How are psyllids affecting California’s citrus trees? Details explored as CDFA issues guidelines to prevent spread of deadly disease

California's $7 billion citrus industry may be at stake as psyllids continue to spread throughout the state, causing a deadly citrus tree disease. Asian Citrus Psyllids (Diaphorina Citri) is a sap-sucking insect that is related to the dangerous citrus tree disease called - citrus greening or Huanglongbing (HLB). The disease affects several citrus fruit trees, including oranges, lemons, limes, grapefruits, and more.

Citrus greening has long affected several states in the U.S. and has cost the industry billions of dollars, on top of thousands of people losing their jobs. Since the citrus trees began to be affected by the disease in 2005, the Florida citrus industry has suffered a similar fate of massive setbacks.

The Florida citrus industry, which was producing over 242 million boxes of citrus fruit earlier (as per Statista), has now dropped to a production estimate of roughly 44.5 million boxes in 2022. The California citrus industry first started experiencing citrus greening nearly a decade ago, but the lack of proper safety measures against the psyllids has left the industry at a standstill as the trees continue to be affected by the disease.

Psyllids are known to feed on the leaves of citrus trees; while feeding on the leaves, these insects spread a bacteria that affects the tree's ability to absorb nutrients. Unable to absorb the nutrients essential for their survival, the trees produce fewer fruits, which are often smaller and bitter in taste. Many citrus trees affected by the disease start turning yellow and can also die over time.

Citrus production, including oranges, could be greatly affected if citrus greening starts spreading to the trees (Image via Barbara Rich/Getty Images)

The California Department of Food and Agriculture (CDFA) has been warning California citizens about the disease while running surveys and safety drives across the state. Speaking on the matter to the press, Victoria Hornbaker, Director of the Citrus Pest and Disease Prevention Division at the CDFA, said:

"In California, we are a fresh fruit state; those beautiful pieces of citrus that you see on your table and at the grocery store, if impacted by this disease, will never fully ripen and have a rancid taste."

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Researchers trying to find potential cures against the psyllids and the Citrus greening disease

As of now, the Citrus greening disease seems to be limited to residential growers' trees. Asian citrus psyllids have not been found in commercial groves in the California region. To limit the spread of pests and deadly tree diseases, several organizations like Florida Citrus Mutual and the Citrus Pest and Disease Prevention Division are working together to reach out to Californians.

Residents are being encouraged to report all possible psyllids infestations and follow safety guidelines to help stop the spread of citrus greening disease. CDFA has been working alongside researchers, professionals, government officials, residents, and business owners to protect California citrus from invasive pests and diseases by finding potential cures and safety measures against psyllids and other potential disease carriers.

oranges, limes, lemons, grapefruits, and other citrus plants may be affected by psyllids (Image via Jonny James/Unsplash)

Florida Citrus Mutual, an organization that advocates for citrus growers, told the press that they are not surprised about the spread of citrus greening or HLB across the country, with Tamara Wood, Communications Consultant for Florida Citrus Mutual, quoting:

"We had hoped that our experience and research here in Florida would have provided California with strategies to prevent the spread of the disease, and while I do believe they are in a better place to combat the effects, we just haven't found that silver bullet to stop it yet."

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A potential cure against psyllids and citrus greening may not be too far out of grasp

As the psyllids continue to affect citrus trees across California, the United States Department of Agriculture (USDA) has recommended a number of things that residents can do to help limit the spread of the disease. The USDA advises residents in regions affected by citrus greening disease to abide by the quarantine rules established by the local authorities and not to transport any fruit or plants outside the affected areas. Transporting the affected fruits or plants can further spread psyllids and deadly diseases to other citrus groves across the state.

The cure for the deadly citrus tree disease may be a long way off, but it's not out of reach. In 2021, the University of California, Riverside, reportedly succeeded in isolating a peptide found in Australian finger limes that could be injected into or sprayed on the plants affected by the disease. Initial trials and studies indicated positive results as the researchers found that the treatment kills the bacteria and helps trigger the citrus plant's immune system, which can further help prevent the infection.

Research on the effectiveness of stable antimicrobial peptide (SAMP) to fight citrus greening or Huanglongbing (HLB) continues and involves over 1,500 citrus trees. Though research is still underway, a potential cure for the disease may not be too far out of reach. The progress of the research can be found on the website - https://citrusindustry.net/2022/04/18/research-update-stable-antimicrobial-peptide/