WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
October 22, 2007

Upcoming Events New IPM Program


Pheromone Trap Counts Plant Pathology Horticulture



December 4-6. – Great Lakes Fruit, Vegetable and Farm Market Expo at the DeVos Place Convention Center, Grand Rapids, MI. For more information go to www.glexpo.com or call 269-424-3990. 

January 22-24. – Annual Meeting and Trade Show of the Virginia and West Virginia State Horticultural Societies at Hotel Roanoke, Roanoke, VA. For more information contact Katy Trenary at 304-263-1027 or at info@orrsfarmmarket.com, or Liz White at 540-667-1165 or at lwhite@green-inc.com

January 29-31. – Mid-Atlantic Fruit and Vegetable Convention at the Hershey Lodge and Convention Center, Hershey, PA. For a copy of the program and registration form go to:  www.shaponline.org. For questions or more information contact Maureen Irvin at 717-677-4184 or at shap@supernet.com.


West Virginia commercial tree fruit growers in the Eastern Panhandle and Potomac Valley Conservation Districts are being provided an opportunity to sign up and receive cost incentives to support the use of advanced IPM practices through the Environmental Quality Incentives Program (EQIP). A minimum of 3 acres (150 total trees) of bearing apple or peach trees must be enrolled in order to participate. 

This year’s sign-up deadline is November 16, 2007 (earlier than in past years). 

Practices and cost incentives include:

How to sign up

  1. Contact your local Natural Resources Conservation Service (NRCS) office.

        ●  Martinsburg - 263-7547

              ●  Ranson - 725-3471

  ●  Romney - 822-3020

  1. Tell the District Conservationist that you want to apply for the Tree Fruit IPM program through EQIP, and set up a time to complete the application.

For more information, contact Henry Hogmire (876-6353, hhogmire@wvu.edu); Alan Biggs (876-6353, abiggs2@wvu.edu); or Rakesh Chandran (293-6131 x4225, RSChandran@mail.wvu.edu).


Delegate 25WG (spinetoram) from Dow AgroSciences was registered by the EPA on September 28 for insect control on pome and stone fruits. Spinetoram is derived from the fermentation, followed by the chemical modification, of a naturally occurring soil organism. This product effects the insect nervous system through both contact and ingestion, with excellent translaminar activity. Targeted pests in this area include internal worms (codling moth, oriental fruit moth), leafrollers, and leafminers on apple; pear psylla on pear; and oriental fruit moth, leafrollers, thrips, and cherry fruit fly on stone fruits. Delegate will only provide suppression of apple maggot and plum curculio. This product has demonstrated excellent control of internal worms and leafrollers in tests conducted on apple in West Virginia. Application rate is 4.5-7 oz per acre, with a season maximum of four applications and 28 oz per acre. To reduce the potential for resistance development, Delegate should not be applied to consecutive generations, but rotated with other chemistries for the management of internal worms and leafrollers. The product has a restricted-entry interval (REI) of 4 hours. The preharvest interval (PHI) is 14 days on peach and apricot; 7 days on apple, pear, cherry, plum, and prune; and 1 day on nectarine.


March 19 0
March 26 2 0
April 2 121 3 0
April 9 54 28 1
April 16 23 93 0
April 23 18 640 68
April 30 22 1220 230 0 0
May 7 6 396 404 3 0 0 0
May 14 1 132 120 33 2 0 33
May 21 0 12 74 17 17 0 23
May 29 0 64 22 22 43 4 30 0
June 4 3 1280 4 17 12 3 15 1
June 11 59 1472 12 5 0 8 12 0
June 18 50 960 33 1 0 1 7 2 0
June 25 50 2656 69 0 3 0 4 1 0
July 2 36 1664 62 0 0 3 4 1 0
July 9 23 640 113 22 0 2 2 1 0
July 16 12 1120 89 1 0 2 1 5 1
July 23 20 1760 49 29 3 3 0 2 2
July 30 38 2368 72 27 0 3 3 4 2
August 6 40 2688 69 10 1 6 5 1 3
August 13 70 704 62 10 5 9 7 2 9
August 20 115 360 127 25 7 4 7 1 14
August 27 56 864 126 11 4 4 7 1 10
September 4 14 544 98 20 3 4 5 1 10
September 10 26 1536 77 14 3 3 4 0 2
September 17 10 1280 117 9 3 4 3 0 1
September 24 1 1408 116 0 1 2 2 1 2
October 1 0 1416 129 5 1 3 0 0 0
October 8 0 344 20 0 1 0 1 0 1

RBLR = Redbanded leafroller; STLM = Spotted tentiform leafminer; OFM = Oriental fruit moth; CM = Codling moth; TABM = Tufted apple bud moth; DWB = Dogwood borer; LPTB = Lesser peach tree borer; PTB = Peach tree borer; AM = Apple maggot.


