Citrus Producers Utilizing Screen Structures to Minimize Greening

Huanglongbing (HLB) or “citrus greening” is a disease that has devastated the citrus industry in Florida. Many large producers are looking for ways to combat this crisis. Some growers are investing in citrus under protected screen (CUPS), which provide a reduced risk environment for the crop.

Citrus greening was first reported in 1919 in China, again in Brazil in 2004 and discovered in Miami, FL in 2005. Since then, the disease has affected most of Florida’s citrus-producing areas leading to a remarkable 75% decline in Florida’s $9 billion citrus industry (USDA).

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Citrus greening is a particularly difficult disease to identify and manage. The insect vector for this disease is the Asian Citrus Psyllid, Diaphorina citri. The psyllid is not the direct the cause of the citrus tree demise.  As the psyllid feeds on the truck, branches, leaves or fruit, bacteria is released in the open wounds. Unfortunately, once infected, the tree will steadily decline in health. Fruit production will drop in number, size and taste each year until the the tree dies. Sadly, at this point, there is no cure, nor a citrus species that is immune to the bacterium.

CUPS can greatly reduce the threat of citrus greening. The grower can once again see normal growth, higher yields, premium-quality fruit and limited fruit drop.  This system also provides the added benefit of more control of nutrients and irrigation. Trees can be grown in the ground or in pots to full maturity within these greenhouse-like structures. CUPS are constructed for all sizes, even covering over 100 acres.

For a CUPS production system to be feasible, the construction cost must offset by the highest yield of premium-quality fresh fruit with a high market price. Florida’s upward trending tangerine market of recent years has been a viable option for this system. Researchers at the UF/ IFAS CUPS facility in Lake Alfred have done extensive study on these production units. Management measures needed for a CUPS operation to succeed are intensive hydroponic practices, with daily or hourly delivery of all essential nutrients through drip fertigation of the trees. High planting densities are needed, with UF/IFAS researchers estimating a range of over 800 and under 1350 trees per acre. Selecting the right tree is key. The varieties used should be heat-tolerant, self-pollinating, seedless varieties without strong alternate bearing habits.  The CUPS system is a new tool in the fight against the citrus greening crisis. But careful, integrated management approaches are need for success.

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Information for this article is from the UF/IFAS EDIS publication: “Citrus Under Protective Screen (CUPS) Production Systems” by A. W. Schumann, A. Singerman, A. L. Wright, and R. S. Ferrarezi