Role of Vector Management and Foliar Nutrition in Prevention and Mitigation of HLB in New Citrus Plantings

Role of Vector Management and Foliar Nutrition in Prevention and Mitigation of HLB in New Citrus Plantings

Report Date: 07/14/2014
Project: 447   Year: 2014
Category: Horticultural & Management
Author: Phil Stansly
Sponsor: Citrus Research and Development Foundation

The objectives of this project are: 1. Evaluate psyllid populations, HLB incidence and intensity, tree growth, soil moisture, soil nutrients, foliar nutrients, and eventually yield in newly planted citrus blocks, 2. Assess separate contributions of vector control and foliar nutritional applications to the above parameters, 3. Evaluate the effectiveness of reflective mulch to repel ACP and reduce incidence of HLB, 4. Provide economic analysis of costs and projected benefits, and 5. Extend results to clientele. ‘Hamlin’ orange on ‘Carrizo’ citrange rootstock was planted 3-4 July on a 10-acre block planted on a 23 x 9 ft spacing at the A. Duda & Sons, Inc. farm in Hendry County south of LaBelle at 26.643 degrees S. -81.455 degrees W and 26 ft elevation. The experimental design of main plots is factorial RCB with 4 replicates and 4 treatments: insecticide alone, foliar nutrition alone, insecticide + nutrition, and untreated control. Each of 16 plots is split into two subplots 5 rows wide and 13 trees long, mulch and no mulch. Mulch provided by Imaflex Inc. is metalized (aluminized/reflective) polyethylene film of 3.5 mils thickness covered with a clear protective polyethylene coat. Metalized mulch was shown in preliminary evaluations on single plots to repel Asian citrus psyllid and together with a drip irrigation/fertigation system increase citrus growth rate over the unmulched control. The block was planted 3-4 July 2012 and monitoring ACP with flush inspection and sticky cards commenced 13 August. Sticky cards are monitored for ACP and other common citrus pests and replaced every other week. 2,655 ACP have been found on sticky cards of which greater than 70% are in no-mulch plots while only 14% have been found in plots that receive insecticide drenches. Only 3% of the ACP found on sticky cards come from plots with both mulch and insecticides. Thus far over 72,270 flush shoots have been observed of which 8,386 were infested with ACP and 1,737 were infested with aphids. Greater than 70% of ACP and aphid infested flush were found in no-mulch plots. Only 599 ACP and 559 aphid infested shoots were found in plots receiving insecticides with 122 ACP and 191 aphid infested shoots found in trees on both mulch treated with insecticide. Leaf samples for HLB testing were collected July 2014 of which there were 55 positive samples 12 of which were trees on mulch,10 from trees treated with insecticide with only 1 positive tree on mulch and drenched with insecticide. The most recent HLB leaf sample for nutrient analysis was collected on 16 June 2014 but results are not yet available. Growth measurements were made 1 July 2014 by measuring trunk area cross section. Trees on mulch and receiving foliar nutrition are now 20% larger than the no mulch no foliar nutrient control. However, trees receiving insecticide drench both with or without foliar nutrition but without mulch were larger than with mulch. The reason may be due to an irrigation system failure during the month of May which impacted trees on mulch more than those not on mulch which made better use of rainfall. Treatments applied: July 9: Foliar nutrition went out monthly Griffin Green 1gpa, August 5: 1 lb Fortress and 1 gal N-Sure in a 50 gallon volume, August 21: the entire field was sprayed by Duda with foliar nutrition 6-0-8 10 gpa, September 3: 1 lb Fortress and 1 gal N-Sure August in a 50 gallon volume. Normal grove care operations continued which included one herbicide application in September of glyphosate, Kocide sprayed monthly for canker control, and one application of Intrepid for leafminer control.


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