January 2024 - 40

PGRs
for these crops pack a one-two punch, by both knocking
off unwanted flowers and enhancing branching.
Anytime you use ethephon, remember all the potential
effects of its application. This is especially important
when trying to avoid unwanted flower abortion close to
target marketing dates - you don't want to turn your
crop too green at the last minute!
Although all ethephon products are currently labeled
for foliar sprays only, a new label for Collate will be
coming out that expands applications to include drenches.
While traditionally applied with sprays, recent research
and trialing has shown that drenches are also an effective
application method for ethephon. This new label will
simply be putting one more tool in your toolbox.
BENZYLADENINE
One of the newer active ingredients on the market,
benzyladenine (BA; Configure) is an excellent tool for
improving the branching and finished plant quality of
annuals and perennials. Using BA allows growers to
enhance branching similar to using ethephon, but without
the other side effects that may be experienced when
using ethephon.
GIBBERELLIC ACID
We spend a lot of time trying to suppress GA in
spring crops, but there are instances where we apply
it to annuals and perennials. For some seedpropagated
perennials, treating seed with GA can
improve germination percentages, improving plug
tray stands. Additionally, it can be used when
growing topiary geraniums. Like poinsettia trees,
the GA are used to help the geraniums gain height
without excessively long crop times.
GIBBERELLIC ACID + BENZYLADENINE
One of the biggest concerns I hear is: " What if I
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40
JANUARY 2024 GPNMAG.COM
use too much growth retardant? " Excessive amounts
can get on plants due to a variety of errors, from
calculating to mixing to application. Regardless of
how it happens, the combination of GA4+7 and BA7
(Fascination, Fresco) can help overcome excessive
growth regulation. Although we mentioned using
GA for topiaries, GA+BA is preferred for overcoming
excessive growth regulation since you are less likely
to get excessive promotion with the combination. As
with any over-regulation remedy, as soon as you can
recognize the error and treat crops with GA+BA, the
more success you'll have turning growth around.
In addition to enhancing growth, GA+BA can also
be used to reduce lower-leaf yellowing on geranium
cuttings in propagation. After geranium cuttings
are harvested from stock plants, packaged and
transported from Central America to greenhouses
across the U.S., their carbohydrate pool can get
depleted. Once the cuttings are stuck and placed in
the greenhouses, lower leaves start to yellow and
fall off, reducing marketability and photosynthetic
area, while increasing the potential for disease.
By spraying geraniums with GA+BA after they are
stuck, the yellowing of lower leaves is suppressed.
Between 2 and 4 ppm is a good place to start.
Additionally, if you use GA+BA on geraniums,
you should also use a rooting hormone, as the
GA+BA can slow rooting (and the auxin promote
it). However, don't apply these as a tank mix. A
spray volume of 2 or more quarts per 100 square
feet may be good for auxin, but not for GA+BA on
cuttings - keep the volume to 2 quarts or slightly
less per 100 square feet to avoid getting runoff to
the base of the cutting.
Chris Currey is an associate professor in the Department
of Horticulture at Iowa State University. If you have
questions, he may be contacted via email at ccurrey@
iastate.edu.
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January 2024

Table of Contents for the Digital Edition of January 2024
