Gaze into the sky tonight and you’ll see a spectacular full
moon ablaze.
With
fall only a few days old, the harvest moon shining bright tonight and tomorrow
is a sure sign for cotton growers that their crop soon will be ready for
picking.
“Growers should start defoliating their fields this week,”
says field scout Damien Jelen. The sure
sign for folks driving around the Valley are warning signs placed around the
border of cotton fields warning workers and the public about upcoming chemical
applications. Two to three weeks after defoliation, the crop will be ready for
picking.
Why are defoliants used to help with the harvest?
The treatment is a traditional cotton management practice
that causes the leaves to drop and plant to start drying. This helps the
harvesting machines pick the cotton cleanly off the plants and lessen the
amount of leaves and debris (we call it trash) collected during the harvest.
The practice improves the quality of the fiber as it is processed at the cotton
gin.
You might describe defoliation
as both an art and a science. If growers defoliate too early, their yields can
be affected because there are too many immature bolls left on the plants. If
the field is defoliated too late, the field could wind up with pest damage.
A common guide to determine when to defoliate is using a
Nodes Above Cracked Boll (NACB) method. Find the highest first position boll
that is cracked and showing lint and then count the number of harvestable bolls
above it. It’s fairly safe to defoliate at three NACB for the Pima varieties
and four for Acala.
Some growers, however, may opt to defoliate
early. They may worry about aphid and whitefly populations threatening the crop
and causing sticky cotton problems – figuring they can sacrifice a little yield
in order to get a head start on harvesting.Of course, there are advantages for
holding off with defoliation and allowing more fruit to mature. Either way,
it’s a decision that’s not taken lightly by growers.
Defoliation of local cotton fields is ramping up. |
“Defoliation is the last operation where management
decisions can have a large impact on profits;a lot of dollars hinge on making
the right decision,” UC Integrated Pest Management says.
Here’s what UC IPM considers the best conditions
for defoliation:
- Moderate to high air temperatures (daytime greater than or equal to 80 degrees, nighttime greater than 60 degrees)
- Relatively low plant and soil nitrogen levels
- Moderate soil water levels (plants not water stressed)
- Relatively uniform crop development; plants at vegetative cutout with limited or no regrowth
- Weeds, insects, and diseases under control
- Ability to get good chemical coverage and penetration of the chemicals into the plant canopy
Pest control advisors
and UC extension specialists can offer recommendations about defoliant products
and application rates.
Growers monitor for sticky cotton. |
Meanwhile, Damien says aphids and whitefly populations have
been under control. That’s important in fields that
haven’t been defoliated yet. “You need to keep monitoring for these pests to
avoid honeydew build up and sticky cotton,” Damien says.