March 24, 2008

Upcoming Events Grower Meeting Sponsors Spray Bulletin


Plant Pathology



April 3, 7:00 p.m. - Spring In-depth Fruit Meeting at Virginia Tech’s Alson Smith Agricultural Research and Extension Center, Winchester, Va.  The agenda will include seasonal updates by VA Tech Extension Specialists and other topics to be determined. For more information contact the Frederick County Extension Office at 540-665-5699. 

April 8, 6:00 p.m. – Tree Fruit Grower Twilight Dinner and Meeting at the WVU Kearneysville Tree Fruit Research and Education Center, Kearneysville, W. Va.  Extension Specialists will discuss new pest management tools, and early-season insect and disease management strategies. For more information contact the WVU KTFREC at 304-876-6353. 

April 9,  9:00 a.m. – 3:00 p.m. – Farm Succession – Bringing in the Next Generation at Adams County Agricultural and Natural Resources Center, Gettysburg, Pa. This workshop will be conducted by well-known AgriVisions lecturer Dr. David Kohl, Virginia Tech Professor Emeritus. Registration fee of $125 for one family member and $20 for each additional family member is due by April 2. For more information, contact Tara Baugher at 717-334-6271 ext. 314 or at

April 24, 6:00 p.m. – Tree Fruit Grower Twilight Dinner and Meeting at Gourmet Central (in Hampshire Industrial Park), Romney, W. Va.  WVU Extension Specialists will discuss new pest management tools, and early-season insect and disease management strategies. For more information contact the Hampshire County Extension Office at 304-822-5013.


The following fruit industry support companies and representatives have contributed to a Grower Education Fund to cover expenses at fruit schools and grower meetings.  Please let them know that you appreciate their support as we do. 

Arysta LifeScience – Alan Kurtz
BASF – Gar Thomas
CBC (America) Corp. – Greg Stamm
Dow AgroSciences – Patti Webb
Durand-Wayland, Inc. – Ron Shrum
Gowan Company – David Pieczarka
Helena Chemical Company - Todd Metzger
Knouse Foods Coop., Inc. – Dave Cox
Suterra – Mark Shannon
UAP – Larry Dell
United Phosporus - John Miller
Valent USA - Hal Blackmore
Winchester Equipment Co. – Doug Rinker


The 2008 Virginia/West Virginia/Maryland Spray Bulletin For Commercial Tree Fruit Growers may be picked up at the WVU KTFREC or obtained by mail for $12.00 each.  A check (payable to West Virginia University) should be sent to the WVU KTFREC, PO Box 609, Kearneysville, WV 25430-0609.


Pear psylla adult

Pear psylla adults overwinter in or near pear orchards.  When daytime temperatures exceed 50F, adults return to pear trees, mate and begin laying eggs (pale cream to yellow-orange colored) in crevices on fruit spurs.  The use of oil during the dormant to white bud stage delays egg-laying because females do not like to lay eggs on oily surfaces.  Oil application shortens the length of the egg-laying period, resulting in a population with a more uniform age structure which makes management easier.  Oil can be used from dormant to the white bud stage, but the rate should be gradually reduced from 3% (dormant) to 2% (green cluster bud) to 1% (white bud).  An effective strategy is to make two applications of oil at 2% each, the first at dormant to bud swell and the second at the green cluster bud stage.  An insecticide to kill adults should be combined with oil, especially with the second of two oil sprays.  A pyrethroid (Asana, Ambush, Battalion, Baythroid, Danitol, Decis, Lambda-Cy, Mustang Max, Perm-UP, Pounce, Proaxis, Warrior) is a good option to combine with oil.  Actara, Assail, Calypso, Esteem, or Dimilin are excellent options at green cluster bud and white bud for prebloom psylla control. Three prebloom applications (dormant-green tip, green cluster bud and white bud) of Surround have also provided very good control of overwintering adults.  Surround should not be tank-mixed with oil.

Pear psylla eggs

In making pest management decisions during the prebloom period on apple, the first question to ask is: “Do I need to control San Jose scale?” The answer to this question should be based on the incidence of fruit injury due to scale (red spotting) at harvest last season. Although fruit injury due to scale would be of more immediate concern in fresh fruit blocks, since peeling of processing apples removes the injury, death of limbs from scale infestation would eventually impact processing blocks as well if control measures aren’t taken. If scale control is needed, the most effective time for management is during the dormant to delayed dormant (1/2-inch green) stage to target the immature overwintering scale. Chemical control options at this stage include oil, Lorsban, Supracide, Diazinon, and Esteem. A dilute application is highly recommended, since thorough coverage of the tree tops is a critical component of an effective management program for this pest.

