Vermont Apple Newsletter, July 1, 1998

Vermont Apple Newsletter

M. Elena Garcia, Lorraine P. Berkett, Jon Clements, Gwen Neff, and Roger Brouillette.

July 1, 1998

Predicted Harvest Dates for 'McIntosh'

Horticulture Notes

Summer Tour

The VTFGA will have its summer tour on Tuesday, July 28th from 9:00 AM-3: 30 PM. This year, we will visit Chapin Orchard in Essex, Adam's Orchard in Williston, and the University's Horticulture Research Farm in S. Burlington. If you would like to attend the tour and have not received the program registration materials, please contact:

Karen Gallott
VFTGA Program Chair
(802) 545-2338
E-mail: jgallot@sover.net

Predicted Harvest Dates for 'McIntosh'

According to the estimates worked out by Glen Koehler (University of Maine) based on two models, Michigan and Cornell, the following dates are the estimated harvest dates for McIntosh for long-term CA storage are:

Location	Bloom date	Predicted Harvest Dates
		Michigan Model	Cornell Model
Burlington	May 6	Sept 12	Sept 16
Shoreham	May 6	Sept 11	Sept 15

Remember that these dates are based on models in which temperatures after bloom are major components of the models. Other factors such as light, soil moisture, rootstock, cropload, pest infection, nutritional status also affect the fruit maturation process. These dates should only be use as a guide for your preparations for the harvest season. Good indictors of when the fruit is ready to be harvest include days from bloom for each particular cultivar, starch index, fruit firmness, fruit color, and seed color.

Summer Pruning

Shading in the interior of the tree canopy may be a problem this year because of the vigorous growth trees have made due an earlier spring, higher than normal temperatures, erratic fruit set, lighter crop load, and in some areas more than sufficient rainfall. One recommended technique to increase light penetration into the canopy is summer pruning.

Summer pruning differs from dormant pruning in that the leaves that are actively producing carbohydrates are removed. When these leaves are removed, the resources that were used to produce these leaves, such as carbohydrates and nitrogen are also removed. An effect of this removal will be a reduction in growth as measured by the net dry matter accumulation for that year, and depending on the type of cut, the timing, and severity, the trees may not be able to overcome this reduction in dry matter accumulation which may result in yield reductions. In addition, pruning while the tree is growing interferes with other physiological functions such as flower bud formation because it disrupts the production and movement of hormones.

So, why is summer pruning a recommenced practice for many orchards? Summer pruning is really unnecessary if the orchard is managed correctly. Generally, well structured trees that are properly dormant pruned do not require any summer pruning other than the removal of water sprouts that grow in the canopy's interior. Also, in tree with a very light crop, summer pruning may not be cost effective. However, if you are concerned about problems associated with low light penetration into the canopy then summer pruning should be an option to consider. For example, research on 'McIntosh' has shown that summer pruning can significantly improve the crop value by improving fruit color, especially in a season with poor coloring weather near harvest.

Reasons for summer pruning

To improve fruit color and quality

The red color development in apples is due to formation of red pigments, anthocyanins. The synthesis of these pigments occurs when light shines directly on the fruit. Summer pruning can be used very effectively to improve light penetration into the canopy thus; increasing fruit color in 'poor coloring' varieties. Besides color improvement, summer pruning has been shown to improve fruit calcium content, thus, reducing the incidence of such disorders as bitter pit of apple.

To regulate growth and control vigor

Summer pruning can be used on young tress to encourage leader development and direct growth into the permanent scaffold structure.
It can be used to alleviate temporary problems with crowding in high-density orchards.
Summer pruning may or may not reduce vegetative vigor depending type of cut, the timing, and severity. The control of vigor in trees should be accomplished by training, dormant pruning, regulation of fruiting, and soil water and fertility programs.

To reduce pests and disease problems

Vigorous growing shoots such as water spouts of some cultivars are susceptible to fire blight infections.
The wooly apple aphid often colonizes the basses of actively growing water sprouts.
Research at UMass has shown that summer pruning consistently reduced the incidence of flyspeck on apple fruit by approximately 50% in each of 2 years in trees where no fungicides were applied.

