Identification of an Idaeovirus in Citrus with Implications as to the Cause of Citrus Blight. K. S. Derrick, M. J. Beretta, and G. A. Barthe, CREC, Lake Alfred, UF /IFAS.

In experiments to determine the cause of citrus blight (CB), subtraction hybridization was done using leaves and roots of an affected tree. Clones were identified that had similarities to Raspberry bushy dwarf virus (RBDV), the only known member of the genus Idaeovirus. The clones covered a 1555-bp region similar to RNA-2 of RBDV including 595 nts of the 3’ end of an ORF that was 60% identical in amino acids to the movement protein of RBDV and a 834-nt ORF that was 65% identical in amino acids to the coat protein of RBDV. RBDV is seed and pollen transmitted, is symptomless in most Rubus species, and only causes bushy dwarf disease with mixed infections of the aphid-borne Black raspberry necrosis virus. Based on RT-PCR assays, the citrus Idaeovirus (CIV) appears to be unevenly distributed in citrus and is present in low concentrations. In a manner similar to raspberry bushy dwarf disease, CB may be a disease caused by a mixed infection of CIV and another virus, such as a strain of CTV. It had been considered that CTV could not be involved with CB, since Carrizo citrange and trifoliate orange, which are very susceptible to CB, are reported to be resistant to CTV. We have shown that mild, decline and stem pitting strains of CTV can infect the roots of these two rootstocks. The virus appears to move into the roots from CTV susceptible scions, but does not move from roots into shoots of Carrizo citrange and trifoliate orange.

Identification of Effective Compounds From Antagonisms for Controlling Foliar Fungal Pathogens of Citrus. Bang-Jau You, Hui-Qin Chen, Lihua Cao, and Kuang-Ren Chung, CREC, Lake Alfred, UF/IFAS.

Saprophytic fungi producing unknown toxic compounds were identified from citrus groves near the CREC campus and were evaluated for controlling the major citrus foliar fungal pathogens causing Alternaria brown spot, melanose, citrus scab, postbloom fruit drop (PFD), or greasy spot in Florida. The toxic compounds present in cultural extracts exhibited a strong growth reduction to citrus fungal pathogens by altering hyphal morphology and/or by inhibiting conidial germination. The inhibitory efficacy was unaffected after heating at 95°C for 15 min. However, production of the toxic compounds by antagonisms was markedly influenced with the compositions of media used in the laboratory. Preliminary test in greenhouse revealed that the saprophytic fungi reduced disease incidences of Alternaria brown spot on tangerine and melanose on grapefruit. We are currently working on the chemical determination of the compounds using Nuclear Magnetic Resonance (NMR). The toxic compounds may be useful in developing effective bio-fungicides and providing an alternative for disease management for citrus growers in Florida. Since the compounds are originally identified from microorganisms that already reside in the citrus community, it may reduce a risk for application and may facilitate registration for citrus in the future.

Effect of Hormone Inhibitors on Yield Production of Citrus Associated With Postbloom Fruit Drop (PFD) Caused by Colletotrichum Acutatum. *Hui-Ling Liao, Hui-Qin Chen, Lihua Cao, and Kuang-Ren Chung, CREC, Lake Alfred, UF/IFAS.

Postbloom fruit drop (PFD) of citrus is caused by Colletotrichum acutatum. The fungus infects flower petals causing brownish lesions that result in fruit drop, leaf distortion, and production of persistent calyces, commonly called ‘buttons’. Studies combined with molecular and biochemical analyses suggested that imbalance of growth regulators such as auxin, ethylene, and jasmonic acid (JA) in C. acutatum-infected flowers may contribute to young fruit drop. Application of auxin transport and action inhibitors such as 2,3,5-triiodobenzolic acid (TIBA), clofibrate, or quercetin, JA biosynthesis inhibitors such as salicylic acid (SA) and aspirin (methyl-SA), or gibberellic acid (GA₃) 7 or 12 d after fungal infection increased young fruit retention. The commercial products ReZist and Actigard, used as systemic acquired resistance (SAR) inducers, also increased fruit retention. The commercial products with wider application windows may provide another alternative for managing PFD in the field since they are targeted on fruit retention rather than on pathogen control per se and can be applied after symptoms develop.

Prospects for Control of Citrus Canker With Novel Chemical Compounds. J. H. Graham, J. K. Burns, CREC, Lake Alfred, UF/IFAS; T. R. Gottwald,USDA-ARS-USHRL, Ft. Pierce and R. P. Leite, Jr.^,Instituto Agronômico do Paraná, Londrina, Paraná, Brazil

The spread of citrus canker, caused by Xanthomonas axonopodis pv. citri, increased greatly in Florida after the hurricanes in 2004 and 2005. Exposure of 80,000 acres as a result of the 2004 storms and the potential for addtitional exposure after the 2005 season, led to the suspension of the removal of exposed tress under the 1900 ft. law in January 2006. If this policy is maintained and the law changed, canker will soon become endemic in Florida and a principle management practice will be bactericidal sprays to limit fruit blemish and canker-induced fruit drop (depending on variety). Field trials conducted in Brazil demonstrate that copper sprays even at reduced rates are consistently effective for control of canker on moderately susceptible orange varieties. New commercial compounds (Actigard and Messenger) that induce systemic resistance (ISR) in the greenhouse are ineffective for control of disease in the field. Basal resistance (BR) is induced by peptides associated with proteins on the surface of the pathogenic bacterium, such as flagellin. Two active peptides induced bacterial disease control activity in the greenhouse, and therefore, merit further testing. Contact materials, including the fungicide Famoxate and the antibiotic Gentamicin are under field evaluation. Alternatives to copper minimize potential risks of bacterial resistance, soil accumulation and environmental contamination.

Comparison of Visual Assessment and Polymerase Chain Reaction Assay Testing to Estimate the Incidence of the Huanglongbing Pathogen in Commercial Florida Citrus. Michael S. Irey, USDA-ARS-USHRL, Ft. Pierce; Tim Gast, Southern Gardens Citrus, Clewiston, FL and Timothy Gottwald, USDA-ARS-USHRL, Ft. Pierce.

Huanglongbing (HLB = citrus greening) is one of the most serious diseases of citrus worldwide. The disease is caused by species of bacteria in the genus Candidatus Liberibacter and was discovered for the first time in the United States in Florida in August, 2005. To date, the Asian form of HLB, caused by Candidatus Liberibacter asiaticus, is the only form of HLB that has been found in Florida. Among the recommended control measures for HLB is the removal of trees (roguing) that express visible symptoms of HLB in order to reduce the potential inoculum reservoir. In areas where HLB is endemic, roguing has been based predominantly on the presence of visible symptoms. Molecular detection protocols are available for the detection of HLB but due to the uneven distribution of the bacterium in the tree, the serological variability of the pathogen, and perceived limitations of the testing methodology, molecular testing generally has been limited to the confirmation of visible infections and not for detecting infections in non-symptomatic plants. Roguing based on visible symptoms does not remove all infected trees but there are little data available to document the actual incidence of infection. In this study, visual surveys were compared to the testing of trees with a polymerase chain reaction-based assay (PCR). Initial results indicate that the incidence of infection based on PCR testing may be up to two times the incidence of infection estimated by visible symptoms alone.

