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 Dr. Scott Croxton who graduated in summer 2015. 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. All evaluated soil parameters parameters were significantly different between compost and no compost: 5.6 vs 6.9, organic matter (%) 1.29 vs 3.13, CEC (meq/100 g) 1.19 vs 5.73, P, K, Ca and MG (mg/kg) 32.05 vs 234.3, 8.73 vs 19.4, 414.6 vs 2071.8, 27.0 vs 113.5 respectively. 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 was divided into 2 subplots: whiteface or metalized mulch. Soil bed temperatures between Jul and Dec 2015 tended to be in non-compost than compost and greater under metalized mulch compared to white mulch: averaging 80.43 (metalized non compost) 78.85 (white non compost, 79.07 (metalized compost) and 77.73 (white compost) 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. Trunk x-section area, canopy area and height have increased significantly more for trees on compost compared to trees with no compost. From Jul 2013 through Jul 2015, non compost trunk area grew from 65 to 2407 mm compared to 61 to 3,333 mm2 with compost, canopy area (m2) from 0.43 to 3.69 m2 non compost vs 0.65-5.34 m2 compost, and tree height from 1.13 to 2.02 m non compost compared to 1.17 to 2.22 m compost. In contrast, growth differences between white and reflective mulch were not significant. Flooding and over irrigation 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. Constraints on increased compost use lie with short supply rather than grower acceptance, in spite of 3 major suppliers in the local tri-county area including a huge facility run by Lee County. One grower even asked me to stop promoting use of compost in citrus because supply was not keeping up with demand.


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