WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
May 19, 2008

Upcoming Events


Pheromone Trap Counts Plant Pathology Horticulture



May 22, 6:00 p.m. – Tree Fruit Grower Twilight Dinner and Meeting at Gourmet Central (in Hampshire Industrial Park), Romney, W. Va.  Following dinner, WVU Extension Specialists will provide an update on orchard conditions and discuss pest management strategies. For more information contact the Hampshire County Extension Office at 304-822-5013. 

May 26. – West Virginia University Holiday. The WVU KTFREC will be closed in observance of Memorial Day. 

May 29, 7:00-8:30 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 a presentation on insects (to be announced) by Dr. Chris Bergh.  For more information contact the Frederick County Extension Office at 540-665-5699. 

June 11, 6:30-8:30 p.m. – Joint MD, PA, WV Twilight Fruit Grower Meeting at Gardenour Orchards in Smithsburg, MD. From Jefferson County take WV-480 north through Shepherdstown, crossing the Potomac River onto MD-34. In Sharpsburg, turn left onto N. Church Street (becomes MD-65, Sharpsburg Pike). Follow MD-65 north until you intersect I-70 (~ 10 miles). Take I-70 east for 5 miles to exit 35 – Smithsburg/Boonsboro (MD-66). Follow MD-66 north (left) towards Smithsburg for 5 miles. At the intersection of MD-66 and Smithsburg Pike/Jefferson Blvd. (MD-64), turn right. Proceed on MD-64 for about 4 miles (around the town of Smithsburg, past the intersection with MD-77 and a turn off for MD-491) to a left onto Gardenour Road (look for a big apple shaped sign for Gardenour Orchards). Gardenour Orchards is about mile down Gardenour Road on the left just after you cross a small one lane bridge. From Berkeley County take I-81 north to I-70 east to exit 35 and follow above. The agenda will include a conservation innovation planting tour by host Bill Gardenour; and tree fruit and small fruit updates by Drs. Alan Biggs, Henry Hogmire, Henry Ngugi, Anne DeMarsay, Greg Krawczyk, Joe Fiola, and Rob Crassweller. Recertification credits for pesticide applicator’s license will be provided.


Warrior II (lambda-cyhalothrin) from Syngenta is a more concentrated formulation of Warrior that was recently registered by EPA. It contains twice the amount of active ingredient (2.08 lb. ai per gallon) compared with Warrior (1.04 lb. ai per gallon), and is labeled on the same crops. Warrior II is cream-colored, instead of blue, and does not have the older volatile solvent that gave Warrior a strong odor. 

Altacor (chlorantraniliprole) from Dupont received a federal section 3 registration by the EPA earlier this month (state registrations are pending) for insect control on pome and stone fruits. Altacor is a member of the anthranilic diamide class of insecticides with a novel mode of action on insect ryanodine receptors. It has some contact activity, but is most effective through ingestion of treated plant surfaces. Insects exposed to Altacor will rapidly stop feeding, become paralyzed, and die within 1-3 days. Altacor has provided outstanding control of internal worms (codling moth, oriental fruit moth) and leafrollers in numerous tests conducted in the mid-Atlantic region. Rate of application is 2.5-4.5 oz per acre on pome fruits and 3-4.5 oz per acre on stone fruits in a minimum of 100 gal of water per acre. Do not use an adjuvant in combination with Altacor on cherries  or within 60 days of harvest on pome fruits. For resistance management, make no more than 3 successive applications per generation of insect species, and treat the following generation with a product having a different mode of action. Restrictions include a seasonal maximum of 4 applications and 9 oz per acre, restricted-entry interval (REI) of 4 hours and pre-harvest interval (PHI) of 10 days on stone fruits and 14 days on pome fruits.