Spatial Analysis of Freeze Events in Florida Using Three Different Interpolation Techniques. Clyde W. Fraisse and Tapan B. Pathak, Agricultural and Biological Engineering Dept., Gainesville, UF/IFAS.

Severe freezes have seriously impacted the agriculture industry in Florida during the last two decades. High impact freezes during 1980’s affected the citrus industry significantly and reduced citrus production in northern citrus production zones. Freezes in 1981, 1983, 1985, 1987, and 1989 severely damaged the citrus growing industry and recovery was almost impossible for many citrus growers. Of the dozen or so devastating freezes that have impacted the citrus industry and other agriculture concerns over the last century in the Southeast, nearly all of them occurred during times of neutral El Nino conditions in the Pacific Ocean. In this study, two of the most severe freeze dates, December 25, 1983 and January 21, 1985, were selected for comparing three different interpolation techniques to map freeze events. Interpolation techniques included inverse distance weighting, kriging, and spline. Weather data for 105 meteorological stations from the National Climatic Data Center were used for the study. All three methods worked well in estimating the minimum surface temperature but the most efficient one was kriging. Minimum surface temperature layers generated by kriging for the two freeze events in Florida were overlaid with citrus production zones layers and areas affected by different temperatures ranges, including 10-14, 14-20, 20-25, 25-28, and 28-32ºF were estimated.

Visual Presentation of the Spatiotemporal Aspects of Diaprepes Root Weevil Diaprepes abbreviatus (Coleoptera:Curculionidae) Abundance in a Small East Coast Citrus Grove from 2000-2003. G. K. Ross and R. C. Adair, Jr., The Florida Research Center for Agricultural Sustainability, Inc., Vero Beach.

Little is known about the spatial distribution patterns or the rate and direction of the spread of Diaprepes abbreviatus infestations in citrus. Weekly adult weevil abundance data obtained from geo-referenced Tedder Traps placed in a diamond-shaped grid were projected geographically by means of a geographic Information System (GIS). The GIS (ESRI ArcGIS) was used to provide spatial interpolation of Diaprepes abundance weekly for a period of one to four years (2000-2003). Animation software (Macromedia Flash) was then utilized to combine the weekly interpolations into an interactive animation that enabled visualization of the spatiotemporal aspects of Diaprepes abundance. In addition, these Diaprepes abundance interpolations were synchronously aligned with weekly rainfall data. The resultant interactive animation successfully portrayed different geographic and seasonal aspects of Diaprepes activity while simultaneously observing rainfall in a smoother transition through space and time than was previously thought possible. The visualization of the spatiotemporal aspects of Diaprepes abundance captured by the Tedder Traps was much more evident when viewed as an interactive animation than could be derived by more conventional analysis of tabular or graph data. The ability to visualize additional factors such as rainfall or soil temperature in conjunction with spatiotemporal abundance could not only elucidate the ecology of Diaprepes but also result in a fully Integrated Pest Management (IPM) program by providing essential timing and location information necessary for precision application of crop protectants.

Web-Based Survey and Modeling Systems for Agricultural Insects and Diseases: Applications in Florida Citrus. J.S. Rogers, Ecostat Inc., Highland City; H.N. Nigg, CREC, Lake Alfred, UF/IFAS; I. Clark, Geostokos Limited, Alloa, Central Scotland; D.S. Hart, Serveon Inc., Wilmington, DE; R. Ehsani, CREC, Lake Alfred, UF/IFAS; D.L. Brock and E.W. Schuster, Massachusetts Institute of Technology, Cambridge, MA.

This paper introduces a web- and PDA-based spatiotemporal survey and forecasting service (“FlyNet”) intended for the Caribbean Fruit Fly Free Protocol certification program. One challenge is how this information can be automatically related to data archived in other global information systems. Our solution is a universal process for acquiring, aligning and analyzing information from any agricultural crop-pest domain. Its foundation is a centralized data representation allowing relationships from different input sources to be explored in real-time through mapping, mathematical modeling and OLAP cube reporting. These features are valuable to growers because retrospective analyses against financial data become easier and insects and diseases can be tracked in real-time to facilitate better management decisions. Such capabilities are also useful to regulators who certify crops for sale to foreign or domestic markets. They can also help researchers who wish to produce and share statistical analyses in real-time rather than wait until the end of an experiment to generate their results. We present our system architecture and show how observational information is acquired by our servers. Results of our first-year mathematical and geostatistical modeling suggest that Caribbean Fruit Fly populations are described by a logistic function and occur with an approximate 30-mile range of influence and 410-day cycle. This study utilizes a new computer language in development at MIT (“M”) that provides an interoperable data organization and modeling environment. The application of M will support automatic alignment and modeling of information from different agricultural, ecological, environmental and financial sources.

Rootstock Effects on ‘Flame’ Grapefruit Trees Grown in the Indian River Region.

William S. Castle and James C. Baldwin, CREC, Lake Alfred, UF/IFAS.

‘Flame’ grapefruit (Citrus paradisi Macf.) trees were planted at 17 x 27 feet as two replicated trials in adjacent beds of Winder loamy sand soil in 1989 or 1990. The eight rootstocks in the 1989 trial had been selected for tolerance to Phytophthora and salinity from hybrids produced in the U.S. D. A. breeding program at Indio, CA. The parents were mostly selections of trifoliate orange (Poncirus trifoliata [L.] Raf.), mandarin (C. reticulata Blanco), and Rangpur (C. limonia Osb.) Tree height among all rootstocks only ranged from 9.7 to 11.7 feet and annual yields were not different when measured in 3 years or when estimated in 2 years. Trees on African shaddock (C. maxima [Burm.] Merrill x ‘English Large’ trifoliate orange were the tallest after 10 years, produced the highest cumulative yield over five seasons (31 boxes/tree) and had the highest survival, 87%. Trees on a Rangpur x C. depressa Hayata hybrid had the lowest cumulative yield of 17 boxes/tree. The 1990 trial was a comparison of blight tolerance among trees on rough lemon (C. jambhiri Lush.), a selection of rough lemon from South Africa, RL-8166, and Swingle citrumelo (C. paradisi Macf. x P. trifoliata). Virtually all trees survived with only an occasional tree loss to blight through the trial period of 12 years. Trees grew to ca. 10 feet in height and there were no differences in annual measured yields. Trees on Swingle citrumelo had the lowest mean yield among the rootstocks in both trials.

Performance of ‘Hamlin’ Orange on 14 Rootstocks in Central Florida. K. D. Bowman, USDA-ARS-USHRL, Ft. Pierce.

