From the Archives: Citrus Greats - Walter T. Swingle

Similar to any scientific field, early researchers paved the way for the current researchers. This post will acknowledge just one of the many monumental discoveries made in the citrus industry. Starting with Walter T. Swingle, he was a botanist sent to Florida from Washington, D.C. He was originally sent to Florida with the goal of researching the citrus disease plaguing groves at the time. During his time in Florida, he became a part of some of the early research concerning hybrids and hybridization. Swingle is specifically credited with creating the Tangelo, a cross between a tangerine and a pomelo.

Hybridization is a beneficial tool because it allows researchers to combine the most desirable characteristics of two different species to create an entirely new species. This is different from genetically modified organisms, or GMOs, because the genes in GMOs have been altered or enhanced while hybridization takes advantage of the natural traits found in each plant species. This can be done by collecting a sample of the DNA found in each species, unwrapping it, and pairing them with one another to create a DNA helix that has one strand from species A and one strand from species B.

Herbert J. Webber worked alongside Swingle to perfect their hybridization techniques. The pair published several papers, books, bulletins, and pamphlets together discussing the research they had conducted and providing growers with helpful information to aid in the efficiency of growing citrus groves. Webber and Leon D. Batchelor then published The Citrus Industry. This book detailed the history of the citrus industry, botany, and methods used to breed citrus. Citrus growers used these books to aid in their growing techniques and to learn more about the citrus industry. Although not mentioned, there are numerous other researchers and scientists who played a fundamental role in the advancements of the Florida Citrus Industry.

Walter T. Swingle was inducted into the Florida Citrus Hall of Fame in 1962 as part of the inaugural class: https://floridacitrushalloffame.com/inductees/walter-tennyson-swingle/.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Sources:

Johnson, Alexander. “How Does Plant Hybridization Work?” ScienceOxygen, September 14, 2022. https://scienceoxygen.com/how-does-plant-hybridization-work/.

Mack, Thomas B. Citrifacts II: A Portion of Florida Citrus History. Bartow, Florida: Associated Publications Corporation, 1998.

From the Archives: Citrus Canker

Citrus canker is caused by a bacteria that eats the flesh and leaves of fruit. This bacteria is not harmful to humans and the fruit is still edible. However, the fruit is now difficult to sell due to the ugly sores that are created by the canker bacteria. This bacteria can also cause fruit to drop from the tree prematurely stopping it from ripening.

In the early 1900s, there was a widespread outbreak of canker throughout Florida. Frank Starling was hired by the Florida Citrus Growers and the Citrus League to see if he could aid in the battle against canker. Between 1913 and 1933, the state of Florida spent approximately $1.3 million in their attempts to eradicate canker. During this battle against canker, infected trees were burnt down to ensure that they could not spread the bacteria to other trees in the area. It is speculated that the canker bacteria traveled to the States via citrus seedlings from Japan.

There was a reemergence of citrus canker in the 1980s, and it was declared eradicated in 1994. However, there was a report of canker in Miami-Dade County the following year, in September 1995. Before the eradication efforts were successful, a hurricane spread the bacteria to several other counties. By 2005, $2.1 million worth of commercial grade citrus had been destroyed. In 2006, the eradication efforts were forced to stop because it had become impossible to eradicate canker due to how widespread it had become.

Currently, canker is still active in citrus groves with the majority of infections taking place between April and July. Growers have learned how to deal with the bacteria; applying copper containing products periodically to produce has been known to deter canker in citrus. Although, it should be noted that copper is not a guaranteed deterrent to the bacteria. As there are no known cures to the bacteria, these methods will have to be sufficient for the time being.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Sources:

Dewdney, M. M., M. Zekri, P. D. Roberts, and J. D. Burrow. “Homeowner Fact Sheet: Citrus Canker.” UF IFAS Extension, University of Florida, June 4, 2018. https://edis.ifas.ufl.edu/publication/PP116. 

 

Mack, Thomas B. Citrifacts. Bartow, Florida: Associated Publications Corporation, 1992.

From the Archives: Soil Science Foundation

In 1939, the Soil Science Foundation was started by a group of farmers in Dade City who were looking to come up with solutions that they were facing with their various crops; the Soil Science Foundation is credited with several scientific accomplishments. Their first headquarters was a small building on the campus of Florida Southern College, and they did not relocate off campus for 10 years.

When the Foundation started, they were running experiments on the fertilization of sandy soils at the Short Grove in Lake County. Sandy soils do not hold nutrients well, meaning fertilization is necessary to ensure that crops are able to obtain the necessary nutrients for growth. However, over fertilization can be harmful for plants as it will change the pH of the soil, suffocate the soil, and cause root damage. The goal of the experiments being run by the foundation was to determine the necessary amount of fertilizer.

