Paint Your Grapes With This Effective Plant Growth Regulator [Slideshow]

The problem with most premium table grape production areas is that it can be difficult to get the lucrative red grape varieties to actually turn red, or “color up.” You need heat units to produce good sugars, after all, but if the temperatures don’t drop enough at night, you can’t get color.

“There are several variables affecting color, but that’s the biggest one, and we can’t control that,” says Rob Fritts, a technical development specialist for Valent BioSciences who works primarily on plant growth regulators.

Scientists have even pinpointed the exact temperature that the nighttime air needs to plunge below to get good color — 68°F. Unfortunately growers in the San Joaquin and Coachella valleys know all too well that there are many nights during the growing season that temperatures don’t touch 70.

No single tool will do the job in coloring up grapes, says Fritts. It requires a program approach, a program that includes consideration of cultivar, rootstock, fertilizer, irrigation, crop load, canopy management/light exposure, and weather. But all that won’t necessarily work without a plant growth regulator (PGR).

Program Approach
One common PGR used by table grape growers is ethephon, which is metabolized by the vine and converted into ethylene, a potent PGR. Ethephon works great and Fritts recommends it highly. But it does have its drawbacks in that in increasing the grapes’ maturity it can soften them up, and you definitely don’t want to soften them too much. That’s why Fritts recommends that ethephon be used in tandem with another PGR, Valent BioSciences’ ProTone.

ProTone is abscisic acid (S-ABA). It’s actually not new, having been discovered in the mid-1960s. One of the five major plant hormones found in all vascular plants, along with auxin, cytokinin, ethylene and gibberellin, it wasn’t readily available until commercialized by Valent BioSciences just a few years ago. It’s extremely safe, with a re-entry interval of just four hours, the bare minimum, according to government regulations.
“If you spray water in California,” notes Fritts, “it’s still four hours.”
The pre-harvest interval is zero days, which Fritts says gives the grower maximum flexibility. “Let’s say application is done one night. If the market changes and you need more fruit, you can go in the next day and get it.”

Shipping Overseas
ProTone is so safe it is exempt from maximum residue limit (MRL) considerations, unlike ethephon, which has an MRL of 1 part per million (ppm) in the U.S. The MRL in Europe is even lower, 0.7 ppm, and some grocers there are trying to distinguish themselves by instituting a limit of 0.35 ppm.

“That’s opened the door for ProTone,” he says, “because it can color the fruit without those issues.”

The lack of an MRL gives the grower greater decision-making power, notes Fritts. “A grower might think he’s going to sell a crop in the U.S., but if he decides later to send it to Europe, he has that flexibility.”

Also, because ethephon does start the softening process, it can be hard to arrange for the crunchy grapes California growers are known for to arrive in perfect eating condition. ProTone makes even the longest tanker ship trips tolerable for crisp-sweet grapes.

But don’t get Fritts wrong. He knows growers have had success with ethephon, and ProTone is not intended in any way to displace it. “In fact, we like to see both products used,” he says, “because they have different modes of action.”

Application Critical
There is one critical difference in when to apply the two materials, says Fritts. With ethephon, growers wait for the grapes to begin to color before application; but with ProTone, they shouldn’t wait. Instead, berry softening is the easiest parameter to determine application time. Even then, though, it depends on the variety, says Fritts. For example, under normal conditions with Flame Seedless you apply ProTone when half the berries are soft; for Crimson Seedless you wait until 95% of the berries are soft. These stages can vary in different conditions, such as in the desert.

Another big difference between ethephon and ProTone is the method of application. Unlike ProTone, ethephon translocates through the fruit. That means the applicator can drive the spray rig relatively fast. But applying ProTone takes more time and effort because the applicator must get good coverage.

This difference is absolutely critical to getting good results, says Fritts.

“Growers try to spray ProTone like its ethephon, so they don’t get the coverage they need. Spray coverage is the deal maker,” he says. “If people don’t get good spray coverage, they won’t get good results. That’s why our logo has a paint brush — you have to paint it on.”

Besides spraying the front and back of the cluster, you need to spray long enough – and with enough water — to get ProTone inside the cluster, says Fritts. “The growers we’ve worked with a lot will use two different sprayers,” he says. “The ethephon guy takes off, and the other guy with the ProTone goes slower, sprays more water, getting really good coverage.”

If you get that good coverage, Fritts says you will realize the benefits.

“In all the countries around world with table grape growing regions, ProTone is a key part of the growers’ programs,” he says, “and that’s a good testament that the product works.”

To The Rescue
ProTone does have one advantage over ethephon in that it can be used to “rescue” marketable table grape clusters that have adequate Brix but don’t have enough color, a time that ethephon should not be used. The fruit must be firm enough to remain on the vine for an additional 10 to 20 days.

The application will allow a grower to sell what previously may have been unmarketable fruit, says Fritts. In fact, a grower can target the application, tailoring it to fit his goals.

ProTone costs roughly $300 an acre, which is certainly expensive when compared to ethephon, but can be easily recouped when you consider it’s nearly always better to pick and sell fruit than leave it in the field.

The grower can decide how much ProTone to apply based on how much fruit he can sell at a given price.

For example, if the grower needs 300 boxes, than the ProTone will only be costing him $1 a box premium that is easily worth it in a decent market.

“Get over the sticker shock,” recommends Fritts. “You can make a business decision.”

