Canopy-shaking mechanical harvesters are increasingly being used in Florida to harvest process oranges. Current canopy shaker machines use a series of six- to seven-foot long tines to shake the tree canopy at a relatively constant shaking stroke and frequency. The goal of this study was to evaluate the actual detachment force exerted on oranges at different locations in the tree canopy while harvested by a tractor-driven canopy-shaking harvesting machine. A multi-node, ZigBee-based wireless mesh-network sensor was developed for this study. Each sensor node was equipped with a 3-D accelerometer sensor. Sensors were placed at various locations in the tree canopy. The field experiment was conducted in different groves with a tractor-drawn canopy shaker. The maximum vibration force and detachment of the fruits were measured at different locations and the pattern of force distribution throughout tree canopy were studied.

10:15 Daily fluctuations in fruit detachment force of Valencia orange are related to temperature and relative humidity.

L. Pozo, A. Malladi, F. Alferez, Y. Lluch, and J.K. Burns, CREC, UF/IFAS [C2]

The force required to remove orange fruit from their stems (fruit detachment force, FDF) is closely related to fruit development. FDF increases from fruit set through peel color break. Thereafter, FDF remains relatively stable throughout the maturation stage, but then declines as fruit senescence proceeds. Throughout the course of our research addressing topics related to abscission, we noted differences in FDF that were dependent upon the time of day measurements were taken. We hypothesized that these daily fluctuations in FDF were correlated with environmental conditions such as temperature and relative humidity. To test this, FDF was measured at 8 am, 11 am, 2 pm and 5 pm for five consecutive days each month, starting in January 2007. FDF readings were taken using five, 10-fruit-replicates harvested from five 6-tree plots. The plots were located within a 17-year-old Valencia grove (Citrus sinensis grafted on Swingle) at the Citrus Research and Education Center/UF, Lake Alfred, Florida. Fruit weight, juice content and soluble solids/acids ratio were determined for samples harvested at 8 am and 2 pm. Hourly averages for temperature, relative humidity, solar radiation and wind speed were provided by University of Florida’s Florida Automated Weather Network (FAWN) for the Lake Alfred location. The results indicate that daily fluctuation in FDF changed 1 to 1.5 kg-force in a period from 8 am to 5 pm daily. The fluctuations were correlated with temperature and relative humidity in that order, and to a lesser extent with solar radiation and wind speed. Furthermore, FDF fluctuations were correlated with fruit weight and juice content, perhaps due to changes in diurnal variations in fruit water content. These results demonstrate that FDF throughout a given day are not static, and that daily changes in FDF are associated with temperature, relative humidity and fruit weight.

10:30 Reconciling grower and processor objectives when deciding to harvest juice oranges.

Jake Searcy, Fritz Roka, and Thomas Spreen, Food and Resource Economics, UF/IFAS. [C3] (Student Competition)

Growers of processed oranges are paid on the total amount of pound-solids they produce. Hence, a grower’s preference of when to harvest would be when pound-solids per acre reach their maximum. The actual harvest date for a specific block, however, is set in conjunction with processor objectives as well. Ratio and color are other quality parameters that need to be considered. Operational capacity at a plant and inventory management decisions within the processing firm are other factors that govern harvest schedules. Overlaying both grower and processor objectives are the availability and cost of harvest crews. This paper develops an optimal harvest-timing model that maximizes combined returns of both growers and processors. One outcome of this model will be to analyze the effect of mechanical harvesting systems on harvesting logistics between growers and processors. Current harvesting logistic is based, in part, on hand-harvest labor. A mechanical system improves harvest labor productivity by 10-fold, hence forcing an increase in the daily trailer allocation to a given harvest site.

10:45 Optimum Nitrogen Rate for Fertigated Young Navel Orange Trees in Arizona.

Ayako Kusakabe, Scott A. White, James L. Walworth, Glenn C. Wright, and Thomas L. Thompson, Soil, Water and Environmental Sci., Univ. of Arizona, Tucson, AZ. [C4] (Student Competition)

A field experiment was conducted during 1999-2002 in central Arizona (AZ) to evaluate effects of N rate and frequency on leaf N concentration and residual soil N of 3-6 yr-old ‘Newhall’ navel oranges (Citrus sinensis) on ‘Carrizo’ citrange (Porcirus trifoliate × Citrus sinensis) rootstock. Trees were grown in a calcareous Gilman fine sandy loam and were well-watered with a small positive leaching fraction. The experiment included non-fertilized control plots, and factorial combinations of three fertigation frequencies (27, 9, and 3 applications year^-1) and three N rates (0.15, 0.30, 0.45 lb N tree^-1 yr^-1) from urea ammonium nitrate (32-0-0) applied through microsprinklers. Maximum yields occurred at N rates of 0.23 to 0.34 lb N tree^-1 yr^-1.These rates were equivalent to only 17 to 34 % of currently recommended N rates for flood irrigated citrus grown in AZ. Fruit size and juice quality were not affected by N rate or fertigation frequency. Leaf N concentrations at yield-maximizing N rates were above 2.7 %. During all three seasons, higher concentrations of residual soil NO₃ resulted from the highest N rate. Our results suggest that optimum N rates for microsprinkler-irrigated ‘Newhall’ navel orange trees in AZ are much lower than currently recommended N rates.

11:00 Georeferenced ground photography of citrus orchards for canopy research and variable rate technology.

AW Schumann, JP Syvertsen, and KH Hostler, CREC, UF/IFAS. [C5]

Citrus canopy measurements with ultrasonic and optical sensors are being used in Florida to control the placement and rate of fertilizers and pesticides with variable rate application (VRA) spreaders. Additional refinement of agrochemical VRA may also be possible if fruit load, leaf nutrient stress or water stress could be measured on the tree canopies. Detection of early (mild) water stress before it becomes visible and reduces yield, could be used to schedule irrigation, manipulate flower and leaf flushes, or improve fruit quality. In this study we developed ground-based digital photography systems to study the characteristics of citrus tree canopies over large areas. A color digital camera mounted on a moving vehicle was used to capture georeferenced overlapping images of tree canopy in entire orchards. Images were stored on a laptop PC and were processed using red-green-blue (RGB) pixel ratios and thresholds to identify and quantify ripe fruit and green leaf pixels in order to estimate yield and canopy health. A monochrome digital camera with visible and infrared bandpass filters was used to develop a multispectral imaging system capable of rapidly detecting early water stress on tree canopies. Significant correlations were achieved between the camera system and the stem water potential measurements used for quantifying water stress in citrus trees. Additional applications such as detecting pest or disease damage, hurricane wind damage, or flooding / salinity stress are discussed.