Peach leaf curl control that is virtually 100% effective can be achieved by a single fungicide application during the dormant season. A dilute application should be made under calm conditions anytime after most (no less than 90%) of the leaves have fallen and before hard freezing weather sets in. Thorough coverage of each bud is essential for controlling the leaf curl fungus. If leaf curl was severe in your peach or nectarine blocks in this year, make fungicide applications this fall and next spring before bud swell. Treatments with copper compounds are recommended where bacterial spot has been a problem. In orchard blocks that have been intensively scouted and where the grower knows with certainty that the disease is entirely absent from the block for a period of two or more years, this spray can be omitted until the disease begins to recur. See the 2007 Spray Bulletin for fungicides and rates of application.

Minimizing calcium-related disorders in apple. This season I’ve seen a higher incidence of bitter pit and cork spot in some West Virginia orchards, particularly on York, but also on other varieties including Gala, Golden Delicious, Fuji, and Crispin (Mutsu). Calcium-related disorders can be especially troublesome when they serve as infection sites for rot fungi – especially Alternaria spp. and bitter rot in seasons with prolonged warm weather in autumn. Let’s review what we know about calcium nutrition in apple and what can be done to minimize the problem in the future. There are three physiological disorders in apple fruit that are sometimes confused.

1. Bitter pit is caused by a nutritional imbalance in the fruit. The symptoms occasionally appear on the tree before harvest, but symptoms most often appear after harvest, during the first 4 to 8 weeks after harvest. Symptoms appear as small blackish-brown sunken areas on the surface of the fruit. The pits are often less than 1/8" in diameter but can be larger, can develop on most varieties, and are most prevalent on the calyx end of the fruit. The tissue just below the skin is brown and corky. Bitter pit is usually associated with low calcium concentrations in the fruit flesh, but it is actually caused by an imbalance of calcium, potassium and magnesium. Thus, fruit with adequate amounts of calcium may develop bitter pit if the levels of potassium and/or magnesium are too high.

2. Cork spot is caused by a calcium deficiency localized in the fruit. Symptoms develop on the tree before harvest and are characterized by dark green or greenish-brown sunken areas on the surface of the fruit. The spots are usually about 1/8" to " in diameter and the spots can develop anyplace on the fruit. The flesh tissue under the spot is brown and corky and may extend " deep. This disorder is associated with low concentrations of calcium in the flesh. Symptoms most often appear on ‘Delicious’, ‘York’, ‘and ‘Empire’. Internal cork is caused by an early-season boron deficiency in the fruit flesh. Occasionally the fruit may be misshapen, but symptoms are usually not obvious until the fruit is sliced. Symptoms are brown corky areas within the flesh. I have seen symptoms on pear, and ‘Delicious’, but ‘York’ is most susceptible to corking.

3. Jonathan spot can develop on several varieties; ‘Jonathan’ is very sensitive. Other varieties, however, such as Wealthy, Yellow Newtown, Grimes Golden, Rome Beauty, Gravenstein, Northern Spy, Winter Banana, and Golden Delicious may be affected. This disorder looks similar to bitter pit and usually develops on the tree as fruit mature. Jonathan spot is not a nutritional disorder, but is caused by volatiles that collect under the skin. The spots are often associated with lenticels. The disease is common after a dry season. It is usually worse on large apples than on small ones. It is worse on late-harvested fruits than on those harvested in prime maturity. Jonathan spot is also worse on fruits cooled slowly or those stored at temperatures somewhat higher than temperatures recommended for the variety.

Calcium movement in soil and plants. The soil is composed of particles of sand, silt, clay, and organic matter, with air spaces between the particles. The particles are coated with a film of water and nutrients are in solution in this film. Growing root tips absorb calcium and other elements from the moist soil. When the soil pH is too low, calcium forms chemical complexes in the soil and is not available for uptake by roots. Upon entering the root, calcium moves up the plant in the xylem. The xylem is composed of tube-shaped dead cells, which are joined end to end to form a pipe system from the roots to the leaves and fruit. Water, containing elements and organic compounds, moves through the xylem up the tree. Stomates, which are small openings on the undersides of leaves, allow gases to move in and out of the leaf. Water evaporates from the stomatal openings in the process of transpiration, and more water is pulled through the xylem and into the leaf. This transpiration pull is responsible for the movement of water, containing nutrients, into the leaf and fruit.

