Late cotton needs special management

The good news for Texas High Plains cotton producers, says Randy Boman, Texas Extension cotton agronomist, is that soil moisture conditions are excellent from much-above-average rainfall over the area; the bad news is much below average heat-unit accumulation.

“Records show from January 1 through June 3 we received about 2.5 times more rain than normal, but our accumulated heat units are about 26 percent below normal,” Boman says.

Lack of heat-units, delayed planting, re-planting, hail and wind damage, seedling disease, and other adverse growing conditions, makes cotton on several hundred thousand non-irrigated and irrigated acres “late” and probably will not bloom until July 24 or later. “And because yield potential on these acres will be lower than normal, producers will need to modify their usual cultural practices,” Boman says.

“Our recommendations for managing late cotton are made with the assumption growing conditions will be ‘normal’ throughout the remainder of the growing season,” Boman says.

Insect control

David Kerns, Extension entomologist, cautions producers to avoid three common mistakes: 1) managing insects as if it were a normal year; 2) deciding not to spray no matter what happens; 3) trying to mature every fruiting form they can set until a killing frost. “Any of these mistakes can result in disaster!” Kerns says.

Proper early season management consists of operations that maximize square set and protects bolls. This means controlling fleahoppers and early Lygus infestations to insure at least 85 percent set of 1st position squares during the first weeks of squaring. Other insects that can later become a problem include bollworms, beet armyworms and aphids.

Kerns sums it up this way: “Make timely decisions based on realistic potential yields and scouting reports, and don't manage insect problems aggressively if you can't water or fertilize as needed.”

Fertilizer management

“It is important not to over-fertilize a late crop as it may result in a flush of vegetation and fruit forms that have no chance of producing acceptable lint. Also, excessive amounts of vegetation may increase insect problems,” Boman says.

If the field has been fertilized based upon expectations of a May planting date, additional fertilizer will probably not be needed. Exceptions could include “sandy” areas where nitrogen leaching might have occurred. These fields, and fields that have not been previously fertilized, could benefit from sidedressing.

“With many dryland field soil moisture profiles full, it is likely that sidedressing nitrogen will pay off in 2007. A good rule of thumb is to apply 30 to 50 pounds of actual nitrogen to dryland fields. Producers should take note of nitrogen fertilization on fields with above normal precipitation. Many growers have had a difficult time applying nitrogen. This is especially true for producers who normally apply fertilizer through center pivots or drip irrigation. We have not yet been irrigating many fields in June, and we need to complete fertilizer application as soon as possible,” Boman says.


“To maximize yield potential, late cotton should not be allowed to stress early in the season. Thus, if initial soil moisture is limited, irrigation during the early growth stages will be necessary for maximum plant growth and early square retention. However, if initial soil moisture is adequate, irrigation may be delayed until blooming begins,” Boman says.

Irrigation should be applied to maintain soil moisture levels adequate to produce a healthy leaf canopy at least through mid-August. Then moisture stress can hasten cutout. LEPA and drip irrigation are well suited for managing water stress in this manner.

“Producers using furrow irrigation should consider terminating irrigation by mid-August to minimize excessive growth and production of undesirable fruit forms,” Boman says.

Weed control

“If the variety being used is ‘conventional,’ growers need to control need weeds conventionally: a herbicide applied preplant or during planting. The rest of the season timely mechanical cultivation and/or a number of herbicides applied using precision post-directed or hooded sprayers may be necessary.

“If older Roundup Ready varieties are being used, over-the-top glyphosate applications should not be used after the 4-leaf stage as yield reductions up to 20 percent can result. However, new Roundup Ready Flex cotton varieties allow growers to spray glyphosate over-the-top from emergence up to seven days prior to harvest,” Boman says.

Growth regulators

“Mepiquat chloride (MC) will not help plants compensate for earlier weather and disease damage or for late plantings,” says Boman. “Under good growing conditions, MC may increase fruit retention, control plant growth, and promote earliness; but do not use MC on cotton that is stressed or likely to become stressed.

MC can affect crop earliness through better early season fruit retention, but this may not be economically feasible for a late crop.

Harvest-aid chemicals

“For higher-yield potential fields, conditioning-rates of boll opening materials (ethephon) followed by a sequential Paraquat application or a freeze may be the best strategy for many fields,” Boman says. “Lower yielding cotton may best be targeted with an initial low rate of Paraquat followed by a sequential application of a higher rate of Paraquat or a freeze.”

Information that can help the producer make decisions about when and how to use harvest-aid-chemicals is available in the Extension publication: High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide available at the Lubbock Center Web site: Information pertaining to all phases of cotton production, including the weekly Focus on High Plains Agriculture newsletter is also available at this Web site.

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