Search Results

You are looking at 41 - 50 of 735 items for :

  • All content x
Clear All
Free access

Joshua D. Klein, William S. Conway, Bruce D. Whitaker, and Carl E. Sams

`Golden Delicious' apples (Malus domestica Borkh.) were treated postharvest with heat (38C/4 d or 42C/24 h) or 2% CaCl2 (applied as a dip or pressure-infiltrated) or a combination thereof and then stored. Decay caused by Botrytis cinerea was virtually eliminated in fruit heated at 38C after inoculation prior to storage, regardless of Ca treatment. Apples inoculated upon removal from storage were almost completely protected from decay if they had been previously pressure-infiltrated with Ca, regardless of heat regime. Heating at 42C or Ca dips were only partially effective in preventing decay. Pressure infiltration of Ca (regardless of heat regime) or heating at 38C (regardless of Ca treatment) resulted in firmer fruit (68 N) than Ca dips or heating at 42C (56 N), which were firmer than nontreated fruit (52 N).

Full access

Denis A. Shah and Lydia Stivers-Young

Data collected on 181 fields from 1998 to 2000 were analyzed for associations among cultural practices in table beet (Beta vulgaris) and levels of decay in the harvested beet roots. Increased risk of decay was associated with short rotations between beet crops, certain crop rotations in the four years before beets, the frequency of row cultivation, and narrow row spacing. Shielding during cultivation was associated with increased risk of decay, but the effect may be an indirect one. Decay levels were not associated with beet variety, the use of manure or preplant fertilizer. Decay did increase with higher rates of nitrogen side dressing. Mean decay differed significantly among growers, and could be explained in part by the set of cultural practices used by a grower. The results suggest that the risk of decay is determined by interacting biological and cultural factors. Manipulation of cultural practices and cropping sequence may be useful in managing levels of beet decay.

Free access

H. Ahmadi, W.V. Biasi, and E.J. Mitcham

Effects of short-term exposure to a 15% CO2 atmosphere on nectarines [Prunus persica (L.) Batsch (Nectarine Group) `Summer Red'] inoculated with Monilinia fructicola (Wint.) Honey (causal agent of brown rot) were investigated. Nectarines were inoculated with spores of M. fructicola and incubated at 20 °C for 24, 48 or 72 hours and then transferred to storage in either air or air enriched with 15% CO2 at 5 °C. Fruit were removed from storage after 5 and 16 days and were examined for brown rot decay immediately and after ripening in air for 3 days at 20 °C. Noninoculated nectarines were stored and treated likewise for evaluation of postharvest fruit attributes to determine their tolerance to 15% CO2. Incubation period after inoculation, storage duration, and storage atmosphere had highly significant effects on fruit decay. `Summer Red' nectarines tolerated a 15% CO2 atmosphere for 16 days at 5 °C. Development of brown rot decay in fruit inoculated 24 hours before 5 or 16 days storage in 15% CO2 at 5 °C was arrested. After 3 days ripening in air at 20 °C, the progression of brown rot disease was rapid in all inoculated nectarines, demonstrating the fungistatic effect of 15% CO2. The quantity of fungal cell wall materials (estimated by glucosamine concentration) was compared to visual estimation of decayed area and visual rating of fungal sporulation. The glucosamine assay defined the onset and progress of brown rot infection more precisely than either of the two visual tests.

Free access

Carl E. Sams, William S. Conway, Judith A. Abbott, Russell J. Lewis, and Noach Ben-Shalom

Heating `Golden Delicious' apples (Malus domestica Borkh.) for 4 days at 38C or pressure-infiltrating them with a 4% CaCl2 solution reduced decay and maintained fruit firmness during 6 months of storage at 0C. Heating reduced decay caused by Penicillium expansum Link ex Thorn by ≈30%, while pressure infiltration with CaCl2 reduced decay by >60%. Pressure infiltration with CaCl2 after heating reduced decay by ≈40%. Pressure infiltration maintained firmness best (>84 N), as measured with a manually driven electronic fruit-firmness probe, followed by heat and CaCl2 (76 N), heat alone (71 N), and no treatment (control) (60 N). Force vs. deformation (FD) curves from a puncture test with a fruit-firmness probe mounted in a universal testing machine showed that fruit heated before storage were firmer than all nonheated fruit, except those pressure-infiltrated with 4% CaCl2. However, FD curves also showed that apples pressure-infiltrated with 4% CaCl2 differed quantitatively from apples in all other treatments, including those heated.