11:15 Effect of winter and spring foliar urea, NPK or K-phosphite sprays on productivity of citrus in Central Florida.

L.G. Albrigo, CREC, UF/IFAS. [C6]

Abstract: Previous work in South Florida indicated that winter bloom and post-bloom nutritional sprays of urea, K-phosphite or NPK mixes resulted in increased yields of citrus on poorer flatwood soils. The issue of whether these sprays could enhance yields of better performing Central Florida groves is addressed by these tests for up to 4 consecutive years on the same trees. In NPK tests, winter urea, and bloom and/or post-bloom NPK mixes in all combinations were applied to navel, Hamlin or Valencia oranges or Flame grapefruit. For P tests, K-phosphite or urea were sprayed during the winter and NK with or without PO₄ or PO₃ were sprayed at bloom and/or post-bloom on Hamlin and Valencia trees in several locations in Central Florida. In the NPK tests, rates ranged from 8 to 16 lbs of urea N/ac/spray with either 4 or 8 lbs of P and K. In the P tests, 0, 2.4 or 8 lbs of P (8 lb rate for PO₄only) were used with 16 lbs N as urea and 8 or 10 lbs of K. In the NPK tests, no significant differences were found in 8 or 17 comparisons (years times sites). In 9 tests (years time sites), NPK applications at bloom or post-bloom had significantly higher or near the highest yields. In 7 cases, treatments that included winter urea were near the lowest yields. For the P tests, 10 of 14 sites had no significant differences in yield. In one test, the control was highest and in another test it was significantly lower than any other treatment. Although there were significant differences in some tests in some years, no consistent pattern was discerned to suggest that foliar sprays of NPK solutions increase yields on blocks that are producing well on standard ground applied fertilizer programs.

11:30 Citrus Water Requirements: Linking Irrigation Scheduling and Fertilizer Strategies.

K.T. Morgan, SWFREC, UF/IFAS. [C7]

Florida citrus trees must be irrigated to reach maximum production due to the low soil water-holding capacity of our sandy soils. Nutrients, especially nitrate-N, move rapidly through theses sandy soils with drainage of excess water. In a highly urbanizing state with limited water resources, improved understanding of soil water uptake and movement is needed to optimize irrigation without leaching nutrients and impacting water quality. In a 25-month field study using mature ‘Hamlin’ orange (Citrus sinensis L.) trees, ET_c averaged 1137 mm yr^-1, and estimated K_c ranged between 0.7 and 1.1. Day of year explained more than 88% of the variation in K_c when soil water content (q) was near field capacity. The value of K_s decreased steadily from 1.0 at field capacity (q = 0.072 cm³ cm^-3) to approximately 0.5 at 50% available soil water depletion (q = 0.045 cm³ cm^-3). Roots were concentrated in the top 30 cm of soil under the tree canopy (0.71 to 1.16 cm roots cm^-3 soil), where maximum soil water uptake decreased as soil water content decreased. Estimating daily plant water uptake and resulting soil water depletion based on root length density distribution under a citrus tree would provide a reasonable basis for a citrus soil water balance. It has been demonstrated that nutreint uptake is relatively rapid in citrus. However, leaching of nutrients by over irrigation must be avoided for several days after fertilizer application. Using a water balance, irrigation amounts can be estimated that would provide adequate water for nutrient uptake and reduce leaching from over-irrigation.

11:45 Effect of Water Management and Soil Application of Nitrogen Fertilizers, Petroleum Oils, and Lime on Inoculum Production by Mycosphaerella citri, the Cause of Citrus Greasy Spot.

S.N. Mondal, K.T. Morgan, and L.W. Timmer, CREC, UF/IFAS and SWFREC, UF/IFAS. [C8]

Greasy spot, caused by Mycosphaerella citri, produces leaf spots and defoliation of citrus trees reducing tree vigor and yield. The fungus produces air-borne ascospores from pseudothecia in decomposing leaf litter on the grove floor. Factors affecting production of inoculum on decomposing leaves were evaluated. Pseudothecial formation and ascospore production increased as greasy spot severity on the leaves increased. Applications of urea, dolomite, or increased irrigation on frequency to leaf litter all reduced inoculum production by 70 to 90 %. Of the N fertilizer materials evaluated, urea and ammonium sulfate were very effective in reducing inoculum, ammonium nitrate less so, and potassium and calcium nitrate were ineffective. Effects of ammonium fertilizers are thought to be due to the toxicity of ammonia gas to the fungus. Soil surface applications of petroleum oils were also reduced inoculum, but had to be applied in large volumes of water for maximum effectiveness. These measures may provide a practical method of reducing inoculum levels and controlling greasy spot and reducing fungicide applications to foliage, but inoculum levels must be reduced greatly to delay symptom development and reduce disease severity.

1:30 The Relative Salt Tolerance Of ‘Rangpur Lime’ Seedlings And ‘Arbequina’ Olive Cuttings.

J. C. Melgar, J. P. Syvertsen, CREC, UF/IFAS,V. Martinez and F. Garcia-Sanchez, CEBAS-CSIC, Murcia, Spain. [C9]

The salinity tolerance of citrus rootstocks varies but citrus trees are generally considered to be more sensitive to salinity stress than olive trees that are usually grown from cuttings. We compared the salt tolerance of six-month-old seedlings of the relatively salt tolerant citrus rootstock, Rangpur lime (Citrus limonia Osbeck) with similar sized rooted cuttings of olive (Olea europaea L. cv. Arbequina). Well fertilized plants were grown in native Candler sand in a greenhouse and watered with either no salt (0 mM NaCl) or 50 mM NaCl for citrus, or with 0 or 100 mM NaCl for olive. Salinity increased Cl^- and Na⁺ content in leaves and roots in both species and reduced total plant growth, net photosynthetic rate and stomatal conductance. High concentrations of Cl^- and Na⁺ caused a decrease in leaf chlorophyll a in citrus but not in olives. Decreased growth and gas exchange was apparently due to a toxic effect of Cl^- and/or Na⁺ and not due to osmotic stress since both species were able to osmotically adjust to maintain higher leaf turgor than the non-salinized control plants. The lower osmotic potential values in salinized olive (100 mM NaCl) than in citrus (50 mM NaCl) imply that osmoregulation was more efficient in olive than in citrus.

