Popular Mechanics

During the 2008-2009 season, 35,600 acres producing 9½ million boxes were mechanically harvested. The economic potential remains strong for existing harvesting equipment to dramatically reduce harvest costs and increase on-tree returns. Several impediments, however, still need to be overcome before the full benefits of mechanical harvesting can be realized. Incorporating fruit loosening abscission chemicals into the harvesting systems, addressing grower concerns about tree health, eliminating gleaning of unharvested fruit, and minimizing harvest debris in trailer loads are four challenges. These issues are being addressed by the collective efforts of Florida growers, harvesters, juice processors, and researchers. Solving these challenges would increase the adoption of mechanical harvesting, greatly enhance the harvesting capacity of existing equipment, and lower overall harvesting costs.

Abscission Obsession

Harvesting late season Valencia is the biggest barrier of current mechanical systems. Once next season’s bloom fruitlets grow to more than 1 inch in diameter, they are readily removed by mechanical harvesting equipment and might cause a reduction in the next season’s yield by at least 25%. Abscission compounds, specifically CMNP (5-chloro-3-methyl-4-nitro-1H-pyrazole), should solve this problem as it loosens fruit and allows equipment to operate with less shaking force. Current research efforts are collecting data that focus on CMNP concentration, harvester settings, and harvest timing. Data from this work is being used to develop a predictive model to ensure CMNP will be applied with the maximum probability of success. Presently, research trials on CMNP are limited to 10 treated acres annually, and all treated fruit must be destroyed.

If EPA grants an experimental use permit (EUP) for CMNP, the number of treated acres should be greatly expanded and treated fruit would be processed for juice. The additional data collected under the EUP will refine the predictive model.

Tree Health

The duration, speed, and intensity of the shaking action during mechanical harvesting can cause leaf loss and visible scarring of tree limbs and trunks. Growers have long been concerned that such damage might lead to reduced tree health and yields and ultimately increased tree mortality. UF/IFAS research trials have repeatedly shown healthy, well-nourished trees suffer no negative effects from mechanically harvesting. Specific studies have examined the effects of leaf loss, root damage, and drought stress in conjunction with mechanical harvesting. Results of these studies confirm citrus trees have the capacity to adapt to a number of stress factors as long as a tree’s nutrition and irrigation requirements are well managed. Application of an abscission agent (CMNP) should ease growers’ lingering tree health concerns in that machines could harvest fruit with less force, and thus reduce visible tree damage.

Gleaning And Machine Design

Harvesting contractors are reporting 75% to 82% fruit recovery with existing catch-frame designs. This means that, in an average block, between 80 and 120 boxes per acre are being gleaned by hand crews at an average cost of $3 per box (pick and roadside). Improved catch-frame design and better synchronization between harvesting units should enhance fruit recovery of a self-propelled canopy shaker and reduce the number of boxes gleaned. Addition of an abscission agent compound (CMNP) should facilitate fruit removal and increase overall fruit recovery.

An important goal is to improve fruit recovery to a point where gleaning becomes uneconomical. An analysis of productivity data indicates when gleaners have access to less than 20 boxes per acre, their productivity falls to less than 3 boxes per hour. If they expect to earn $9 per hour, their piece rate to glean fruit has to be increased to at least $3 per box. With the additional costs of roadside and fruit hauling, gleaning would only be profitable under extremely favorable market conditions.

Harvest Debris

Mechanical harvesting, without an abscission agent, has been shown to increase the amount of harvesting debris loaded into trailers and transported to processing plants. Juice processors are concerned woody debris can damage processing equipment, cause downtime in plant operations, and diminish overall juice-yield recovery. Although some of this debris removal might actually be good for the trees, an application of an abscission agent, along with mechanical harvesters, has been shown to reduce harvesting debris to equivalent levels of hand-harvested loads. Self-propelled canopy shakers need to fill at least 20 trailers a day to operate efficiently. Juice processors who control the daily load allocations to harvesting sites around the state have little economic incentive to accommodate these systems if their operating costs increase due to excess harvest debris.

