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Guidelines for CA Storage of Apples Treated with SmartFresh (1-MCP)

'Empire'

SmartFresh (1-MCP) on 'Empire' apples increases the risk for external CO₂ injury, and the use of ReTain further increases this risk. The best precaution is to drench with DPA (greater than or equal to 250 ppm) at harvest time and then standard CA (2.5% O₂ + 2.0% CO₂ at 2°C) can be used. Note - DPA is registered as an inhibitor of superficial scald and thus must be applied according to the label for that purpose. An alternate precaution is to hold the CO₂ concentration below 0.5%, especially for the first 30 days of storage. However, there may still be a small risk of external CO₂ injury without the use of DPA. Research in New York by Watkins et al. recently showed that if 'Empire' fruit are not cooled after SmartFresh treatment and before application of CA then there is a substantial increase in the risk of CO₂ injury development. CA storage for longer than 8 months increases the potential for internal browning and low temperature disorders in 'Empire'.

'McIntosh'

SmartFresh on 'McIntosh' apples also increases the risk for external CO₂ injury, and ReTain further increases this risk. Similar to 'Empire', the best precaution is to drench with DPA at harvest time and then standard CA (2.5% O₂ + 2.5% CO₂ 1^st month and 4.5% CO₂ thereafter, at 3°C) can be used. An alternate precaution is to hold the CO₂ concentration below 2.5%, but there may still be some risk of external CO₂ injury without DPA. Elevated CO₂ improves the firmness retention of 'McIntosh' in long-term storage, so its reduction could lead to greater softening as the effects of SmartFresh become reduced with time. CA storage for longer than 8 months increases the potential for internal browning and low temperature disorders in 'McIntosh'. Therefore, maintaining the recommended storage of 3°C is important, although senescent core browning may become a problem with increased storage duration.

Other Cultivars

The standard CA recommendation of 2.5% O₂ + 2.5% CO₂ at 0^oC for 'Delicious', 'Idared', 'Northern Spy', and 'Spartan' can also be used when these fruit are treated with SmartFresh. Conversely, 'Gala' treated with SmartFresh should be stored in standard CA (2.5% O₂ + 2.5% CO₂) at 3°C due to chilling sensitivity.