Index

Workshop

There will be a morning workshop scheduled at two locations, at the UVM Horticulture Research Farm in S. Burlington on April 7 th, and at the Extension Office in Brattleboro on April 9^th. Cultivar recommendations, rootstock updates and plant nutrition will be the discussion topics for the workshop. The section on nutrition will be conducted as a grower discussion group. More detailed information will be sent to you in a separate letter.

According to USDA statistics, the 1997 apple crop utilization for 1997 was estimated at 10.2 billion pounds, 2 percent less than the last 2 years. Production increases in California, Michigan and New York were not enough to offset an 11 percent drop in production in Washington. Michigan's production was up 50 percent from 1996's drought-reduced crop. Washington's drop in production in 1997 was due primarily to smaller-sized fruit. In Vermont, the utilized apple production for 1997 was estimated 929,000 bushels, slightly higher than last year. According to Steve Lacasse of Vermont Apple Orchards, the price of larger apples (>3 inches) is selling for 2 to 3 dollars a bushel higher than the smaller apples (<2 5/8 inches). Also, there is a surplus of juice apple. The price of concentrate is lower than it has been in recent years.

Other News

It appears as if there was only minimal damage to the apple industry due to the ice storm in January. According to the Farm Bureau, only two growers have reported damage to their trees. This lower damage to apple trees in comparison to ornamental and forest trees is understandable when one thinks of the training and pruning that is given to apple trees. Apple trees are trained to withstand a crop load. There has been some spur damage reported, but this does not appear to be extensive.

Pruning

By now, most of you are in the midst of the most important and expensive management practice of your orchard, and that is pruning. Since each apple grower trains and prunes according to his/her individual objectives and skills, it is difficult to make specific recommendations, but if you keep in mind the following facts and tips; your pruning outcomes will be enhanced.

The objectives of pruning should be to balance vegetative growth and production, and to maximize light penetration and distribution within the tree canopy.

1. Improved light penetration into canopy resulting in

1. improved fruit quality and size
2. increased spur fruitfulness

1. Renewal of bearing surface
2. Improved spray penetration resulting in

1. improved insect and disease control

1. Increased vegetative vigor
2. Delayed cropping
3. Reduced yield

In order to maximize the benefits of pruning, you should have a planned approach to pruning. A general knowledge of the physiology of tree growth should help you understand the response of any pruning practice.

Apical dominance is the inhibition of growth of lateral buds on a shoot due to the effect of growth hormones, particularly auxin, produced by the actively growing cells at shoot tips. Auxin moves downward, by gravity, in the shoot towards the roots. One of the effects of auxin is the blockage of growth of the lateral buds. Apical dominance influences the number of shoot forming lateral buds, the length of the lateral buds, and the angle at which the shoot develops relative to the limb. The shoot tip acts as a strong sink directing nutrients from roots, photosynthates, water and other resources to the growing tip. By removing the shoot tip, you are removing the supply of auxin and thus the inhibition of growth of the lateral buds.

Root to shoot ratio. The auxins produced by the shoot tips are transported downwards to the roots, where they enhances root development and branching. Roots are the site of another hormone, cytokinin. Cytokinins, which are transported upwards to shoot tips, are important in cell division and bud break. Pruning reduces the number of growing points that are producing auxin, which in have an effect of reduced root growth and decreased cyokinin production. This in turn affects shoot growth. Pruning is generally considered a dwarfing process. As you reduce the amount of vegetative surface, not only will there is a hormone imbalance affecting both the upper and lower portion of the tree, but you are also removing the source of carbohydrate production that supports the roots.

Before you set out to prune your orchard, ask yourself the following questions:

1. What tree response (s) do I want to create?
2. What type of cuts is necessary to achieve this response (s)?
3. What was the tree production last year, and what level do I want on a per tree basis?

There are two general types of cuts, heading back and thinning, and these cuts will give you different responses. When a heading cut is made, the terminal bud is removed. Generally, 1/3 to 1/2 of the shoot is removed, but this not always the case, and it is usually made to 1 or 2 year old wood. In a thinning cut, the whole shoot or branch is removed at the point of origin. This type of cut is usually made to 2+ year old wood.

Heading cut response

1. Release of the buds bellow the cut from dormancy because the effect of auxin in these buds is removed, resulting in the stimulation of lateral branching
2. Local invigorating effect

 Thinning cut response

1. Larger portions of the scion are removed altering the root/shoot ratio
2. May increase overall vigor
3. In younger trees, change in the vegetative/cropping ratio may result in decreased fruiting
4. In mature trees, this type of cut may improve fruit quality and cropping due to the increased light penetration 

Nutrition

Pruning and training should not be the only practices used to control growth and tree development. Nutrition will also help determine the ultimate tree size, and soil and foliar analysis should be used to determine the nutritional status of the tree. One of the most effective nutrient management practices in an apple orchard is the maintenance of the soil pH in the range of 6.0 for the subsoil to 6.5 for the topsoil because the pH influences the availability of the various elements to the plant. Figure 1) shows the availability of some essential nutrient elements as influenced by the soil pH. For example, as the soil pH becomes acidic (pH <5.5), the phosphorous in the soil becomes unavailable to the plant. It does not matter if there is an adequate amount of phosphorous in the soil; the roots are unable to uptake it.

Under common orchard practices, the soil tends to become more acidic over time, and a regular liming program is required to maintain the soil at the proper pH. Table 1 lists the commonly used nitrogen fertilizers and their residual effect on pH. Soil pH and texture are commonly used to determine the lime requirements. Leaf tissue analyses indicate the amounts of the various elements that have been taken by the tree and translocated to the foliage. In other words, soil analysis tests will give you an assessment of the acidity and the fertility of the soil before the growing season, whereas leaf analysis gives you the nutritional status of the plant during the growing season. Soil and 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.

