WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
July 5, 2005

Upcoming Events Zimmerman Retires


Pheromone Trap Counts Plant Pathology Horticulture



July 13, 5:30 p.m. - Joint WV, VA and MD Twilight Fruit Growers Dinner and Meeting at the WVU Tree Fruit Research and Education Center, Kearneysville, W. Va.  The agenda will include BBQ chicken dinner, exhibits, equipment demonstrations, updates by Extension Specialists, and a tour of research plots.  Reservations for dinner were required by June 30.  For more information contact the WVU KTFREC at 304-876-6353.

July 14, 12:00-7:00 p.m. - Fruit Grower Field Day at the Penn State University Fruit Research and Extension Center, Biglerville, Pa.  The agenda will include concurrent research and educational tours, and conclude with a dinner and invited speaker.  Registration of $10, which includes educational handouts, drinks, and dinner, was required by June 30.  For more information contact the PSU FREC at 717-677-6116 ext. 0.

August 2, 6:00 p.m. - Twilight Fruit Growers Dinner and Meeting at Jefferson Orchards, Kearneysville, W. Va.  The orchard is located on State Route 9, 1.5 miles east of Kearneysville.  Following dinner, seasonal updates will be provided by WVU Extension Specialists and a tour will be conducted by host Ron Slonaker.  For more information contact the WVU KTFREC at 304-876-6353.


Dr. Richard Zimmerman, Extension Specialist - Horticulture at the WVU KTFREC, retired on June 30, 2005 after almost 33 years at West Virginia University.  During his four years at the WVU KTFREC he made significant contributions in assisting growers to diversify into small fruits, and has established bramble and blueberry variety trials at Kearneysville.  Richard has been in Illinois since the latter part of June to assist with family issues following the death of his father.  He does plan to continue some work with his small fruit plantings.  A fall retirement celebration is being planned.


Codling moth adults (2nd flight) began to emerge last week, based on pheromone trap capture at the WVU KTFREC.  In order to prevent fruit injury, control of the second generation should be implemented in those orchards where the pheromone trap capture exceeds 5 moths per trap per week.  Recommended options include Intrepid, Esteem, Assail, Calypso, Clutch, or Rimon at 1150 degree days (DD) after biofix (2% egg hatch, expected on July 9), or Avaunt, Azinphos-methyl (Guthion) or Imidan at 1250 DD after biofix (6% egg hatch, expected on July 13).  An initial spray of any material should be followed by a second complete application in about 10-14 days (300 DD), or three additional alternate-row-middle applications 5-7 days apart.  Through July 4, 1025 DD have accumulated since biofix (May 6) at the WVU KTFREC.  Based on  DD accumulations since biofix, development on this date is about 10 days behind last year.

Codling moth larva in fruit

Oriental fruit moth second generation egg hatch is estimated at 76% complete through July 4, based on an accumulation of 1520 DD since biofix on April 11 at the WVU KTFREC.  The optimum timing for intiating control on apple and the second application on peach with organophosphates or Avaunt (apple only) was 1450-1500 DD after biofix (65-72% egg hatch), in those orchards where the pheromone trap catch has exceeded 10 moths/trap/week.

Japanese beetle adults and leaf injury on apple

Japanese beetle adults began emerging during the latter part of June in area orchards; however, abundance has been low up to this point, probably related to the dry soil conditions.  The most important threat from this insect is to dwarf and non-bearing apple trees, and to stone fruits near and during harvest.  Feeding injury on apple leaves results in a "lace-like" appearance as beetles consume the leaf tissue between the veins.  Injury to apple fruits is not common and usually only occurs on mature fruits that have already been damaged by some other factor.

All stone fruits are highly susceptible to attack as they reach maturity.  Beetles are often found in clusters on fruit that is within two weeks of harvest.  Since feeding may be "clumped" or unevenly distributed, care should be taken in looking at a representative sample before making a spray decision.  Control is recommended if fruit feeding injury exceeds one percent.  Sevin is the most effective material available for control on both apple and stone fruits.  The XLR Plus formulation of Sevin is considered to be less disruptive to mite predators than other formulations.  The rate of Sevin XLR Plus in the 2005 Spray Bulletin is too low for insect control on apples.  The correct rate is 2 pts/100 gal dilute and 6 pts/acre concentrate.  Other options include Lannate, Assail and Surround.

Japanese beetle adults on peach

Japanese beetles feeding on apple

European red mite populations have increased in  the past 1-2 weeks to levels requiring control in some orchards. Orchard blocks should be monitored closely over the next couple of  weeks, as mites can increase to very high levels in a short time with the warmer temperatures that we're experiencing.