1:45 Shade effects on salinity tolerance of ‘Valencia’ orange trees on contrasting rootstocks.

J. P. Syvertsen and F. García-Sánchez, CREC UF/IFAS, V. Martínez,CEBAS, CSIC Universitario de Espinardo, Murcia, Spain and J. C. Melgar, Universidad de Córdoba, Spain. [C10]

We studied the effects of shading and salinity stress on two-year-old potted ‘Valencia’ orange trees on either Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive) rootstocks to determine if shading could reduce the negative effects of salinity stress. Trees were grown either under 50% shade cloth or left unshaded in full sun light and half the trees were salinized with 50 mM Cl during two 9 wk salinity periods in the spring and fall interrupted by our normal 11 wk rainy period while the other half received no salinity treatment. As expected, the shade treatment generally reduced midday leaf temperature and evaporative demand while the salinity treatment reduced growth. In non-salinized trees, the shade effect increased midday photosynthesis and stomatal conductance but not leaf transpiration. Shade also increased leaf chlorophyll and water use efficiency of trees on both rootstocks and increased tree growth in Cleo trees. Shade decreased Cl^- concentrations in leaves of salinized Carr trees but had no effect on leaf or root Cl^- of trees on Cleo. The growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na⁺ than unshaded trees after the first salinity period and this shade-induced elevated leaf Na⁺persisted after the second salinity period in trees on Carr. Although shading reduced Cl^- accumulation in ‘Valencia’ on Carr, shading did not alleviate the negative effects of salinity on growth and Na⁺ accumulation in trees on either rootstock.

2:00 Performance of ‘Hamlin’ Orange Trees on Flying Dragon Trifoliate Orange, Changsha Mandarin, and Koethen Sweet Orange x Rubidoux Citrange Rootstocks at Three In-Row Spacings in a Flatwoods Site.

W.S. Castle, J.C. Baldwin, and R.P. Muraro, CREC, UF/IFAS. [C11]

‘Hamlin’ orange trees on Flying Dragon trifoliate orange (FDT), Changsha mandarin, or a citrange (Koethen sweet orange x Rubidoux trifoliate orange [KxR]) rootstock were planted in a commercial site of Riviera series soil near Indiantown in April 1982. The split plot trial was planted on double-row beds with 21 ft between rows and in-row spacings of 7.5, 10, and 12.5 feet. In-row spacing did not affect tree survival which was ca. 85 % after 21 years. Tree losses were mostly from citrus blight. The trees on FDT were smaller (< 7 ft) at age 10 years than those on the other rootstocks which were 8.5 to 9.0 ft tall. Plant height increased as the distance among trees in the row increased, but the differences were small. The trees on FDT had 8.3 boxes/tree at age 10 years in cumulative yield regardless of spacing over 5 seasons between 1986 and 1994. The FDT cumulative yield extrapolates to 67% higher productivity for a hypothetical acre of trees at 7.5 ft in-row spacing versus 12.5 ft. The cumulative yields/tree for those on the other rootstocks at the closest and intermediate row spacings were ca. 10 boxes for Changsha and 8.5 boxes for KxR; however, with both rootstocks, yields increased to 12.8 and 11.2 boxes, respectively, at the 12.5 spacing. Mean juice quality measured in 4 seasons was ca. 6 pounds-solids/box. There were no treatment differences. Overall, the results indicated that medium- to small-sized trees were most productive at 7.5 ft in-row spacing. An economic interpretation will be provided.

2:15 Field Performance of ‘Hamlin’ Orange on 27 Rootstocks in Lake County.

K.D. Bowman, G. McCollum, and U. Albrecht, USDA-ARS-USHRL, Ft. Pierce. [C12]

Twenty-seven rootstock selections consisting of 25 new numbered hybrids, and two named cultivars were tested as rootstocks for ‘Hamlin’ orange, Citrus sinensis L. Osbeck. The test included six single-tree replications in randomized complete blocks on sandy soil typical of the center of Florida. Four-year cumulative fruit production, fruit quality, tree growth, and tree health were measured and compared among the rootstocks. In cumulative fruit production, the standard rootstock Carrizo citrange was significantly more productive than Swingle citrumelo, while both rootstocks were intermediate in their effect on tree productivity as compared with the new numbered hybrids. The hybrid selections US-1242, US-1235, and US-1239 were significantly more productive than Swingle citrumelo, while the hybrid selections US-1221, US-1223, and US-1224 were significantly less productive than either Swingle or Carrizo. The rootstocks also differed significantly in their effect on fruit brix and soluble solids production. Some of the new hybrid rootstocks appeared promising for more widespread commercial trials.

2:30 Creating an Improved Sour Orange Rootstock.

K.D. Bowman, U. Albrecht, USDA-ARS-USHRL, Ft. Pierce. [C13]

Sour orange is widely regarded in Florida and other parts of the world as the standard for ideal rootstock performance, except for the major fault of susceptibility to a tristeza virus-induced decline. Although the origin of sour orange was formerly unknown, recent molecular studies have made it clear that it is derived from a cross of pummelo (Citrus grandis) with mandarin (C. reticulata). Over the past several years the USDA rootstock program has focused on developing an improved sour orange-type rootstock, by making crosses between pummelo and mandarin. The objective is to produce a better rootstock with the broad soil adaptation and all the other good attributes of sour orange, but without the sensitivity to tristeza-induced decline. Thousands of candidate Supersour hybrids have been produced and about 200 of the most promising of these hybrids have been selected for more careful testing. The use of molecular markers and several types of specialized testing for disease and soil factors are keys to finding the handful of Supersour candidates with the best characteristics. The final selection of the few Supersours for industry release will be based on performance in field trials. Some preliminary information will be presented on approach and progress in the generation of a Supersour rootstock.

2:45 Screening citrus rootstock genotypes for tolerance to Phytophthora-Diaprepes under field conditions.