Knowing the leaf analysis standards for apple, your soil and leaf analysis results, and personal, visual observations should help you make decisions in determining what nutrients are causing an unwanted response, and what treatments are necessary to change or enhance the response. Due to the many variables involved, such as cultivar, rootstock, soil pH and type, age of tree, the grower is the only person should make the final call on tree fertilization. Table 2, with minor modifications, was compiled by D. Schmitt and J. Clements, under the supervision of Dr. Costante in 1993. It is an attempt to familiarize you with information regarding the role of macro and micro nutrients, nutrient disorder symptoms, and corrective measures. This information has been adapted from several publications, particularly useful was the Orchard Nutrition Management (142IB219 $4.00) by W. C. Stiles and W. S. Reed from Cornell Cooperative Extension. This is a very detail, extensive and informative bulletin, and it is available from:

Cornell University Resource Center

7 Business & Technology Park

Ithaca, NY 14850

Telephone: 607-255-2080

Fax: 607-255-9946

Tables 3 and 4 are the leaf analysis standards and the fertilizer chart recommendations, respectively, for young- nonbearing trees.

Nutrition pointers

Care of young trees

1. Special attention should be given to phosphorous fertilization at pre-plant site preparations. Surface applications of phosphates in established orchards are likely to contribute to surface water contamination.
2. Young trees can be fertilized by a split application in early April and early June.
3. Try to band in a circle 12 to 18 inches from the trunk. A leaf analysis program should begin a year before the trees will produce a commercial crop.

Fig. 1. Availability of some essential nutrient elements as influenced by soil acidity or alkalinity

pH

Table 1. Nitrogen FERTILIZERS, their COMPOSITION, and RESIDUAL EFFECT on pH

Table 1. 1998 Apple Team Mineral Nutrition Bearing Orchard Fertilization Summary  

Table 3. LEAF ANALYSIS STANDARDS FOR YOUNG, NON BEARING APPLE TREES

Table 4. YOUNG TREE FERTILIZER RECOMMENDATION CHART

As you consider your options for European Red Mite (ERM) management this year, please remember that you should 'rotate' your miticides from year to year in order to help prevent the development of resistance. This is a very important issue. If you used Apollo or Savey in 1997, you should not use either of these materials this year. Consider Oil prebloom and/or an Agrimek application at petal fall as alternative early season management options.

Encourage Biological Control of European Red Mites by Choosing Pesticides Carefully.

Over the past two years, we have been participating in a collaborative, New England-wide project led by Dr. Jan Nyrop from Cornell University to introduce the predacious mite, Typhlodromus pyri, as a biological control agent for ERM. Three sites in Vermont were involved in this project: Larrabee Point Orchard in Shoreham, Allenholm Farms in So. Hero, and the UVM Hort. Res. Center in South Burlington. Results of the project were presented at the Vermont Tree Fruit Growers Association Meeting In February, 1998 and a summary is currently available on the UVM Apple Orchard website: http://orchard. uvm.edu/uvmapple/ The good news is that not only did T.pyri become established in the release trees in each orchard, it was found naturally occurring in other trees in the orchard as well.

One of the stipulations of participating in the project was that pesticides known to be harmful to the predacious mite would not be used and it appears that this allowed not only the released predators to survive but also allowed naturally occurring populations to increase in number. The following graph illustrates how the percentage of T.pyri in the predator mite complex increased on 'control trees' (i.e., trees in which T.pyri were not released) in each orchard over the two years of the project.

T.pyri is an effective predator of ERM. Experiments conducted by Cornell researchers have shown that it can completely eliminate the need for miticides.

It is exciting to know that T.pyri naturally occurs in Vermont. What can you do to encourage biological control in your orchard? Choose your pesticides carefully. Avoid using materials known to be toxic to T.pyri such as pyrethroids, Lannate, Vydate, and Carzol. Also, limit the use of EBDC fungicides and use them only prebloom to try to minimize their impact. These would be the first steps in conserving any naturally occurring populations of T.pyri in your orchard.

Currently, research on T.pyri is continuing. For example, Dr. Jan Nyrop is examining better ways to enhance collection and establishment of this important predator. We will keep you posted on any new developments in this important area of research.

As the title of this publication implies, it is a collaborative effort among extension personnel representing the New England states. Glen Koehler of the Univ. of Maine Coop. Ext. Pest Management Office is spearheading its publication this year. He expects it to be "off the press" by April 1. As soon as we get current pricing, we will send out order forms to all Vermont growers and mail out the publication as quickly as possible.

Farewell to Gwendolyn Neff ...

The UVM Apple Team will truly miss Gwendolyn Neff who has accepted the position of Project Coordinator for the 'People Grow' Project at the Vermont Chapter of NOFA. Gwen had joined the UVM Apple Team in October, 1995 and her intellect, insights, and organizational skills quickly became valued assets in all aspects of our research and extension program. We sincerely thank her for all of her efforts and contributions in support of the UVM Apple Program and the Vermont apple industry. Her new position addresses community food security. Gwen will be bringing together anti-hunger, food, and farm organizations with communities to increase people's options in meeting their food needs.

 Please join us in wishing Gwen the very best in her new career !!

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.

206 Hills Bldg.

University of Vermont

Burlington VT 05405-0082

Phone: 802/656-2824

Fax: 802/656-4656

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

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 the product use. Disregard any information in this newsletter if it is in conflict with the label.