WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
May 3, 2004

Upcoming Events


Pheromone Trap Counts Plant Pathology Horticulture



May 11, 7:00 p.m. - Spring In-depth Fruit Meeting at the Alson Smith Research and Extension Center, Winchester, Va.  Dr. Mark Brown, USDA entomologist, will discuss "Stinkbugs in Peach and Apple Trees".  Dr. Chris Bergh, VA Tech entomologist, will discuss "Mating Disruption in Orchard Systems".  For more information contact Cyndi Marston at 540-665-5699 or at cmarston@vt.edu.

May 27, 6:00 p.m. - Tree Fruit Grower Twilight Dinner and Meeting at Gourmet Central (in Hampshire Industrial Park), Romney, W. Va.  Following dinner, seasonal updates will be provided by Extension Specialists from the WVU Kearneysville Tree Fruit Research and Education Center.  For more information contact the Hampshire County Extension Office at 304-822-5013.


Plum curculio is an important direct pest of both apple and peach, causing injury to developing fruit in the early postbloom period.  Adult beetles, which overwinter in hedgerows, trashy fields and woods, usually begin moving into orchards during the bloom stage.  Maximum activity occurs when  temperatures reach 70F and above.  The primary injury results from egg-laying, consisting of a crescent-shaped scar on the fruit surface.  In apples that remain on   the   tree,   most   larvae   do   not  complete development as they are crushed by the expanding fruit.  Larvae successfully complete development in peaches and fallen apples.  Typically, most of the injury from this insect has occurred in apple blocks of mixed cultivars with a wide range in bloom periods.  Injury usually occurs on the earlier blooming varieties while waiting for the later blooming varieties to reach petal fall.  Recommended control options on peach include azinphos-methyl (Guthion), Imidan, Actara and Surround, and on apple, these same options plus Avaunt, Assail and Calypso.

Rosy apple aphid can cause significant indirect injury to apple fruit in the early posbloom period in orchards where prebloom control was not effective.  As aphids feed within curled leaf clusters, their saliva is translocated to nearby fruits which causes them to remain small and become deformed and unmarketable.  Many orchards experienced substantial fruit injury from rosy apple aphid in 2003.  Conduct a thorough inspection of apple orchards for this insect prior to the petal fall spray application.  Make a 3-minute examination of 5-10 trees per block and count the number of fruit clusters showing curled leaves with live aphids.  Pay particular attention to the center region of trees.  Also, inspect root suckers around the trunk for colonies which could disperse later into the tree canopy.  Apply Provado, Actara, Assail or Calypso at petal fall if an average of one or more infested fruit clusters per tree are found.

Plum curculio adultPlum curculio fresh egg-laying injuryRosy apple aphid fruit injury

European red mites which hatched from overwintering eggs become adults around the petal fall stage of apple, which is when females begin depositing eggs on the leaves.  Consideration should be given to implementing preventative control strategies for mites this year in blocks where pyrethroids or Lannate are likely to be used in June for periodical cicada control (discussed in next newsletter).

Determine mite abundance from a sample of 5-10 leaves (collected from the middle of a fruit spur) from 5-10 trees per block of the same cultivar.  If oil or another acaricide has already been applied, examine each leaf and determine the average number of mites/leaf for the total leaf sample.  If no oil or other acaricide has been applied, examine each leaf for the presence or absence of one or more motile mites, and calculate the average percentage of mite-infested leaves for the total leaf sample.  Refer to Table 1 below and determine the expected number of mites/leaf for a given percentage of mite-infested leaves.

Table 1.  European red mite densities predicted
from the percentage of mite-infested leaves.

Percentage of
infested leavesa
Expected density
in mites/leaf
40 0.7
45 0.9
50 1.1
55 1.3
60 1.6
65 2.0
70 2.6
75 3.4
80 4.7
85 6.8
90 11.4
95 26.4

aLeaves with at least one motile stage.

A preventative acaricide should be considered if mite density averages two or more per leaf.  The most effective treatments include Agri-Mek, or the ovicides Apollo or Savey.  To minimize the development of resistance, do not use Agri-Mek or either one of the ovicides in two successive years.  Agri-Mek, which will also control spotted tentiform leafminer and white apple leafhopper, should be applied within 7-10 days of petal fall and combined with 1 gal/acre of oil.  Other preventative strategies, although usually less effective, include the early postbloom application of Vydate (can be substituted for Sevin as a thinner), or the use of Damoil or Ultra-fine oil at 2 gal/acre at petal fall, first and second cover.