Full access

Peter Sholberg, Paula Haag, Rod Hocking, and Karen Bedford

Vapors of several common vinegars containing 4.2% to 6.0% (= 2.5 to 3.6 mol·L-1) acetic acid effectively prevented conidia of brown rot [Monilinia fructicola (G. Wint.) Honey], gray mold (Botrytis cinerea Pers.:Fr.), and blue mold (Penicillium expansum Link) from germinating and causing decay of stone fruit (Prunus sp.), strawberries (Fragaria ×ananassa Duchesne), and apples (Malus ×domestica Borkh.), respectively. Fruit were fumigated in 12.7-L sealed containers in which vinegar was dripped on to filter paper wicks or vaporized by heating from an aluminum receptacle. Vapor from 1.0 mL of red wine vinegar (6.0% acetic acid) reduced decay by M. fructicola on `Sundrop' apricots (Prunus armeniaca L.) from 100% to 0%. Similarly, vapor from 1.0 mL of white vinegar (5.0% acetic acid) reduced decay in strawberries by B. cinerea from 50% to 1.4%. Eight different vinegars, ranging from 4.2% to 6.0% acetic acid, of which 0.5 mL of each vinegar was heat-vaporized, reduced decay by P. expansum to 1% or less in `Jonagold' apples. The volume of heat-vaporized white vinegar (5.0% acetic acid) necessary to reduce decay by P. expansum on `Jonagold' apples to zero was 36.6 μL·L-1 of air. Increasing the number of conidia on the apple surface reduced the effectiveness of vinegar vapor. The number of lesions caused by P. expansum on `McIntosh' apple decreased exponentially with increasing time of fumigation, approaching zero after about 6 hours. These results suggest that vinegar vapor could be an effective alternative to liquid biocides such as sodium hypochlorite for sterilization of surfaces contaminated by conidia of fungal pathogens.

Free access

Peter Sholberg, Paula Haag, Rod Hocking, and Karen Bedford

Vapors of several common vinegars containing 4.2% to 6.0% (= 2.5 to 3.6 mol·L-1) acetic acid effectively prevented conidia of brown rot [Monilinia fructicola (G. Wint.) Honey], gray mold (Botrytis cinerea Pers.:Fr.), and blue mold (Penicillium expansum Link) from germinating and causing decay of stone fruit (Prunus sp.), strawberries (Fragaria ×ananassa Duchesne), and apples (Malus ×domestica Borkh.), respectively. Fruit were fumigated in 12.7-L sealed containers in which vinegar was dripped on to filter paper wicks or vaporized by heating from an aluminum receptacle. Vapor from 1.0 mL of red wine vinegar (6.0% acetic acid) reduced decay by M. fructicola on `Sundrop' apricots (Prunus armeniaca L.) from 100% to 0%. Similarly, vapor from 1.0 mL of white vinegar (5.0% acetic acid) reduced decay in strawberries by B. cinerea from 50% to 1.4%. Eight different vinegars, ranging from 4.2% to 6.0% acetic acid, of which 0.5 mL of each vinegar was heat-vaporized, reduced decay by P. expansum to 1% or less in `Jonagold' apples. The volume of heat-vaporized white vinegar (5.0% acetic acid) necessary to reduce decay by P. expansum on `Jonagold' apples to zero was 36.6 μL·L-1 of air. Increasing the number of conidia on the apple surface reduced the effectiveness of vinegar vapor. The number of lesions caused by P. expansum on `McIntosh' apple decreased exponentially with increasing time of fumigation, approaching zero after about 6 hours. These results suggest that vinegar vapor could be an effective alternative to liquid biocides such as sodium hypochlorite for sterilization of surfaces contaminated by conidia of fungal pathogens.

Free access

Juan C. Díaz-Pérez, Albert C. Purvis, and J. Thad Paulk

Bolting causes significant economic losses in sweet onion (Allium cepa L.) production. Although temperature and photoperiod are considered to be the main factors that initiate bolting in onions, preliminary results suggested that low N fertilization rates increased bolting. The objective of our study was to determine the relationships of bolting, yield and bulb decay with N fertilization rates. The N fertilization rates applied ranged from the infraoptimal to the supraoptimal (from 102 to 302 kg·ha-1 N). Shoot and bulb N content increased with increasing N rates, but there were no differences in the respective shoot and bulb N contents among cultivars. Bolting incidence declined steadily with increasing N fertilization rates up to 197 kg·ha-1 N. Bolting incidence was among the highest in the cultivar Pegasus. The percent of decayed bulbs also increased at a steady rate with the rate of N applied. Total (14.7 t·ha-1) and marketable (0.8 t·ha-1) yields at the lowest N rate (102 kg·ha-1 N) were lower (P ≤ 0.01) than those at higher N rates. Rates of N ≥145 kg·ha-1 had no significant effect on either total (mean = 33.6 t·ha-1) or marketable (mean = 21.6 t·ha-1) yields. Losses in marketable yield were primarily a combination of bolting and bulb decay and were minimized at 162 kg·ha-1 N. Yield losses at low N rates were mostly due to bolting while yield losses at high N rates were mostly due to decay. Thus, excess applications of N fertilizer should be avoided since they have little effect on yields or bolting but they increase bulb decay.

