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Q.U. Zaman, A.W. Schumann, and H.K. Hostler

Many citrus groves in Florida were affected by hurricanes in Summer 2004. A commercial 42-acre `Valencia' sweet orange (Citrus sinensis) grove of 2980 trees was routinely scanned with an automated ultrasonic system to measure and map tree canopy volumes. We estimated tree damage by comparing canopy volumes measured before and after the hurricanes of 2004. Ultrasonically sensed tree canopy volume was mapped and the relative tree canopy volume loss percentage (TCVL%) for each tree was calculated and classified into six categories [≤0 (no damage), 1% to 24%, 25% to 49%, 50% to 74%, 75% to 99%, and 100%]. Authenticity of the ultrasonically sensed missing trees was established by ground truthing or matching visually observed and georeferenced missing tree locations with ultrasonically sensed missing trees in the grove. Ninety-one trees were found missing during ground inspections after hurricanes and they exactly matched with ultrasonically sensed missing tree locations throughout the grove. All of the missing trees were in TCVL% categories 5 and 6 (≥75% damage). Some canopy volume was still detected with ultrasonics at the missing tree locations because of the presence of tall grass, weeds, or branches of large adjacent trees. More than 50% of trees in the grove were damaged (completely or partially) and generally larger trees (>100 m3) were damaged more by the hurricanes than small or medium size trees in each tree canopy volume loss category. The automated ultrasonic system could be used to rapidly identify missing trees (completely damaged) and to estimate partial tree canopy volume loss after hurricanes.

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Ed Stover, Dominick Scotto, and James Salvatore

Pesticide spray practices for citrus (Citrus spp.) in the Indian River region of Florida were surveyed in 2001 as the first step in identifying opportunities for improving efficiency and reducing potential environmental impact. The survey covered 73% of grapefruit (C. paradisi) acreage in Indian River, St. Lucie, Martin and Palm Beach counties, comprising 70% of all Indian River commercial grapefruit. Large differences in spray practices were revealed. The focus of this survey was grapefruit spraying, since grapefruit represent 59% of fresh citrus shipped from the Indian River region, and are sprayed more intensively than citrus fruit grown for processing. In commercial groves, almost all foliar sprays to grapefruit are applied using air-assisted sprayers pulled through the groves by tractors. Use of engine-driven and power-takeoff-driven sprayers were reported with equal frequency and accounted for 89% of spray machines used. Lowvolume Curtec sprayers comprised the remainder. Spray volume for grape-fruit varied: 7.6% of acreage was sprayed at 25 to 35 gal/acre (230 to 330 L·ha-1) for all sprays; 4.2% was sprayed at 100 to 170 gal/acre (940 to 1600 L·ha-1) for all sprays; 15.3% was sprayed at 200 to 380 gal/acre (1900 to 3600 L·ha-1) for all sprays; 28.2% was sprayed at 450 to 750 gal/acre (4200 to 7000 L·ha-1) for all sprays; and 44.5% of grapefruit acreage was sprayed in a progressive manner from lower to higher volume as the season progresses. Many mid and high spray volume growers reported unacceptable results when they lowered spray volume. Although correlation was moderate (r = 0.35 to 0.45), regressions indicated that both total foliar pesticide spray material costs, and annual fungicidal copper (Cu) use increased with spray volume used for postbloom fungicides. Mean Cu use per acre was in the middle of the recommended range. All growers reported adjusting nozzling for tree height within a grove, and since Indian River groves are bedded, growers adjusted sprayer output differently for trees on bed tops versus furrows on 85% of acreage. Sprayers were shut off for missing trees on 83% of acreage, but this was done only for two or more adjacent trees on almost half of this area. Sensor-actuated sprayers were used to minimize off-target application on 14.7% of grapefruit acreage, but for an additional 21% of acreage, growers reported trying and abandoning this technology. While 88% of grove acreage was sprayed during the day, 75% of acreage sprayed using less than 100 gal/acre was sprayed at night. Growers reported no defined protocol for ceasing spray operations based on environmental conditions.

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affected than small or medium-size trees. The ultrasonic system rapidly identified missing trees and estimated partial tree canopy volume loss. Fast-growing Green Industry impacts U.S. economy The U.S. environmental horticulture industry (Green Industry

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Madhulika Sagaram, Leonardo Lombardini, and L.J. Grauke

variance (ANOVA) and Student's t test using SAS (Version 9.1; SAS Institute, Cary, NC). ANOVA was structured to allow unequal replications for each seedstock resulting from occasionally missing trees. Differences ( P ≤ 0.05) between means were determined

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Robert E. Rouse, Monica Ozores-Hampton, Fritz M. Roka, and Pamela Roberts

before the appearance of HLB ( Rouse et al., 2010 , 2012 ). Planting and replanting citrus were at an all-time low between 2006 and 2010. Many growers were reluctant to reset missing trees in existing groves or replant entire blocks because of concern

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Thomas A. Obreza and Arnold Schumann

, avoiding the row middle. For small trees, manual or electronic spreader adaptations deliver fertilizer rates accurately to the root zone while leaving out the nonrooted area between rows and spaces with missing trees. Fertigation with microsprinklers or

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Arnold W. Schumann

a tree canopy in left- or right-hand rows ( Fig. 7 ). Most importantly, spaces with missing trees are never fertilized, which significantly reduces application of unnecessary nutrients, fertilizer costs per hectare, and groundwater pollution while

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Bruce W. Wood

plots were not absolutely uniform regarding off-varieties and missing trees, the associated variation was essentially homogeneous across the study orchard and treatments. The occasional off-cultivar was ‘Sumner’—relatively late ripening compared with

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Norman Lalancette, Daniel L. Ward, and Joseph C. Goffreda

missing trees and/or poor fruit set, 10 and 11 of the 33 cultivars in 2007 and 2008, respectively, had only three replicate data values as opposed to the designated four replicates. Furthermore, one cultivar in 2007 (D88-59) and two cultivars in 2008

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William R. Okie and Bryan Blackburn

temperate trees: Is there something missing? Tree Physiol. 26 1165 1172 Linsley-Noakes, G.C. Louw, M. Allan, P. 1995 Estimating daily positive Utah chill units from maximum and minimum temperatures J. S. Afr. Soc. Hort. Sci. 5 19 24 Mahmood, K. Carew, J