B-Nine + Cycocel: The advantages for poinsettias and pansies

July 9, 2002 - 08:57

Research on B-Nine/Cycocel tank mixes at Clemson University helps determine optimal combinations of these PGRs for use on poinsettias and pansies.

B-Nine and Cycocel have been effectively used as a tank mix
growth regulator application for many years. The major benefit of this tank mix
is that it provides an easy-to-apply, medium-activity growth regulator
application. The spray volume is not crucial, so any grower can effectively and
safely use it. The B-Nine and Cycocel tank mix (B-Nine/CCC) is particularly
useful in situations where B-Nine and Cycocel are individually insufficient to
control plant height. Thus, B-Nine/CCC fits a niche between the lower-activity
products (B-Nine and Cycocel) and the higher-activity products (Bonzi and
Sumagic).

Growers have different methods of determining the best
B-Nine/CCC combination to use. A common technique is to identify the rate of
Cycocel that provides a reasonable measure of control without causing any
phytotoxicity, then to adjust the rate of B-Nine to provide the desired
strength of growth regulator effect. Our approach was to apply a range of
B-Nine (0-4,500 ppm) and Cycocel rates (0-1,500) to identify the interactive
effects of these two products when applied as a tank mix. We applied 14
combinations of B-Nine/CCC (see Table 1, page 60) to poinsettias and pansies
with the goal of identifying the optimal tank mix combination.

Poinsettia

Rooted cuttings of ‘Freedom Red’, ‘Success
Red’ and ‘Winter Rose Dark Red’ were potted on July 26 and
grown as straight-ups (unpinched). Short days were started on August 14, and
growth regulators were also applied during the first short day. Growth
measurements were recorded at first pollen.

B-Nine/CCC affected final plant height and total bract area
similarly for all three poinsettias grown in this study (see Figure 1, page
58). The highest rate of B-Nine/CCC (4,500:1,500 ppm) decreased the heights of
the three cultivars Á between 16 and 21 percent compared to the control
(0:0 ppm; see comparison photos, page 56). B-Nine and Cycocel each had a linear
effect on height reduction, i.e., each additional amount of B-Nine or Cycocel
applied resulted in an additional reduction in height. B-Nine had a greater
impact than Cycocel on overall height; however, a wider range of B-Nine rates
(0-4,500 ppm) were applied compared to Cycocel (0-1,500 ppm).

The total bract area (the total area of the six largest
bracts) of Freedom and Success, and the flower head diameter of Winter Rose
decreased by 42, 28 and 19 percent, respectively, when comparing the highest
rate of B-Nine/CCC (4,500:1,500 ppm) to the control (0:0 ppm; see Figure 1,
above). Individually, B-Nine and Cycocel resulted in a linear decrease in bract
area. B-Nine/CCC did not decrease the internode length between the transitional
bracts, so the flower head was not more vertically compact.

We don’t see many growers using B-Nine alone on
poinsettias, but our data suggest this would be a very effective product to use
during the vegetative stage of poinsettia Á

production, e.g. on stock plants, in propagation or shortly
after transplant and before short days. Considerable data suggests that B-Nine
will delay flowering of poinsettias. For this reason, we applied B-Nine in this
study during the first short day, i.e., the first day of flower initiation, and
did not observe any effect on time to flower. Growers in cooler climates and
lower-light conditions will observe potentially greater negative effects of
B-Nine on poinsettia flowering. So, caution is urged. B-Nine should never be
applied after the start of short days, and in Northern climates September 1
might be a safe cut-off date for natural-daylength poinsettia crops. Please conduct
your own trials before risking an entire crop on a new growth regulator
application.  

Pansy

Plugs of ‘Delta Pure Yellow’, ‘Majestic
Giants Purple’ and ‘Colossus Yellow Blotch’ pansies were
potted on August 16. The same 14 B-Nine/CCC treatments were used on the pansies
as were used on the poinsettias. The treatments were applied on August 29 and
repeated on September 5 and September 13. Data were collected when two flowers
had fully opened. 

