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Maria E. Monzon, Bill Biasi, Elizabeth J. Mitcham, Shaojin Wang, Juming Tang, and Guy J. Hallman

The external and internal quality of ‘Fuyu’ persimmon fruit (Diospyros kaki L.) was evaluated after heating with radiofrequency (RF) energy to 48, 50, or 52 °C, holding at the target temperatures for durations ranging from 0.5 to 18 minutes, hydrocooling, and ripening at 20 °C for 12 days. These treatment conditions were identified for control of third instar Mexican fruit fly larvae (Anastrepha ludens). The treatments had no commercially significant effect on firmness, soluble solids content, titratable acidity, or weight loss of the fruit. RF-treated persimmon fruit attained a deeper orange–red skin color than control fruit. There was a greater incidence of slight to moderate flesh browning in fruit heated to 50 and 52 °C as compared with 48 °C. Calyx browning increased slightly in all RF-treated fruit and was the highest in the longer treatments at each temperature. Heating persimmon fruit with RF to 48 °C and then holding for 6 or 12 minutes showed the least damage, and the latter treatment was longer than should be required for a quarantine treatment against the third instar Mexican fruit fly. Holding persimmons for 6.6 minutes at 48 °C should provide control of the Mexican fruit fly and maintain fruit quality. Confirmation tests with infested fruit should be conducted.

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J.D. Hansen, M.L. Heidt, M.A. Watkins, S.R. Drake, J. Tang, and S. Wang

Quarantine regulations require domestic sweet cherries (Prunus avium) exported to Japan to be treated to control codling moth [Cydia pomonella (Lepidoptera: Tortricidae)]. The current procedure, methyl bromide fumigation, may be discontinued because of health, safety, and environmental concerns. To examine a potential alternative method, `Bing' sweet cherries were each infested with a codling moth larva, submerged in a 38 °C water bath for 6 minutes pretreatment, then exposed to various temperatures generated by radio frequency and held at that temperature for different times: 50 °C for 6 minutes, 51.6 °C for 4 minutes, 53.3 °C for 0.5 minutes, and 54.4 °C for 0.5 minutes. Insect mortality was evaluated 24 hours after treatment and fruit quality was evaluated after treatment and after 7 and 14 days of storage at 1 °C. No larvae survived at the 50 and 51.6 °C treatments. Fruit color of non-infested cherries was darkened as temperature increased. Stem color was severely impacted after 7 days of storage, even in a warm water bath of 38 °C for 6 minutes, as was fruit firmness at the same treatment. Fruit quality loss increased after 14 days of storage, compared to after 7 days of storage. The amount of pitting and bruising of cherries increased with temperature and again this increase was more evident after 14 days of storage.

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J.D. Hansen, M.L. Heidt, M.A. Watkins, S.R. Drake, J. Tang, and S. Wang

Efficacy of using radio frequency (RF) at 27.12 MHz was evaluated as a postharvest quarantine treatment against fifth instars of the codling moth [Cydia pomonella (Lepidoptera: Tortricidae)], in apples (Malus sylvestris). Tests under the given conditions demonstrated that the energy fields between the RF unit's electrodes were neither predictable nor uniform. Moving fruit submerged in water during RF exposure may improve uniformity, but pulp temperatures varied considerably among fruit, among sites on the same fruit, and at different depths within the same site. As a result of these inconsistencies, quarantine efficacy was not obtained either using a range of final average temperatures from 40 to 68 °C (104.0 to 154.4 °F) or at holding times up to 20 minutes. We concluded it would be difficult to obtain the appropriate parameters for treatment efficacy and fruit quality maintenance using this technology under these conditions.

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C. Stevens, V. A. Khan, J. Y. Lu, A. Y. Tang, and A. E. Hiltbold

Partial steam and chemical sterilization of soil rich in organic matter increased the soil nutrients, little information exists with regard to the effect of soil solarization (SS) in this regard. A study was established to determine the effects of SS in combination with wheat residue and subsequent crop residue on increased growth response (IGR) of cole crops and soil fertility for two years. SS for 90 days increased K+, P, Ca++ and Mg++ 3 times more within five months after SS. The SS effect released higher levels of total N in the soil. However, increase levels of N was lower than that required for maximum IGR of collard. The IGR of cole crops without fertilizers was higher in SS plots as compared to bare soil. The IGR of collard was evident almost two years after SS.

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Wayne Brown, Theo J. Blom, George C.L. Chu, Wei Tang Liu, and Lisa Skog

The sensitivity of easter lilies (Lilium longiflorum) to either ethylene or methane (products of incomplete burning in gas-fired unit heaters) was tested during rooting [3 weeks at 18 °C (65 °F)], vernalization [6 weeks at 6 °C (43 °F)] and subsequent greenhouse forcing (15 weeks at 18 °C). Starting at planting, easter lilies were exposed for one of seven consecutive 3-week periods (short-term), or for 0, 3, 6, 9, 12, 15, 18, or 21 weeks starting at planting (long-term) to either ethylene or methane at an average concentration of 2.4 and 2.5 μL·L-1(ppm), respectively. Short- or long-term exposure to ethylene during rooting and vernalization had no effect on the number of buds, leaves, or plant height but increased the number of days to flower. Short-term exposure within 6 weeks after vernalization reduced the number of buds by 1 bud/plant compared to the control (no ethylene exposure). However, extensive bud abortion occurred when plants were exposed to ethylene during the flower development phase. Long-term exposure to ethylene from planting until after the flower initiation period resulted in only two to three buds being initiated, while continued long-term exposure until flowering caused all flower buds to abort. Short-term exposure to methane at any time had no effect on leaf yellowing, bud number, bud abortion, or height and had only a marginal effect on production time. Long-term exposure to methane from planting until the end of vernalization increased both the number of buds, leaves and height without affecting forcing time, leaf yellowing or bud abortion.