Frequent low rate application of 2, 4-D and cytokinin to study plant symptom reduction in HLB affected trees – grower tests

Frequent low rate application of 2, 4-D and cytokinin to study plant symptom reduction in HLB affected trees - grower tests

Report Date: 02/01/2016
Project: 776   Year: 2015
Category: ACP Vector
Author: L. Gene Albrigo
Sponsor: Citrus Research and Development Foundation

Although harvests are not complete for the Hamlin tests at all three of the sites, leaf drop and fruit drop counts are completed through different dates in December for each site. Leaf drop was not greatly different between the sites, nor were large differences found between the low concentration treatment and the control trees. Total leaf drop for Treated vs Control at each site was 370 vs 340; 243 vs 254, and 231 vs 233 total leaves for the fall count period. There was very little difference between 1 rated and 3 rated (decline) trees. Leaf drop was much heavier during September and early October than later. In one case almost 70 % of the leaf loss occurred by October 8th. This late summer, early fall leaf drop did not occur prior to HLB. Fruit drop was more uniform from late September until December. Per site drop rates for Treated vs Control trees was 19 vs 15.5, 18.8 vs 19.4 and 24.5 vs 25.1. There was usually only 1 or 2 % difference between 1 and 3 rated trees. Although fruit drop was reduced by the low concentration sprays of PGRs a year ago, there does not appear to be any effect on this year’s drop in the Hamlin cultivar. Valencia data is now being collected.


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