A survey is under way to estimate the cost of handling debris at a juice-processing plant. The results of this survey should help focus an industry discussion on what would be the most cost-effective way to handle or avoid harvest debris. Faculty at UF/IFAS are working with the Florida Department of Citrus’ Harvest Research Advisory Council, the Southwest Florida Mechanical Harvesting Advisory Committee, and AgroSource, the private company contracted by the DOC to submit the CMNP registration package to EPA and to commercialize CMNP once it is approved by the EPA. To learn more, visit

Leave a Reply

2 comments on “Popular Mechanics

Featured Stories

All Vegetables Stories >All Fruits Stories >All Nuts Stories >All Citrus Stories >

The Latest

Insect & Disease UpdateMountains Of Data Being Used To Combat Citrus Greening
August 20, 2014
As HLB research evolves, new methods need to be developed to effectively utilize information. Read More
VegetablesAnnual Santa Maria Vegetable Meeting To Cover Progressi…
August 20, 2014
University of California Cooperative Extension will host annual vegetable meeting focusing on nutrient management, plant growth, weed management, and more. Read More
Leafy VegetablesTanimura & Antle Introduces New Lettuce Variety 
August 20, 2014
The California grower now offers George T’s Colossal Romaine Heart, in honor of the company's founder, George Tanimura. Read More
CitrusBorder Crisis Not Helping Farmers
August 19, 2014
As thousands cross into the U.S. seeking refuge, calls for ag labor reform are lost in the uproar. Read More
Cucurbits24 Sweet Watermelon Varieties [Slideshow]
August 19, 2014
Browse the slideshow below for information on 24 watermelon varieties from the nation’s leading seed breeders and distributors. Read More
FruitsHandheld Produce Quality Meter Debuts At 2014 Internati…
August 19, 2014
Researchers to present data measuring dry matter, color, and sugar content of cherries and other product pre- and postharvest. Read More
GrapesNew York State Assists Grape Growers Hit By Harsh Winte…
August 19, 2014
State to open winegrape market to grapes grown outside the state. Read More
FruitsEuropean Fruit And Vegetable Growers Hit By Russian Ban…
August 19, 2014
Angry at European Union/United States sanctions over Ukraine, Russia has banned many food imports. Read More
Apple Grower of the YearGet The Latest News On The Nation’s Apple Crop
August 19, 2014
American and Western Fruit Grower editors will be tweeting in real time this week from the Apple Crop Outlook & Marketing Conference. Read More
OrangesSour Forecast For 2014-2015 Florida Orange Crop
August 18, 2014
Paltry prediction signals lowest output in 50 years. Read More
Crop ProtectionBioConsortia Inc. Bolsters Executive Team
August 18, 2014
Industry veterans Christina Huben and Dr. Susan Turner bring experience to plant biotechnology firm. Read More
Stone Fruit‘Ladderless’ Peach, Nectarine Orchards Explored
August 15, 2014
University of California researchers explore the concept of so-called pedestrian orchards. Read More
CitrusU.S. Sugar Buying South Florida Sugar Cane And Vegetabl…
August 15, 2014
Purported deal worth $100 million to purchase farmland and assets of Knight Management Inc. Read More
CitrusFlorida’s Future Farming Leaders Dig Up Knowledge…
August 15, 2014
Class 3 of FFVA's Emerging Leader Development Program learn a lot from road trip to California's Salinas Valley. Read More
CitrusWater Bond Will Appear On California Ballot
August 14, 2014
Voters will decide if thirsty state will spend $7.5 billion, including $2.7 billion for storage. Read More
BerriesFamiliar Face Settles In As New Florida Strawberry Asso…
August 14, 2014
Kenneth Parker’s deep roots in the community and knowledge of production challenges make a good combination for executive director role. Read More
Insect & Disease UpdateIs There Light At The End Of The Tunnel For Florida Cit…
August 14, 2014
Time is of the essence in the race to beat greening. Read More
Insect & Disease UpdateCoca-Cola Shares Additional $1.5 Million To Fight Citru…
August 14, 2014
Grant to help UF/IFAS researchers work toward a solution for devastating disease. Read More