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Apple Maturity, September 15, 1999

Starch-index values suggest that McIntosh ripening is progressing at a time and rate only slightly advanced from the average of the last 13 years. Standard and Marshall McIntosh index values collected to date are listed below. McIntosh drop is well underway. Where Retain was used and trees are not overly stressed, McIntosh drop is delayed. Thankfully, the end of last week gave some relief to the drought conditions and some cooler weather. Red color that was lost during the previous week is developing again.

As noted last week, ripening is quite variable from orchard to orchard and from block to block. Also, indications are that varieties may not ripen in the same sequence as they have in the past, and the interval between the harvest of different varieties may vary from normal. Therefore, it is imperative that each grower monitor ripening by block to assess harvest needs accurately.

Gala index values are increasing, and in Belchertown, Gala harvest is in progress. The average index value on Monday for Gala in Belchertown was 6.8 – not much starch left! Index values for Cortland and Macoun are on average less than 2 at all locations, suggesting that the season is not advanced for these two varieties.

Standard strains of McIntosh
Date	Location	Starch index value
8/30	Belchertown	3.5
8/31	Littleton Lunenburg	1.7 1.7
9/1	Sterling	1.3
9/2	Peabody	1.3
9/8	Sterling	2.1
9/10	North Andover	4.0
9/13	Deerfield Hawley	4.4 3.6

Marshall McIntosh
Date	Location	Starch index value
9/26	Methuen Peabody	1.6 1.4
8/30	Belchertown	3.6
8/31	Fitchburg	2.2
9/1	Sterling Lunenburg Berlin	1.9 2.5 3.0
9/2	Methuen Peabody	2.4 1.8
9/8	Sterling Fitchburg	3.0 2.6
9/9	Northborough	4.5
9/10	Berlin Methuen	5.6 3.1
9/13	Deerfield Hawley	4.0 3.8

Data for this report were collected by Jim Krupa, Jim Williams, Bob Rondeau, Duane Greene, Rick Bartlett, Mo Tougas, Ellen Krause, and Howie Vinton. If you are assessing starch index values in your orchard, it would be very much appreciated if you call those data into Wes Autio (413-545-2963). In your message, please leave your name, the date of sampling, the variety (and strain for McIntosh and Delcious), and whether or not trees received Retain. If you need chemicals or charts, call Wes Autio.

Boron! Now?

Over the last couple of weeks, I have gotten a few calls from growers concerned about brown, corky streaks in apple fruit. I have not seen any of those fruit yet, but descriptions point to boron deficiency. In some of these cases, growers have religiously applied boron (soil or foliar) in the spring; however, the drought certainly reduced boron uptake from the soil and very likely is the cause of this deficiency. In last week's issue of Abbot Laboratories' Harvest the Potential Report, Charlie Embree notes similar problems this year in Nova Scotia fruit.

What does this mean for boron management? Next year, assuming normal moisture levels, trees will be able to take up normal amounts of boron, so extraordinary practices next year likely will not be necessary. However, the trees are boron stressed now! Even if you do not see deficiency in the fruit, your trees likely are deficient where you did not irrigate. Remember also that flower buds were set (hopefully) and have grown in the midst of a severe drought. Exposure of these water-starved, boron-deficient buds to cold temperatures may cause a significant number to die. Even if they make it through the winter, they may not set well next year. (Remember a few years in the early 1990's when we had a good bloom following a drought year but very little fruit set.) Therefore, it is important to do everything possible to assist the tree in strengthening their buds now.

Warren Stiles recommends foliar application of boron and urea in the fall to strengthen buds. It may not be enough, but this is the year where investment in this treatment may pay off significantly. Treatment should be applied as soon as possible after harvest and while leaves are still in good condition. Spray as dilute as possible, and do not exceed 6X. Rates of application follow:

 Johnny Come Lately

There is no question that the statewide population of immigrating apple maggot flies has been remarkably low this season, with peak and total trap captures roughly one-third of those observed over the past several years. While we would jump at the opportunity to take credit for this phenomenon, it is more directly linked to recent environmental conditions. Some factors contributing to the dip in numbers of invading AMF were outlined in previous issues of Healthy Fruit, including the lack of fruit on unmanaged host trees in 1998 (reducing the overwintering population) and the dangerously dry soil conditions this season (reducing emergence of AMF adults).

Given the lack of AMF pressure, most growers have been able to stretch the interval between treatments, reducing the total input by one or more applications. Early- and mid-ripening varieties have already weathered the threat of AMF infestation, as harvest of these cultivars is either complete or well under way. However, this season?s weather and ripening trends may accentuate the perennial problems encountered in AMF control on late varieties.

Trap-capture patterns over the past two weeks indicate that AMF pressure in later-ripening varieties (Empire, Red Delicious, Golden Delicious, Fuji) has increased in September. Recent increases in immigration are likely a result of delayed AMF emergence inspired by wet soil and a higher level of immigration into commercial orchards after unmanaged trees shed their fruit. Unfortunately, late-ripening cultivars in Massachusetts have been known to harbor substantial numbers of fertile AMF well after mid-season varieties have been harvested.

Growers who have had problems with AMF damage on late varieties in the past should be aware that this year?s late fly emergence, lack of residual coverage, and concentration of flies on fruit remaining in the orchard after most varieties are harvested may all contribute to continued risk. If it is felt that some treatment is necessary, we do not recommend use of Guthion or Imidan, but feel that an application of Sevin (with a 3-day preharvest interval) will offer an appropriate level of control to deal with the late-season threat.

Along with keeping most insect pests at bay, the dry weather of July and August contributed to suppression of flyspeck and sooty blotch. However, recent rains have inspired a substantial increase in appearance of FS on fruit. Over the past two weeks, FS incidence on McIntosh has doubled in most areas, suggesting that late (particularly light-skinned) varieties may be open to rapid buildup of FS. In areas of such varieties that are prone to annual buildup of FS, growers may want to consider a treatment with Benlate, which offers some retroactive control (~100 hours of wetness) rather than Captan, which probably will leave too much visible residue. The following is excerpted from the New England Apple Pest Management Guide:

For the final application of the season, the 3 oz./100 gal. rate of Benlate is better for extended preharvest protection against summer disease fungi in the more southern regions of new England where weather conditions are more favorable for disease development. Benlate appears to be somewhat more effective than Topsin-M against sooty blotch and flyspeck. Benlate does not protect against bitter rot. Restricted entry interval 24 hours. Preharvest interval 14 days.

Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, Wes Autio, and Duane Greene except where other contributors are noted. Edited by Dan Cooley. 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.