Some apple harvests in 2022 were impacted by adverse weather in February and March, as well as the difficult labour situation.
Growers had no control over those situations, but as the 2022-23 season gets underway, Nufarm Technical Advisor Andy Davis says it’s worth revisiting the fruit quality attributes of a long-established plant growth regulator which is one management tool they can control.
“ReTain has been helping New Zealand apple growers get the best out of their crops for many years,” says Andy.
“Much of that focus has been on its value as a tool for manipulating crop maturity dates for different blocks and varieties, smoothing out harvest peaks and optimising available picking and post-harvest workforce.”
Equally important, however, ReTain has been shown¹ to help harvested fruit hold its flesh firmness and pressure, and slow moisture and weight loss in long-term storage.
“We know in ReTain-treated fruit we can stave these changes off longer in storage than with untreated fruit,” Andy says. “This can make a measurable difference when fruit is packed and shipped. The better it goes into storage, the better it comes out.
“Labour has been such a pressing issue for the industry in recent years we have perhaps overlooked the other ways that ReTain can help us once we do get the crop off the trees.
“Also, with any product that has been around for 20 years, especially one as widely used as this one, it can be easy to take it for granted sometimes.”
ReTain contains a naturally occurring plant growth regulator that temporarily inhibits production of ethylene in developing fruit, slowing maturation, ripening and development of abscission tissue while allowing continued fruit growth².
This in turn extends the apple harvest by up to 7 to 10 days without affecting fruit quality. Capturing the full benefit of this delay is all about careful planning, Andy says.
“Now’s the time for growers to start reviewing their schedule for ReTain applications to allow optimal lead times, and also other crucial factors like planned calcium treatments and temperature data.”
For example, growers need to allow a minimum of seven days between calcium (Ca) sprays and ReTain, and it should not be applied if Ca residues are present or if previous Ca use has damaged lenticels.
Historical crop harvest records can help determine application timing for different blocks. It’s also very important to monitor temperature conditions around planned time of application.
“ReTain has to be applied with Freeway® organosilicone adjuvant at the correct rate for the variety being treated to work properly. Applying the adjuvant to hot fruit is not advised, because it increases the risk of lenticel damage, hence the recommended best practice is to apply ReTain in the cool of the morning.”
Andy says other key guidelines for optimal results include leaving a 24-hour interval after ReTain before applying any other sprayed horticultural product or irrigation; laying down foil mulch or reflective film after applying it, not before; and avoiding spraying if rain is expected in six hours.
For more advice on using ReTain to get the best out of the 2023 apple harvest, talk to your local Fruitfed Supplies Technical Horticultural Representative.
ACVM registration number: ReTain® #P004890. Read the registered label before use.
¹ Volz et al Hort Research, ReTain storage potential, 1989.
² Volz et al Hort Research, ReTain harvest parameters, 1989.
