25 Jun 2024
Huanglongbing infected orange trees

Identification of citrus greening based on visual symptoms: A grower’s diagnostic toolkit

Citrus greening is one of the world’s most serious diseases of citrus that affects all cultivars and causes the systematic death of trees worldwide. The disease is caused mostly by the bacteria Candidatus Liberibacter species. The wind, rain, and touch of infected workers cannot transmit this infectious disease. The Asian Citrus Psyllid (ACP), a minuscule insect, is one of the main vectors that transmit the disease by feeding on citrus leaves. Citrus greening management is also quite expensive since no successful treatment for the cure has been found, except to remove all affected vegetables from healthy crops to eliminate the bacterial spread.


25 May 2021

CRISPR/Cas technology could enable early diagnosis of devastating citrus disease

Scientists from Penn State and the U.S. Department of Agriculture have developed a diagnostic test that enables early detection of Huanglongbing (HLB) by detecting the presence of the bacterium that causes the disease, i.e. Candidatus Liberibacter asiaticus (CLas). Early detection of CLas is vital in controlling the spread of HLB because trees that have been infected by CLas can serve as a disease reservoir for years before symptoms are visible.


29 Jun 2020
Citrus Rehabilitation from HLB

Rehabilitation of HLB infected citrus trees using severe pruning and nutritional sprays.

Citrus trees infected with Huanglongbing (HLB) bacteria become weak and develop dieback, resulting in lost production. These trees eventually decline to a production level that is not economical to maintain in a citrus operation. Sixteen-year-old ‘Valencia’ (Citrus sinensis Macf.) orange trees on Swingle citrumelo rootstock [C. paradisi × Poncirus trifoliata (L.) Raf.], 100% infected with HLB, in decline and losing production, were severely pruned (buckhorned) to stimulate regrowth and the new flush treated with foliar nutritional sprays. Nutritional sprays included the “Boyd cocktail” and two other nutrient treatments that contained phosphites plus nickel and cobalt. Heavily pruned trees and unpruned standard control trees were compared for shoot growth and canopy development.


29 Jun 2020
Cover Crops

Can cover crops save Florida’s citrus?

Citrus greening has devastated the Sunshine State’s orange industry. Researchers and pioneering farmers see cover crops as a road to recovery.

For the last couple of decades, a tiny insect called the Asian citrus psyllid has fed on the stems and leaves of the orange trees in Florida, infecting them with bacteria that cause a lethal disease called citrus greening. The bacterial disease, huanglongbing (HLB), originated in China and has destroyed 90 percent of the state’s groves, devastating its $9 billion citrus industry.


27 Mar 2020
Koppert Studies

Spain: Koppert studies efficacy of beneficial fungus for the biological control of HLB

Beneficial microorganisms are becoming increasingly important in the biological control of citrus pests, as a complement to the release of auxiliary insects. Proof of this is the research carried out by Koppert Spain, which aims to confirm the efficacy of an entomopathogenic fungus that could help control Trioza erytreae, one of the insects that transmits huanglongbing (HLB), or citrus greening. “Koppert’s objective is to develop a biological solution that may be available to producers if the insect that transmits the HLB arrived in Spain,” said Javier Calvo, researching entomologist at Koppert, in the framework of a Citrus Technical Conference held in El Rompido (province of Huelva) and Palma del Río (province of Cordoba).


31 Jul 2019
Orange Juice

New study on citrus greening disease


Orange juice is a staple on many breakfast tables, but the future availability of citrus products is threatened by the global spread of huanglongbing (HLB), also known as citrus greening disease.

Knowing which environmental conditions are suitable for disease transmission and where those conditions occur is vital for crop management. A new study published by researchers at Virginia Tech with a team of international researchers in Journal of Applied Ecology investigates the thermal suitability for transmission of citrus greening with implications for surveillance and prevention.


31 Jul 2019
Citrus greening

Citrus greening research in Florida yields new tool in battle against disease

Paul Brinkmann

ORLANDO, Fla., May 2 (UPI) — A new machine being developed in Florida might provide another weapon against the spread of citrus greening disease, which has decimated crops worldwide.

The automated system would help detect and count the tiny pin-sized bugs that carry the disease, also called Huanglongbing or HLB. It would then give farmers a map of where the bugs have shown up in their fields, allowing for targeted precise insecticide spraying.

The device, known as an Automated Psyllid Detection System, is under development at University of Florida’s agricultural research station in Immokalee.


22 Jun 2019
Asian citrus psyllid

Being Vigilant: HLB and South Africa

Hein Gerber and Christine Spreeth
First Fruits Consulting

Citrus greening disease takes two forms: Huanglongbing (HLB), the devastating Asiatic strain of citrus greening disease caused by the bacterium Candidatus leberibacter asiaticus and African greening disease, caused by the bacterium Candidatus lebiribacter africanus. Both forms can be spread by infected plant material or by citrus psyllid vectors, namely Diaphorina citri (Asiatic greening) and Trioza erytreae (African greening) (Gottwald et al., 2007). When a vector is carrying the bacteria, it is called a ‘hot vector’ (Jansen, 2019). The psyllid vectors transfer the disease-causing pathogens when they feed on plant sap from citrus leaves (Grafton-Cardwell et al., 2006).