UMass Healthy Fruit: Vol. 9, No. 18, August 7, 2001

FRUIT ADVISOR HOME | CONTACT | ABOUT

Volume 9 -- 2001

Healthy Fruit is written by Jon Clements, Ron Prokopy, Dan Cooley, Arthur Tuttle, Gerald Lafleur, Wes Autio, Bill Coli, Duane Greene, Bill Bramlage, and Sarah Weis and is presented with the cooperation of New England Fruit Consultants and Polaris Orchard Management. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.

Issue 18 - August 7, 2001

Predicting Harvest Dates for McIntosh

By now you may be wondering about the timing of the start of McIntosh harvest. Various formulas have been developed that predict the start (and end) of McIntosh harvest based on the date of full bloom (FB) and temperatures during the three to four week period following bloom. (Phil Schwallier, Michigan State University Extension, personal communication; 'Predicting Harvest Date windows for Apples‚' G.D. Blanpied and Kenneth J. Silsby, CCE Information Bulletin 221). Using the FB date at the UMass HRC in Belchertown (May 6), and average temperatures recorded during the 21-30 day period after bloom there, it‚s predicted McIntosh harvest should commence September 7, and the last apple destined for CA storage should be harvested by September 21. That is a two-week interval, which is typical for Mac harvest. Of course your start and end dates will vary depending on location.

Duane Greene 'Harvest the Potential Report' for August 7

Weather during the past week has been very warm with scattered thunderstorms. In areas where no rain fell and no irrigation is in place, trees will be stressed. Based upon experience in previous years we do not believe that the stress has become severe enough at this point to compromise the drop control capability of ReTain. Fruit maturity appears to be close to historical norms. We are approaching the time when ReTain should be applied to McIntosh and Gala. Marshall McIntosh can be sprayed with ReTain starting now through the upcoming week. Later maturing strains of McIntosh should receive ReTain sometime next week. There is a window of opportunity to Apply ReTain, since the exact time of ripening is uncertain at this point. ReTain is especially effective on Gala. In some instances we have seen ripening delayed by as much as 4 weeks. If you plan to treat extensive acreage with ReTain it may be prudent to treat a portion of these with a reduced rate to avoid delay of ripening of large numbers of fruit. We suggest that you select a good day with little breeze to make your application to assure good coverage. Silwet L-77 and Sylguard 309 are the only approved surfactants that are readily available on the East coast. We strongly urge you to include one of these with your ReTain at a rate of 0.05% to 0.1%. Surfactants will not only improve ReTain performance, but based upon research done last season, they may also impart some rain-fastness. Fruit continue to grow with fruit size in monitored blocks of McIntosh, Delicious, and Gala at 2.49 in., 2.38 in., and 2.28 in., respectively. In dry areas, however, fruit size is being affected by lack of moisture.

Managing Apple and Pear Harvest with ReTain

Note: Article adapted from New Jersey Plant and Pest Advisory (), July 31, 2001: Win Cowgill, Area Fruit Agent, Jeremy Compton, North Jersey Tree Fruit Technician, and Jon Clements, UMASS Extension Tree Fruit Specialist

As the 2001 apple harvest approaches, growers need to manage their apple and pear harvest with a focus on fruit quality. In the current marketing environment, all factors demand only the highest quality fruit. ReTain plant growth regulator (Valent) has proven to be a tool that allows for increased flexibility in harvest management decisions and has also proven to increase fruit quality and grower profitability with certain apple cultivars.

ReTain has been commercially available to apple growers since 1997. A single ReTain application before harvest helps growers manage fruit maturation and ripening to optimize harvest time for maximum quality and storage potential. With ReTain growers can extend harvest 7-10 days without affecting (losing) fruit firmness. By temporarily inhibiting the biosynthesis of ethylene in plant tissues, ReTain results in the following benefits: improved harvest management; reduced fruit drop; a wider harvest window that may enhance fruit size and color; improved storage potential; and better fruit condition after harvest.

The active ingredient of ReTain is the naturally occurring product amino-ethoxy-vinyl-glycine (AVG), which is produced by fermentation. The fermentation process required to produce AVG is very difficult and very expensive. As a result, ReTain retails for $270 - $290 per acre. Therefore, ReTain should only be used in high value blocks with large crops of unblemished fruit. Valent has a built in calculator to determine the cost benefits of using ReTain at: http://www.valent.com/retain/default_BOTT.htm.

Fruit treated with ReTain can be picked during the normal harvest period for enhanced retention of firmness in regular cold or Controlled Atmosphere (CA) storage, or harvest may be delayed -- without significantly sacrificing fruit firmness -- allowing the fruit to continue to grow and develop red color for an extended time. But one of the greatest benefits of using ReTain is reduction in pre-harvest drop, often as much as 30% with McIntosh.

Research has also shown that stem-end split (SES) and internal ring crack (IRC) may be reduced on susceptible varieties, such as Gala and Fuji, with the use of ReTain. Although these disorders will not be eliminated, ReTain reduces the stress fluctuations that are thought to cause these disorders.

ReTain must be applied four weeks prior to anticipated harvest. Projected ripening dates for each orchard in which you plan to use ReTain this season should be calculated. As noted above for McIntosh and Gala, the Œfour weeks before harvest window‚ is here in many Massachusetts orchards. Therefore, we are recommending ReTain application to McIntosh and Gala be made during the period August 10 to 17.

Important Considerations to Follow with Retain Applications

Use the full rate of ReTain (1 pouch or 333 grams/Acre of formulated product) with an organosilcone surfactant at 0.05% to 0.10 % (v/v).
ONLY use one of the following organosilcone surfactants: Silwet L77 at 6.5-13 fluid ounces per 100 gallons, or Sylguard 309 at 6.5-13 fluid ounces per 100 gallons. When high temperatures prevail, the lower rate of surfactant is recommended.
Apply 4 weeks before anticipated harvest (28 days). It is better to apply slightly earlier rather than later.
ReTain should be applied with a sufficient amount of water to ensure thorough wetting of the fruit and foliage while avoiding spray run-off. Adjust water volume based on tree size and spacing. No alternate row spraying. In many cases, 100 gallons per acre or 2X Tree Row Volume (dilute) have been shown to be effective.
For optimum results apply during periods of slow drying weather conditions. Ideally, no rainfall or irrigation should occur within eight hours following ReTain application, although use of a surfactant will improve rain-fastness.
Do not apply ReTain to trees under stress -- they may not respond to the benefits of ReTain.
Do not tank mix ReTain with other agricultural products.
NAA may be used according to label directions after the use of ReTain if very long drop control is desired, or fruit begin to loosen. Be aware that NAA may accelerate fruit maturation.
The interaction of ethephon products with ReTain is not well understood and is still being investigated. No recommendations for combinations can be made.
The pre-harvest interval (PHI) has been changed in 2001. It is now 21 days instead of 28. Note, however, that the recommendation is still clearly to apply ReTain 28 days (four weeks) before anticipated harvest.