March 2003

Tank-Mixing PGRs By Jim Faust and Kelly Lewis

B-Nine and Cycocel tank mixes have been effectively used bygrowers for many years. However, there are still many growers who have not yettaken full advantage of this useful tool. The primary advantage of theB-Nine/Cycocel tank mix is that it provides a medium-activity product,comparable to A-Rest, that is easy to apply. In other words, the tank mixusually has a higher activity than B-Nine or Cycocel used alone and is easierto apply than the higher-activity products, Bonzi and Sumagic. (We haven’texperimented with Topflor yet, but you can find extensive Topflor research onpage 48.)

During spring 2002, we applied six different B-Nine/Cycocelcombinations to 12 different bedding plants. The three tank mix rates used are alla 3:1 ratio (B-Nine:Cycocel). ç There is not a magic ratio of B-Nine andCycocel, but a 3:1 ratio provides a broad range of rates that typically avoidsphytotoxicity (foliar chlorosis or damage). A fixed ratio also allows growersto apply a high concentration to one crop, then dilute the tank mix with waterto provide a lower concentration to another crop.

We received 288 plugs from Raker’s Acres and transplantedthem into 6-0-6 bedding plant flats. The first PGR applications were made fivedays after transplant. Plants were re-evaluated one week later (Day 12 aftertransplant). If plants looked like they would benefit by receiving anotherapplication, one was made. This process was repeated one week later (Day 19after transplant), thus the different species received one, two or threeapplications of the same B-Nine/Cycocel combination. The tall, upright speciestypically received the most applications. We applied the growth regulatorsuntil run-off.

Interpreting the Results

Table 1, page 46, displays the relative results of our spraytrials. Excessive growth regulation, or stunting, did not occur. The responsescan be grouped into a few different categories.

Celosia, coleus, dianthus, salvia, snapdragon and vinca areexamples of plants that were responsive to both B-Nine and Cycocel. The tankmix provided the beneficial additive effect of the two PGRs. These species arethe best candidates for using B-Nine/Cycocel tank mixes.

Ageratum, petunia and begonia are examples of plants thatwere primarily responsive to one product, but not the other. As a result, thetank mixes were effective. However, this response could be attributed to justone product in the mix. Ageratum and petunia were primarily responsive toB-Nine, while begonia was primarily responsive to Cycocel. Thus, the individualgrowth regulators would be the more logical application rather than the tankmix for these species.

Impatiens and pansies are examples of plants that did notsignificantly respond to the individual growth regulators, but showed somebeneficial response to the higher rates of the tank mixes. Stronger growthregulation would require multiple applications. If you have experience applyingthe higher-activity PGRs, consider using Sumagic on impatiens and Bonzi onpansies. If you do not have experience with these products, the B-Nine/Cycoceltank mix provides a safer option, although chemical costs will likely behigher.

Growers should view these data as a starting point fromwhich to develop their own test trials before making applications to commercialcrops, since different climates, seasons, spray techniques and varieties willimpact the results.

“Hold” versus “grow-on” rates

Growth regulators can be used for different purposes.Ideally, a growth regulator is used at a relatively low rate to”tone” growth. ç Multiple applications are made to maintaintoned growth. However, sometimes crops require a higher rate to put the brakeson a little stronger. Obviously, growers must avoid stunting the plants, butweather or sales can dictate that a crop needs a stronger growth regulatorapplication. In Table 1, below, we would interpret the single asterisk as atoned appearance, while three asterisks represent plants that have been slowedconsiderably, but without the stunted effect that can occur withhigher-activity growth regulators such as Sumagic and Bonzi.

Side Effects

Growth regulators will not only reduce stem elongation, butthey frequently delay flowering. The following data refers only to the 4,500 ppmB-Nine and 1,500 ppm Cycocel tank mix. Although ‘New Look’ celosia is a varietythat does not require a flower to sell, flowering was delayed by 28 days.B-Nine significantly intensified the bronze coloration of the foliage.Flowering of salvia, vinca and zinnia were delayed by one week. This isparticularly significant during spring production when turning the bench spaceis critical. One additional production week represents a 25-percent increase inproduction time on vinca, which required only four weeks without any growthregulator and five weeks with one tank mix application. Dianthus flowering wasdelayed by five days, and petunia flowering was delayed three days. Theremaining species did not experience a delay in time to flower.

Phytotoxicity commonly occurs on foliage or flowersfollowing a PGR application. Typically, the symptoms are minor, and new growthwill cover up the discolored or damaged foliage. Nonetheless, caution should beexercised. In this study, ageratum showed some phytotoxicity in response to the1,000- and 1,500-ppm Cycocel treatments, while begonia leaves were less bronze(more green) with the B-Nine applications. B-Nine also altered the color on thecoleus variety used in this study. Whether this should be considered positive ornegative is a matter of personal taste. Impatiens showed some phytotoxicity onthe foliage in response to the 1,500-ppm Cycocel treatments used alone or incombination with B-Nine.

Summary

The primary benefit of tank mixes is that a higher degree ofgrowth regulation can be achieved compared to applying individual products.This does not suggest that something magic occurs when the two products aremixed. Rather, a small dose of one product added to a small dose of anotherproduct provides a moderate dose when mixed together.

For bedding plants, different species will have differentsensitivities to different growth regulators. The beauty of a tank mix is thatyou can choose a tank mix rate that has a moderate effect on multiple specieseven though one species is responding more strongly to one product than theother. Thus, you can prepare a particular tank mix, make an application to afew species, then dilute the tank and make applications at a lower rate to moreresponsive species or plants that need less growth regulation. This cansimplify your growth regulation program.

Our study suggests that B-Nine alone is the best choice for’Blue Danube’ ageratum and ‘Madness Burgundy’ petunia, while Cycocel alone isthe best choice for ‘Cocktail Gin’ begonia. ‘Accent Red’ impatiens and’Magestic Giants’ pansies may require multiple tank mix applications at thehigher rates, thus other PGRs may provide more cost-effective growthregulation. New Look celosia, ‘Black Dragon’ coleus, ‘Telstar Crimson’dianthus, ‘Vista Red’ salvia, ‘Montego Red’ snapdragon, ‘Cooler Red’ vinca, and’Dreamland Rose’ zinnia benefited from tank mix applications of B-Nine andCycocel. Your own trials will determine the best rates to use at your locationand climate.

The authors would like to thank Raker’s Acres and UniroyalChemical/Crompton Corp. for their support of this project.