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Cool spring hits SJV cotton

California’s San Joaquin Valley cotton crop says it is June, but the calendar says it is July.

The 300,000-acre crop is far behind where it should be. Some believe it may be as much as 21 days later than last year. (For more information on managing late cotton, see the following video link:

It is lagging so far from the historic norm that veteran University of California Cooperative Extension Farm Advisor Dan Munk says it is gong to be challenging to basket a normal Acala cotton crop, since the flowering period will be so short.

In a normal length growing season, growers will focus on setting a bottom crop to pay the bills and a top crop for profit. Pete Goodell, UC IPM specialist, says the bottom crop will be all or nothing. There will be no time to compensate for a lost bottom crop by trying to make a top crop.

Regarding Pima, Munk and Goodell were blunt with growers at a Dos Palos, Calif., field day sponsored by San Joaquin Sustainable Farming Project: Lower your expectations. Where a four-bale Pima crop potential was possible last year; this year Munk told growers they should be willing to settle for three to three and a half bales and be glad if they get it.

“There is not much of a chance this year of making the five-year average on Pima,” Munk said.

Pima is a longer season crop. Its fruiting cycle is 45 days, and time has already run out to set a full crop and gather it before the fog rolls in this fall.

Munk’s observations are based on the accumulated degree days for the period of March 15 through June 6. DD60s for that period were the lowest since 1998; the second lowest in two decades, and “right down on the bottom of the 20-year average.”

Placing the lateness in an even starker reality, Pima plants he mapped on June 21 averaged 3.4 fruiting nodes. Last year on June 25, there were almost 11 fruiting nodes. This year’s mapped crop went in on May 4. Last year the Pima field he mapped was planted April 16.

Comparing yields for 1998 with 2009 is frightening. Pima averaged 941 pounds in 1998, while last year the statewide average yield for ELS cotton was 1,474 pounds per acre. Twenty-one years ago the Acala average was only 887. Last season it was 1,613.

As Goodell pointed out, the 1998 crop was not only late, but there was heavy lygus pressure. The same insect year seems imminent this season.

Munk tempered his dire prediction with the comment that varieties this season are “better” than those planted in 1998 and cotton management strategies have improved over the past two decades.

The first bloom in 1998 in the Valley was recorded on July 20. Munk expects a “number” of 2010 fields to be that late or later. That compresses the season for growers striving to set as much fruit as possible by the Aug. 15-20 time period. This is considered the last boll growers can reasonably expect to put in the picker basket at fall harvest.

It would help if the temperatures remain mild through the summer, as they have in the spring. However, the high reached 108. Ideal fruiting weather is the low 90s.

High heat stress in late July and early August would also result in extreme water stress while the crop matures.

Irrigation and nitrogen use will be delayed this year. Munk said it will be more critical than ever to use CIMIS evapotranspiration data with a cotton coefficient (13 percent to 20 percent of CIMIS Eto); pressure bomb measurements and factoring in canopy size to mitigate water stress and optimize irrigation management.

Plant growth regulator management will be critical and timing also will be delayed.

“Fruit retention will be more of an issue this year. The crop will be more sensitive to any kind of stress than in the past. Loading and holding the bottom crop early and not being forced to try to make it up on the end of the season will be the key to this season. There still is season left for Acala,” he said. He added that in a year like 2010, the first fruiting branches may be higher on the plant than normal.

Munk reminded Pima growers that ELS bolls are much smaller than an Acala boll. “It takes roughly three Pima bolls to make one Acala boll. Pima tries to set fruit on every fruit position.” This makes fruit retention even more critical with Pima.

Munk is a strong supporter of drip irrigation on cotton. He says it could really pay off in 2010 in giving growers far more control of irrigations.

Goodell says the weather has been so mild that it has allowed a second generation of lygus and other pests to develop in wild hosts like mustard. This, he said, likely will lead to higher pest pressures throughout the Valley. It was high early in the season in the south Valley and was moving north.

He encouraged growers and pest control advisers (PCAs) to focus on plant mapping to determine the number of fruiting branches to correlate with bug counts.

A high lygus count where there is no fruit does not necessarily warrant treatment. “A lot of PCAs are not doing this. They are just relying on bug count or ‘the crop does not look good — you need to spray,’” he said.

“You need to count the number of adults and nymphs in sweeps and how they correspond to crop development.”

However, do not expect to hold 75 percent to 80 percent of squares through the entire plant. He said to shoot for the highest bottom crop retention possible in 2010.

“It is not the time to panic, but it is time to invest in the cotton field to find out what is going on to make sure you are setting fruit that should be set early and not worry about what you cannot expect to hold later in the season,” he added.

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TAGS: Cotton
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