Fourteen rootstock selections consisting of 12 new numbered hybrids, and two named cultivars were tested as rootstocks for ‘Hamlin’ orange, Citrus sinensis L. Osbeck at the Whitmore Foundation Farm in Lake County. Trees were planted at 3.0 m x 7.6 m spacing and the test included four single-tree replications in randomized complete blocks on Astatula fine sand soil with a pH of 6.2 and. Irrigation in the block was by overhead rotary sprinkler until conversion of the block to under-tree microjets in 2005. Cumulative fruit production over five years, fruit quality, tree growth, and tree health were measured and compared among the rootstocks. The standard rootstocks Carrizo citrange and Swingle citrumelo were intermediate to good in their effect on fruit productivity, while the new numbered hybrid selections ranged from high productivity to very low productivity. Cumulative production (2001-2005) ranged from 787 kg of fruit per tree for US-1209 rootstock to 400 kg of fruit per tree for US-1206 rootstock. The rootstocks also differed significantly in their effect on fruit brix and other fruit quality traits. The rootstocks Swingle citrumelo and US-1201 typically produced fruit with low brix values, while the rootstocks US-1209 and US-1206 produced fruit with higher soluble solids concentrations. Some of the new hybrid rootstocks appeared promising for more widespread commercial trials.

Diaprepes, Phytophthora and Hurricanes: Rootstock Selection and Pesticide Use Affect Growth and Survival of ‘Hamlin’ Orange Trees in a Central Florida Citrus Grove. Robin J. Stuart, Clayton W. McCoy, William S. Castle, James H. Graham, and Michael E. Rogers, CREC, Lake Alfred, UF/IFAS.

We compared the growth and survival of young ‘Hamlin’ orange trees budded to five rootstocks (C-22, C-32, and C-35 citranges, Cleopatra mandarin and Swingle citrumelo) planted within a declining mature citrus grove infested with the root weevil, Diaprepes abbreviatus. The study used a split plot experimental design and all young trees received chemical applications for pest control from planting in September 2001 through 20 months of growth. Subsequently, half the trees received chemical treatments based on a pest-monitoring program whereas the others remained untreated. Over the next two years, treated trees had higher growth rates (except Cleopatra mandarin), larger tree canopies, and less tree decline than untreated trees; and trees on C-32, C-35, and Swingle citrumelo generally outperformed those on C-22 and Cleopatra mandarin. Roots damaged by weevil larvae were often infected by the plant pathogen Phytophthora nicotianae, which appeared to be a major factor in tree decline. In the fall of 2004, the grove sustained three hurricanes that killed 18.6% of the young trees and caused major damage to an additional 27.2%. Differential storm damage occurred among rootstock and pesticide treatments at least partly because larger healthier trees suffered more broken branches and fatal trunk injury whereas smaller weaker trees had less damage overall but were more frequently uprooted. Despite hurricane damage, differences in canopy volume showed similar patterns in May 2004 and 2005. This study demonstrates the importance of rootstock selection and effective pesticide use for maintaining citrus groves under stress from Diaprepes and Phytophthora.

Rootstock Effects on Murcott Tangor Trees Grown in a Calcareous Alfisol or a Spodosol. William S. Castle and James C. Baldwin, CREC, Lake Alfred, UF/IFAS.

Two replicated rootstock trials were planted with ‘Murcott’ tangor (putative Citrus reticulata Blanco x C. sinensis [L.] Osb.) as the scion. The first trial was planted in 1990 near Sebring in Smyrna sand, a Spodosol. Trees on 9 rootstocks including the dwarfing ‘Flying Dragon’ trifoliate orange (Poncirus trifoliata [L.] Raf.), mandarins, and ‘Milam’ lemon (putative C. jambhiri [Lush.] hybrid) were planted within an established commercial grove. Tree survival was 100% except for trees on sour orange (C. aurantium [L.]) that declined from citrus tristeza virus. Tree height after 11 years ranged from 9 feet (‘Flying Dragon’) to 11 feet (all other rootstocks). There were no large yield differences based on estimates at age 5 and 11 years. The second trial was planted in 1994 near West Palm Beach in Riviera sand, an Alfisol. Trees on 31 rootstocks that were mostly citranges (C. sinensis x P. trifoliata [L.] Raf.), citrumelos (C. paradisi Macf. x P. trifoliata), mandarins and somatic and sexual hybrids were planted but data were collected from only trees on 10 of those rootstocks. Tree survival varied from 100 to < 30% (somatic hybrids). The trees on Swingle citrumelo were 9.2 feet tall at age 10 years and those on most other rootstocks were up to 2 feet taller. Yield, as measured in three seasons and estimated in two seasons, was consistently highest in the trees on Volkamer lemon (C. volkameriana Ten. & Pasq.). Trees on Volkamer lemon and Smooth Flat Seville performed best in the calcareous areas of the site.

Machine Vision-Based Citrus Yield Mapping System. Radnaabazar Chinchuluun, Won Suk Lee, Thomas F. Burks, Agricultural and Biological Engineering, Gainesville, UF/IFAS.

Knowing the variability of fruits in citrus groves is important for growers to make right management decisions. Current citrus yield mapping systems require hand harvesting, which is labor intensive. Detecting occluded and non-occluded fruits from acquired images in outdoor scenes are one of the major problems in computer vision-based agricultural applications. Moreover, detecting occluded fruits from acquired images has received much attention in computer vision-based agricultural applications since there are no completely robust and efficient methods. This paper presents an automatic machine vision system with two charge coupled device (CCD) cameras, ultrasonic sensors, an encoder and a Differential GPS receiver to estimate citrus yield in natural outdoor scenes. An alternative computer vision algorithm is proposed to recognize visible and partially occluded citrus fruits from images. The average fruit size is determined from images using ultrasonic sensors measuring a distance between the cameras and the fruit laden trees. Finally, a citrus yield map will be created based on position information and the distance measured by the encoder.

Relating Citrus Canopy Size and Yield to Precision Fertilization. A.W. Schumann, H.K. Hostler, S. Buchanon, and Q.U. Zaman, CREC, Lake Alfred, UF/IFAS.

Modern granular fertilizer spreaders with variable rate application (VRA) capability can reduce fertilizer requirements and environmental impacts in Florida citrus groves by improving fertilizer application efficiency by up to 40%. A key component to their success is the real-time canopy sensing system which measures the size of the trees before the appropriate dose of fertilizer is dispensed. In this study, the performance of two types of sensors (ultrasonic and photoelectric) used in two different configurations (distance sensing versus discrete on/off) were compared in citrus groves. The correlations between fruit yield and various sensor output combinations in a 40-acre grove were then compared in order to find the best real-time sensor-based estimator of fruit yield and therefore fertilizer requirement. Young tree fertilization requires particularly fast canopy sensing and a ‘look-ahead’ feature that is automatically synchronized with ground speed. We tested two different ‘look-ahead’ control systems using either wheel rotation encoders or the Differential Geographic Positioning System (DGPS) to determine ground speed. Both field measurements and simulations demonstrated that a well-tuned fertilizer spreader with high-speed sensors, control electronics and hydraulics can precisely fertilize any tree size from resets to mature hedgerows. The fertilizer doses applied automatically to a range of young non-bearing reset tree sizes approximated the IFAS-recommended rates.