White apple leafhopper nymphs are beginning to appear on the undersides of apple leaves.  White to yellow in color, first generation nymphs are more abundant on spur leaves, with the second generation more abundant on shoot leaves.  Feeding injury ranges from light stippling to complete chlorosis that is visible on the upper surface of leaves.  High populations can result in sufficient honeydew deposits to cause black speckling on the surface of fruit.  To monitor leafhopper populations, determine the average number of nymphs per leaf by examining the undersides of 10 leaves on 5-10 trees per block.  The action threshold for control is an average of 3 nymphs per leaf.  Materials rated excellent include Actara, Assail, Calypso, Carzol (cannot be applied after petal fall), Lannate and Provado.  Materials rated as good include Agri-Mek, Avaunt, Dimethoate, Sevin, Surround, Thionex, and Vydate.

White apple leafhopper nymphs

White apple leafhopper injured leaves (right)

Catfacing insects refers to a complex of pests that cause various types of injuries on peach and nectarine fruits.  Feeding on young fruits up until pit hardening results in fuzzless, corky, depressed areas and fruit deformity called "catfacing injury".  Feeding on slightly larger fruits results in scarring injury, which is similar to catfacing injury but without deformity.  The primary insects responsible for this early season injury in West Virginia are tarnished plant bug, and brown and dusky stink bugs.

This pest complex is difficult to manage because they are not full time residents of fruit trees, but move frequently between broadleaf weed hosts and fruit trees to cause injury.  Maintaining thorough and frequent spray coverage with pyrethroids, azinphosmethyl (Guthion), Imidan or Actara from shuck split until a few weeks after shuck fall is critical to minimizing fruit injury.  Pyrethroid use should be limited to reduce the likelihood of mite outbreaks.  Practicing good broadleaf weed control will also reduce the injury from this pest complex.

Catfacing injury

Scarring injury

Codling moth adults have been emerging since April 30 (biofix), which is the same as last year, based on pheromone trap capture at the WVU KTFREC.  Using a base temperature of 50F and upper temperature of 88F, degree days (DD) should be accumulated from biofix in order to properly time spray applications (more in next newsletter) in those orchards where the pheromone trap capture exceeds 5 moths/trap/week.

Pheromone traps should be installed at this time for the monitoring of dogwood borer in apple orchards.

Codling moth adult


March 22 0                
March 29 54 0              
April 5 12 11 0            
April 12 33 208 3            
April 19 41 256 44            
April 26 36 250 200 0 0   0    
May 3 4 62 52 39 3   2    

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.
1In a commercial orchard adjacent to an abandoned orchard near Kearneysville.


Apple scab. We recorded five wetting periods in the two weeks since the last Orchard Monitor, bringing the season's total number of favorable wetting periods to seven. Two of the wetting periods were initiated at night (N) and may therefore be significant only in orchards with high inoculum levels or already established scab lesions. Scab lesions were observed on unprotected trees in the Winchester area on April 29.

Table 2. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2004.

No. Date 2004 Hours/ degrees F
1. March 31 - April 3 62 hr/44 F
2. April 11 - 14 71 hr/43 F
3. April 20 - 21 (N) 9 hr/57 F
4. April 23 - 24 13 hr/62 F
5. April 25 - 27 40 hr/55 F
6. May 1 - 2 (N) 7 hr/66 F
7. May 2 - 3 9 hr/60 F

Fire blight. We recorded six fire blight infections recently (Table 3). High risk (according to Maryblyt) fire blight conditions occurred daily during the period April 18 - 25, 2004. Wetting during any of these days could have led to infection. We recorded wetting at WVU - KTFREC on April 20, 22, 23, and 24 during this period, with infection potential (EIP) well above the threshold level of 100 (Table 3). Infection also could have occurred this past weekend, May 1 - 2.

Table 3. Dates and conditions for fire blight infection periods at the WVU - KTFREC, 2004.

No. Date 2004 Infection potential (EIP)
1. April 20 331
2. April 22 206
3. April 23 214
4. April 24 170
5. May 1 230
6. May 2 246

At this writing, forecasted temperatures appear unfavorable for fire blight infection through the remainder of the week. See our "Current Conditions" Web page for details that are updated at least three times weekly.


Small Fruit Update.

New Guthion label: EPA has announced the new label for Guthion, effective August 21, 2003.  Grapes and strawberries are now deleted from the label.  Guthion remains available for caneberries, nectarines and peaches until 2005.  Guthion remains for use on apples and crabapples, blueberries, cherries, and pears.  Guthion Solupak will be the only formulation available.  Raspberry crown borer soil treatment has returned to the Guthion label; both soil and foliar treatments remain on the Sniper and Azinphosmethyl 50 labels.  All caneberry labels are still scheduled for elimination after 2005.  The Preharvest Interval for U-pick operations has been extended to 30 days.

SpinTor registered on caneberries: SpinTor 2SC (spinosad) is now registered on caneberries for control of several pests. While the label primarily addresses Lepidoptera, several non-lepidopterans are included in the label's pest list: raspberry fruitworm and sawfly (Hymenoptera).  The use rate is 4-6 fl oz/A.  The PHI is 1 day.  

