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- Author or Editor: Joseph K. Stewart x
Abstract
Cantaloupes treated with 135° F water for 15, 30, or 60 seconds had significantly less stem-scar mold and surface mold than melons treated with 71° water (wet check). A 30-sec immersion controlled stem-scar mold slightly better than a 15-sec immersion. The addition of 600 ppm captan to the water at 135° significantly reduced stem-scar mold and surface mold compared to the hot-water treatment alone. Alternaria, Fusarium, and Rhizopus spp. were the fungi most frequently associated with these infections. Quality was evaluated after holding the melons for 7 days at 46° plus an additional 3 days at 72°.
In 3 of the 6 tests, the hot-water treatments significantly increased suture browning of the melons compared to the wet check. The fungicide did not influence suture browning.
General appearance of the melons treated at 130°, 135° or 145° was significantly better than that of the wet check (71°) melons, because of mold control by the hot water.
Abstract
Storage atmospheres with 2-1/2, 5 or 10% CO2 caused a physiological injury to lettuce almost identical to the brown stain observed in lettuce from rail cars and trailers in which CO2 concentrations exceeded 2% at destination. Carbon dioxide injury, or brown stain, was not always evident when lettuce was removed from the controlled atmosphere, after 7 days at 38°F, but became more evident during a subsequent 4 days at 50° in air. About 16% of the heads held at 2–1/2% CO2 developed brown stain while 38% and 86% of the heads developed the disorder in lots held at 5% and 10% CO2, respectively.
Significantly more heads developed brown stain when the CO2 was combined with 3% oxygen than when combined with 21% Ο2 Decay, pink rib, and tipburn were not significantly influenced by the O2 or CO2 level.
Increased levels of CO2 reduced the severity of butt discoloration in lettuce examined immediately after storage in the controlled atmosphere, but after an additional 4 days at 50°F in air, the differences were not evident. The danger of physiological injury from 2-1/2 to 10% CO2 during storage or shipping outweighs the small improvement in butt color and general appearance.
Abstract
Lettuce (Lactuca sativa L.) held in an atmosphere of 3% O2 plus 1.5% CO for 7 days at 3.3°C had a better appearance before and after the wrapper leaves were removed, than lettuce held in atmospheres with various other combinations of CO, CO2 and O2. Butt discoloration and pink rib also were inhibited by this atmosphere. These effects were no longer apparent after an additional 4-day holding period in air at 10°. Rusty brown discoloration was not affected by any of the atmospheres tested during the initial 7 days, but after 4 additional days in air, the incidence of objectionable rusty brown discoloration was higher in lettuce previously held in atmospheres with CO2 than in those without CO2.
Abstract
Vacuum fumigation for 2 hours with 0.5, 1.0, or 1.5% ethyl formate (EF) killed 93–97% of the green peach aphids [Myzus persicae (Sulzer)] in film-wrapped, packed head lettuce (Lactuca sativa L.). EF at 0.5% did not injure the lettuce, but 1.0 or 1.5% EF injured 30 and 97% of the heads, respectively. Regardless of the EF dosage used, about 75% of the fumigant was sorbed by the lettuce within 1 hour. A 1-hour vacuum fumigation using 0.5% EF appears to be optimal to control the green peach aphid in film-wrapped, packed lettuce.
Abstract
Added CO (1½%) or low O2 (3%) increased the susceptibility of head lettuce (Lactuca sativa L., ‘Great Lakes’ type) to CO2 injury (brown stain). The combination of low O2, added CO, and high CO2 (2½ − 10%) was particularly damaging.
Abstract
Acetaldehyde (Aa), a volatile produced in small quantities by plants, is a potential fumigant for killing the green peach aphid, Myzus periscae (Sulzer), on harvested head lettuce, (Lactuca sativa L. var. capitata). Concentrations of 3.0 to 6.0% Aa killed 100% of the green peach aphids on harvested head lettuce, but induced dark-green, water-soaked, necrotic areas on the outer leaves of the heads and occasionally caused a type of injury, similar to russet spotting, which we call tan flecking. Concentrations of 1.5 to 2.0% Aa, which killed all of the aphids, did not injure the lettuce.
Abstract
Vacuum fumigation at 560 mm Hg for 3 hr with acetaldehyde (Aa) at 1.75% in 70% CO2 killed 100% of western flower thrips Frankliniella occidentalis (Pergande), on strawberries (Fragaria × ananassa Duch.). However, the Aa treated berries were generally detectable in taste tests during the ensuing 3 days. Some panelists could distinguish the different taste of the treated strawberries from control samples even after 7 days. Ethyl formate (EF) in concentrations as low as 0.5% for 1 hr at 30 mm Hg pressure killed 100% of the thrips. EF fumigation affected neither taste nor odor of the berries during a subsequent 9 days of storage at 1°C. Fumigation with Aa in 70% CO2 decreased berry decay by 69%, but EF had no effect on decay. The concentration of EF, which was determined on the day of treatment and during the ensuing 4 days, was 0.2 ppm or lower in the treated strawberries. This concentration did not differ significantly from that in the controls and is at least 100 times less than the odor threshold concentration for EF.