Precision Agriculture Technologies for Control and Monitoring Aldicarb Application. Masoud Salyani, William M. Miller, Sherrie Buchanon, and Roy D. Sweeb, CREC, Lake Alfred, UF/IFAS.

In Florida citrus, aldicarb (a soil-applied pesticide) has been found very effective in controlling certain insects, mites, and nematodes. However, due to its high toxicity and concerns about leaching into ground water, its applications require a 300/1,000 ft (91.4/304.8 m) buffer zone around all drinking water wells. A prototype machine was fabricated that featured both ground- and motor-driven mechanisms, commonly used in citrus applications. The machine was equipped with various controllers and electronic circuits. Three Digital GPS-based approaches were investigated. The first consisted of a DGPS antenna and a low-cost data logger. It could record latitude, longitude, and On/Off status of the discharge mechanisms for monitoring purposes. The second system used a pocket computer with variable rate (VRA) software. With this system, it was possible to achieve On/Off control of both discharge drives based on prescription map. The third system utilized a more sophisticated VRA controller, which allowed detailed operator-machine interface. It could generate variable rate maps and information on application rate, acreage, and total material usage. This paper reports on performance evaluation of the three systems under simulated field conditions. Each system showed certain merits and limitations but all were capable of providing spatial information on actual product application.

The Impact of Harvest Timing on Fruit Quality, Yield and Next Year’s Crop. L. Gene Albrigo, CREC, Lake Alfred, UF/IFAS.

Following the freezes of 1980, numbers of processing and packinghouses were decreased as a result of reduced availability of fruit. At the same time, the shift from FCOJ to NFC required increased cold storage capacity as more juice was being held as single strength. Processors preferred for growers to delay harvest and hold fruit on the tree rather than increase processing storage capacity. Several adverse conditions for the grower resulted from these circumstances and decisions. Late season harvests result in more pre-harvest drop along with reduced juice content and higher ratios of the remaining fruit. These ratios are usually above the preferred range for best consumer acceptance. Finally, later harvests reduce the next years crop because the current crop competes for carbohydrates needed for subsequent flower bud formation and fruit set. ‘Valencia’ orange trees are the most severely affected, but data show that ‘Hamlin’ oranges and grapefruit are also adversely affected. Problems and costs from these practices to growers and potential solutions to minimize such problems will be discussed.

A Grower’s Perspective of Constraints on Harvest Management. Peter McClure, Evans Properties, Inc., St. Lucie County.

The move to NFC orange juice can be seen as beneficial for Florida growers by providing us a competitive advantage over more distant competitors. This has caused a desire by processors to extend the harvest season so fruit can be stored on the tree. This increases management and logistical problems along with costs to growers. Harvesting costs often double because of increased competition for seasonal labor, warm weather related poor working conditions, and because fruit store better on older, larger trees than on small trees. High temperatures and humidity coupled with increasing fruit senescence reduces fruit in-trailer storage time, which increases logistical problems with picking and hauling. Early or late harvest can reduce total pounds solids per acre and thus reduce grower returns. Late harvest can adversely affect the yield and return of the following crop. Harvesting during the rainy season can exacerbate disease control. Possible solutions to the on-tree storage/extended season problems include premiums paid to growers for early and late fruit, better communications and logistics in picking and hauling, better tree size control and crop management, improved disease management, improved scion varieties and rootstocks, abscission chemical registration, and improved mechanical harvesting techniques.

Harvesting methodology economics and constraints to consider. F. Roka, SWFREC, Immokalee, UF/IFAS.

Mechanical harvesting technology offers the potential to significantly reduce harvesting costs. Hopes of lower harvesting costs with mechanical systems rest on the concept of economies of scale, the spreading of the fixed amount of ownership and other non-operational costs over an increasing number of units of harvested boxes. The concept of economies of scale is straightforward and intuitively simply but achieving that reality within the current state of the Florida citrus industry is exceedingly difficult. Maximum economy of scale will at the very least, capturing the full economic potential of mechanical harvesting and will force the Florida citrus industry to rethink some of the fundamental relationships that traditionally held growers, harvesters and processors together. Meeting the efficiency requirements of mechanical harvesting systems will impose constraints on growers and processors that were never imagined when using conventional hand harvesters. Examples of these constraints will be discussed.

Logistic Issues Associated with Mechanical Harvesting. Thomas H. Spreen, Food and Resource Economics, Gainesville, UF/IFAS.

A shift from hand harvesting to mechanical harvesting of processed citrus offers several challenges for coordination of harvest scheduling with processing plant scheduling. In the present system, the rate at which fruit is harvested can be easily adjusted to meet the needs of the processing sector. Since the marginal cost of hand harvest is mostly labor, harvesters can adjust to fruit demand by processors simply by adding or subtracting the number of pickers. The key to costs of a mechanical harvesting system, however, is to maximize the number of hours that the harvester machine operates. In addition, the rate of fruit removal associated with mechanical harvest is far greater compared to hand harvest. These two factors will likely lead to a coordination problem between harvesters and processing plants. In this paper, the coordination problem is discussed and possible resolution of the problem is presented.

Managing Harvesting Constraints as a Fruit Buyer: a Collective Viewpoint. Robin Bryant, Magnolia Consulting Inc., Palmetto.

Many constraints are introduced into the harvesting process that must be managed by a fruit buyer. Each juice processing plant has daily load allocations that must be met, but not exceeded. These load allocations may also change during a day based on processing capacity or plant breakdowns. Beyond load allocations, a fruit buyer must manage against changes in underlying fruit quality as defined in contracts. In addition, most growers have some expectation of the timing for harvesting their crop. Finally, management of resources including labor and equipment must be considered. Sufficient amounts of work and monetary compensation must be maintained to prevent hand labor from moving to another harvesting crew. Many times, the acquisition of labor requires the use of complex government programs with their own combinations of limitations. Each of these can have an impact on the fruit quality during the season and grove production in the next season.

Harvesting Requirements of Citrus Juice Processors for NFC and FCOJ Quality. Fran Becker, Peace River Citrus Products. Abstract not Available.

Potential Harvesting Solutions for the Florida Citrus Industry to Maintain Juice Quality and Grove Productivity. Robin Bryant, Magnolia Consulting Inc., Palmetto.

With the continual reduction in the number of processors in the Florida citrus industry, the available processing and storage capacity continues to decrease. Growers and harvesters are being asked to extend the harvesting season later each year in order to compensate for these decreases. As an industry, growers, processors, and harvesters need to determine ways to efficiently utilize the available capacities while maintaining juice quality and grove productivity. By implementing new technologies for mechanical harvesting and quality prediction, a more consistent and higher quality product can be delivered to the consumer.

Converting Soil Phosphorus Readings Based on Mechlich-3 Extraction Method into Mechlich-1 in Two Florida Flatwoods Citrus Groves. Esa Ontermaa, Lykes Bros. Inc., Lake Placid.

