Understanding and Manipulating the Interaction of Rootstocks and Constant Nutrition to Enhance the Establishment, Longevity and Profitability of Citrus Plantings in HLB-Endemic Areas

Understanding and Manipulating the Interaction of Rootstocks and Constant Nutrition to Enhance the Establishment, Longevity and Profitability of Citrus Plantings in HLB-Endemic Areas

Report Date: 07/30/2018
Project: 05-013   Year: 2018
Category: Plant Improvement
Author: Jude Grosser
Sponsor: Citrus Research and Development Foundation

Objective 1. (Greenhouse experiment): Leaf nutrition results: There was no significant differences in the N,P,K, Mg and Ca levels in any of the rootstock / fertilizer combinations. Plants growing in the Harrell�s nursery mix treatment had boron levels 5-6 folder higher in all rootstocks when compared to Swingle. Additionally, Mn levels were double in all rootstocks when compared to Swingle. When both Mn and Bo was applied simultaneously to supplement the Harrell�s nursery mix, their levels were doubled in all rootstocks except the GFT+50-7 and X639. Harrell’s St Helena Mix as well as the Florikote IFAS blend resulted in enhanced levels of Bo and Mn in all rootstocks. These levels were twice that observed in plants growing in the Harrell�s nursery mix. Most of the rootstocks stick grafted with HLB + budwood were infected with no significant differences in the rate of infection between the different treatments / rootstock combinations. However, WGFT+ trifoliate orange 50-7 rootstocks on the St Helena mix exhibited higher cT values (lower bacterial titers) when compared to the other rootstocks. Additionally, this rootstock also performed better across the board (generally higher cT values) in all the other fertilizer combinations (note that this rootstock is also showing good tolerance in several field plantings, and is being considered for commercial release). Most trees, even though infected, continue to grow exceptionally well, except for treatment #3, where trees are not showing much growth and somewhat yellow. Objective 3: Report for April-June 2018. To evaluate the effect of complete, balanced and constant nutrition on HLB-affected mature trees (composition, delivery and economics).In March fruit were harvested from both locations, Arcadia and Fort Meade. The initial analysis shows that there has been significant improvement in yield and fruit quality with the use of CRF and Tiger micronutrients (20%-50% higher rates on Manganese, Boron, and Iron) over the control treatment (IFAS recommendation). The yields at Arcadia site were compromised due to Hurricane Irma therefore, the two sites show some amount of variability in the data. Overall, the yields seems to have improved with use of CRF and tiger micronutrients in combination. With the collection of year 3 data on yield and quality, we will have more confidence in results and be able to develop some guidelines for growers. The yield data was presented at OJ Break on May 15th, 2018 and at SWFREC on May 16th, 2018. Detailed results of year 1and 2 of this experiment will be presented at Citrus Expo 2018. The third year application of fertilizer has been initiated, March and June applications were completed. The year-3 tree health data has been collected. Everything is now going according to schedule. Objective 5. (funded by Lee Groves, using donated fertilizer products): Alligator Vernia/Rough Lemon Enhanced Nutrition Experiment � Treatments: 6 tree plots (randomized), 2 plots per treatment � treatments 2 times per year. Positive results showing a therapeutic affect from overdoses of manganese against HLB is being presented at the annual ASHS meeting in Washington DC (manuscript also being prepared.


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