Calcium moves very slowly in the tree and it may take more than a year for calcium to move from the roots to the leaves. Because most transpiration occurs in the leaves, calcium moves preferentially into shoots and leaves, rather than into the fruit. Anything that reduces transpiration, such as high humidity, very low light levels, or drought stress, also slows the movement of calcium up the tree. Poor spring root growth due to drought stress may interfere with calcium uptake (note: many locations had less than one inch of rain in May, 2007).

Calcium is not evenly distributed throughout an individual fruit. Calcium concentrations are lowest just under the skin and at the calyx end of the fruit. This is why bitter pit develops at the calyx end. In cold storage there is a redistribution of calcium from the core area into the fruit flesh.

Let’s not overlook the cold temperatures that we had this spring as being potentially related to our current bitter pit problems. Evidence exists that relates seed count to a fruit's ability to draw nutrients like calcium. With cold temperatures earlier this year, growth and development of the fruit may be inhibited in spite of good soil moisture regimes and adequate feeding of trees if individual ovules were killed by cold temperatures.

Why is bitter pit severe in some years and not in others? Bitter pit can be severe in years with an unusual combination of conditions. Following a fairly dry winter and spring, early-season soil moisture levels were very low. The dry soil inhibited spring root growth and calcium uptake was less than normal. Most calcium is taken up by the roots in the spring by the new root growth. During enlargement, as the fruit increases in volume, the amount of calcium in a fruit as a whole remained fairly constant, but as the fruit volume increased, calcium was diluted, resulting in lower calcium concentrations at harvest time. In addition, transpiration was probably less than normal because the summer was very dry, possibly causing the stomates on the leaves to remain closed more than usual.

All fruit are not created equal. Some fruit on some trees within an orchard are more susceptible to bitter pit than others. Trees with light crops tend to take up less calcium than trees with moderate to heavy crops. Additionally, fruit on trees with light crops tend to be large and have low flesh calcium concentrations. The combination of these two factors makes fruit on light cropping trees very susceptible to bitter pit and cork spot. The largest fruit on a tree will have relatively low calcium concentrations and are most likely to have calcium-related disorders. Fruit developing on or near vigorously growing shoots tend to be prone to bitter pit because they can not compete with the shoots for calcium. Fruit on vertically oriented shoots have the same problem because upright shoots tend to be vigorous. Young trees have vigorous shoot growth because growers push these trees to fill their space quickly. In addition, young trees are not allowed to crop heavily and the large fruit on young vigorous trees is very susceptible to cork spot and bitter pit. Bitter pit development is also related to the maturity of fruit at harvest. Immature fruit are most likely to develop bitter pit in storage, and simply delaying harvest for 7 to 10 days may drastically reduce the severity of the disorder in storage.

Cultural practices to minimize physiological disorders

1. Spraying trees with boron at pink and again at petal fall or first cover may minimize cork spot and internal cork.

2. Bitter pit and cork spot can’t be totally eliminated, but in most years improving the balance of calcium, potassium, and magnesium concentrations in the fruit can minimize these disorders. Below are some ways to reduce calcium-related disorders. Use dolomitic lime only when soil tests indicate that magnesium levels are low.

a. Maintain soil pH between 6.0 and 7.0 so calcium will be available for plant growth. If liming is recommended to raise soil pH, choose the type of lime based on the amount of magnesium in the soil. If soil test results show that magnesium is medium to high, then choose a high-calcium lime.

b. Avoid excessively large fruit by developing good thinning programs to prevent alternate bearing.

c. Avoid excessive applications of nitrogen that can induce vigorous vegetative growth that can compete with fruit for calcium. Heavy nitrogen application can also increase fruit size and large fruit are prone to bitter pit and cork spot.

d. Avoid heavy pruning that induces vigorous shoot growth. Annual moderate pruning facilitates management of tree vigor and annual cropping, and should improve fruit quality.

e. Avoid applying excessive amounts of potassium and magnesium fertilizers because high concentrations of either element in the soil can compete with calcium uptake and reduce calcium uptake. High concentrations of potassium or magnesium in the fruit can cause bitter pit even when fruit calcium concentrations are adequate. Potassium and magnesium should only be applied when leaf levels are below the sufficiency range and when soil tests indicate that soil levels are low. Sometimes potassium levels in the leaves are low, but potassium levels in the soil are medium or high. In these situations adding potassium to the soil is a waste of money because there are already adequate levels in the soil.

f. Provide adequate soil moisture, especially during the first half of the season, when growing roots take up calcium.

g. Include calcium in every cover spray. The amount of calcium chloride per acre per application should be 2 to 8 pounds. There are many formulations of calcium on the market. Fruit researchers have not tested all of these materials, but research results show that the formulation is much less important than the amount of actual calcium applied. Calcium chloride is generally recommended because it is inexpensive, it is effective, and we have a lot of experience with it. No formulation has been shown to be more effective than calcium chloride. The major drawback with calcium chloride is its corrosiveness.