Some of you who have been in the orchard business for a while will recognize the following is a chart my predecessor J. Costante published in The Apple Press summarizing the effects of summer pruning. It was initially prepared by D.C. Ferree, Ohio State University. I will reprint this table, with some modifications, for those of you new to the business and also because I find it quite useful and informative

*Table 1. General influence of summer pruning on tree size, growth and fruiting of apple trees in the field*
PARAMETER	INCREASED	DECREASED	NO EFFECT
*Vegetative Growth*
Shoots the year of pruning		X
Shoots the year following pruning	X
Regrowth in cuts in 1 yr. Wood	X
Regrowth in 2-3yr. Wood		X
Regrowth of cuts done in June	X
Regrowth of cuts done in Aug.		X
Tree size		X
Trunk and limb diameter growth		X
Spur number and size (cuts in June)	X
Leaf N content (cuts in June		X
Leaf Mg content (cuts in June)		X
*Flowering and Fruit Set*
Flowers/cluster	X
Time of bloom the following year	X
Flower initiation (cuts in June)	X
Flower initiation (cuts in Aug.)			X
Fruit set (cuts in June)	X
Fruit set (cuts in Aug.)			X
*Yield and Fruit Quality*
Fruit color^a	X
Fruit size ^b	X
Fruit size (severe pruning)		X
Cork spot		X
Watercore		X
Soluble solids^b			X
Soluble solids (severe pruning)		X
Fruit shape			X
Firmness			X
% of crop in interior spurs	X

^{a No effect on highly color strains; increased color on poorer-color
varieties.

^bC. R. Rom, University of Arkansas

The above information should be used as a general guide for effects
of summer pruning. Remember that the response to summer pruning varies with the timing,
the type and the severity of pruning

Timing of Summer Pruning

Early summer pruning (generally not recommended)

It is done before terminal bud formation.

Generally induces some regrowth which can be detrimental because it alters the leaf to
fruit ratio. Ways in which early summer pruning can have negative effects include loss of
buds, reduced flower bud formation delayed hardening, there may be decreases in fruit size
and/or soluble solids content, and some trees may require more pruning during the dormant
season.

After terminal bud formation

This is the time summer pruning is recommended, which corresponds to
late July and early August. At this time the trees have entered physiological dormancy,
and will generally not respond with renewed growth. It has the effect of reducing total
leaf area. However, the total accumulation of carbohydrates does not decrease because the
leaves found deep in the interior of the canopy are now exposed to increased light levels,
stimulating their photosynthetic output.

Type and Severity of Cut

Complete removal of vigorous water sprouts by thinning cuts.
Fruiting branches that have too much vigorous growth can be
headed-back to just above the fruiting cluster, and should be removed during dormant
pruning.
Upturned branches can be thinned to a lateral branch.

Tips to help you with your summer pruning

The preferred time during the season is late July though August.
Remember, the earlier summer pruning is performed, the more regrowth that will occur
during the summer. In addition, early summer pruning can lead to decreases in fruit size
and lower soluble solids content.
To generate fruiting wood on bare scaffold branches, select shoots
that are as horizontal as possible, that have a good crotch angle, and that will provide a
well spaced (12" to18") canopy along the length of the canopy branch. Head these
shoots to about 18".
About 90% of the cuts should be on the current season's growth and
two-year old wood.
Start by pruning the upper third of the tree. This will create
pathways for the sunlight to penetrate into the interior of the canopy.
Do not summer prune trees with moderate to low vigor.
Spend only 5 to 10 minutes per tree.

In conclusion, because of the complex interactions of summer-pruning
timing, severity, and types of cuts with the physiological processes of the plant, summer
pruning should be used only for specific purposes and with certain limitations. It should
be closely supervised to reduce severe crop damage and losses. One should work towards the
goals of not having to summer prune at all by placing the emphasis on well-designed tree
structure.

Time for Leaf Analysis

Soon it will be time to go into your orchard to collect leaves for
nutrient leaf analysis. Leaf tissue analyses indicate the amounts of the various elements
that have been taken by the tree and translocated to the foliage. The time for collection
is between July 20th and August 20th. Leaf testing is available through UVM Agricultural
and Environmental Testing Laboratory (phone: 802-656-3030 or 1-800-244-6402). If you have
any questions on the interpretation of your results, please contact me. The will be more
details on this subject in the August newsletter.

IPM News

Contact Information

A Commitment to Excellence and Service:

We a committed to excellence and service to you. If you have any
questions, problems or want to arrange for an orchard visit regarding your concerns,
please call or write.

For horticulture questions contact:

M. Elena Garcia

Tree Fruit Specialist

Plant and Soil Science Dept.

306 Hills Bldg.

University of Vermont

Burlington VT 05405-0082

Phone: 802/656-2824

Fax: 802/656-4656

E-mail: elena.garcia@uvm.edu

For IPM questions contact:

Lorraine P. Berkett

Plant Pathologist and IPM Specialist

Chair, Dept. of Plant & Soil Science

University of Vermont

Burlington, VT 05405

Phone: 802/656-0972

Fax: 802/656-4656

E-mail: lorraine.berkett@uvm.edu

Where trade names or commercial products are used for
identification, no discrimination is intended and no endorsement is implied. Always read
the label before using any pesticide. The label is the legal document for theproduct use.
Disregard any information in this newsletter if it is in conflict with the label.}

Table of Contents:

Horticulture Notes

Summer Tour

Predicted Harvest Dates for 'McIntosh'

Summer Pruning

IPM News

Contact Information

Horticulture Notes