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: 10/01/2015
Project: 447   Year: 2015
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, gene expression, 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 to the above parameters, 3. Evaluate 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. Management of the experimental block (‘Hamlin’ orange on �Carrizo citrange� planted 3-4 July on a 10-acre block at A. Duda & Sons, Inc. farm in Hendry County was turned over to the grower having completed the planned 3 years. Trees will still be harvested by plot this year and the data used to complete a planned paper. A field day was conducted in conjunction with the company on 19 June attended by about 25 citrus growers and 14 other participants to present the results of the 3-year study. Part of the study was included in a dissertation completed by now Dr. Scott Croxton who graduated this summer. Another trial planted 5 May 2013 at SWFREC consists of 24, 250 ft. rows of �Ray Ruby� grapefruit on �smooth flat Seville� divided into 8 main plots, half receiving organic amendments since 1993, including 12 tons/acre composted yard trimming waste (YTW) applied in a 6 ft swath to the plant drill prior to planting. The plot had been underlain with drain tile and is flat except for 6 in high beds 32 inches wide on 18 ft centers covered with polyethylene film mulch and irrigated through two drip tape lines. Each 3-row plot is divided into 2 subplots: whiteface or metalized mulch. Soil bed temperatures have been about the same under white or reflective mulch over the last 3 months. Trunk x-section area, canopy area and height have been consistently for trees on compost compared to trees with no compost whereas growth differences between white and reflective mulch have not been significant. Sticky card captures have been 5 times greater on white mulch, but twice as high on compost compared to no compost. Infested flush followed similar trends. Incidence of HLB was 4% on metalized mulch compared to 13% on white (over both compost treatments) and 11% on compost compared to 6% on no-compost over both mulch treatments. Flooding caused considerable foot rot this summer. Soil samples were taken for microbiota analysis in Sep 2015. Plastic mulch was removed in Oct to evaluate the planned transition to microjet irrigation. Fertigation is used at the Vero Beach experiment usingliquid 6-0-8 (with minors) fertilizer injected continuously with all irrigation events. Herbicides are applied via herbicide boom to both the composted Urban Plant Debris (UPD) and the Bare Ground (BG) treatments in a 9 ft band 2.5 ft from edges of the 4 ft wide Metallized Reflective Mulch (MRM) ~2.5 ft.) beds to create 9 ft. wide weed free zone. Tree opening ins MRM are treated with spot sprays of glyphosate. Belay 2.13 SC and Admire Pro) were applied by soil drench for ACP control and Ridomil Gold SL using a calibrated electric timed liquid applicator. Insects and mites are monitored weekly. ACP adults and nymphs, Diaprepes Root Weevil, and orange dog larvae have been half or less on MRM than other treatments whereas Sri Lankan weevils and citrus leafminer were unaffected. Soil moisture readings as percent Volumetric Water Content (%VMC) for each treatment are also recorded.


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