Deploying Oak Mulch to Contain and Suppress HLB Disease in Citrus

Project Overview

Project Type: Graduate Student
Funds awarded in 2020: $12,347.00
Projected End Date: 08/31/2022
Grant Recipient: University of Florida
Region: Southern
State: Florida
Graduate Student:
Major Professor:
Lorenzo Rossi, Ph.D.
University of Florida

Information Products


  • Fruits: citrus


  • Pest Management: mulches - general

    Proposal abstract:

    Huanglongbing (HLB; also known as citrus greening) is a bacterial disorder that is severely reducing global citrus production. It is caused by the bacterium Candidatus Liberibacter asiaticus (CLas) and vectored by the Diaphorina citri psyllid. It was first detected in Florida in 2005 and is now widely distributed throughout the commercial citrus-growing regions. As of today, there is no cure for HLB, and there are no commercial citrus cultivars, varieties, or scion-rootstock grafting combinations with natural resistance to infection. Thus, searching for alternative mitigation strategies is an urgent priority for a sustainable citrus industry. Anecdotal reports from Florida growers have claimed that citrus growing within the drip line of large oak trees have minimal HLB symptoms, while citrus trees nearby but not under the oak tree drip line have severe symptoms. As a result, some growers are now using oak mulch in their citrus groves, and they noticed an overall increase in production. Following these observations, the main objectives of this study are (i) to study the capability of oak mulch to contain and suppress CLas, (ii) to measure the effect of oak mulch on HLB-affected citrus physiology, and root growth and development, and (iii) to study the effect of oak mulch on the rhizobiome. Soil, leaf and root samples will be collected monthly, along with root images. The products of this research will lead to the reduction of traditional treatments methods, while improving citrus industry sustainability and productivity and ensuring continued availability to the public of healthful citrus products.

    Project objectives from proposal:

    • Study the capability of oak mulch to contain and suppress¬†CLas


    • Measure the effect of oak mulch on HLB-affected citrus physiology and root growth and development


    • Study the effect of oak mulch on microbial life biodiversity within the rhizosphere (rhizobiome)


    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.