The use of plant growth regulators to help with harvest management and improve fruit quality is an important tool in many orchards. ReTain plant growth regulator is used to slow ethylene synthesis in ripening fruit to delay maturity and reduce preharvest drop. Given the dry and hot conditions experienced this summer, drop potential is high, and growers should plan on treating their orchards more often than not. One or two applications may be made at the rate of one pouch (11.7 oz) per acre each. Application 21 to 28 days prior to normal harvest will delay ripening 7-10 days and improve fruit storability. ReTain is especially recommended on McIntosh, and reduced rates (1/2 pouch each application) suggested for Macoun and Honeycrisp. ReTain also improves fruit quality on Cortland and Gala. ReTain is not just for fruit destined for wholesale markets. In fact, it is an excellent tool to help stretch harvest out and reduce ‘Monday morning drops’ in U-pick blocks. It also helps to maintain fruit quality both on-tree and in short-term storage.
Jim Wargo from Valent USA has a good list of specific recommendations for ReTain use here.