San Jose scale fruit injury
Rosy apple aphid nymphs

After addressing the issue of San Jose scale, the next question to ask is: “How do I want to manage rosy apple aphid?” If Lorsban, Supracide, Diazinon, or Esteem are applied for scale (dormant to delayed dormant), these materials will also provide initial control of rosy apple aphid nymphs that hatch from overwintering eggs. However, in some situations in recent years, these products have not provided complete control, and supplemental management has been needed at pink or petal fall to minimize fruit injury. If scale is not an issue, one can still choose to use one of these products, or a pyrethroid insecticide, for initial control of rosy apple aphid, knowing that supplemental control measures may be needed later. However, a more effective approach is to wait and control rosy apple aphid during the tight cluster to pink stage with products such as Actara, Assail, Calypso, or Beleaf. These products would be more effective in higher pressure situations, and typically provide complete control with a single complete application at this stage. Actara should not be applied later than early pink, or within 5 days of placing beehives in the orchard, since it is toxic to bees exposed to direct treatment or residues on blooming crops. Beleaf is relatively non-toxic to bees, whereas Assail and Calypso are toxic through direct contact (before sprays have dried). In addition, these products also have activity against some other prebloom pests. Actara, Beleaf, and Calypso would also provide control of tarnished plant bug and mullein bug, whereas Assail and Calypso during pink to bloom would also be effective against European apple sawfly and early egg hatch of oriental fruit moth. The application rates of Assail and Calypso depend upon the pest being targeted. If rosy apple aphid is the only target, Assail 30SG at 2.5-4 oz and Calypso 4F at 2-4 fl oz will provide excellent control. Where control of the other pests is also desired, rates must be increased to 5.5-8 oz for Assail 30SG and 4-8 fl oz for Calypso 4F.


Rosy apple aphid fruit injury

Pheromone traps should be installed at this time for monitoring of redbanded leafroller, and the beginning of April for monitoring of oriental fruit moth.


Fire blight. Fire blight bacteria overwinter in cankers, often at the ends of pruning cuts where blight strikes were was cut in the previous season. A good way to reduce the risk of a severe fire blight outbreak is to make a late dormant application (no later than 1/4 inch green on fresh-market fruit) of a copper-containing material (i.e. Bordeaux mixture, C-O-C-S, Kocide, Tenn Cop 5E, just to name a few) that acts to kill a large percentage of the bacteria on the plant surface (and provides some early-season protection against apple scab). Although this spray does not eliminate the possibility that fire blight could become epidemic this year, in some years it may reduce considerably the amount of inoculum available for blossom infections. The effectiveness of the treatment may depend on how much rain we receive in the prebloom period. This dormant application is recommended where fire blight was present last year and on young trees of susceptible apple cultivars such as Gala, Fuji, York, Jonathan, and Rome Beauty (whether fire blight was present last year or not), or on any cultivar on M.9, Mark, and M.26 rootstock.

Given that the bacterium moves easily from unsprayed blocks to adjacent sprayed blocks, it may be useful to apply copper to blocks (or rows) of less susceptible trees that are adjacent to blocks of more susceptible trees. Most copper formulations are compatible with oil, although copper sulfate by itself is not. Streptomycin should be applied to blossoms of susceptible apple and pear cultivars when weather conditions favor infection.

There is additional information on fire blight biology and management in the Spray Bulletin and online. Monitor our WWW Site for up-to-date information on the disease at

Apple scab. Resistance to DMI fungicides (Nova, Rubigan, and Procure) was documented in all but one of the nine West Virginia orchards sampled in 2005 and 2006 (note: scab was hard to find in 2007 due to very dry conditions). Note that only one complete control failure with these fungicides has been observed in West Virginia orchards (e.g. in a WVU orchard insecticide research block in 2005). Nevertheless, growers will need to reassess their use of these materials in the next year or two, if they haven’t already. I interpret the test results that indicate "resistance" to mean that a control failure could occur at any time if it hasn’t already occurred. Observations in New York suggest that in the year preceding a control failure, one would expect to see an increase in fruit scab into the range of 1 to 5%. I have heard a couple of reports in which this could be the case in W.Va. The past two seasons of dry weather have helped us by keeping scab populations very low in most orchards.

