one of the most ”spread out” crops in terms of planting dates. Overall, good stands have been achieved despite some very hot and dry weather the first part of June.
Scattered showers in June have helped in most areas of the Georgia Cotton Belt but have added to the challenges of weed control, sidedressing nitrogen and insect control on cotton in stages anywhere from just-planted to squaring.
Volunteer peanuts appear to be more of a weed control problem compared to past years. Insecticide applications for stinkbug control will be critical as May-planted cotton begins to bloom.
The normal window for sidedress nitrogen and boron applications will also be greatly extended due to the wide range in planting dates. Some acres targeted for June-planted cotton after wheat harvest did revert back to soybeans.
It will also be important for producers with irrigation, which is approximately 40 percent of our cotton acres, to stay ahead of schedule. Following our typical dry May and early June, subsoil moisture is probably lacking, and once you get behind, it is hard to catch up and reach your targeted yield goal.
Hopefully, by the time you receive this magazine, your cotton is blooming. July is really our last time to have much influence on earliness and final plant height with plant growth regulators (various forms of mepiquat).
Remember that cotton has a natural way to control plant height and avoid rank growth. It is called boll load. We can’t shrink cotton with mepiquat. What we can do is reduce growth for about 10 to 14 days after the application of mepiquat.
Mepiquat is best seen as a tool we can sometimes employ to help control rapid growth until boll load takes over. When does boll load take over? It normally takes over in the first couple weeks of bloom. Our research suggests that applications made after this point are a waste of time and money.
The increase in acres planted to Bollgard II should reduce foliar insecticide applications for the budworm and bollworm complex. This may allow more stinkbug damage if producers are not scouting for this problem. Producers should be monitoring for stinkbug damage throughout bloom.
Recent studies by Dr. Jack Bacheler and other southeastern entomologists suggest that yield losses due to stinkbug damage are more likely during weeks three through five of the bloom period. A lower threshold of 10 percent internal damage to quarter-sized bolls is recommended during this period.
This is definitely not a time you want to let down your guard on stinkbugs.
Irrigation timing will be key to high yields this season. With the price of diesel fuel on the rise, it is difficult for many producers to water young cotton. However, this year timely irrigation early will help to ensure timely maturity of this later-planted crop.
Fields where irrigation was initiated in the middle of June were growing additional nodes every two and a half to three days. In other fields where irrigation was delayed, plants produced a node every four to five days.
Timeliness of irrigation and other pesticide applications will be crucial to keeping this cotton crop on track. Maintaining high fruit retention this season will be very important so that further delays can be prevented. Manage nitrogen applications carefully in July. The crop is already late in Arkansas, and additional nitrogen applications in July may cause more delays, rank growth and some expensive defoliation bills.
The cotton crop in Mississippi is in a wide range of growth stages. We have cotton as small as four- to six-leaf as well as cotton that is beginning to bloom. After starting out with a cool, wet spring, many Delta fields are in need of a shower as we roll into the beginning of July.
Pest pressure has been fairly light; however, tarnished plant bug numbers began increasing over the weekend of June 14. Isolated applications for two-spotted spider mites were also made.
Due to the lateness of the crop this year, the utility of a plant growth regulator is important, especially in areas that have adequate soil moisture and vigorously growing plants.
However, plant growth regulator applications should be approached with caution. Although we did have a wet spring, the weather has turned from too wet to too dry in several areas of the state.
Application of a plant growth regulator to cotton that is under stress (including drought stress) should not be made. Monitor each field on an individual basis and avoid blanket applications of a plant growth regulator.
Dry weather and high input prices are not the only obstacles that central and south Alabama producers have faced this season. Plant bug pressure was high during June, especially where wild plants were drying down quickly as a result of the dry weather.
Cotton grown in close proximity to wheat and other small grains was also fair game and required multiple treatments to keep the pests from severely damaging yield potential.
Perhaps the most damaging of the insect pests over the next month in our area of the state will be stinkbugs. Although stinkbugs can sometimes be found earlier in the growing season, the primary control window generally centers around late July and early August for most of central and southern counties in Alabama.
According to Shannon Norwood and Amy Winstead, regional agents in north Alabama, the 2008 Precision Ag and Field Crops Day will be July 10 at Isbell Farms in Cherokee, Ala. The Alabama Cooperative Extension System (ACES) Precision Ag Team has partnered with the University of Georgia Precision Ag Team, Alabama Farmers Federation, Auburn University and the USDA National Soil Dynamics Laboratory for this event.
Topics to be addressed include: grain bin storage, irrigation, variable rate seeding, Continuously Operating Reference Stations (CORS), bioenergy gasifiers and weed and nitrogen management in conservation tillage systems.
More information on this and other row crop events can be found at www.alabamacrops.com, which will serve as the new hub for the row crop information from ACES.
The Tennessee cotton crop has progressed nicely after getting a late start. With most of our cotton being planted two to three weeks later than normal, we really need to manage for an early crop this year. Timely application of plant growth regulators is a must! The bigger the plant, the more PGR is needed per application.
Make it a priority to have vegetative growth under control by mid-bloom. Also, make sure to stay on top of the insect situation. Loss of early fruit to plant bugs or stinkbugs will lengthen the time needed to mature the crop. Watch those post-directed applications of glyphosate in Roundup Ready cotton. Getting sloppy can cause delays in maturity if new fruit does not pollinate correctly.
A final thought for mid-season management is that for most of Tennessee the last effective white bloom date is between Aug. 10 and Aug. 12. Keep these dates in mind as you are planning late-season inputs. Attempting to manage for “top-crop” bolls after these dates typically does not pay off.
With fertilizer costs skyrocketing, High Plains producers need to recognize that nitrogen is still an important input for higher yielding cotton. Many producers may be tempted to use a gallon of this or gallon of that to replace a sound fertilizer program.
The cotton plant has a physiological need for nutrients. With the somewhat late and rough start this year, producers need to be looking at yield potential in their fields. Our yields are pretty much driven by irrigation capacity of individual center pivots or sub-surface drip-irrigated fields in dry summers.
Each bale of yield goal requires about 50 pounds of actual nitrogen. Adjust nitrogen rates to fit yield potential for irrigated fields. Generally speaking, about 30-50 pounds of actual nitrogen per acre are adequate for dryland cotton in the High Plains. The higher rates should be used if the yield potential (stored soil moisture) is sufficient for higher lint yields.
The amount of organic residue of the previous crop is also important and will potentially affect nitrogen availability. If the previous crop was grain sorghum or if cotton was planted into terminated small grains cover, then producers should consider increasing nitrogen fertilizer rates by around 20-30 pounds per acre in order to have adequate nitrogen for the cotton crop due to microbial immobilization of previous crop residue.
As I am writing this report in early June, I can look back 40 days to May 4 when the cotton crop was planted in Louisiana. Prior to the 2008 Beltwide Cotton Conferences, a publication titled “The First Forty Days: The Most Critical Period in Cotton Production” was published. The work was the collective agreement of more than 65 cotton experts from around the country.
These experts represented
every discipline and geography and came from the university and consultant
ranks. To assess the first 40 days of the 2008 Louisiana crop, some
of these BMPs are explained below to help understand the crop we have
now and develop future strategies.
Almost all Louisiana cotton
has been planted with a fungicide seed treatment – Avicta Complete
Cotton, Aeris seed treatments, or some component of the two. Early
planted cotton emerged in challenging conditions, and some stand loss
would have occurred if not for fungicide seed treatments. The amount
of protection needed is basically a function of how quickly cotton
emerges. Prolonged cool weather also contributed to the problem.