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Abstract
Cultivars of sweet cherry (Prunus avium L.), nectarine [P. persica (L.) Batsch var. nectarina (Ait.) Maxim.] peach [P. persica (L.) Batsch], pear (Pyrus communis L.) and plum (Prunus salicina Lindl.) differed in their phytotoxic responses to methyl bromide (MB) fumigation treatments designed to control the Mediterranean fruit fly (Ceratitis capitata Wied.) without use of a subsequent cold treatment. Phytotoxic responses were relatively mild or negligible in most cultivars fumigated at 21°C with 48 g MB/m3 for 2 hours, 48 g/m3 for 3 hours, or 32 g/m3 for 4 hours. A few of the cultivars tested were very susceptible to MB injury. In some cultivars, both the control and fumigated lots exhibited symptoms of injury that apparently were not related to the fumigations but were caused by packinghouse handling or orchard practices. The fumigations slowed the ripening of cherries and plums. Decay of nectarines was slightly greater in fumigated than in control lots of fruit.
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.