The Mechlich-3 soil phosphorus extraction method (M3-P) is more versatile than Mechlich-1 (M1-P) and is reported to accommodate a wide range of soil conditions. Yet, adoption of the M3-P by Southern States has been slow. To benefit from the versatility of the M3-P in Florida, a farmer either has to accept the recommendations devised by commercial soil testing laboratories or must convert the M3-P readings into M1-P values and then apply appropriate soil nutrient recommendations. The relationship of M1-P to M3-P varies markedly between nutrients and appears to be distinct to each region of the US where studies have been made. This suggestion of local dependency was confirmed by this study where 105 soil samples taken from two citrus groves less than 20 miles apart showed the conversion equation from M3-P to M1-P to be distinctly different for each location. In a grove with sandy soils, the linear regression between methods resulted in an R-square of 0.29 and the slope of 0.28. Regression using a natural logarithm transformation increased the R-square to 0.41. In a second grove with loamy soils, the regression resulted in an R-square of 0.53 and a slope of 0.79. We found M3-P > M1-P when soil pH <= 6.3 and when pH > 6.3, M1-P > M3-P. The average pH for soils with pH > 6.3 was 6.95. These observations suggest that soil pH is a more significant factor influencing an increase of Mechlich-1 P over Mechlich-3 P than soil P concentration.

Fertilization of Young ‘Minneola’ Tangelo Trees on Bedded Groves with Banded Poultry Litter Overlaid with Wood Chips. J. Ferguson, Horticultural Sciences Dept., Gainesville, UF/IFAS; M. Ziegler, Agricultural Resource Management, Vero Beach; J. Hebb, St. Lucie County Extension Service, Ft. Pierce, UF/IFAS and W. Graves, Tetley Groves, Vero Beach.

Poultry litter is usually disked into the soil to conserve nutrients but such soil incorporation can damage surface roots of citrus trees grown on bedded groves. Using an alternative application method, young ‘Minneola’ tangelo trees on Cleopatra mandarin rootstock on bedded groves in southeast Florida were fertilized for 18 months after planting. Surface-banded poultry litter (PL) was overlaid with wood chips (WC). PL was applied at 12.5, 25, or 37.5 tons per treated acre in a 2-ft wide band within the dripline and overlaid with 25, 50, or 75 tons of WC twice a year. Other treatments included poultry litter applied at 25 tons per treated acre to a 10-ft wide strip in the middle of the bed twice a year and 1 lb of controlled release fertilizer (10-3-7) applied three times per year within the dripline. After 18 months, trunk diameter and plant height were generally similar except for trees to which poultry was applied in the bed middle, suggesting that the lowest PL/WC rate was adequate for tree growth during this time. Percent soil organic matter measured beneath the PL/WC treatments did not increase but leaf P, K, Ca, Mg, and Fe levels were excessive. Total per unit N input costs per year were higher for banded PL/WC and broadcast PL treatments than for the controlled release N treatments. Total cost per treated acre was greatest for the highest PL/WC rate and lowest for the controlled release fertilizer.

The Basis for Citrus Nitrogen Fertilization Recommendations. K.T. Morgan, Southwest FL REC, Immokalee, UF/IFAS; T.A. Obreza, Soil and Water Science, Gainesville, UF/IFAS and T.A. Wheaton, CREC, Lake Alfred, UF/IFAS.

A survey of drinking water wells conducted in Florida between 1988 and 1991 found that nitrate nitrogen (NO₃-N) concentrations in surficial well water near citrus groves on Entisols in central Florida exceeded maximum contamination levels (MCL) of 10 mg L^-1. Of 3949 drinking water wells surveyed, 2483 (63%) contained detectible concentrations of NO₃-N. Of these contaminated wells, 584 (15%) contained NO₃-N in excess of MCL. The proportion of wells in Florida contaminated with NO₃-N was similar to that of a nation-wide survey, however, the proportion of wells contaminated above MCL was an order of magnitude higher. Eighty-nine percent of wells contaminated above MCL were located in the central Florida counties of Lake, Polk, and Highlands. Citrus in these counties are grown on Entisols which are uncoated sands with low water holding capacities of 0.04 to 0.09 cm³ cm^-3, and are thus particularly vulnerable to nutrient leaching. To reduce potential ground water contamination due to citrus production, best management practices were established and UF/IFAS publication SP169 was written with a recommended N fertilizer application upper limit of 200 lbs N ac^-1 yr^-1 for mature bearing citrus trees. Prior to publication of SP169, the UF/IFAS recommendation was 0.4 lbs N per box of fruit per acre per year based on Bulletin 536D. Publication SP 169 is currently being revised and updated. Based on controlled experiments conducted since 1990, arguments are given for a recommendation based on production levels of soluble solids per acre per year.

Gramoxone Inteon – A New Formulation for Weed Management in Citrus. Shiv D. Sharma and M. Singh, CREC, Lake Alfred, UF/IFAS.

A series of experiments were conducted at different locations to examine the bioefficacy of Gramoxone Inteon. Several common weeds were present but there were different weeds in the mixed flora at different locations. Bioefficacy of Gramoxone Inteon formulation was compared with Gramoxone Max and Touchdown (glyphosate). Gramoxone Inteon at 1.5 and 2 qt/A, Gramoxone Max at 1.0 and 1.3 qt/A, Touchdown at 1.0 qt/A were applied alone and as a tank mix with and Solicam (3.0 lb/A). Non-ionic surfactant X-77 (0.25%) was tank mixed with all the treatments for better spread. Application of Gramoxone Inteon or Max showed almost complete control of grasses and broadleaves weeds even at the lower rates. Highest control was recorded one week after treatment (WAT) and thereafter, percent control values of all weeds were similar until 4 WAT. Addition of Solicam with Gramoxone showed improvement in percent control, however, there was no significant difference with and without Solicam on grasses. In general, the percent control of both types of weeds was significantly higher with any of the Gramoxone formulation than with Touchdown. Both the formulations of Gramoxone proved to be equally good in controlling mixed weed flora in citrus groves. However Inteon formulation has more user-friendly features than Max formulation. This fast, effective herbicide provides broad-spectrum control that is ideal for diversifying a grower’s weed control program. Application of Gramoxone Inteon may also help in minimizing the risk of herbicide resistance management.

Tree Thinning Studies to Improve Production and Harvesting of Florida Oranges.

S. H. Futch, T. A. Wheaton, J. D. Whitney, CREC, Lake Alfred, UF/IFAS.

Since the 1960s, higher density plantings have produced more fruit early in the grove’s life with quicker returns on investment. These groves may decline, however, after trees reach containment size. In a closely spaced Manatee County grove of 9- to 10-yr-old trees (at the beginning of the study) of ‘Hamlin’ or ‘Valencia’ oranges on Carrizo and Swingle rootstock, respectively, selected trees were sheared above the ground to reduce trees per acre and to determine the effects of tree thinning on yield per acre, fruit quality and tree growth. Trees were in hedge rows on two-row beds at 24 feet between rows and 8 feet in-row, providing 227 trees per acre. Tree density was reduced by removing every other or every third tree providing 113 and 151 trees per acre, respectively, and then compared to original hedge rows. For both varieties, yields were significantly reduced with decreased density. Cumulative box yields for ‘Hamlin’ over a 6-year period were 4,813, 4,247, and 3,956 for densities of 227, 151 or 113 trees per acre, respectively. Likewise, cumulative box yields for ‘Valencia’ over a 5-year period were 2,863, 2,319, and 1,998 boxes for the same densities. Harvesting efficiency increased with tree removal compared to hedgerow. Tree growth, as measured by trunk circumference, was greater for both varieties with decreasing tree density. During the 6 year study period, high density hedgerows provided highest cumulative yields with differences between treatments decreasing with time.

