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- Author or Editor: Preston Hartsell x
Methyl bromide (MB) penetration rates, sorption levels, and concentration.time (CT) products were compared in returnable plastic containers (RPCs) and corrugated grape boxes (CGBs). During a 2.5-hour fumigation, sorption of methyl bromide in RPCs and CGBs was 9.8% and 18.1%, respectively. The lower sorption in RPCs increased the exposure of grapes (Vitis vinifera) to MB. Equilibrium concentrations of MB (concentrations that had stabilized) in RPCs and CGBs were 68.2 and 59.2 g·m-3 (4.26 and 3.70 lb/1000 ft3) respectively. The CT products in RPCs and CGBs were 170.5 and 147.6 g·h-1·m-3 (10.66 and 9.19 lb/h/1000 ft3), respectively, and far below phytotoxic concentrations according to the U.S. Department of Agriculture schedule.
Callus tissue grown from `Marsh' grapefruit (Citrus paradisi Macf.) albedo tissue was grown at 30C for ≈ 40 days. Calli were preconditioned in normal air for 5 days at 10 or 30C before being fumigated for 2 hr with 0, 32, or 48 g of methyl bromide (MB)/m 3. Calli were then held at 10C and K+ leakage was measured after 1, 10, 20, and 30 days. The amount of K+ leaked from MB-fumigated calli was greater than that for nonfumigated calli and increased with higher MB dose. Leakage also increased with time following fumigation. Leakage of calli preconditioned at 30C and fumigated with 48 g MB/m3 was 140%, 196%, and 260% greater than leakage from nonfumigated calli 10, 20, and 30 days after fumigation, respectively. Leakage from calli preconditioned at 10C for 5 days before MB fumigation was less than that from calli held at 30C. MB doses of 32 and 48 g·m-3 increased leakage of calli preconditioned at 10C by 6% and 43% and for those preconditioned at 30C by 99% and 140%, respectively, 10 days after fumigation. In addition to K+ leakage, MB induced the development of a tan to orangish-brown discoloration.
Abstract
The tolerance of six cultivars of nectarine [Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim.] to methyl bromide (MB) quarantine treatments was determined. A treatment, 48 g MB/m3 for 2 hr at 21C, which controlled codling moth [Cydia pomonella (L.)], caused no significant phytotoxic response in any of the cultivars. The threshold for injury at the above time and temperature was ≈64 g MB/m3 in ‘Summer Grand’, ‘May Grand’, ‘Fantasia’, and ‘Firebrite’; between 48 and 64 g MB/m3 in ‘Red Diamond’; and between 80 and 96 g MB/m3 in ‘Spring Red’. All fumigated nectarines were significantly firmer than the control fruit after storage for 7 days at 2.5C, but subsequently ripened satisfactorily; soluble solids content of the fruit was not affected by the fumigations used in this study. Inorganic bromide residues in fruit treated with the 48 g·m−3 dosage at 21C or above ranged from 3.5 to 7.2 ppm, well below the U.S. tolerance of 20 ppm. Organic bromide residues were <0.01 ppm within 48 hr after treatment.
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.