A
cotton plant is an indeterminate perennial, and produces vegetative and
reproductive growth simultaneously. PGRs, or Plant Growth Regulators, are
synthetic plant hormones that can be used to balance vegetative and
reproductive growth in cotton. When PGRs
are applied, there is good potential for change in the plants energy allocation
away from potentially wasteful vegetative growth. Generally PGRs keep developing cells from elongating,
leaving the plants with shorter and more efficient internodes. This does not necessarily increase yield, but
it does help keep the plant more compact and potentially more water efficient. Producers often make use of PGRs at the match
head square stage to better prepare for expected hot and dry conditions latter
during the growing season.
There
are three types of growth hormones that PGRs can impact in the plant, gibberellins,
cytokinins and auxins. Gibberellins are
most closely related to vegetative growth and promote cell division and
expansion. Most PGRs reduce the
concentration of this hormone in the plant, and prevents the cells from
elongating, leaving a more compact plant (1).
This compact plant has the potential to be more drought efficient, and
consume less water than it would if it were larger. These synthetic hormones can also alter where
the plant tends to bear fruit, and can cause a more compact fruiting zone.
Plant hormones
work in very low quantities, and since PGRs are synthetic plant hormones, they
work in very low doses as well.
Increasing the amount of PGRs early will not increase or lengthen their effects. As the season progresses, PGRs can be applied
several times in the season, but they should never be applied to a stressed
plant (2). If they are applied to a
plant that is stressed later in the season, PGRs can push a plant to cutout and
reduce its yield potential.
We are one of
the few areas in the country that commonly uses cotton strippers instead of
cotton pickers. A cotton stripper’s
efficiency is at its maximum when the cotton height is below 36 inches. Another reason to keep our cotton shorter
than 36 inches is that tall, rank cotton plants tend to produce too much late
fruit or bolls with little hope of maturing before an average freeze date. This means we need to watch our cotton’s
height a little more closely than other regions might need to. Latter in the growing season, the top five
internodes on our blooming cotton fields ideally would average to be about 1
inch in length. If those internodes
start getting larger than 1.2 inches long, it would be time to consider
applying a PGR. Conversely, blooming
cotton with internode lengths of 0.8 inches are already experiencing drought
stress.
Applying blanket
PGRs very early in the season is not uncommon, especially in this area. When the cotton reaches the match head square
stage, many producers apply PGRs often mixed with a herbicide treatment in the
effort to prepare for coming water stress latter in the growing season. Fields with PGRs applied this early may fare
better when the latter stress and heat inevitably set in during boll set. Right now, our cotton has seen wind damage
and has been exposed to some early hot and dry conditions, but few fields can
be considered drought stressed yet. Even
in this drought, it should be safe to apply PGR for good benefit as fields
reach that minimal match head square stage.
Good
Luck! Please
call or come by the office if you have any questions. Thanks!
Kate Blayne
Written by Kate Harrell, Intern
with the Plains Pest Management Association and Texas A&M AgriLife
Extension – IPM, Hale & Swisher County.
References
1 http://www.caes.uga.edu/extension/irwin/documents/PGRPublicationUGA.pdf
. Philip
Jost,Jared
Whitaker, Steve M. Brown, Craig Bednarz. Department of Crop and Soil Sciences
College of Agriculture and Environmental Sciences Cooperative Extension
Service. Bulletin 1305-Date April, 2006.
6/26/13
2 http://agfax.com/2013/06/26/texas-cotton-plant-growth-regulator-considerations/
. AG
FAX Fields of Facts on June 26, 2013. 6/26/13
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