1-Methylcyclopropene Improves Selectivity of Ethephon Foliar Abscission Sprays in Citrus. Luis Pozoand Jacqueline K. Burns, CREC, Lake Alfred, UF/IFAS.

1-Methylcyclopropene (1-MCP) is a gaseous ethylene binding inhibitor used to control or delay ethylene-related postharvest problems in a range of horticultural commodities. To evaluate the potential of 1-MCP to prevent unwanted defoliation when using ethephon to loosen mature citrus fruit, branch and canopy sector tests were conducted in ‘Hamlin’ and ‘Valencia’ orange [Citrus sinensis (L.) Osb.] using 400 mg^.L^-1 ethephon (chloroethyl-phosphonic acid) in combination with 1, 2.5 and 5 mM 1-MCP. Although no difference in mature fruit loosening was measured between ethephon alone and ethephon + 1-MCP treatments, 1-MCP reduced defoliation and gummosis caused by ethephon. Combining 1-MCP with ethephon in the spray tank followed by application to the canopy was more effective in controlling unwanted defoliation when compared with 1-MCP applications 24 h before or 24 h after ethephon application. Subsequent studies on the effect of 1-MCP + ethephon application on flower and fruitlet abscission demonstrated unwanted abscission in these organs could also be reduced. The results suggest that ethephon-induced phytotoxicity can be reduced with 1-MCP, but the gaseous nature of 1-MCP is an impediment to uniform application. A sprayable 1-MCP formulation is being developed for preharvest use in many horticultural crops.

Defoliation after Harvest with a Trunk Shaker Does Not Affect Canopy Light Interception in Citrus Trees. Kuo-Tan Li, Jim Syvertsen, and Jill Dunlop, CREC, Lake Alfred, UF/IFAS.

Tree productivity can be directly related to light interception by the canopy. To determine the effects of defoliation and twig loss during mechanical harvesting on canopy light interception, we measured mid-day interception of direct and total light by mature ‘Hamlin’ and ‘Valencia’ sweet orange trees (Citrus sinensis) with a 16.3 m²point-grader and a photosynthestically active radiation ceptometer. Light interception measurements were made before and after harvest either by hand or with a linear-type trunk shaker. Leaves and twigs removed during harvest were collected to estimate defoliation and twig loss. Canopy volume and leaf area the following year were estimated. Before harvest at solar noon, well-developed citrus tree canopies intercepted 80% of the direct light and 88% total light per projected area of canopy. Although excessive trunk shaking can remove up to 15% leaf area compared to about 2% by hand harvesting (Li et al., 2005), little change in mid-day canopy light interception before and after harvest were recorded regardless of the harvest method. Canopy volume and total leaf area the following year were not correlated to previous harvest methods. The partial removal of leaves and old twigs by trunk shaking might have improved ventilation and light availability to the inner canopy and thus compensated for the loss of leaf area.

Improving Efficacy of Abscission Sprays for Mechanically Harvested Oranges.

Jacqueline K. Burns, Luis Pozo, CREC, Lake Alfred, UF/IFAS; Kelly Morgan and Fritz Roka, SWFRC, Immokalee, UF/IFAS.

The selective abscission compound 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) improves mature fruit removal of mechanically harvested orange trees in Florida. Uniform fruit removal depends on peel contact by CMNP sprays. With conventional air-blast (AB) sprayers, the increase in nozzle-to-tree distance as tree height increases often results in variable upper canopy coverage and reduced spray penetration. As a result, fruit removal is variable, especially in denser canopies. We compared efficacy and fruit removal when CMNP was applied with an AB or a novel ‘GreenTech’ (GT) sprayer. The GT sprayer uses a 5.5 m (18’) vertical boom with 6 independently-powered fan/nozzle assemblies that can be adjusted to the canopy contour, improving coverage and spray penetration. CMNP (250 mg^.L^-1) was applied at 1873 and 2810 L^.ha^-1 (200 and 300 gal^.acre^-1) with the AB or GT sprayers to ‘Hamlin’ orange [Citrus sinensis (L.) Osb.] in Immokalee, FL. Four days after application, fruit detachment force (FDF) at 1, 2 and 4 m (approx. 3’, 6’ and 12’) height at inside and outside canopy positions were determined. Fruit from GT-sprayed trees had low and uniform FDF at all canopy locations and heights. In contrast, fruit from AB-sprayed trees had greater variability in FDF, especially at the top and inside the canopy. Fruit were mechanically harvested using a trunk-shake-and-catch system. Mature fruit removal was greater and less variable in GT-sprayed than AB-sprayed trees. The results demonstrate that uniform CMNP coverage can minimize variation in efficacy and improve mature fruit removal of trees harvested with a trunk shaker.

Microbiological Evaluation of Mechanically-Harvested Citrus Fruit. R.M. Goodrich and R. Ehsani, CREC, Lake Alfred, UF/IFAS.

For Florida to effectively compete in the world citrus industry, significant reductions in harvesting costs will be necessary. Mechanical harvesting can be thought of a two-step process: removal of fruit from the tree and retrieval from the ground and/or collection area. A citrus fruit pick-up machine developed by OXBO International Corp. is being evaluated for its picking rate, picking efficiency, field capacity, and its efficiency for removing undesirable fruit and leaf trash. The performance test is being conducted under different ranges of forward speed, orange varieties and grove conditions. A UF-IFAS machine is also being evaluated for the same criteria. This study evaluates the microbiological aspects of mechanically-handled fruit with respect to fruit surface microflora. Three treatments were evaluated: hand-harvested fruit (control), mechanically-harvested fruit (picked up directly from ground) (MH fruit), and mechanically-harvested fruit in combination with the OXBO or UF-IFAS pick-up machine (MH/PU fruit). Microbial analysis included total plate count (TPC), acidophilic organisms (OSA), generic E. coli (as an indicator of potential contamination) and Salmonella. In general, hand-harvest control fruit had fewer microbes on the surface of the fruit than either MH or MH/PU fruit. Neither E. coli nor Salmonella were detected in any of the samples. There were substantial and significant differences between the two fruit surface microflora runs conducted to date which may be due to a variety of factors including the differing mechanical action of the machines, weather, equipment sanitation, grove location and tree/fruit treatments during production.

Processing and Handling Section

Disaster Response for Retail and Distribution Center Perishable Product Companies. M. T. Talbot, J. P. Emond, Agricultural and Biological Engineering Depart., UF/IFAS.