During this time, the Foundation also researched the sustainability of Florida flatwoods for citrus planting. Florida flatwoods make up a large portion of Florida’s landscape. Flatwoods are ideal for citrus cultivation because of their sandy moist soils. Citrus does well in sandy soils because it provides good drainage, which prevents root damage from taking place. Planting in flatwoods also helps with irrigation because of the water deposits that are typically found within these flatwoods. However, there may be some disadvantages to planting citrus on these lands. During wet seasons, the soil can become overly saturated due to the water deposits already existing in the soil, they are at risk to develop frost that can cause freeze in citrus, and cultivating citrus in these regions could negatively impact the environment and decrease the biodiversity of the region. The goal of the experiments targeting citrus cultivation on the flatwoods was to determine if using the flatwoods would result in significantly better yields.


To learn more about the Soil Science Foundation, please check out the Soil Science Foundation Records at the McKay Archives: https://www.flsouthern.edu/getattachment/96400c75-e443-47c6-9fc7-690feef0137c/Soil-Science-Foundation-Records-Finding-Aid.pdf.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Source:
 

Mack, Thomas B. Citrifacts. Bartow, Florida: Associated Publications Corporation, 1992.

From the Archives: Cattle Feed

In the 1900s, growers began to feed cattle the leftover pulp, peels, and seeds that were left behind after the desirable parts of citrus fruit had already been canned for production. Because pulp has a high liquid concentration, it went bad faster than the cattle could eat it. This left much of the feed to rot out in the pastures. This led researchers to run feed tests to determine if the citrus by-products were providing any nutrition for their cattle. This research found that only the pulp had any actual nutritional value that would be beneficial to the cattle while both the peel and seeds did not have any value to them.

Upon this discovery, there was a race to patent citrus pulp as feed. Everyone wanted a chance at reaping the rewards for this invention. The Pratt Food Company was one of the first plants that popped up in Tampa with the sole purpose of processing citrus waste. After this, several other companies opened branches that were responsible for dealing with citrus waste.

In order for the pulp to be fed to the cattle, it had to be dried. Reducing the liquid concentration in the pulp allowed the growers to store the pulp for later use without it going bad due to the liquids being held inside the pulp. There are many advantages to using dried citrus pulp for feed. Citrus pulp is a very bulky carbohydrate meaning cattle do not need to eat a lot of it and pulp is high in calcium. However, pulp is low in phosphorus, one of the major nutrients that cattle need, meaning it must be supplemented with other forms of feed to ensure that cattle stay healthy. Citrus pulp is still being used for feed today; however, it is not used for milking cows as it can cause a decrease in milk production.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Source:
 

Mack, Thomas B. Citrifacts. Bartow, Florida: Associated Publications Corporation, 1992.

From the Archives: Big Freeze

During harsh winters, citrus groves will freeze over - killing the trees to the ground. The first big freeze was in 1835, which was extremely discouraging to early growers. One can understand why Central Florida became a hub of citrus production in the United States, with the optimal climate it's a no-brainer! The optimal climate for citrus production is warm areas with ample sunshine, and 55-100 degrees Fahrenheit is the best range for citrus growth. There are few varieties of citrus that are able to grow in colder temperatures below 50 degrees, but even then, they cannot withstand temperatures lower than 45 without freezing.

When a freeze takes place, the fruit will drop from the tree either instantly or slowly over a period of time. The juices inside of the fruit become frozen making them unideal for selling. Crystals of ice will also form inside the plant tissues throughout the actual tree. During severe cases of freeze, the tree may die; in less severe cases, the tree may be damaged, but it will survive. In the years following a freeze, the trees and branches of affected areas may continue to die; it is difficult to determine the extent of damage done to a grove after a freeze has taken place.

After the freeze has taken place, it is important to monitor the state of the grove, especially for later care of the region. There are several tactics that can be used to ensure the plant is able to recover post freeze which include minimizing pruning, applying less fertilizer (depending on the current state of the tree), and minimizing irrigation.

Overall, a freeze can be extremely detrimental to a grower as it can kill the entire grove of current plants. If not killed, affected plants will need additional care in the months and years following a big freeze.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Source:
 

Mack, Thomas B. Citrifacts. Bartow, Florida: Associated Publications Corporation, 1992.

From the Archives: Citrus Families and Citrus Labels

Crate labels have a long-standing history in the Florida Citrus Industry illustrating important objects, people or landscapes to the specific brand and grower’s association. This can be seen in many labels that illustrate different family members of Citrus company owners. 