Apogee for Control of Apple Tree Growth - As an Aid for Reduced Pruning.

The primary objectives of pruning are to: control tree size, reduce shading within the tree canopy, increase spur vigor, promote spray penetration, maintain tree structure, and promote good fruit color, size, and quality. Many apple cultivars are grown on vigorous rootstocks and require much pruning, especially in tops of older trees. Ideally, growers should prune annually; but in order to cut costs and/or to reduce labor requirements, a grower may choose to prune every second or third year. Dense canopies caused by current season shoot growth and/or by not pruning in some years, may be detrimental to pest control, fruit quality, color, spray application costs, and yields in subsequent seasons. The advantage of Apogee sprays compared to pruning is that growth inhibition occurs early and continuously throughout the season, which cannot be accomplished by dormant pruning.

Prohexadione calcium (Apogee 27.5DF) applied soon after bloom (1 to 3 inches shoot growth) and at intervals of approximately 3 weeks to apple trees will reduce the current season's shoot growth (shoot length and weight), reduce the number of pruning cuts, pruning time, and pruning weight per tree, and increase the number of nodes on the lower 40 cm of long shoots. Flower bud formation, fruit diameter, soluble solids, starch, individual fruit weight, fruit drop, and fruit cracking (Stayman), typically will not be affected, but fruit set per tree may be slightly increased. Apogee applications did not interfere with thinner activity if applied as a tank mix or before or after the spray. Fruit color and firmness were slightly increased in only one experiment. The amount of growth suppression will be related to tree vigor. Thus, growth will be suppressed more by Apogee when trees are cropped heavily or stressed by drought, and when trees are grown on dwarfing rootstocks. Registered rates for Apogee are 6-12 oz/100 gal dilute or 24-48 oz/acre. Calcium in hard water or Calcium chloride added to the spray solution will reduce or inactivate Apogee. To reduce interference from calcium in the spray water, ammonium sulfate should be added to the tank before Apogee, at the same rate per 100 gal of spray mix as for Apogee. Based on research at Winchester, the combination of 6 oz of Apogee plus 6 oz of ammonium sulfate per 100 gal is suggested for moderately vigorous trees. An adjuvant such as Regulaid should be included to improve systemic uptake of Apogee.

Vigorous trees might be more responsive to the 12 oz Apogee rate than to the 6 oz rate. Multiple applications are typically needed to obtain season-long growth suppression. Tree vigor, soil moisture, crop load, rootstock, etc. will influence the need for additional applications. For maximum effectiveness it is critical that the first application be made in the late bloom (1 to 3 inches of shoot growth), the second application should be made before growth begins again at the most vigorous tips (approximately 3 weeks). Since maximum growth suppression is obtained before growth resumes, the vigorous trees in the block should be observed so that any additional applications are well timed. If vigorous trees have no crop and there is adequate soil moisture, more than 4 applications may be required to obtain adequate shoot growth suppression. Do not apply more than 99 oz/acre per year or 48 oz/acre in any 21-day period. Do not apply to Empire as fruit cracking may occur.

Use of Apogee for Fire Blight Shoot Blight Suppression.

Apogee (prohexadione-calcium) is registered for suppression of fire blight shoot blight. Shoot blight suppression results from hardening off of vegetative shoot growth starting about 10 days after the initial Apogee application, which should be made at late bloom when active shoot growth is 1-3 inches long. Studies at Winchester indicate that Apogee may be tank-mixed with Agri-Mycin, allowing Apogee to take effect while there is residual protection from streptomycin. Registered rates for Apogee are 6-12 oz/100 gal dilute or 24-48 oz/acre. To reduce interference from naturally occurring calcium in the water used for spraying, ammonium sulfate should be added to the tank before Apogee, at the same rate per 100 gal of spray mix as for Apogee. Based on research at Winchester, the combination of 6 oz of Apogee plus 6 oz of ammonium sulfate per 100 gal is suggested for moderately vigorous trees. Vigorous trees might be more responsive to the 12 oz Apogee rate than to the 6 oz rate.

Shoot blight suppression is related to early hardening off of shoot tip growth within 10-14 days after bloom. Vigorous trees might benefit from further protection with additional Apogee applications in mid-season if shoot growth is resumed. Studies in WV showed that Apogee reduced shoot blight infections that occurred with hail injury in June. Do not apply more than 48 oz/A within a 21-day period. Practical usefulness of Apogee for shoot blight suppression in a given year might be estimated by the potential severity of fire blight based on the number of infection days that occurred during the bloom period, as well as tree vigor, cultivar susceptibility, and disease history. Apogee is not to be considered a replacement for streptomycin sprays for blossom blight control. Apogee treatment for shoot blight suppression is strongly suggested for vigorous young trees that have nearly filled their tree space.


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

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