Topics: , , ,

Leave a Reply

Fruits Stories
UF/IFAS developmental biologist Dennis Gray looks at the progress of grapevines in a vineyard.
Crop ProtectionResearcher Using ‘Precision Breeding’ To Create Disease-Resistant Winegrapes
May 20, 2015
Breakthrough would mean significant savings on pesticide and fungicide sprays. Read More
Expansion groundbreaking for Southwest Florida Research and Education Center
CitrusSouthwest Florida Research And Education Center Embracing New Expansion
May 20, 2015
A 7,000-square-foot addition to the UF/IFAS facility will house labs and offices for potential new faculty members. Read More
storm clouds
CitrusSouth Florida Rainy Season Could Wind Up On Drier Side
May 20, 2015
National Weather Service anticipating El Niño to play a hand in possible below-normal conditions. Read More
Food SafetyProduce Safety Alliance Offers Course To Become A Certified Trainer
May 20, 2015
The Produce Safety Alliance (PSA) has announced dates for their first two Train-the-Trainer courses this June. The first of the Read More
GrapesMatthew Fidelibus To Be Recognized For Extension Work
May 20, 2015
The American Society of Enology and Viticulture (ASEV) recently announced that Western Fruit Grower™ magazine contributor Matthew W. Fidelibus, of Read More
Apples & PearsGrants Available For Farmworker Education
May 19, 2015
Grants are available for farmworkers and their families interested in attending adult educational programs through the Washington Apple Educational Foundation Read More
Fruits$10 Million Available For California Water Conservation Program
May 19, 2015
Applications for the California Department of Food and Agriculture’s (CDFA) California State Water Efficiency and Enhancement Program (SWEEP) are now Read More
The Latest
Operation Outdoor Freedom participants
CitrusFlorida Proud To Be Home Of The Brave [Opinion]
May 25, 2015
Operation Outdoor Freedom invites wounded service members and veterans of the U.S. military to enjoy recreational activities in state forests and on private lands. Read More
FruitsQ&A With Penn State’s New Young Grower Alliance Coo…
May 22, 2015
Erin Dugan recently joined Penn State University extension as a specialty crop innovations program manager and Young Grower Alliance coordinator. Read More
FruitsHow To Start A Young Grower Association
May 22, 2015
You have recently returned to your family’s business. You have friends and family you can tap for their knowledge and Read More
Expansion groundbreaking for Southwest Florida Research and Education Center
CitrusSouthwest Florida Research And Education Center Embraci…
May 20, 2015
A 7,000-square-foot addition to the UF/IFAS facility will house labs and offices for potential new faculty members. Read More
storm clouds
CitrusSouth Florida Rainy Season Could Wind Up On Drier Side
May 20, 2015
National Weather Service anticipating El Niño to play a hand in possible below-normal conditions. Read More
Food SafetyProduce Safety Alliance Offers Course To Become A Certi…
May 20, 2015
The Produce Safety Alliance (PSA) has announced dates for their first two Train-the-Trainer courses this June. The first of the Read More
Fruits$10 Million Available For California Water Conservation…
May 19, 2015
Applications for the California Department of Food and Agriculture’s (CDFA) California State Water Efficiency and Enhancement Program (SWEEP) are now Read More
CitrusBad Weather Or Not, Preparation Always On Radar For Flo…
May 19, 2015
You cannot prevent a natural disaster from taking everything you have, but you can lessen the blow if and when it happens. Read More
FruitsGreen Fruitworm Numbers High In Pennsylvania
May 19, 2015
In their latest insect report, David Biddinger and Grzegorz Krawczyk, tree fruit entomologists discuss the timing of pest control applications Read More
FruitsUSDA To Invest $21M To Help Growers Cope With Drought
May 18, 2015
USDA’s National Resources Conservation Service (NRCS) will allocate $21 million for growers and ranchers to apply conservation practices in the Read More
BB Hobbs Inc. warehouse in Plant City, FL
CitrusBB Hobbs Bolsters Business In Central Florida
May 18, 2015
Irrigation specialists celebrate opening of new branch warehouse in Plant City. Read More
Disease ControlHow To Control Disease During Rainy Weather
May 18, 2015
The recent warm, wet weather conditions are prime for fungal and bacterial diseases, says Annemiek Schilder of Michigan State University Read More
FertilizerBioWorks Launches New Fertilizer And Biostimulant
May 15, 2015
BioWorks, Inc., launched ON-Gard, a new organic fertilizer and biostimulant. ON-Gard is a 100% plant-derived product with organic nitrogen and Read More
CitrusHouse Votes To Stop “Flawed” Waters Of The United State…
May 15, 2015
The U.S. House of Representatives approved this week bipartisan legislation that requires the withdrawal of the Waters of the United Read More
CitrusPointers On How To Save Money, Increase Sprayer Efficie…
May 15, 2015
Using clean water when calibrating a pesticide sprayer and carrying extra nozzles for quick repair of simple problems in the Read More
Wes Roan of Lipman Produce talks with participants of FFVA's Spring Regulatory Tour.
CitrusFlorida Farming Show & Tell Earns Regulators’…
May 15, 2015
FFVA's annual Spring Regulatory Tour allows those who write regulations controlling water, crop protection chemicals, food safety, and more an opportunity to see production practices firsthand. Read More
CitrusUSDA Announces $11.9M In Assistance For Organic Certifi…
May 14, 2015
Following on the heels of the USDA’s announcement of record growth in the organic sector, the USDA’s Agriculture Marketing Service Read More
CitrusBeekeepers Lost 40% Of Bees In 2014-15
May 14, 2015
Beekeepers across the U.S. lost more than 40% of their honey bee colonies from April 2014 to April 2015, according to the latest results of Read More