J. H. Graham, K. D. Bowman, D. B. Bright and R. C. Adair, Jr., CREC, UF/IFAS, USDA-ARS-USHRL, Ft. Pierce and FLARES, Vero Beach. [C14]

Rootstock germplasm from USHRL breeding program was evaluated in each of three growing seasons at the FLARES. The screening site is located on Winder and Manatee fine sand soil naturally infested with Diaprepes abbreviatus, and Phytophthora nicotianae and P. palmivora. Seedlings grown in conetainers were planted into a mixture of rhizosphere soil with fibrous roots from beneath Sunburst trees on Swingle rootstock supporting both Phytophthora spp. adjacent to the test block. The established trees also served as a source of egg laying adults of D. abbreviatus. Seedlings were planted in May 2002 and 2003 and in January 2005 and harvested after 6, 7 and 10 months, respectively. At harvest, soil samples were taken from each tree for enumeration and identification of Phytophthora spp. Root systems were visually rated for root rot by the fungi and feeding damage by the weevil on a scale from 1-5 (1=no damage, 5=no undamaged roots). When 2002 and 2004 data were combined, there was a significant positive correlation between whole root system damage and total Phytophthora populations. Among the genotypes, mandarins and pummelo hybrids showed greater tolerance to PD complex than trifoliate and some of its hybrids. In 2005, screening focused on hybrids of pummelo and sour orange. The tolerance of genotypes in the third year was greater than for those tested in the first two years of screening. These findings confirm the promise of certain pummelo and mandarins as parents for hybrids with requisite Phytophthora resistance to develop rootstocks tolerant to the PD complex.

3:30 Progress in the Development of New Rootstocks Tolerant of the Diaprepes/Phytophthora Complex.

J.W. Grosser, J.H. Graham, D. Bright, A. Hoyte, and H.M. Rubio, CREC, UF/IFAS. [C15]

Our primary strategy for dealing with the Diaprepes/Phytophthora problem has been to develop complex rootstock hybrids that have the capacity to tolerate mechanical damage caused by weevil feeding and then recovery by exhibiting vigorous root growth in challenging soils inoculated with both Phytophthora nicotianae and P. palmivora. We have continued with annual crosses of superior allotetraploid somatic hybrid rootstocks and screening of resulting seed in high pH calcareous ‘Winder’ soil inoculated with both Phytophthora spp. in greenhouse flats. Vigorous healthy “tetrazyg” seedlings are selected and propagated by grafting to vigorous rootstocks and subsequently rooted cuttings. Replicated Diaprepes force-feeding assays are conducted in conetainersâ, and hybrids selected for reduced mechanical damage are replanted in a ‘Winder’/Phytophthora mix to assess recovery potential. During the past year, 3 large sets of new hybrids from 2004 crosses were screened, and several promising hybrids were identified that show excellent capacity for complete root system recovery in this greenhouse test. These are now being propagated for more extensive field evaluation. Data from these assays will be presented. Citrus rootstock breeding and selection at the tetraploid level maximizes genetic diversity and selection efficiency, and shows great promise for generating new rootstocks that can tolerate the Diaprepes/Phytophthora complex.

3:45 Use of landscape cloth to manage Diaprepes Root Weevil in citrus groves.

L.W. Duncan, S.L. Lapointe and R.J. Stuart, CREC, UF/IFAS and USDA-ARS, Ft. Pierce. [C16]

Significantly fewer Diaprepes abbreviatus and Artipus floridanus weevils were recovered from ground traps adjacent to young trees growing in soil covered by woven landscape fabric compared to trees growing in bare soil. After four years of growth, the mean cross sectional trunk area of trees growing in fabric-covered soil was 36% greater (P<0.02) than that of trees growing in bare soil. The trees are growing on the central ridge at a site with low prevalence of D. abbreviatus and the effects of herbivory and other factors such as soil temperature on tree growth are unknown. A second trial at a flatwoods site with high prevalence of D. abbreviatus was initiated using mature trees in March 2007. The effect of landscape fabric on weevil emergence from soil during the annual peak emergence period (Spring 2007) will be presented.

4:00 Integrated approaches for managing the Asian citrus psyllid (Homoptera: Psyllidae) in Florida.

Jawwad A. Qureshi and Philip A. Stansly, SWFREC, UF/IFAS. [C17]

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is an invasive insect pest of citrus in Florida. It is an efficient vector of the bacterium, Liberobacter asiaticum, causal organism of citrus greening disease or “Huanglongbing” (HLB). The pest was first detected in Florida in 1998 and now occurs on all citrus throughout the state. HLB was first detected in Florida 2005 and is spreading rapidly. Effective means of control are required to manage pest and disease while maintaining ecological and economic sustainability. Generalist predators such as the ladybeetles, Curinus coeruleus, Olla v-nigrum, Harmonia axyridis, and Cycloneda sanguinea, and lacewings such as Ceraeochrysa spp. and Chrysoperla spp. were observed to make significant contribution to the mortality of ACP resulting in 80-100% reduction in psyllid populations. In contrast, parasitism by Tamarixia radiata, a species specific parasitoid of ACP, was variable and generally low in southwest Florida, averaging less than 12% during May through September and 50% in November. Foliar applications of insecticides reduced psyllid populations for a short time at best, but also suppressed the populations of predatory ladybeetles. Soil application of aldicarb provided limited control of ACP while drenches of imidacloprid to young trees were effective for two months or more. Our results suggest that the contributions of biological control agents to mortality of ACP need to be conserved and enhanced for successful long term management of pest and disease. Conservation of the natural enemies will require insecticides to be used selectively and at times relatively safe to key predators and parasitoids. The contribution of parasitism should be enhanced by mass release and/or introduction of additional parasitoid species.

4:15 Effectiveness of several soil-applied systemic insecticides for managing the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae).

Michael E. Rogers, CREC, UF/IFAS. [C18]

The Asian citrus psyllid [Diaphorina citri Kuwayama (Homoptera: Psyllidae)] is the insect responsible for transmission of the Asian strain of the citrus greening pathogen (Candidatus Liberibacter asiaticus) in Florida. In citrus producing countries where both citrus psyllids and greening disease occur, insecticide use to reduce psyllid populations is an important component of greening management programs. Foliar insecticide applications, along with the soil application of aldicarb, are currently the most widely utilized methods of controlling psyllids on large bearing citrus trees in Florida. Under typical growing conditions in Florida, these large trees produce 3-4 major flushes during a year. Insecticide applications for psyllid control are thus timed to reduce psyllid populations during these major flushing periods. Blocks of young non-bearing citrus trees and resets within mature groves present a different management problem. These young trees produce many additional flushes throughout the year which often occur at times when mature trees are not producing new leaf flushes. Thus, these trees will likely attract psyllids and facilitate the increase of psyllid populations within a grove if additional protection is not provided. These trees may also have the potential to become infected by the greening pathogen at a much higher rate than mature trees within the same grove. The most reliable method of protecting non-bearing trees from pests such as psyllids is the use of the soil-applied systemic insecticide imidacloprid. However, due to the potential for insecticide resistance to develop due to widespread use of imidacloprid, additional soil-applied systemic insecticides are needed. Presented are the results of a study to evaluate the effectiveness of other soil-applied systemic insecticides for controlling psyllids on non-bearing citrus.

