Switching gears to Pima cotton defoliation in California, UCCE Farm Advisor Steven Wright discussed the always tricky process of Pima defoliation and harvest in the late-season cotton before traditional fall rains arrive. If harvested too early, Pima yield and fiber quality can be reduced. The same can be true if the crop is harvested late.

“As we move into late October and November, there is a greater risk of rainfall which can trigger fog and dew,” Wright said. “These conditions can delay the start time for harvest until late in the morning, or even mid-day.”

Pima is a popular crop with growers due to the price premium paid for the extra-long-staple cotton and fiber quality.

Wright’s research has focused on whether Pima harvest aid product applications can be started earlier to escape possible exposure to late-season rain and other poor weather conditions without much negative impact on yield and fiber quality loss.

The short answer is yes.

The traditional time to begin harvest aid applications in Pima cotton in California is when cotton reaches 3-4 nodes above cracked boll (NACB).

In the UCCE Pima defoliation research conducted at the West Side Research Center in Fresno County from 2009-2013, various cotton varieties were defoliated at 4-5 NACB and 6-7 NACB with multiple applications of defoliation products, including different rates of Ginstar, Ethephon, and other products.

The field trial results suggest that Pima cotton can be defoliated 7-14 days earlier than the original 3-4 NACB timing with minimal impacts on yield and fiber quality.

Wright offered these tips for Pima growers interested in the earlier defoliation and harvest of a vigorous Pima crop.

  • Consider your own experience on how many days of harvest is needed from the harvest of the first field to the last field.
  • Keep an eye on the 1-14 day weather forecast.
  • Determine the last harvest date deemed an acceptable risk. Count back about 21 days from the desired harvest dates. Start with the defoliation program on those dates regardless of the plant’s maturity stage (NACB) of the plant.
  • Consider this approach in some fields but not all fields. Growers can start some harvest operations at an earlier date when weather conditions are more favorable.

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