Codling moth control is justified to prevent fruit injury in those orchard blocks where the pheromone trap catch has exceeded 5 moths/trap/week.  The best timing for spray applications, based on degree day (DD) accumulations after biofix, depends on the insecticide used. Some materials (Rimon, Intrepid, Assail, Calypso, Esteem) perform best when applications are initiated before the beginning of egg hatch. The ideal timing to initiate applications is 50-150 DD (now) for Rimon and 150 DD (now) for Intrepid, Assail, Calypso, and Esteem. Applications of Altacor, Delegate, Avaunt, Azinphosmethyl (Guthion), Imidan, Diazinon, or CM granulosis virus (Cyd-X, Carpovirusine) should be initiated at 250 DD (3% egg hatch, predicted on May 28). An initial spray should be followed by a second complete application in about 14 days (7-10 days for CM granulosis virus), or three additional alternate-row-middle applications 5-7 days apart (3-5 days apart for CM granulosis virus). Through May 18, 141 DD have accumulated since biofix (May 2) at the WVU-KTFREC.

Codling moth fruit injury

Lesser peachtree borer adults have been emerging for about two weeks.  Moths are active during the day, with mating and egg-laying occurring soon after emergence.  Female moths are attracted to damaged and previously infested trees, and deposit eggs in cracks or under bark scales of wounded sites.  Eggs hatch in seven to ten days and larvae burrow, feed and develop in the inner bark and cambium tissue for 40 to 60 days.  An infestation of lesser peachtree borer is almost always associated with previously damaged trees.  The problem tends to be more severe in older orchards that have a greater incidence of Cytospora canker, winter injury, and pruning and other mechanical wounds.  Infestation occurs in these damaged bark areas from the ground to a height of about eight feet.  Although the majority of injury occurs in the upper trunk and scaffold limbs, small diameter branches also may be infested.  Larval feeding enlarges the wounded area, which eventually results in complete girdling of the trunk, scaffold limb, or branch.   The primary and earliest impact is a gradual decline in production on damaged limbs, which when girdled will break under a fruit load.  With time, tree loss will occur from trunk girdling.  Lesser peachtree borer feeding can also afford entry for disease organisms, eventually resulting in limb and tree death.

In addition to monitoring adult emergence with a pheromone trap, inspect wounded areas on the upper trunk, scaffold limbs and branches when moth flight is increasing to determine the average number of empty pupal cases per tree protruding from the bark.  Treatment is recommended if there are more than a total of two larvae or empty pupal cases per tree for each of two generations.  Good control of adults can be achieved with an airblast sprayer application of a pyrethroid insecticide (Ambush, Asana, Baythroid, Lambda-Cy, Mustang Max, Perm-UP, Pounce, Proaxis, Tombstone, Warrior, and Warrior II) when moth flight is peaking, as determined with pheromone traps.  This strategy is not recommended however if mites are already present in the orchard, since pyrethroid use will increase mite populations.  An alternative, and more effective strategy, is to control the larval stage in late May to early June (1st generation) with a pyrethroid (if no mites) or Endosulfan (Thionex), and/or in August (2nd generation) with chlorpyrifos (Lorsban 4EC, Lorsban 75WG, Nufos 4EC, Yuma 4EC) applied with a handgun to thoroughly wet all wounded areas.  Chlorpyrifos is best used after harvest since spray contact with fruit is prohibited.  Blocks that receive a pyrethroid application should be monitored closely for mite outbreaks.

Lesser peachtree borer adult
Lesser peachtree borer larvae and wood injury
Lesser peachtree borer empty pupal case


March 17 0
March 24 6 0
March 31 31 17
April 7 98 376 2
April 14 74 2688 84
April 21 109 1152 376 0
April 28 33 392 329 3 0 0
May 5 12 114 210 19 3 0 1
May 12 1 114 138 14 16 0 12
May 19 1 37 51 30 31 1 38

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.


Infection periods and general disease update.  We’ve recorded five additional infection periods since the last Orchard Monitor on May 5, 2008. When I use the term "high disease pressure" - this is what I mean. On May 8 – 9, we had leaf wetting for 16 hours at 59 F. On May 9 – 10, we had leaf wetting for 10 hours at 52 F. On May 11 – 13, we had leaf wetting for 43 hours at 46 F. On May 15 – 16, we had leaf wetting for 17 hours at 56 F. On May 17 – 18, we had leaf wetting for 13 hours at 57 F. Total rainfall for May, as of May 19, 2008, is 4.92 inches (normal for May is 3.8 inches). All of these infection periods are considered to be secondary scab infections, as we recorded our first visible scab lesions on May 5th. Diseases showing up in area apple orchards include primary and secondary apple scab, cedar-apple rust, frogeye leaf spot (black rot), and primary and secondary powdery mildew. In peach orchards, peach leaf curl is easy to find.

Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2008.


Date 2008

Hours/ degrees F


April 25-26

16 hr/62 F


April 26-27

15 hr/56 F


April 28

16 hr/52 F


May 4

10 hr/55 F

Scab lesions observed May 5, 2008


May 8-9

16 hr/59 F


May 9-10

10 hr/52 F


May 11-13

43 hr/46 F


May 15-16

17 hr/56 F


May 17-18

13 hr/57 F

Summer fungicide programs.  Excellent control of our summer disease complex can be achieved with well-timed fungicide sprays. Timing is one of the most important aspects of effective disease management. A good general rule to follow is to re-apply fungicide following 2 inches of rain or 21 days, whichever occurs first, and before the next wetting event. As always, read the labels for more detailed information about these materials.

1. EBDC fungicides (Dithane, Manzate, Penncozeb, Polyram): Will provide excellent control of summer diseases when combined with Captan, Ziram, or Topsin-M. EBDC’s can be applied up to 77 days before harvest when using the extended application schedule at the 3 lb per acre rate. Early use of these materials provides the foundation for managing summer diseases for the remainder of the season.

2. Topsin-M: Highly effective against sooty blotch, fly speck, and the Botryosphaeria rots (black rot and white rot). In wet growing seasons, the spray interval should not be longer than 14 - 21 days, or 2 inches of rain. Adjust the rates of Topsin-M toward the high end of the rate range (10 oz per acre) when disease conditions are highly favorable. Use Topsin-M in mixtures with protectant fungicides to help prevent the emergence of fungal strains resistant to Topsin-M.

3. Protectant fungicides (Captan, Ziram, Sulfur): Captan and Ziram applied by themselves or in combination will provide adequate control of summer diseases if applied often enough at the proper rates (6 to 8 lb per acre total). Spray intervals should be 21 days under moderate disease pressure, and should be shortened to 10 - 14 days under prolonged, highly favorable conditions. The 8 lb per acre rate also is preferred under highly favorable conditions. Sulfur by itself is only fair, at best, in limiting these diseases. However, sulfur and copper are the only choices for organic spray programs. Under extreme disease pressure, the addition of Topsin-M at a "half rate" improves control of Botryosphaeria rots and sooty blotch and fly speck. Where scab is well established, captan (8.0 lb. per acre) is the better choice to limit secondary infections.

4. Strobilurin fungicides (Sovran, Flint, and Pristine): These fungicides are very effective for controlling fly speck and sooty blotch and could be used as substitutes for Topsin-M + protectant (captan or ziram) sprays during summer. If strobilurins were used to control scab at tight cluster and pink, then they should not be used again prior to second cover. Strobilurins suppress sporulation of scab lesions, so their use at this time may be beneficial if your control of primary scab hasn’t been completely effective. If strobilurins were applied at petal fall and first cover, then additional summer applications of these materials would need to be delayed until July or August because of the requirement for intervening applications with some other class of fungicides. The strobilurins have residual activity against fly speck, although recent research suggests that the residual activity is not equivalent to that provided by Topsin-M. Fruit treated with Pristine prior to harvest may exhibit lower levels of blue mold and gray mold in storage. When calculating the tree-row-volume rate of the strobilurins, do not use less than the lowest per acre rate on the label (i.e., never use less than 2 oz. of Flint, 4.0 oz. of Sovran, or 14.5 oz of Pristine per acre).

Summary. Control of early-season diseases with a program that includes an EBDC material, alternated with the strobilurin fungicides, provides a solid foundation for controlling summer diseases. The most flexible program for controlling sooty blotch and fly speck is ziram or captan + Topsin-M, and optionally alternated with two applications of the strobilurin fungicides. This program may need to be modified if other summer diseases occur at moderate to high levels. For example, the combination of ziram + Topsin-M is rated as only "good" (rather than "excellent") against white rot and black rot, and is only "fair" against bitter rot. Alternating applications of ziram + Topsin-M or captan + Topsin-M with full rates of ziram or captan alone will improve your management of the summer rots. Remember that management of diseases with fungicides is improved if other cultural practices that reduce inoculum and improve coverage are employed. Good disease management may require some flexibility in application timing and rates of materials.

