Florida's Orange Industry Decline: Causes of Citrus Greening and Scientific Solutions

Business Insider

Summary:

Florida's orange industry faces its worst season in a century, primarily due to Citrus Greening disease (HLB), exacerbated by hurricanes and freezes. The disease, spread by the Asian citrus psyllid, blocks nutrient flow in trees, leading to small, misshapen, and less sweet fruit that often falls prematurely. This has caused a 90% drop in production over two decades and driven many growers out of business. Scientists at the University of Florida are actively researching solutions. These include using pink clay and reflective mulch to deter psyllids, individual protective covers for young trees, and optimized nutrient delivery for infected trees. Long-term efforts focus on breeding HLB-resistant orange varieties, a complex process that could take over a decade but offers the most sustainable solution.

Introduction [00:00]

Florida's orange industry is currently in crisis, facing its worst season in nearly a century. This decline is attributed to a combination of factors including back-to-back hurricanes in 2024 and, most significantly, a devastating disease called citrus greening.

• The disease, spread by an insect, has been ravaging Florida's citrus trees for decades.
• Citrus greening produces small, misshapen fruit and can ultimately kill the tree.
• It has infected nearly every citrus grove in the state and slashed Florida's orange production by over 90%.
  • This decline has cost the state tens of billions of dollars and forced many growers out of the industry.
• A fifth-generation farmer, Larry, recounts how his groves, once full of beautiful green trees, are now severely affected, highlighting citrus greening as the most challenging issue in his career.

Citrus Greening [01:33]

Citrus greening, or Huanglongbing (HLB), first reported in China in 1918, has spread across continents, devastating citrus groves globally.

• The disease made its way to Florida in 1998, with the Asian citrus psyllid appearing on an orange jasmine plant in Palm Beach County.
• It rapidly spread throughout the state via infected rootstocks, though visible signs of greening on orange trees didn't appear until 2005.
• Larry discovered his first infected tree in 2005, recognizing the severe threat it posed.
  • His initial attempts to remove sick trees were ineffective as the insect spread faster than he could control.

How Orange Trees Are Infected [02:58]

The Asian citrus psyllid transmits bacteria that causes greening into the tree's vascular tissue.

• The bacteria replicates and blocks the essential pathways for moving nutrients throughout the tree.
• Below ground, the root systems of infected trees thin and die out.
• Above ground, visible symptoms include:
  • Yellow patterns and dark green spots on leaves.
  • A sparse canopy, indicating a very sick tree.
• While infected trees continue to bear oranges for a few years, the fruit essentially never ripens.
  • The fruit remains small, green, and often has an odd shape when cut.
  • Although edible, the juice from these oranges has a lower sugar content (Brix) and is less sweet.
  • Approximately 40% of infected oranges fall off the tree prematurely.
• The bacteria ultimately starves and kills the tree over time.
• Today, an estimated 90% of all orange trees in Florida carry the bacteria.

  

How Scientists Are Fighting The Disease [04:08]

Scientists at the University of Florida are developing horticultural techniques to keep infected trees productive and find long-term solutions.

• Studying Psyllid Movement and Deterrents
  • Lauren Diepenbrock, a Professor of Entomology, studies psyllid behavior to identify deterrents.
  • Methods to collect psyllids for study include an aspirator ("pooter").
  • Deterrent methods being researched:
    • Pink Clay Spray: Sprayed on trees to visually hide leaves from the psyllid, which uses light wavelengths to find host plants. One study found it more effective than insecticides.
    • Reflective Mulch: Eight-foot-wide sheets of plastic laid on the ground around trees. The mulch reflects light, potentially blinding psyllids or creating a visual deterrent, reducing infection rates.
• Using Protective Bags (Individual Protective Covers - IPCs) [05:30]
  • Farmers discovered that plastic bags around baby trees help them grow stronger before infection.
  • Lauren is researching the effectiveness of these IPC mesh covers.
    • The mesh allows wind, sun, and rain to pass through but aims to keep psyllids off the tree.
    • Baby trees grow inside IPCs for about two years, giving them a stronger start compared to trees grown in open fields.
• Providing Infected Trees With Nutrients [06:14]
  • Scientist Trippy Vashish believes the key lies in the soil and nutrient delivery.
  • Infected citrus trees have small, fewer roots, making them inefficient at absorbing nutrients.
    • This is likened to one person doing the job of ten, overwhelming the roots.
  • Research shows that giving smaller, more frequent doses of fertilizer and water helps sick roots absorb nutrients more effectively.
    • This approach is compared to humans eating six small meals a day rather than three large ones for better absorption.