4:30 Defoliation of Canker Infected Citrus Trees by Diquat.

Shiv D Sharma, M Singh, CREC, UF/IFAS; Eric K. Rawls and John B. Taylor, Jr., Syngenta Crop Protection, North Palm Beach. [C19]

Studies were conducted in winter, spring and fall of 2006 on mature trees to evaluate the potential of diquat (Reglone) as a defoliant in case of canker outbreak. All the leaves were dead after Reglone application. Leaf defoliation gradually increased from 0% at 1 DAT to 90% (grapefruit) in winter; to 79%, 84% (grapefruit), 83%, 85% (oranges) in spring; and 83%, 74% (grapefruit), 90%, 73% (oranges) in fall season, with 1, 2 pt/A Reglone, respectively 14 DAT. Further shaking of trees achieved 100% defoliation. Similarly fruits defoliation successively increased with time until 14 DAT in spring and fall seasons. The values of fruit defoliation at 14 DAT were 94% (grapefruit) in spring and 95% (grapefruit), 100% (oranges) in fall with 2 pt/A Reglone. Shoot desiccation was also successively increased and recorded highest at 14 DAT. Regrowth of new leaves and shoots was recorded in winter season only which started from the end of desiccated shoot in grapefruit 14 DAT. Regrowth increased with the time and >95% of the branches bloomed with new flush in grapefruits and 15 to 20% branches in oranges under both Reglone rates at 28 DAT. Application of Reglone 1 pt/A may be enough to defoliate leaves or fruits with in 14 DAT. Canker inoculums remain viable on green leaves and fruits and due to application of Reglone, the leaves and fruits are dead, became bronze colored and fallen on the earth. Thus defoliation of leaves and fruits may prevent the potential spread of citrus canker disease.

4:45 Severe pruning for control of citrus canker in São Paulo State Brazil.

J. Belasque Jr., Luciane M. Ribeiro, Antonio J. Ayres, and Nelson Gimenes-Fernandes. Fundo de Defesa da Citricultura, Araraquara, São Paulo, Brazil. [C20]

In São Paulo state Brazil, where citrus canker was first detected in 1957, the law related to disease eradication does not allow for the use of severe pruning as an alternative method to tree removal. To evaluate the efficacy of severe pruning for citrus canker control, 20,255 trees of sweet orange (Citrus sinensis) in 31 orchard blocks on 9 farms were pruned in three different experiments. Prior to pruning, the incidence of diseased trees per block varied from 0.09 to 100%. Up to two years after pruning, periodic inspections detected diseased trees in 13 orchards (42% of the cases) and the diseased trees detected were not necessarily those that were diseased before pruning. Pruned trees started to produce fruits after two years, and averaged 1 to 2 boxes (40.8 kg) per tree. In São Paulo state, the removal of diseased trees and those suspected of being infected is the most effective method to achieve eradication of the pathogen, whereas severe pruning may be considered a strategy for reducing the inoculum to prevent further spread of the disease.

Tuesday June 5

10:00 Citrus leafminer control and copper fungicide sprays for management of citrus canker on lemon in Tucumán, Argentina.

B. Stein, J. Ramallo, L. Foguet, J. H. Graham, Estación Experimental Agroindustrial O. Colombres, and CREC, UF/IFAS. [C21]

Abamectin and copper bactericides applied alone or in combination with other products for Citrus leafminer (Phyllosnictis citrella) and citrus canker (Xanthomonas axonopodis pv citri) control, respectively, in lemons were evaluated for three seasons in a commercial lemon orchard in Tucuman, Argentina. Treatments were applied on six dates from petal fall to February each year at 28-day intervals with a high volume air blast sprayer. Citrus canker incidence on fruits was reduced significantly by all spray treatments compared with the nonsprayed control. Canker control achieved with copper oxychloride and copper hydroxide was not significantly different. High application rates of copper hydroxide (0.20%) were more effective in controlling the disease than low rates (0.15%). The combination of copper oxychloride with spray oil as an adherent or quaternary ammonium and disinfectants did not improve disease control on fruit. Disease incidence on fruit was reduced 19%, average two years, by abamectin treatment for citrus leafminer (CLM) control applied every 15 days during the period of high CLM pressure. Disease incidence on fruits was not improved by CLM control, when abamectin was combined with 6 copper sprays during the growing season.

10:15 The Impact of Citrus Greening and Canker on Florida Grove Care Management Practices and Costs.

Ronald P. Muraro, CREC, UF/IFAS, Thomas H. Spreen and Jordan C. Malugen,

Food and Resource Economics, UF/IFAS. [C22]

With the 2005 finding of citrus greening disease (Huanglongbing or HLB) in Florida citrus along with the discontinuation of the federal-state mandated citrus canker eradication program, Florida citrus growers have initiated new grove care practices to manage these diseases. The new citrus grove practices include the additional sprays for controlling the Asian citrus psyllid insect vector that transmits the HLB bacteria, the copper sprays to control the spread of citrus canker in the grove and the field inspections for identifying trees infected with citrus greening and for certification of a fresh fruit block free of citrus canker. This paper will explore the costs of the additional grove care practices being used to manage citrus greening and canker. The impact that these additional costs will have on replanting of citrus will also be discussed.

10:30 The Projected Impact of Citrus Greening in Sao Paulo and Florida on Processed Orange Production and Price.

Thomas H. Spreen, Food and Resource Economics, UF/IFAS, Mark G. Brown, FDOC Economic-Market Research Department, and Ronald P. Muraro, CREC, UF/IFAS. [C23]

Citrus greening is a highly destructive disease that attacks a number of plant and tree crops including citrus. The only known control for greening is eradication. Therefore, the presence of greening will affect fruit production and tree mortality. Currently, greening is present in both Sao Paulo, Brazil and Florida, who collectively account for 80 percent of world processed orange production. In this paper, projections of future orange production and prices are provided in which the likely effects of greening are incorporated.