Accumulated wetting hours.  As of May 19, 2008, we have accumulated 34 wetting hours since a petal fall date of May 3 (last year at this time AWH = 41). Accumulated wetting hours are useful for predicting the appearance of sooty blotch on nonsprayed fruit. Symptom development for these diseases is highly dependent upon temperature and moisture conditions surrounding the fruit. The appearance of sooty blotch symptoms has been predicted with reasonable accuracy by using accumulated wetting hours (AWH). Visible signs of sooty blotch may appear following approximately 260 - 300 AWH (earlier in the season (260 AWH) if the disease was severe last year, later in the season (300 AWH) if not). The AWH threshold for making the decision to include Topsin-M in the spray program is 225 for high disease pressure and 275 for low disease pressure. Each of these threshold values presumes that 25 additional AWH will occur in the next 5 days after reaching the threshold.

See our "Current Conditions" Web page for details that are updated at least three times weekly. To view the "Current Conditions" page, click here, or go to the WVU - KTFREC Home Page at: http://www.caf.wvu.edu/kearneysville/wvufarm1.html and select "Current Conditions" from the menu.


Post-bloom thinners, such as NAA, 6BA, and carbaryl, are typically used when developing apple fruits are between 7 mm and 15 mm. The activity of these chemical thinners is best when applications are made during a period when daytime highs are in the 70F range. Thinner efficacy declines when temperatures are sub-optimal.

The challenge this year has been for growers to find the minimum window of 3-4 days with daytime highs of 70F or higher for getting a good response to chemical thinners. Meanwhile apple fruits have continued to grow at a somewhat surprising rate, despite the sub-optimal temperatures. With the current and forecasted temperatures, it can be anticipated that the response to chemical thinners will be less than was desired.

Ideally you want fruit between 7 and 15 mm, with a minimum of three days of highs in the 70's. If a grower does have to spray with sub-optimal temperatures, NAA / carbaryl tank mixes have the best efficacy. Thinners with 6BA as the active ingredient simply will not work with maximum temperatures below 68F. Cool temperatures not only reduce a thinner's effect, but also slows the rate at which chemical thinners work. This means that it will take longer to determine what response you got from your first round of thinning. The first discernable response to thinners is a cessation of fruit growth. Growing fruit are setting fruit. Fruit that have ceased growing are going to thin. This change in growth becomes apparent in about 7 days after the thinner is applied under warm conditions, and after about 10 days during cool weather. This may be a year to take careful measurements every other day, and to carefully distinguish between small and large fruits. Cutting fruits open to assess the seeds may also be helpful to determine which fruits are alive and which are going to thin. Healthy seeds in setting fruit are pearly, fat and turgid, while seeds in thinned fruits are yellowing, thin and soft.

Once you have determined what number and sizes of fruit seem likely to be coming off, you can develop a sense of how much additional thinning is needed. When fruit diameter reaches 18 mm, apples become difficult to thin with NAA or 6BA. If the crop load hasn't been adequately reduced by your previous efforts, the two chemistries that are still effective are carbamates (Sevin and Vydate) and ethephon (Ethrel, Ethephon II). Apples grow about 1 mm per day in warm weather, so if your fruit are at 18 mm, you have about four days to thin chemically. Once the fruit reach 22-24 mm, they become unresponsive to chemical thinners. For mild thinning try carbaryl at 1 lb active ingredient per acre. Add 1 quart of spray oil per 100 gallons of finished spray mix to the carbamate to increase its activity. Remember, oil and captan causes phytotoxicity , so if you are using oil in this spray, keep captan out of the orchard for a couple weeks.

If a strong thinning combination is called for, then combine ethephon, 1.5 pints per 100 gallons, plus 1 qt. Sevin and 1 qt. of spray oil. Remember that Goldens and Romes are quite sensitive to ethephon, so reduce the ethephon rate to 0.75 pint for these varieties. (Adapted from Apple Thinning Advisory by Dr. James Schupp, PSU horticulturist).


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
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
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