Monitor the mite population on 5-10 trees of the same cultivar (e.g., Delicious, Fuji, or York) randomly scattered throughout the block.  Collect 10 middle age leaves from each tree, count the total number of motile mites and calculate the average number of mites per leaf. Using figure 1 below, estimate the projected production per acre (harvested bushels) for the affected block.  Select the threshold line on the figure for the appropriate time of the growing season.  For a given time of the growing season and a given estimated crop load, if mites per leaf exceed the threshold then some control is needed, either by predators or by application of miticides. If you are using the alternate-row-middle (ARM) system of spraying to make your miticide applications, reduce the action threshold to one-half the value in the figure since you are only spraying one-half of the tree.  If the mite population does not exceed the action threshold, it should be reassessed within 5-7 days.  If the mites per leaf exceed the action threshold, the predator population should be assessed.

Although the black ladybird beetle, Stethorus punctum (SP), has historically been an  important predator of mites in the mid-Atlantic region, its abundance has generally been very low in recent years.  Determine their abundance by counting the number of adults and larvae observed during a 3 minute period, while slowly walking around the periphery of each tree sampled for mites.  Divide the 3 minute SP count by the number of motile pest mites per leaf.  For example:  25 SP adults and larvae divided by 10 motile mites per leaf equals a predator-to-mite ratio of 2.5, which is generally sufficient for biological control to occur.

Predatory species of mites have been more abundant in recent years, and can provide significant biological control of pest mites.  The two most common predatory mites in mid-Atlantic apple orchards are Amblyseius fallacis (AF) and Zetzellia mali (ZM).  AF is similar in size to pest mites, clear to straw colored, oval to pear shaped, and moves rapidly over the leaf surface.  An AF-to-pest mite ratio of at least 1:10 has a good probability of  providing biological control.  ZM is smaller than pest mites or AF and lemon-yellow to reddish-orange.  Although there are no validated management thresholds for ZM, populations averaging 2-3 per leaf can reduce pest mite levels.  Determine the average number of predatory mites per leaf on the same leaves sampled for pest mites.

If the action threshold has been reached and the predator-to-pest mite ratio is insufficient to provide biological control, then a miticide application is justified.  Options include Nexter (formerly Pyramite), Fujimite, Kanemite, Zeal,  Acramite, Kelthane, Vydate and Vendex.  Savey and Apollo may also be used if at least 28 and 45 days, respectively, remain until harvest.  Since these products act primarily as ovicides, they should be tank-mixed with one of the other miticides if motile mite stages are especially abundant.  The orchard should be checked again in 5-7 days after application to determine if retreatment is necessary.   A different miticide should be used if retreatment is needed.  If the predator-to-pest mite ratio is only slightly too low, a half spray (ARM application) may be sufficient to  allow predators to become abundant enough  to provide biological control.

European red mite motile stages and summer eggsStethorus punctum adult (right), larva (center and ERM (left)Amblyseius fallacis adultZetzellia mali adult


Woolly apple aphid may be more problematic this year in apple orchards that experienced injury from periodical cicada last year.  During the spring, nymphs that overwintered on the root system crawl up the tree to initially establish colonies on branch wounds (pruning cuts, cicada oviposition scars, cankers).  During the summer, colonies will also occur on foliar growth at leaf axils and on watersprouts.  Heavy infestations result in an accumulation of honeydew and subsequent sooty mold on fruit and leaves, and gall formation at leaf axils.  Aphids that are crushed during harvest can result in red sticky residues on fruit, and on the hands and clothing of pickers. Severe root infestations can reduce growth and production, especially of young apple trees.  Various predators and parasites, especially syrphid fly larvae and a tiny wasp, aphelinus mali, are very important in helping to keep woolly apple aphid in check in most orchards.  However, many pesticides, especially pyrethroids used last year for periodical cicada, are highly toxic to these biological control agents which can lead to woolly apple aphid outbreaks.

Monitor orchards for woolly apple aphid colonies by inspecting pruning cuts, cicada scars, and foliar growth (leaf axils, watersprouts).  Although no threshold is available, treatment with Diazinon, Thiodan, Provado or Actara is recommended if honeydew or sooty mold begins appearing on fruit.  Increasing the spray volume will likely improve control since colonies are difficult to penetrate because of their waxy outer covering.

Woolly apple aphid colony

Woolly apple aphid colony at leaf axil


March 21 0            
March 28 3 0            
April 4 17 9 0            
April 11 73 720 3            
April 18 51 896 42            
April 25 34 1372 186            
May 2 7 256 89 0 0 0 0    
May 9 8 140 53 15 7 0 0    
May 16 5 94 163 32 76 0 18    
May 23 2 15 23 21 131 1 24    
May 31 0 0 5 4 108 2 14 0  
June 6 0 52 10 9 144 1 14 0  
June 13 34 1280 9 23 132 0 37 3  
June 20 121 704 6 7 50 17 28 0  
June 27 135 1728 14 1 9 13 13 3 0
July 5 122 1312 30 8 1 15 11 2 0

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.  We recorded no new infection periods since the last Orchard Monitor was published on June 20th. In fact, it is quite dry here, with wetting hours accumulating with only an occasional dew.

Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2005.

No. Date 2005 Hours/ degrees F
1. April 7 - 8 14 hr/58 F
2. April 22 - 23 33 hr/52 F
3. April 30 - May 1 19 hr/57 F
4. May 14 - 15 15 hr/64 F
5. May 19 - 21 18 hr/54 F
6. May 21 - 22 13 hr/48 F
7. May 23 - 25 42 hr/54 F
8. June 2 - 3 33 hr/60 F
9. June 6 - 7 12 hr/64 F
10. June 9 - 10 13 hr/70 F

Accumulated wetting hours.  As of July 5, 2005, we have accumulated 148 to 194 wetting hours, for petal fall dates of May 14 and May 7, respectively. 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.

Brown rot.  Incidence of brown rot fruit infection is proportional to temperature and wetness duration. Optimum temperature range is 72-77 F for infection of peach fruit and infection can occur following only 3 hr of wetness at high inoculum concentrations. Longer wet periods during infection result in shorter incubation periods. Insects (nitidulid beetles and honeybees) also can be important as vectors of the brown rot fungus during fruit ripening, carrying conidia to injury sites produced by oriental fruit moth, Japanese beetle, green June beetle, stink bugs, and other insects, or birds, that injure fruit. Wounded fruit are infected much more readily than nonwounded fruit. Hail damage near harvest can lead to a devastating brown rot problem. At harvest, apparently healthy fruit usually are contaminated with spores or latent infections that, under favorable conditions, may later produce decay during storage and marketing.

Effective control of brown rot depends on attention to orchard sanitation; proper pruning of trees to facilitate drying and penetration of spray materials; monitoring for disease every 3 to 5 days during the preharvest period, being aware of favorable weather and the potential for bird, insect and hail damage; and use of effective fungicides at 7 to 10 day intervals during the preharvest and harvest periods. See the 2005 Spray Bulletin for suggested chemicals and rates of application. The sterol-inhibiting fungicides, Orbit, Elite, and Indar, are the best fungicides for controlling the disease and show generally similar performance in preharvest assessments. Fruit treated with Indar right before harvest generally shows less rot in the postharvest environment. Recent data from studies in Virginia, New Jersey, and California show that the recently-registered reduced-risk fungicides Pristine and Elevate are very good to excellent for managing pre- and post-harvest brown rot. Reduced-risk fungicides have a low impact on the environment, high specificity to target organisms, low potential for groundwater contamination, and low potential for human health risks. Pristine is registered for use on all stone fruits, whereas Elevate is limited to use on peaches, nectarines and cherries.

Alternation of the sterol-inhibiting fungicides with Pristine or Elevate may help reduce the risk of the brown rot fungus becoming resistant to the SI's. If fruit are washed during the packing operation, the efficacy of Pristine and Elevate for preventing wound infections is likely to be reduced relative to the sterol-inhibiting fungicides. For this reason, in years when the risk of brown rot is high or if packing conditions are unsanitary, the use of an SI fungicide right before harvest is recommended.

Scholar (fludioxonil), another reduced-risk material, is available for postharvest use on all pome and stone fruits (excluding cherries). Data show that infections of wounds that occur in the field at harvest are effectively stopped by post-harvest treatments with Scholar, which is typically done on the same day that fruit are harvested. Including Scholar as a postharvest treatment may be useful in years when inoculum pressure is high, conditions at harvest are favorable for brown rot infection, or packinghouse conditions are unsanitary. Scholar is stable in 100 ppm chlorine.

See our "Current Conditions" Web page for details that are updated at least three times weekly.


Weed Management Update.  Systemic herbicides like glyphosate are not very effective when sprayed under drought conditions.  Plants under stress absorb and translocate much lower amounts of a systemic herbicide than that applied under optimum growing conditions.   Hence, reduced weed control may be observed if glyphosate was applied during the dry period we had recently.   If you plan to apply glyphosate or any other systemic herbicide, please wait till the plants come out of stress (a few days after moderate showers).  Contact herbicides like paraquat are less effected by drought conditions; however, repeat application may be necessary to control perennial weeds.

Demonstrations were set up at Kearneysville (WVU-KTFREC) and Romney (Shanholtz Orchards) to evaluate different preemergence herbicides used in tree fruits.  Twelve different PRE herbicides were applied at labeled rates along with glyphosate @ 1 lb/acre as a burndown treatment.   The demonstration at Kearneysville was treated on May 6th and is replicated.  The demonstration at Romney is not replicated and was treated on May 19th.  Ratings taken 4 and 6 weeks after treatment indicate no significant differences in overall weed pressure among the different treatments.  Most treatments provided >90% bare ground.  However, the untreated plots can be easily spotted!  Plot maps are available at both locations for those interested in making observations.  (Rakesh Chandran, WVU Weed Scientist)


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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