The mission of the Center for Food Distribution and Retailing (CFDR) is to provide the food industry and the scientific community with a unique environment for developing knowledge that will assure food quality and safety through the whole distribution chain. In light of recent large scale disasters and the potential for future natural and man-made disasters, a need was identified to develop a new initiative related to disaster response for retail and distribution center perishable product companies. This project will expand the CFDR mission and there is excellent potential for coordination with the Extension Disaster Education Network (EDEN). This new research project area is presented, including potential partners (FDEM, DHS/FEMA, DoD, USDA, NASA). Initial project activities include assessment current impact of disasters on the whole retail food chain, inventorying existing plans for post disaster activities, fact-finding industry working groups to develop dialog, with the overall objective of establishing industry norms and areas of research needed. Potential projects could investigate movement of perishable products prior to the disaster, providing mobile electric energy capability, use of short-term cryogenic cooling, certification of food quality for redistribution, decontamination of food materials if required, alternatives to a land-fill disposable of destroyed food materials, methods to improved food resupply and distribution to the disaster area from distance sources. Industry input will assist with establishing project priorities and determining the state of the industry in dealing with the food distribution system disrupted by disasters, methods to maintain refrigeration cooling energy during disasters, efficient and economical waste disposal, etc.

Living with Citrus Canker and Citrus Greening – How will Florida’s Citrus Industry and its Regulators Respond? Mark Estes, FDOACS, DPI: Bureau of Pest Eradication and Control, Winter Haven, FL.

Since 1915, Florida’s citrus industry has battled citrus canker by eradication. The first two canker campaigns were successful, but the most recent effort, entitled the “Citrus Canker Eradication Program” (CCEP), was suspended on January 10, 2006. The decision that the eradication program was no longer feasible resulted largely from scientific predictions of the effects of Hurricane Wilma presented by USDA ARS Scientists, Dr. Tim Gottwald and Mike Irey. These predictions showed that up to 220,000 acres, in addition to the 80,000 acres associated with previous hurricanes, would be lost under current protocols. With USDA’s withdrawal of funding, irrepressible disease spread during legal battles, and the hurricanes of 2004 and 2005, enforcement of the 1900 foot rule and mandatory destruction of trees was officially suspended. However, with guidance from USDA, FDACS, UF- IFAS and industry stakeholders, a new plan, named the “Citrus Health Response Plan” (CHRP), is evolving which combines both citrus canker and greening disease management. The first official draft of the CHRP was released on March 6th, and work has continued to rapidly sort out details of the new program and to stimulate state and federal legislation in support of the industry. The process and outcome of these negotiations are discussed, along with developing protocols designed to sustain the viability of the citrus industry in Florida.

Potential of a New Reduced-Risk Fungicide Fludioxonil for Postharvest Decay Control of Florida Citrus Fruit. Jiuxu Zhang, Florida Dept. of Citrus, Lake Alfred, FL.

Fludioxonil is a reduced-risk, and newly registered compound for the postharvest disease control of fresh fruits including citrus. The efficacies of fludioxonil for the control of stem-end rot and green mold caused by Lasiodiplodia theobromae and Penicillium digitatum on Florida citrus fruit were evaluated. Fludioxonil actively suppressed the mycelial growth of both pathogens. The ED₅₀ of fludioxonil against L. theobromae and P. digitatum was 0.033 and 0.034 ppm, respectively. Application of fludioxonil at rates of 500 to 1,200 ppm using a simulated commercial drench system before fruit degreening with ethylene reduced stem-end rot incidence by 85.5 to 93.7%, which were similar to the results obtained from standard postharvest fungicide thiabendazole or imazalil at 1,000 ppm. Aqueous application of fludioxonil at 1,000 ppm using a simulated commercial packingline reduced the incidence of green mold and stem-end rot by 73.4% and 74.3%, respectively. The efficacy of fludioxonil for decay control was reduced when it was mixed with a packing wax. Fludioxonil appears to provide good potential for postharvest disease control on Florida citrus. Fludioxonil could also play an important role in fungicide resistance management since it has a different mode of action compared to thiabendazole and imazalil.

FreshSeal ® CHC Reduces Shrivel and Decay of Pepper (Capsicum annum). Mark A. Ritenour, IRREC, UF/IFAS, Fort Pierce; Mark P. Kohout, Paul Johnson, and Huating Dou, BASF Corporation, Dinuba, CA

BASF FreshSeal® CHC is a naturally occurring, polymer-based postharvest coating, and has been commercially applied to many horticultural crops including tomatoes and peppers. Experiments were conducted to evaluate the effects of FreshSeal® CHC application on postharvest quality retention of fresh peppers (Capsicum annum) in Florida. Packed cartons each containing approximately 80 ‘medium’ green bell peppers grown in the West Palm Beach / Wellington area were obtained on 1 March 2006 from a commercial packinghouse and treated within 24 hours of harvest. The cartons were randomized and the peppers treated with FreshSeal® CHC (0.5% a.i.) or water (control) by hand sprayer, or by running over a small packingline brush bed. Hand applications completely wet the pepper surface, whereas brush applications covered approximately 70% of the pepper surface. The peppers were then stored for 6 days at 45^oF before transferring to room temperature (~76^oF). Fruit were weighed, inspected for visible mechanical injury, and evaluated for shrivel and decay 7 days after treatment, and then following an additional 2 days at room temperature. The experiment was a factorial design with two factors (treatment and application method) and five replicates (cartons). Peppers treated with FreshSeal had about 38% less shrivel than the control on day 7, and about 21% less shrivel and 52% less cumulative decay than the control at the end of the experiment. Pepper water loss was not significantly different between treatments or application methods. While brush application in general significantly increased cumulative decay, there were no significant differences in shrivel between hand and brush applications.

BASF FreshSeal ® Postharvest Coating Extends Tomato Shelf-Life and Increases Saleable Fruits. Huating Dou, Mark Ritenour, Paul Johnson, and Mark Kohout, BASF Corp., Dinuba, CA; Steven Sargent, Horticultural Sci. Depart., UF/IFAS.

During the past two seasons, the effect of BASF Freshseal postharvest coating in round tomato shelf-life was investigated in eight trials in commercial packinghouses. Fruit were examined under the observation of packinghouse staff . Two trials were conducted at University of Florida (UF) in the year of 2005. The fruit color development, shriveling, and decay incidence were investigated in these trials since they are the major packer’s concern in postharvest from the commercial standpoint of view. The trials conducted at UF showed only four of the control fruits and one of mineral oil treated fruit succumbed to decay while no FreshSeal fruits developed decay. The trials are repeating this season to demonstrate concrete evidence that FreshSeal imparts resistance to decay. The five trials in Virginia indicated a general reduction of postharvest loss (decay and shriveling) from 10% in mineral oil waxed fruits to 2-3% of Freshseal coated fruits 12-14 days after storage at 45 F and 85% relative humidity. The trials conducted in January in South Florida reduced total postharvest loss from 39% in waxed fruits to 26 % in FreshSel treated 14 days after storage at 45 F and %RH. The results indicate an increase of total 3 -9 saleable fruits per 60 fruits carton. Assuming that per 60 fruits box cost $20 at the retail level, Freshseal application increases the economic-return of $ 1.00 to 3.00 per carton. In addition to the previously discussed results, Freshseal application accelerates fruit color development at least 1 stage earlier than waxed fruits. This benefits the primary packer/handler as well as the re-packer by a flexible transiting of fruits during the postharvest marketing period.