With the highest application rate of B-Nine/CCC (4500:1500
ppm), height or shoot length of Colossus Yellow Blotch and Delta Pure Yellow
decreased by 29-37 percent compared to the control, but height of Majestic
Giants Purple decreased by only 8 percent (see Figure 2, above).

We measured several different morphological characteristics,
but found that the potential benefit of B-Nine/CCC was most accurately
represented by the tilt. “Tilt” is our term describing the degree
to which the primary shoot tip slanted away from the center of the pot (see
Figure 3, page 61). Tilt describes the floppiness of the pansy in the pot. Tilt
decreased in Colossus Yellow Blotch, Delta Pure Yellow and Majestic Giants
Purple by 49, 59 and 27 percent with the highest tank mix rate (4,500:1,500
ppm) compared to the control (see Figure 2, above).

We also observed that petiole length was slightly reduced by
the growth regulator applications; however, each variety appeared to respond
differently to B-Nine and Cycocel. For example, B-Nine reduced petiole length
of Colossus Yellow Blotch and Majestic Giants Purple while Cycocel reduced
petiole length of Delta Pure Yellow.

Searching for the perfect combination

Our data suggest that there isn’t a perfect
combination of B-Nine and Cycocel to apply to poinsettias or pansies. Many
different combinations will provide very similar results. For example, in our
study the 1,000:1,000, 1,500:500 and 2,000:0 B-Nine/CCC treatments produced
very similar results. Thus, we don’t believe there is a perfect
combination. Any combination that provides a total plant growth regulator
concentration of 2,000-3,000 ppm B-Nine and Cycocel will provide similar
results on the poinsettia varieties used in this study. However, lower rates
are required to control the height of less-vigorous varieties. The bottom line
is that the exact ratio of the two products is not critical. Growers must
identify the overall strength of application that is required and choose a
combination that will provide the desired effect. As a starting point we often
use a 3:1 B-Nine/CCC ratio. For example, 1,500:500 ppm provides a low rate,
3,000:1,000 ppm provides a medium rate and 4,500:1,500 provides a high rate for
poinsettias. The overall effectiveness depends on plant vigor and the current
growing conditions (temperature and light).

Pansies showed more variability between varieties in
response to B-Nine/CCC, although the reduction in tilt was similar for the
three varieties tested. Relatively high rates of B-Nine/CCC and multiple
applications were required to produce beneficial results on pansies.

Phytotoxicity

Cycocel is typically effective at rates greater than 1,500
ppm; however, the potential for phytotoxicity keeps most growers from
experimenting with higher rates. The typical Cycocel damage produces
“bleached-out,” yellowed spots on the leaves or along the leaf
margins. Interestingly, we observed Cycocel damage on only one treatment in our
study: 0 B-Nine, 1,500 Cycocel on Winter Rose poinsettia. We did not observe
any damage to Winter Rose when the same concentration of Cycocel (1,500 ppm)
was applied in combination with any rate of B-Nine. We have also heard growers
report less phytotoxicity when B-Nine is combined with Cycocel versus Cycocel
being applied alone. This suggests that rates greater than 1,500 ppm Cycocel
should be examined in the future when Cycocel is tank-mixed with B-Nine.

Synergism

The term “synergism” has been used to describe
the interactive effectiveness of B-Nine and Cycocel. Synergism implies that the
activity of the two individual products is enhanced when combined. Our data
suggests that B-Nine and Cycocel have an additive effect. In other words, the
individual responses to B-Nine and Cycocel are added together when the products
are combined. There does not appear to be any enhancing effect as a result of
the tank-mix combination.

Future Work

At Clemson University, we are currently in the process of
screening an array of bedding plants for their responses to B-Nine/CCC. This
information will published in a future issue of GPN.

About The Author

Kelly Lewis is a research specialist, Jim Faust is an assistant professor and Jay Sparkman is an undergraduate student in the Horticulture Department at Clemson University, Clemson, S.C. They may be reached by phone at (864) 656-4966 or E-mail at jfaust@clemson.edu.

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