When using materials other than calcium chloride, be sure to apply the appropriate amount of calcium per acre. The labeled recommendations for some formulations do not provide enough calcium to minimize bitter pit. When comparing the price of different materials, be sure to calculate the price per unit of actual calcium.

h. Do not harvest immature fruit because these fruit will be most susceptible to bitter pit development in storage. (adapted from an article by Rich Marini, Minimizing calcium-related disorders in apple. Virginia Fruit 16(4):2-4).

Calcium management summary

Some calcium do’s and don’ts

  1. Maintain a soil pH of 6 - 7.0; test your good soils about every three years; test any soils under a corrective program every year.

  2. Don’t promote vigorous shoot growth on bearing trees. Highly vegetative trees have an excessive number of growing points that will always win any competition with the fruit for calcium.

  3. Maintain adequate soil moisture during hot weather. Soft vegetative growth stressed by heat will draw moisture from wherever it can get it, including the fruit. Some calcium will go with the moisture, it won’t come back.

  4. Do not apply potassium or magnesium fertilizers unless soil or tissue sample indicate a need. Both materials compete with calcium.

  5. Calibrate your sprayer to insure uniform coverage of the fruit throughout the tree. Removing vigorous growth from the center of the tree early to mid-summer will aid spray coverage for both calcium and pesticides, remove some of the competition for calcium by growing points, and help improve the finish on red coloring varieties of fruit.

  6. Begin adding calcium to your cover sprays as soon as the fruit begins to size and continue as close to harvest as possible. Surfactants are not needed when calcium is applied with regular cover sprays.

  7. Calcium sprays can cause injury to foliage and fruit under certain conditions. It is generally recommended to NOT apply calcium if temperatures are above 90 F (particularly when the humidity is also high) or if it has not rained at least inch since the last calcium application. When leaf injury is noticed, reduce calcium chloride to one-half rate in the next spray.

  8. Calcium chloride in water has a high pH and when applied with other pesticides may limit their effectiveness (this can be taken care of by 2/3 of an ounce of vinegar per pound of calcium chloride to the spray solution; alternatively any material that buffers to about pH 6 may be used). In more northern locations, calcium applications may cause advanced maturity of some varieties (Honeycrisp, Empire, McIntosh), although this has not been studied in the mid-Atlantic region.


New web site for WV farms & farmers markets

A new website, Collaborative for the 21st Century Appalachia (www.WVfarm2U.org), is now available to help consumers find West Virginia products. 

This new website was made possible by a grant from the Claude W. Benedum Foundation, a USDA Specialty Foods grant from the West Virginia Department of Agriculture, and a USDA-NESARE grant courtesy of WVU professor Cheryl Brown. For more information, contact Allen Arnold, Director of Collaborative for the 21st Century Appalachia at aarnold@wvfarm2u.org, or Cheryl Brown, WVU Assistant Professor in Agricultural Economics at cheryl.brown@mail.wvu.edu.

New Marketing Specialist and newsletter

The University of Maryland Cooperative Extension has hired a Marketing Specialist, Ginger Myers, who will be housed at the Western Maryland Research and Education Center in Keedysville. Ginger was previously with Howard County Economic Development. She publishes a quarterly newsletter, “Mastering Marketing”, with the Fall 2007 issue available at: http://extension.umd.edu/local/WMREC/files/AgMktgNewsFall2007.pdf. Ginger may be contacted at 301-432-2767 x338, or at gsmyers@umd.edu.


Trade and brand names are used only for the purpose of information, and the West Virginia University Extension Service does not guarantee nor warrant the standard of the product, nor does it imply approval of the product to the exclusion of others which may also be suitable. The West Virginia University Extension service assumes no responsibility in the use of hazardous chemicals.

Individuals requesting an accommodation at a meeting because of a disability should contact one of the Extension Specialists at the WVU Kearneysville Tree Fruit Research and Education Center at 304-876-6353 at least five days prior to the event.

Helping you put knowledge to work

P. O. BOX 609
PHONE:  304-876-6353
FAX:  304-876-6034
WEB:  www.caf.wvu.edu/kearneysville

The West Virginia University Cooperative Extension Service, U.S. Department of Agriculture, West Virginia County
Boards of Education and County Commissions Cooperating.  Equal Opportunity / Affirmative Action Institution

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