Edible Coatings for Lychee Fruit to Maintain Color in Storage. Anne Plotto, Jan A. Narciso, and Elizabeth Baldwin, USDA/ARS, Citrus & Subtropical Products Laboratory, Winter Haven, FL; Nithiya Rattanapanone, Dept. of Food Science and Technology, Chiang Mai University, Thailand.

The bright red pericarp of lychee (Litchi chinensis Sonn.) fruit quickly turns brown after harvest due to peel dehydration, anthocyanin degradation, and fungal growth on the fruit surface. Lychee fruit, cv. Mauricious and Brewster from Florida, and Hong Hauy and Juckapat from Thailand, were dipped in acidic treatments (2-3% citric acid, 2% ascorbic acid, 2% acetic acid, 1% isoascorbic acid), antioxidants (0.5% acetylcysteine, 0.02% hexyl-resorcinol), antimicrobial treatments (peroxyacetic acid (Storox), 5 or 20% ethanol) and various coatings (chitosan, carrageenan, hydroxypropylcelulose [HPC], sucrose fatty acid esters, pectin oligomers, carnauba wax), alone or in combination. Ascorbic and citric acid gave the best results in the Thai experiments. HPC performed well on the Thai fruit, but not on the Floridian fruit. In the Florida experiments, the mixture of isoascorbic acid with acetylcysteine and hexylresorcinol, and 5% ethanol consistently gave higher chroma readings with the L*a*b* color measuring system, indicating higher color intensity. Ascorbic acid, isoascorbic acid, and acetylcysteine alone gave higher chroma in one experiment. Visual evaluation was higher for these treatments after 15 and 21 days storage at 5 °C, as well as for the sucrose fatty acid ester. There was a high anthracnose (Collectotrichum spp.) pressure for the Florida harvested fruit in the first year, and in the second year, Collectotrichum and Alternaria were isolated from the fruit surface. Future efforts will also aim at reducing pathogen pressure in the field, as well as after harvest.

Atmospheric Change and Broccoli Floret Quality in Plastic Containers Maintained under Simulated Household Refrigerator Temperatures. Guiwen W. Cheng, Donald J. Huber, and Steven A. Sargent, Horticultural Sciences Dept., UF/IFAS.

The dynamic changes in atmospheric composition and the quality of broccoli florets in plastic containers under household conditions have not been studied. The objectives of this study were to monitor CO₂ and ethylene accumulation in unvented and vented (a port in the lid) plastic containers with broccoli florets under simulated household conditions. Within unvented containers, carbon dioxide concentration rose quickly to >20% at 10^oC and to >8% at 4^oC after 3 days and 39.6% at 10^oC and 30.8% at 4^oC after 6 days. With vented containers the headspace CO₂ was maintained at or below 3%. Ethylene levels were much lower in vented than unvented containers but did not exceed 0.3 ppm in any of the treatments. Higher weight loss was observed with vented containers as storage time extended. The florets degreened quickly in vented containers. Strong sulfurous odors developed in unvented containers but not in vented containers. The accumulation of CO₂and ethylene was positively associated with the amount of florets in the sealed containers but not in the vented containers. The presence of an ethylene scrubber prevented the accumulation of ethylene in both unvented and vented containers. However, reduction of container ethylene levels had no evident effect on of CO₂accumulation. The results indicate that the quality of broccoli florets kept in household plastic containers can be best preserved through a proper built-in ventilation.

Resistance to Postharvest Fungicides in Florida Citrus Packinghouses. David J. Hall, Agri-Chem Consulting, Clermont, FL.

Developed resistance to postharvest fungicides are a serious problem in many citrus packing areas. Florida has apparently avoided this problem for many years. During the past 25 years resistant mold assays have been conducted in Florida citrus packinghouses. While rarely encountered, those cases where resistance was encountered can help understand how the problem nay be avoided.

Enzyme-peeled Oranges for Fresh-Cut Slices. Simona Pinnavaia, IVTPA, Via Venezian 26, Milano, Italy; Anne Plotto, Elizabeth Baldwin, and Jan Narciso, USDA/ARS, Citrus & Subtropical Products Laboratory, Winter Haven, FL 33881

Oranges can be satisfactorily processed for fresh slices using a process of enzyme infiltration under vacuum. Scored ‘Valencia’ and ‘Hamlin’ oranges were placed under 90 kPa vacuum in a 0 ppm (water-infused) or 1000 ppm enzyme solution (Ultrazyme) at 30 °C for 2 min, followed by 30 min incubation in air. Peel was then removed, peeled fruit were washed, blotted dry, cut, and slices were then dipped in water or 1% citric acid (CA) for 2 min. Drained slices were then placed in 16 oz deli containers and stored at 5 °C for up to 21 d. One additional treatment involved vacuum infiltrating scored oranges in 1% CA, without further dipping the cut slices. All ‘Valencia’ slices had <1.0 log₁₀(cfu/g) after 7 d storage, and fruit infused without enzyme but with CA had <1.0 log₁₀(cfu/g) after 21 d storage. For ‘Hamlin’, CA controlled bacterial growth on slices from water-infused oranges, except at 14 days. Enzyme-infused oranges resulted in slices with lower counts in both experiments. CA –treated sliced (post enzyme treatment or by infusion) had higher titratable acidity initially (‘Hamlin’) and after 14 days (‘Valencia’). When presented to a taste panel, ‘Valencia’ slices from enzyme-peeled fruit were preferred for texture after 2 and 8 d in storage. In contrast, slices from fruit infused with water or citric acid were least preferred, were firmer, and had thicker membrane. Appearance of enzyme-treated fruit was preferred for ‘Hamlin’ oranges. Enzyme or CA treatments did not affect overall flavor of ‘Valencia’ or ‘Hamlin’.

Fumigation of Tomato Fruit with Chlorine Dioxide: Dose Affects Fruit Quality. M. J. Mahovic *, J. A. Bartz, Dept. of Plant Pathology, UF; A. D. Berry and S. A. Sargent, Horticultural Sciences Dept., UF/IFAS, Gainesville, FL.

Chlorine dioxide (ClO₂) gas has been proposed as a fumigant for fresh market tomatoes. Treatment with 1 to 2 mg of ClO₂/kg of tomato produced a major reduction in recoverable bacterial populations and in the incidence of soft rot in inoculated wounds. However, treatment with up to 99 mg/kg led to a bleaching and damaging desiccation of wounds and stem cars. In this study, standard round tomatoes (cv. “Florida 47” for field pack, all others cv. “Soraya”) from three commercial harvest/handling steps were treated with two concentrations (standard and 10× standard) of ClO₂ and then ripened. Tomatoes samples were: 1) harvested at light-red stage, 2) harvested green from field bins (prior to transfer to dump tank, and 3) at green