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.
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.
California nectarines [Prunus persica (L.) Batsch. var. nectarina (Ait) Maxim.] packed in single-layer corrugated fiberboard boxes were fumigated with methyl bromide (MB) at a rate of 48 g·m-3 for 21 hours at 21C and normal atmospheric pressure and a 50% load (v/v) as a quarantine treatment for codling moth (Cydia pomonella L.). When the boxes were loosely stacked with spaces between them or tightly stacked and forced-air fumigated, concentration multiplied by time (C × T) relationships were > 68 g·m-3·h-1, which is recommended for efficacy. Tightly stacked boxes that were not forced-air fumigated had C × T products <68 g·m-3·h-1. Organic bromide residues were <0.001 μg·g-1 and inorganic bromide residues were < 7.0 μg·g-1 after 3 days. A trace to slightly phytotoxic response was observed in `Summer Grand' and `Fantasia' nectarines in 1989 but not in 1990.
Residues and the toxic effects of methyl bromide (MB) were determined in fumigation tests with six cultivars of nectarine [Prunus persica (L.) Batsch. var. nectarina (Ah.) Maxim.]. `Fantasia', `Firebrite', and `Summer Grand' were treated in wooden field bins in a commercial facility, whereas `May Fire', `May Glo', and `May Diamond' were fumigated in smaller fiberglass chambers. The treatment of 48 g MB/m3 for 2 hours at 21C and normal atmospheric pressure with a load factor of 50% (179 kg·m-3) was that proposed for quarantine eradication of the codling moth (Cydia pomonella L.). The appearance of the fruit, as well as the soluble solids content, were not affected by the MB fumigation; however, ripening of `May Grand' and `Firebrite' was delayed slightly. Sorption of MB was 55%. Desorption rates of organic bromide were not significantly different among the six treated cultivars; all fruits contained <0.001 μg·g-1 after 7 days of storage at 2.5C. Inorganic bromide residues in all treated fruits were <8.0 μg·g-1.
Increasing environmental concerns and legislation in many states and in other countries require that we take a more comprehensive sustainable “best management” approach to production techniques in nursery and greenhouse operations. This is particularly important because these production facilities are typically intense users of resources that are applied to relatively small land areas. We have developed an online knowledge center to facilitate the implementation of more sustainable practices within the nursery and greenhouse industry. A web-based knowledge center provides the most cost-effective mechanism for information delivery, as our potential audiences are extremely diverse and widespread. We currently have a registered user database of over 450 educators, growers, and industry professionals, and undergraduate and graduate students. A gateway website provides an overview of the issues and the goals of the project. The associated knowledge center currently has 25 in-depth learning modules, designed in a Moodle learning management framework. These learning modules are designed to actively engage learners in topics on substrate, irrigation, surface water, and nutrient and crop health management, which are integral to formulating farm-specific strategies for more sustainable water and nutrient management practices. Additional modules provide assessment and implementation tools for irrigation audits, irrigation methods and technologies, and water and nutrient management planning. The instructional design of the learning modules was paramount because there can be multiple strategies to improve site-specific production practices, which often require an integration of knowledge from engineering, plant science, and plant pathology disciplines. The assessment and review of current practices, and the decision to change a practice, are often not linear, nor simple. All modules were designed with this process in mind, and include numerous resources [pictures, diagrams, case studies, and assessment tools (e.g., spreadsheets and example calculations)] to enable the learner to fully understand all of the options available and to think critically about his/her decisions. Sixteen of the modules were used to teach an intensive 400-level “Principles of Water and Nutrient Management” course at the University of Maryland during Spring 2008 and 2009. The water and nutrient management planning module also supports the nursery and greenhouse Farmer Training Certification program in Maryland. The Maryland Department of Agriculture provides continuing education credits for all consultants and growers who register and complete any module in the knowledge center. Although these learning resources were developed by faculty in the eastern region of the United States, much of the information is applicable to more widespread audiences.