One example of this is the Baby-Ade label. The label features a baby with an orange and a tropical landscape. The baby on the label is a part of the Lee family - the father of Elizabeth Lee Barron. The Baby-Ade brand was a part of the Lee family corporation out of Tampa, Florida. This citrus company grew and processed oranges, grapefruits, and tangerines. Many of the other Lee family members were also featured on their company’s label including Aunt Miriam, Aunt Rosemary, Aunt Rowen Katherine, and even the family dog named Juno, also known as “Goo Goo.” 

Citrus label families have even seen cross over into the Florida Citrus Queen competition. The Prevatt family featured Ruby Prevatt on their Ruby label. The Ruby brand was a part of the Lake Region Packing Association and was owned and operated by the Prevatt family. Ruby Prevatt was a part of the 1939 Florida Citrus Queen competition and was sponsored by the Tavares Woman’s Club. She is also the daughter of Florida Citrus Hall of Fame inductee Jennings Bryant “Babe” Prevatt.

Label advertisement and artwork played a large role in promoting the citrus industry. The ability to implement family members or scenes into the labels allows for a greater connection to customers and the importance of citrus in the family diet. 

All of the labels mentioned above and more can be viewed in the McKay Archives Citrus Label digital collection at https://archives.flsouthern.edu/digital/collection/labels/search/page/1. 

 

Written by Emily Allen, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Sources:

Calise, Gabrielle. “A Tampa Librarian Wants to Save Florida’s Vanishing Citrus Labels — And Her Family History.” Tampa Bay Times (St. Petersburg, Florida), March 16, 2021. https://www.tampabay.com/life-culture/history/2021/03/16/a-tampa-librarian-wants-to-save-floridas-vanishing-citrus-labels-and-her-family-history/. 

[Miss Ruby Prevatt]. The Orlando Sentinel (Orlando, Florida), January 22, 1939.

From the Archives: Traveling Citrus in Egypt

In 1992, Dr. Prevatt visited the Nile Delta region of Egypt as a citrus expert for six weeks in May and June. During this time, he worked with the Agricultural Cooperative Development International program; the goal of this program was to create a line of dialogue between Egyptian and American farmers and researchers. Prevatt was selected to be the citrus expert because of his background knowledge in citrus. The main objective of his role was to help the growers in the region of interest with any issues they may be facing regarding their crops.
 

Upon arrival, Prevatt was tasked with determining what the major problems in the area were. He concluded that the region was plagued with poor irrigation, Phytophthora foot rot and psorosis were killing trees, lack of a hedging program, excessive use of chemical fertilizers, and closed plantings.
 

At the time, farmers had begun growing citrus in a region referred to as the “New Lands.” This area is made up of sandy desert soils. Other regions where citrus production takes place have silt soil. This means that the same farming practices cannot be used in both regions due to the differences in the soil. Silt soil is a combination of sand and clay. It is an extremely fertile type of soil because it is very good at water retention. Due to the aforementioned fertility of silt, it does not need to be fertilized often. Silt soil is one of the ideal soils for citrus production due to its loose form and drainage properties; Prevatt comments on the effects over-fertilization is having on the crops. For centuries, the Nile River would flood and deposit more silt on its banks. This flooding was later controlled by the production of the Aswan Dam in 1968. Sandy soil is made up of fine particles and is loosely packed. Due to this loose packaging, sandy soil tends to need to be fertilized because it does not hold on to nutrients well. Besides this, it is a good soil for citrus production as long as it is fertilized to ensure there are adequate nutrients present.
 

However, the biggest problem with citrus production in the New Lands is the lack of water. The Egyptian government was attempting to install canals and waterways to aid in agriculture. Due to a lack of funds and resources, the installation of these irrigation systems was not an easy one. Regardless, Dr. Prevatt made attempts to give help where applicable. Dr. Prevatt comments on an interaction he had with a farmer in Cairo. Upon meeting this farmer for what Prevatt thought was the first time, the farmer exclaimed “I know you” to Prevatt. After some discussion, they realized that the farmer had visited Florida Southern College years ago as part of a citrus exchange program. The Agricultural Cooperative Development International program has helped people all over the world and given people the opportunity to visit places they may have never seen.

Written by Tanzy Zviitwah, Florida Citrus Hall of Fame Fellow
In partnership with Florida Southern College’s McKay Archives Center
Spring 2024

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Source:
 
Mack, Thomas B. History of the Citrus Institute, Florida Southern College, 1947-1993. Lakeland, Florida: Florida Southern College, 1993.