Scientists at the University of California, Riverside (UCR) have found the first substance capable of controlling Citrus Greening Disease, which has devastated citrus farms in Florida and also threatens California.
The University of Florida has also been working towards a solution, as reported in March 2020.
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.
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.
The presence of Diaphorina citri (Asian citrus psyllid, or ACP), the primary vector of the dreaded Huanglongbing disease (HLB, or Asian Citrus Greening), was first reported in east Africa in Tanzania (2015) and Kenya (2016). Surveys that CRI conducted in collaboration with local scientists, confirmed the presence of ACP in the eastern regions of Tanzania. Recently HLB, previously known to occur in some parts of Ethiopia, was detected on the east coast of Kenya (Fig. 1). The recent detection of HLB in Kenya brings it considerably closer to citrus production in Southern Africa. CRI has engaged in a process with Department of Agriculture, Land Reform and Rural Development (DALRRD) to encourage Kenyan partners to scope the possibility of containing and eradicating the disease in the region.
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).
Florida citrus growers have always understood the importance of soil health and the positive influence of microbial activity and diversity in production. As citrus greening (also known as HLB) has spread, reducing production by more than 70%, interest in how these tiny organisms can improve root health is increasing. Research showing the disease, which is spread by the Asian citrus psyllid, can reduce citrus fibrous-root density by 30% to 50% before symptoms become visible above ground only intensifies the interest to learn more.
Sarah Strauss, Davie Kadyampakeni, Ramdas Kanissery, Tara Wade, Lauren Diepenbrock and Juanita Popenoe
Citrus Industry
Cover crops are specific crops not intended for sale but for soil improvement and sustainability. They are increasingly common in the agricultural fields of the Midwest and other grain-producing regions because of the wide range of benefits not just for the soil, but also the cash crop. In those systems, cover crops improve water and nutrient retention, promote microbial activity, reduce weed growth and insect pests, and improve plant growth. Similar impacts have been found in tree crops like apples and peaches, where cover crops are planted in row middles.
https://www.sciencedaily.com
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.
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).