10:45 Culturing Fastidious Prokaryotes - Points to Consider When Working with Citrus Greening.

M. J. Davis and R. H. Brlansky, CREC, UF/IFAS [C24]

The first of the fastidious prokaryotic plant pathogens to be grown in axenic culture was the phloem-limited Spiroplasma citri which causes stubborn disease of citrus. Others followed and include Spiroplasma kunkelii (Corn stunt) and Spiroplasma phoeniceum (Periwinkle yellows). The vast majority of spiroplasmas are associated with arthropods and don’t cause plant diseases. The axenic culture of fastidious xylem-limited bacteria followed the work on these phloem-limited fastidious bacteria. The Gram-negative bacterium causing Pierce’s disease of grapevines and now known as a pathogenic variant of Xylella fastidiosa was the first isolated in culture in 1978. The Gram-positive coryneform bacterium causing ratoon stunting disease of sugarcane and known as Clavibacter xyli subsp. xyli (Liefsonia xyli subsp. Xyli) was the second. Media formulations for culturing these bacteria have served as models for the development of other media for the culture of fastidious plant-associated microbes. Knowledge gained in such efforts may lead to the culture of the citrus greening bacterium. The importance of culturing the causal agent as a tool for the management of citrus greening is discussed.

11:00 Characterization of recently introduced HLB and CTV isolates.

W. Dawson, S. Garnsey, C. Robertson, S. Gowda, S. Tatineni, M. Irey, P. Sieburth, and M. Hilf,

CREC, UF/IFAS, and USDA Horticultural Research Laboratory, Ft. Pierce. [C25]

Severe stem-pitting isolates of Citrus tristeza virus (CTV) were found in Florida citrus 5 years ago, followed by the discovery two years later of the citrus greening disease (Huanglongbing: HLB) caused by the bacterium Candidatus Liberibacter asiaticus. The new CTV isolates are members of the VT group, which contains isolates more severe than the mild and decline isolates now common in Florida. These new isolates are apparently moving rapidly into commercial citrus. Individual VT isolates from the same field vary considerably in severity, suggesting that the virus population may be still evolving. Grapefruit seedlings inoculated with some of the VT isolates have shown severe reactions, but effects on larger trees remain unknown. Additionally, severe CTV-like symptoms were observed in some of the trees initially discovered with HLB infections, suggesting that additional severe isolates of CTV may have been co-imported with the citrus greening pathogen. The similarity of these isolates is under investigation. The establishment of greening in Florida poses a major threat to future production, so development of effective management strategies is urgently needed. Using information and techniques developed for studying CTV, we are examining the movement and distribution of Liberibacter to optimize sampling times and patterns for better detection, especially in trees without definite visual symptoms. We also are examining the relationship between symptom expression and Liberibacter titers in infected trees.

11:15 Update on the Southern Gardens Diagnostic Laboratory and the procedure for submitting diagnostic samples for Huanglongbing.

M. S. Irey, P. Z. Mai, US Sugar Corp., and T. Gast, Southern Gardens Citrus Corp., and J.H. Graham, CREC, UF/IFAS. [C26]

Citrus Huanglongbing (HLB, syn=citrus greening) is considered to be the most severe of all citrus diseases worldwide. The disease greatly debilitates trees and results in losses in crop production. HLB was reported for the first time in Florida in late August, 2005. Since the initial discovery in Dade County, the disease has been found in at least 15 counties, primarily in southern Florida and the number of known infected properties increases almost daily. As the number of infected groves continues to increase, grower awareness and concern has also increased. This has resulted in an increased need to have laboratory testing available to growers and homeowners to verify and confirm the presence of HLB on their properties so that control measures can be implemented. In late October, 2006, Southern Gardens Citrus Corporation in cooperation with the IFAS, University of Florida, opened up a testing facility available to all growers to test samples for the presence of the Candidatus Liberibacter asiaticus, the causal organism of HLB in Florida. In the first 16 weeks of operation, the facility has tested 8,213 samples with an average throughput of 483 samples per week. The average turn around time from receipt of the sample to the reporting of results during this period was 16 days. Results are reported directly back to the grove owners and summary reports are turned in to the Florida Department of Agriculture and Consumer Services and USDA-APHIS to be incorporated into databases maintained by both agencies. Any findings of regulatory significance are resampled and retested by both agencies before being released as official findings. Detailed sampling procedures and the process for sample submission can be obtained from the Highlands County Citrus Growers Association website at: http://www.hccga.com/posgreen/061221mikeirey.pdf or by contacting Mike Irey directly.

11:30 Seasonal and spatial variability in the titer of Candidatus Liberibacter asiaticus in sweet orange and the Asian citrus psyllid as it relates to sampling.

M. S. Irey, US Sugar Corp., D. G. Hall and T. R. Gottwald, USDA-ARS, and T. Gast, Southern Gardens Citrus Corp. [C27]

Citrus Huanglongbing (HLB, syn=citrus greening) is considered to be one of the most severe diseases of citrus worldwide. Among the control measures recommended to mange HLB is the early identification and removal of infected trees, i.e. roguing. Since its discovery in Florida in late August, 2005, the initial identification and verification of HLB has been problematic due to the similarity of some HLB symptoms to symptoms of nutritional, physiological, and other disease problems. Therefore the initial confirmation of the disease is usually based on laboratory testing employing one of several polymerase chain reaction (PCR) assays that are available to screen for the presence of Candidatus Liberibacter asiaticus(CLA), the causal agent of HLB in Florida. Although the tests are well documented in the literature, it is also well documented that testing for the presence of CLA can be problematic, presumably due to the low titer and incomplete distribution of CLA in the plant. However, reliability could be related in part to seasonal and spatial variability of the titer and distribution of CLA in the trees. The present study was conducted to determine if the titer of CLA in infected trees and psyllids varies over time and location sampled within the tree. Tissue samples were taken from multiple locations on naturally HLB-infected Valencia trees from a commercial grove in south Florida and tested on a monthly basis for the presence of CLA using a real-time PCR assay. Psyllids were also collected and tested on a monthly basis using yellow sticky traps hung in HLB-infected trees. Over the 10 month period studied, CLA titer from the plant samples, as measured by CT values, was highest in the months preceding the spring flush (January and February), then declined during the spring flush and succeeding months (March, April, May), and then gradually increased from June to October. The effectiveness of testing based on % PCR-positive results from known HLB-infected trees was highest in January, February, March, September, and October. HLB was seldom detected in May, June, and July. Titer also differed by tissue type. CLA was detected in psyllids only during January, February, and April, however these data were affected by the low numbers of psyllids that were trapped late in the year after an intensive psyllid control program was implemented in the commercial grove.

