Interest Continues To Grow In Protected Citriculture

Interest Continues To Grow In Protected Citriculture

Perhaps our earliest exposure to citrus production under cover was in Japan. More than a decade ago, Japanese citrus farmers began moving mandarin acreage into high-tech greenhouse structures. The focus of the Japanese program was greater control of growing conditions (temperature, light, inputs, water, etc.) to ensure production of high-quality, blemish-free citrus. Thanks to consumer preference and unique market forces, Japan has achieved its goal. The citrus from these operations commands a premium in the marketplace and the higher cost of production was justified.

Spraying indoor citrus

Working inside structures, some manual caretaking activities can almost be completely eliminated.
Photo courtesy of UF/IFAS

Intrigued by the Japanese model, some Florida growers studied the possibility of using similar, but lower cost structures in Florida to produce blemish-free fruit for the fresh market. At that time (2007-2008), the economics didn’t seem to make sense and growers never moved forward.

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Jump ahead to 2015. The goal of citrus production under screen has transitioned from an exclusive focus on external quality and grade, to the achievement of an Asian citrus psyllid (ACP)-free environment. Growers are weighing the benefits of HLB-free trees grown in a high-density setting, in a high-cost structure against the increasingly high cost of conventional production. Of course, the elimination of HLB from the equation increases quality, eliminates drop, and may lower input requirements.

UF/IFAS has done some excellent research on this issue (called Citrus Undercover Production Systems, or CUPS), and efforts are ongoing at both the CREC and IRREC.
The work of Dr. Arnold Schumann, Dr. Barrett Gruber, and Dr. Brian Boman has inspired several citrus growers to move this concept from research to reality. Two such operations are located in the Alturas area: Citrific and KLM Farms. I reached out to the UF/IFAS team and the owner/managers of the two Alturas operations for insight into this exciting effort.

Growers continue to seek input and guidance from UF/IFAS researchers on this issue, indicating an expanding interest in the possibilities. Gruber and Schumann addressed some common questions about CUPS.

Q: What is the average cost of construction for the pole and cable structures used for CUPS?

A: The structures that we have been working with are very customizable and, therefore, the cost per acre will depend greatly upon how the grower designs it, and what type of additions that they will include. For the design used at the IRREC site, and for a structure less than one acre in size, the expected cost will be in the neighborhood of about $2 per square foot. A 10-acre structure of the same design would cost less than $1 per square foot. So, buying in bulk has its advantages. The economy of scale is much more beneficial as the area of the proposed structure increases. Other factors that might noticeably affect the price per acre will be the height of the structure and the type of doorways and entryways that are installed. It is challenging to give a single price point because ultimately it will depend upon how the grower designs each structure. This is very much like constructing a residential home — the final price will be dictated by the types of features each individual chooses to include.

Q: It appears that there will be a great deal of manual pruning and hand work in these structures. What is a typical production cost/acre?

A: There doesn’t have to be a great deal of manual pruning. A bar hedger mounted on an ATV might be a good option for pruning quickly. In any event, we are planning a strategy for limited pruning of branches only smaller than about an eighth of an inch, anything bigger will stay. Over-pruning will lead to excessive vegetative growth, which we want to avoid. Pruning should be a targeted and precise activity. Thus, spending an inordinate amount of time and labor on pruning over the course of the year might indicate an over-zealous pruning program.

Working inside the structures, there will be other activities that can almost be completely eliminated. For example, herbicide application should be almost eliminated altogether. Good preparation in constructing the houses with a pre-establishment application of herbicide, with the possible use of ground cloth, will go a long way in preventing significant weed growth inside the structures. At the IRREC site, we applied a post-emergent herbicide within the footprint of each structure immediately after construction was completed and right before trees were established. Since then, we have not had to apply any herbicides inside the screen enclosures.

After construction of the houses, we anticipate the annual care-taking costs to be no greater than a conventional grove.

Managing annual caretaking costs should be considered in the initial planning and development of screenhouse construction. The pruning example is a good one. If that activity is considered to be an important one, adequate space inside the screenhouses should be allocated for any type of potential equipment that will need to be purchased.