Here are some general observations on the usefulness of the common scab fungicides:

  1. Mancozeb fungicides at 3 lb/A are probably still the cheapest option for prebloom scab control, but they must be applied at 5 to 7-day intervals during rainy weather rather than at 10-day intervals as was common with DMI + mancozeb combinations.

  2. If one compares 3 lb/A of Captan 50W (or the equivalent of another formulation) with 3 lb/A of mancozeb, captan will almost always provide better scab control than mancozeb. Captan usage is limited, however, by its higher pricing, its incompatibility with oil sprays, and its minimal activity against rust diseases. Where incompatibility with oil is not a factor, combinations of mancozeb and captan are a great choice for prebloom scab sprays. I would like to see the total pounds per acre at around 4.5 to 6 depending on scab history and weather conditions (based on captan 50W formulations; this will be less if using captan 80W formulations).

  3. Dodine may still work in some orchards, but don't trust it unless you've had leaf samples tested for fungicide resistance and I’ve told you the results. Significant crop loss can result from just one or two early-season applications of dodine in dodine-resistant orchards.

  4. Vangard and Scala fungicides usually provide scab control similar to that provided by mancozeb at 3 lb/A.  However, Vangard and Scala can both provide 48-60 hr of post-infection activity against apple scab (counting from the start of the wetting period), whereas mancozeb sprays will provide only 18-36 hr of "kickback" activity when counting from the start of wetting periods, with the longer duration limited to colder infection periods. Vangard and Scala do not redistribute well, so combinations of mancozeb at 3 lb/A plus either 3 oz/A of Vangard or 5 fl oz/A of Scala are recommended when these products are used. Vangard may lose effectiveness at temperatures above 70 F.

  5. Flint, Sovran, and Pristine are excellent protectant fungicides that provide better scab control than mancozeb or captan used alone. They can also arrest spore production if visible scab lesions are present in trees. However, they will not stop epidemics as effectively as DMI fungicides did in DMI-sensitive orchards if they are applied after scab infections are established. Do not rely on them for postinfection or "kickback" activity beyond 48 hours. They are a good choice for use at petal fall and first cover if you suspect resistance or if you have experienced failure of the DMI fungicides.

  6. DMI fungicides in combination with either captan or mancozeb might still be used at petal fall and first cover unless resistance is documented or unless an increase in fruit scab at harvest has been observed in the past two years when using a DMI program. Continuing to use the DMI’s after resistance is documented but before a control failure is noticed represents a period of risk that should be considered seriously if these materials are to be used. DMI's applied at that timing will provide significant suppression of powdery mildew as well as postinfection activity against any scab and rust infections that may have slipped through during the prebloom and bloom sprays. Using DMI's in two applications after bloom should minimize selection pressures for DMI-resistant scab while still maximizing the other benefits that DMI's provide for apple disease management programs. A good choice would be Indar 2F – one of the "second generation" of DMI fungicides with greater activity against the scab fungus than the "first generation" (Nova, Rubigan, and Procure). In tests in New York, Indar provided better control of resistant scab isolates when compared to Nova and Rubigan. I suspect that additional "second generation" DMI materials will be available in the next couple of years.

Phytophthora root rot can be managed with mefanoxam (Ridomil Gold EC and Ridomil 5G) and will aid in the control of crown, collar, and other root rots caused by Phytophthora spp. on both bearing and non-bearing apple trees. Ridomil 5G can be used in nonbearing orchards only. Applications should be made on a preventative schedule before symptoms appear, especially in orchards where conditions are favorable for disease development. For best results, make one application at the time of planting or in the spring before growth starts. Make another application in the fall after harvest.

Dipping the roots of nursery-grown trees into a solution of the fungicide Aliette prior to planting may reduce inoculum on infested rootstocks. To use, thoroughly mix Aliette at a rate of 3.0 lbs./100 gallons of water, in the desired volume of water and dip the entire root system for 30 to 60 minutes in the mixture prior to planting in the field.


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.

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PHONE:  304-876-6353
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