Deploying Oak Mulch to Contain and Suppress HLB Disease in Citrus

Project Overview

GS20-225
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:
Lukas Hallman
Email
Major Professor:
Lorenzo Rossi, Ph.D.
Email
University of Florida

Information Products

Commodities

  • Fruits: citrus

Practices

  • Pest Management: mulches - general

    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 were collected monthly, along with root images. Overall, oak mulch led to increases in soil moisture, soil phosphorus, soil potassium, and soil magnesium. Additionally, oak mulch increased diversity and microbial biomass in the rhizosphere. However, oak mulch did not greatly impact root growth and was not effective at suppressing HLB.

    Project objectives:

    • 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.