Handling & Processing Section

Monday June 4

10:00 BASF FreshSeal® CHC Helps Keep Packed Tomatoes Firmer and Fresher Longer.

Mark P. Kohout, BASF Corporation, Sarasota; Mark A. Ritenour and James J. Salvatore, IRREC, UF/IFAS. [HP1]

FreshSeal® CHC is a naturally occurring, polymer-based edible coating marketed to improve the postharvest quality of fresh horticultural products such as tomatoes and peppers. A series of packinghouse experiments in Florida evaluated the effects of FreshSeal® application on tomato (Lycopersicon esculentum Mill) fruit ripening and quality retention under commercial and simulated commercial conditions. These experiments were designed to compare non-treated fruit, FreshSeal® CHC-treated fruit, and fruit coated with a commercial wax using commercial varieties of round and Roma tomatoes treated on the day of packing. Fruit were harvested at either the vine ripe or mature green stage and consisted of five replicates of approximately 50 or 100 fruits for round and Roma, respectively; all fruit were exposed to ethylene. In addition to total unmarketable fruit including soft and decayed fruit, individual fruit firmness, skin peel puncture resistance, external color, and water loss were quantified. In general, FreshSeal® treated tomato samples were significantly firmer than the control at both one and two week(s) after packing and contained less decay. In addition, coating mature green tomatoes with FreshSeal® CHC resulted not only in more rapid and uniform color development but also produced a unique color.

10:15 Effect of Edible Coatings and Other Surface Treatments on Pericarp Color of Thai Lychee Cultivars.

Nithiya Rattanapanone, Chiang Mai University, Chiang Mai, Thailand; Anne Plotto, and Elizabeth Baldwin, USDA/ARS Citrus & Subtropical Products Laboratory, Winter Haven. [HP2]

Lychee fruit have a brilliant red pericarp upon harvest that turns brown during shipping and storage. ‘ Hong Huay’ and ‘Jugkapat’ lychee fruit (Litchi chinensis Sonn.) were harvested at the commercial stage (90-100% red pericarp) in Thailand. In four separate experiments, fruit with pedicels were dipped for 30 s in various treatment solutions including: no dip and water as controls, ascorbic acid (AA), citric acid, acetic acid, chitosan, HCl, and two Semperfresh products, in an effort to retard browning of the percarp. Fruit were air-dried, and stored at 2 or 10 °C with 90% relative humidity for 1-3 weeks. Total soluble solids (TSS), tritratable acidity (TA), weight loss, total ascorbic acid (TAA) and color (hue angle and chroma) were measured every day or once a week. During storage, TSS and pH generally increased while TA and TAA generally decreased (except for those treatments that included AA). Most treatments reduced weight loss compared to untreated fruit. Treatment of lychee fruit with acidified coatings including Semperfresh, acidified Semperfresh (with 2% citric acid), Semperfresh Lychee Treatment Power (LTP) + citric acid and chitosan + HCl sometimes resulted in brighter, redder color than control fruit, as evidenced by lower hue angle or higher chroma values.

10:30 Optimization of a HPMC, Bee’s Wax and Shellac Edible Coating for ‘Valencia’ Oranges and ‘Marisol’ Tangerines.

Maria-Llanos Navarro-Tarazaga and M.-Bernadita Pérez-Gago, Instituto Valenciano de Investigaciones Agrarias, Valencia, Spain; Anne Plotto and Kevin L. Goodner , USDA/ARS Citrus & Subtropical Products Laboratory, Winter Haven. [HP3]

Commercial coatings used for citrus fruit include carnauba- and shellac-based waxes or resins, which provide an attractive shine to the fruit, but are not necessarily made of 100% food grade ingredients. A new food grade formulation based on bee’s wax, shellac resin and hydroxypropylmethylcellulose (HPMC) was tested, along with an experimental polyethylene-candellila (PE) wax emulsion, and two commercial citrus coatings (shellac and carnauba based). ‘Valencia’ oranges from a local grove were washed, hand-coated, dried, and stored 2 weeks at 23-25 °C. The PE and carnauba coatings provided the best weight loss control, and were preferred for appearance by a taste panel. The HPMC coating provided the least shininess, and rated similarly to control for appearance. On the contrary, shellac coated fruit were the shiniest, but had intermediate appearance preference ratings. Shellac coated fruit had high levels of ethanol and CO₂, followed by HPMC-coated fruit. These indicators of anaerobiosis are known to produce off aromas. The HPMC formulation was modified to increase permeability to O₂ and CO₂and were tested on ‘Marisol’ tangerines from Spain, and stored at 23 °C for 3 weeks. A reduction of the HPMC:glycerol ratio from 2:1 to 1:2 improved gas permeability and sensory quality of tangerines stored 1 and 2 weeks at room temperature. Increasing solid content (SC) from 5% to 8% reduced weight loss. Therefore, HPMC formulation with HPMC:glycerol ratio of 1:2 and at 8% SC was retained for further applications with tangerines.

10:45 Relationship between Weight Loss and Visual Quality of Fruits and Vegetables.

Cecilia N. Nunes, Food Science and Human Nutrition, UF/IFAS, and Jean-Pierre Emond, Agricultural and Biological Engineering, UF/IFAS. [HP4]

Loss of water from harvested fruits and vegetables is a major cause of deterioration during the postharvest period. Loss of substantial amounts of water may result in important quality and economic losses, and even when weight losses are subtle the visual, compositional and eating quality of produce may be impaired. Fourteen freshly harvested fruits and vegetables were stored at 20°C and 85 to 95% relative humidity, and weight loss and visual quality attributes (firmness, wilting, shriveling or/and browning) were evaluated every day or every other day until each individual fruit or vegetable was considered unacceptable for sale. A highly significant correlation was found between weight loss and visual quality attributes for each fruit and vegetable evaluated. As weight loss increased, firmness decreased, and wilting, shriveling and browning increased. A maximum acceptable weight loss before each selected fruit or vegetable became unacceptable for sale is suggested.