      

How Growers Are Changing Their Methods [07:00]

Larry, the fifth-generation farmer, has adopted several strategies to combat greening and sustain his operation.

• He uses custom-designed fertilizers tailored to his trees' specific needs.
• Increased Planting Density: Larry is planting young trees at higher densities, with 300 trees per acre compared to the previous 140-150.
  • The logic is that if all trees will eventually get infected, planting more increases the chances of some surviving and producing.
• Other Short-Term Solutions: Growers have also tried releasing predator wasps and applying insecticides.
• While no single solution is a "silver bullet," these combined short-term approaches have helped slow the decline, enabling the industry to "survive" rather than "thrive."
• Financial Impact: These new approaches add an extra $600 per acre to production costs.
  • Growers' revenues are down by more than half, leading to significant losses.
  • By early 2022, half of Florida's orange growers had exited the industry due to these unsustainable losses.

How Oranges Are Harvested [08:12]

Despite the challenges, harvesting continues using traditional and modern methods.

• Workers manually pick oranges, dropping them into bags, and then into baskets in the grove.
• The collected oranges are then trucked to a nearby packing facility.
• At the packing facility, eight digital cameras photograph each piece of fruit on the conveyor belt.
  • An electronic sorter separates the oranges by color.
• Oranges that are sufficiently orange are cleaned and coated with a layer of natural wax to preserve them and extend their shelf life.
• Due to HLB, Larry now packs only half as many boxes as he did 17 years ago.
• Greener oranges, difficult to sell fresh, are sent for juicing.

How Oranges Are Juiced [08:52]

Larry and other local growers jointly own the Florida's Natural juicing plant in Lake Wales, which processes a significant portion of the state's orange crop.

• About 90% of Florida's oranges are processed into orange juice.
• The factory faces reduced fruit volume, leading to less efficiency and the closure of one of its three processing lines.
  • The plant now receives 60,000 boxes of oranges daily, 30,000 fewer than before HLB.
• Within 24 hours of harvesting, the fruit is juiced.
  • Machines squeeze juice from every orange, removing seeds and collecting pulp for later addition if desired.
• The juice is then pasteurized and packaged into cartons.
• To counteract the lower sugar content of greening-infected oranges, Florida's Natural must blend them with sweeter oranges from other regions or seasons to maintain a consistent taste.
  • This ensures the juice still tastes like orange juice, though it may be less sweet than historically.
• The factory's output is about a third less than before greening, highlighting the need for a solution to sustain grower operations and maximize fruit value.

Potential Solutions to Citrus Greening [10:05]

Many scientists believe the ultimate long-term solution involves re-engineering nature.

• This could involve genetically modifying the psyllid or, more favorably, naturally breeding citrus trees.
• Breeding HLB-Resistant Orange Varieties:
  • Fred Gmitter and his team at the University of Florida are working to breed orange varieties resistant or tolerant to HLB.
  • The goal is to develop trees that will not get sick even if infected with the disease.
  • This involves crossing a tree with desirable fruit qualities with a tree known to be resistant to the disease.
  • The process is highly challenging and complex, akin to finding a genetic "needle in a haystack."
  • Fred estimates it could take more than a decade to develop a viable resistant variety.
• Such a "miracle resistant tree" would not only address citrus greening but also better prepare the industry for future diseases in an interconnected world where plant diseases move freely.
• While science continues to develop new tools, citrus greening remains a persistent challenge for Florida's orange industry.