Free access

Mark A. Ritenour, Peter J. Stoffella, Zhenli He, Jan A. Narciso, and James J. Salvatore

Previous research showed that mature green tomato fruit dipped 1 to 4 min in a 1% CaCl2 solutions before storage had significantly increased peel calcium content and reduced postharvest decay. The present experiments, conducted over 3-day periods (reps), evaluate treatment effectiveness under commercial packinghouse conditions. Three cartons of 5 × 6 sized mature green `FL 47' tomatoes were collected from the line (control). CaCl2 was then added to the packinghouse 15,142-L dump tank to a concentration of 1% before more fruit were run through the line and three additional cartons collected. The cycle was repeated after bringing the concentration in the dump tank up to 2% CaCl2. After storage for ≤24 days at 20 °C, postharvest decay was significantly reduced in fruit receiving the 2% CaCl2 treatment. Calcium content in the tomato peel tended to increase with each successively higher CaCl2 treatment, but differences were nonsignificant. Laboratory tests showed Rhizopus more affected by 3% CaCl2, while Alternaria was affected by 2% and 3% CaCl2 solutions. Results were recorded as colony diameter, but colony morphology and sporulation were also affected. Inoculation studies of tomatoes dipped in 1% CaCl2 after wounding with Rhizopus or Alternaria showed better decay control when compared to treating before wounding.

Full access

Mark A. Ritenour, Ed Stover, Brian J. Boman, Huating Dou, Kim D. Bowman, and William S. Castle

Rootstock significantly affected the development of stem-end rind breakdown (SERB) on `Valencia' and navel oranges (Citrus sinensis), but not `Ray Ruby' grapefruit (C. paradisi) or `Oroblanco' (C. grandis × C. paradisi), and affected postharvest decay on navel orange, `Ray Ruby' grapefruit, `Oroblanco' and one of two seasons (2002) on `Valencia' orange. In `Valencia' and navel oranges, fruit from trees grown on Gou Tou (unidentified Citrus hybrid) consistently developed low SERB. `Valencia' oranges on US-952 [(C. paradisi × C. reticulata) × Poncirus trifoliata] developed high levels of SERB in both years tested. Relative SERB of fruit from other rootstocks was more variable. Navel oranges, `Ray Ruby' grapefruit, and `Oroblanco' fruit from trees on Cleopatra mandarin (C. reticulata) rootstock consistently developed relatively low levels of decay, and in navel this level was significantly lower than observed from trees on all other rootstocks. In three of five trials we observed significant differences between widely used commercial rootstocks in their effects on postharvest SERB and/or decay. Given the expanding importance of sales to distant markets, it is suggested that evaluations of quality retention during storage be included when developing citrus rootstocks and scion varieties for the fresh market.

Free access

R. Potjewijd, M.O. Nisperos, J.K. Burns, M. Parish, and E.A. Baldwin

Varying the cellulose component of coating formulations affected the survival of two yeast biocontrol agents, Candida guillermondii (Castelani) Langeron and Guerra strain US7 and Debaryomyces sp. strain 230, when these yeasts were incorporated into the coating. Using methylcellulose as the main film-former gave the most recovery of the yeasts after an incubation period for both strains. Significant control of decay on naturally infected `Pineapple' and `Valencia' oranges [Citrus sinensis (L.) Osb.] was demonstrated for US7 in a methylcellulose-based coating for the first 2 to 4 weeks of storage at 16C and 90% relative humidity. During this time, US7 in methylcellulose formulations was similar in decay control to a commercial shellac coating with imazalil at 2000 mg·liter–1. A US7 concentration of at least 105 colony-forming units/cm was maintained on the coated fruit surface of `Valencia' oranges for 3 weeks of storage. Suppression of decay by US7 was improved by the addition of glucose and calcium chloride to the coating formulation. Although nearly equal in concentration recovered, Debaryomyces strain 230 was not as effective as US7 in disease suppression of `Pineapple' oranges. The addition of US7 to Nature Seal, a coating material made with methylcellulose, had neither a quantitative nor a qualitative effect on the pathogen population compared to the same formulation without the antagonist. Chemical name used: 1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl]-1H-imidazole (imazalil).