11:00 Changes in the Postharvest Quality of a Datil Selection and ‘Datil Dew’ Hot Peppers as Affected by Storage Temperature.

Elena E. Lon Kan, Steven A. Sargent, Nicole L. Shaw, and Daniel J. Cantliffe, Horticultural Sciences, UF/IFAS, and Amy Simonne, Family, Youth and Community Sciences, UF/IFAS. [HP5]

Two yellow hot peppers (Capsicum chinense), a local selection named Datil selection and a commercial variety with Datil background, ‘Datil Dew’, were studied . Both peppers were grown hydroponically in greenhouses. Ripe peppers were packed in vented clamshells and stored the day of harvest at 5, 10 or 20^oC. After 14 days containers were transferred to 20^oC for 4 days. General appearance, weight loss, respiration rate, pH, acidity, total soluble solids, and carotenoids (HPLC) were evaluated. Average of Datil selection and ‘Datil Dew’ peppers were: Respiration rate (ml CO₂/kg-hr) at: 5^oC = 11.10 and 16.49; 10^oC = 15.10 and 18.39; 20^oC = 41.95 and 52.58. The weight loss for 6, 14 and 18 days for Datil selection at 5^oC = 2.74%, 4.65% and 15.05%; 10^oC = 5.03%, 9.25% and 18.02%; 20^oC = 16.82%, 33.59% and 40.16%; ‘Datil Dew’ was at 5^oC = 1.52%, 2.52% and 7.81%; 10^oC = 2.36%, 4.16% and 8.47%; 20^oC = 8.54%, 16.47% and 20.09%; Datil selection and ‘Datil Dew’ lutein contents (mg/g) were: at 5^oC = 68.70 and 52.44; 10^oC = 94.49 and 49.75; 20^oC = 100.57 and 48.14; beta-carotene content (mg/g) were: at 5^oC = 31.51 and 6.37; 10^oC = 43.86 and 6.74; 20^oC = 15.65 and 6.48. Both peppers did not show chilling injury after 14 days storage at 5^oC; those stored at 10^oC had slight signs of shriveling; however at 20^oC the peppers became unmarketable by 11 days due to shriveling and mold decay.

11:15 A High Sensitivity Continuous Ethylene Monitoring Device for Postharvest Applications.

Reza Shekarriz, Fluid Analytics, Inc., Portland, Oregon. [HP6]

As a fruit ripening hormone, ethylene gas is effective at greater than 0.1 ppm. Constant ethylene monitoring is essential because automotive emissions, plastics, and fluorescent lights all increase ethylene gas levels. Ignoring the ethylene gas produced by or surrounding fruit, at various stages postharvest could be costly. Here, a new approach for post-harvest ethylene sensing is presented. It is based on electrochemical oxidation of the ethylene molecules flowing past the sensor. The signal generated from the oxidation of ethylene on a nanoporous gold catalyst provides a direct measure of the gas concentration. The overall system for electrochemical sensing is relatively simple and requires few components, thus providing a very cost effective gas monitoring system. Furthermore, the direct contact between the molecules in air and electrocatalytic surface renders this process more sensitive than conventional diffusion-type electrochemical cells. The electrochemical sensor developed by Fluid Analytics, ETH-1010, has been packaged into a complete field portable unit. It continuously samples and monitors the ethylene in air at a specified flow rate, commonly between 100 ml/min and 1000 ml/min. The sensor detection thresholds are less than 100-ppb although detection thresholds of 10-ppb and better have been tested. Bundled with CO₂, oxygen, temperature, and humidity sensors, one is able to use this system to monitor the ethylene production and respiration rates for a single apple, or the real-time concentrations in a warehouse full of apples. This system is currently being deployed for fruit maturity monitoring, CA room ethylene monitoring, and general scientific use in the laboratory.

1:30 Harvesting Carambola at Different Ripeness Stages Affects Postharvest Quality.

Oren Warren, Marcio E. Pereira, Adrian D. Berry, and Steven A. Sargent, Horticultural Sciences, UF/IFAS. [HP7] (Student Competition)

Carambola (Averrhoa carambola) fruit grow well in south Florida. The fruit is usually harvested commercially at the color break stage, while the fruit is still firm, to minimize mechanical injury. A study was conducted to determine the effect of carambola harvested at three ripeness stages (color break, half yellow, and full yellow) on postharvest quality. Treatments were +/- a commercial carnauba-based wax, three ripeness stages, and either holding for 7 d at 5 ^oC before transferring to 20 ^oC or holding constantly at 20 ^oC in four replications. At full-ripe stage (orange) the non-waxed fruit typically showed more shriveling at the stem end, had rib softening, and lost about twice as much weight as the waxed fruit; however, the waxed fruit held initially at 5 ^oC then at 20 ^oC displayed non-uniform color development and internal tissue browning. Those fruit that were held constantly at 20 ^oC had non-uniform color and fermented flavor. Fruit harvested at the yellow color stage had a higher initial soluble solids content (7.9 ^oBrix) and lower total titratable acidity (0.25%) than the fruit harvested at the color break (6.7 ^oBrix, 0.28% acid) and half yellow stages (7.1 ^oBrix, 0.31% acid). Sugar-acid ratios for these respective harvest stages were: color break 23.3, half yellow 22.6, and full yellow 31.9.

1:45 Ripening of ‘Tainung 1’ Papaya Fruit Delayed by 1-Methylcyclopropene.

Marcio Eduardo Canto Pereira, Horticultural Sciences, UF/IFAS; Djalma Barbosa dos Santos, Aline Simoes da Rocha Bispo, Silvia Barbosa dos Santos, Embrapa Cassava & Tropical Fruits, Cruz das Almas, BA, Brazil. [HP8] (Student Competition)

The ethylene inhibitor 1-methylcyclopropene (1-MCP) has proven that this compound is highly effective in delaying ripening and/or extending shelf-life of many horticultural products. In order to investigate the effects of postharvest application of 1-MCP on papaya ripening, an experiment was carried out at the Embrapa Cassava & Tropical Fruits Research Center in Cruz das Almas, Bahia State, Brazil. Fruits of ‘Tainung 1’ papaya were harvested at the color break stage, washed and immersed in water with 100 ppm free chlorine for three min and air dried. Fruit was treated with gaseous 1-MCP (100 or 300 nL.L^-1), obtained by dilution of the commercial p