Evaluating the role of greasy spot and peel disorders in the greasy green defect on citrus fruit

Evaluating the role of greasy spot and peel disorders in the greasy green defect on citrus fruit

Report Date: 07/12/2022
Project: 21-012   Year: 2022
Category: Other
Author: Megan Dewdney
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them:The objectives are to 2) determine if the flush cycle and infection period for Z. citri-griseum have changed due to the influence of HLB on citrus physiology or changing environmental factors; 4) evaluate the potential promotion of “greasy-green” symptoms related to nutrition programs or to peel reactions like a chemical “burn” from different pesticide and combinations of pesticide tank mixes; and 5) evaluate if postharvest degreening treatments might be modified to adequately remove the green coloration while mitigating poor shelf life from anticipated longer degreening times.   Most of the progress to date have been on objective 2.  Two sites were established in grapefruit groves n the Indian River region.  These sites were identified to have significant problems with the greasy green disorder afftecting the grapefruit industry.  In each block, twenty trees were selected for uniform canopy without excessive thinning or obvious sectoring from HLB and mapped, and ten flushes per tree were tagged to be observed for greasy spot symptoms later in the season.  Every two weeks from the beginning of May, ten leaves and one fruit per tree are collected.  The leaves and fruit are cleared and 5mm disk samples are examined under the microscope to observe whether there is epiphytic growth.  We will hopefully determine the extent of epiphytic growth and when the epiphytic growth is the most prevalent to compare with what is known from previous work.  Ideally, this will allow us to adjust when applications occur to better control greasy spot as part of the greasy green disorder. Initial survey attempts of fresh fruit growers have not generated many responses about the greasy green disorder.  Plans are underway to potentially conduct in person interviews to get the information needed to inform experiments in the next season. 2. Please state what work is anticipated for next quarter:  Field sampling will continue.  Post-harvest work will be planned and started with the upcoming harvest season.  Interviews will be conducted with growers on the greasy green disorder to give us more information to inform experiments in the next season.   3. Please state budget status (underspend or overspend, and why): No over or underspend on budget currently    


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