WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
April 30, 2007

Upcoming Events


Pheromone Trap Counts Plant Pathology



May 3, 7:00 p.m. – Joint Virginia and West Virginia 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 and WVU Extension Specialists, and Dr. Rongcai Yuan will discuss fruit thinning. For more information contact the Frederick County Extension Office at 540-665-5699, or email Josh Marvel at jmarvel@vt.edu.

May 4, 12:00-12:45 p.m. – US Apple is hosting a biweekly conference call on ag labor and immigration reform legislation. You and other interested industry leaders are invited to join the call for an update from the last two weeks on local/state political activities and on legislative developments on Capitol Hill. In the first conference call, industry leaders shared ideas which have worked in their states to focus attention on the ag labor issue and gain the support of their Members of Congress. Growers from California, Michigan, Washington and other states reported their congressmen have heard from a significant number of growers at local meetings.  State leaders who recently joined the Apple Action Network reported they gained insight and new ideas through the call and are making plans to implement those ideas in their own local regions and states.  One grower from Utah picked up on the idea of having computers and internet access at a grower meeting so everyone there could access US Apple’s website and send an email message to elected officials on Capitol Hill. To access the call, please dial (866) 336-4290 and enter the pass code "528850" followed by the "#" sign.  If you have a problem, please call US Apple at (800) 781-4443.

May 24, 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 WVU Extension Specialists. For more information contact the Hampshire County Extension Office at 304-822-5013.


Honey bees have recently experienced a dramatic and widespread die-off of tens-of-thousands of colonies referred to as Colony Collapse Disorder (CCD). A research group, the Colony Collapse Disorder Working Group is currently trying to determine the factors that are responsible for these losses. Although nothing definitive has been determined at this point, chemical contamination of hives is one of several possible contributing factors that is being investigated. The neonicotinoid class of insecticides (Actara, Assail, Calypso, Clutch, Provado) has come under suspicion. Use of this insecticide class has increased dramatically in recent years and is now the most widely used class of insecticides in the U.S., including application in agriculture, lawn care, golf courses and structural pest control. There is conflicting information about the affects of neonicotinoids on honey bees and members of this insecticide class differ in toxicity to honey bees, with Actara, Clutch and Provado being the most toxic. Until additional information becomes available, it is strongly recommended that growers refrain from using neonicotinoids until honey bees are removed from the orchard, in order to protect these pollinators. To keep informed of current developments on this issue visit http://maarec.cas.psu.edu/index.html

Mustang Max (zeta-cypermethrin) is a 0.8EC pyrethroid insecticide from FMC Corporation that was recently registered by EPA for the control of numerous insect species on pome and stone fruits, brambles, blueberries, and grapes. Rate of application is 1.28 to 4.0 fl oz per acre, with a season maximum of 24 fl oz per acre. The restricted-entry interval (REI) is 12 hours, and the pre-harvest interval (PHI) is 14 days on pome and stone fruits; 1 day on berries and grapes. As with other pyrethroids, this product is highly toxic to mite predators, and postbloom use is more likely to result in an increase in mite populations.

Oriental fruit moth adults have been captured in pheromone traps for about 10 days, with biofix set on April 21 (21 days later than last year) at the WVU KTFREC.  Using a base temperature of 45F and upper temperature of 90F, degree days (DD) should be accumulated from biofix in order to properly time spray applications.  Pheromone traps should be monitored on a weekly basis to determine if control is needed.  Control of the first generation is justified where the pheromone trap capture exceeds 15 moths/trap/week in peach and 30 moths/trap/week in appleIn peach, an application of pyrethroid (Ambush, Asana, Baythroid, Pounce, Proaxis, Warrior), or Imidan is recommended at 170-195 DD (10-15% egg hatch, normally about shuck split).  A second application at 350-375 DD (55-60% egg hatch) may be needed if pest density is high.  In apple, control with an application of Assail or Calypso at 250-275 DD (25-30% egg hatch, normally petal fall), or Avaunt, azinphosmethyl (Guthion) or Imidan at 350-375 DD, (55-60% egg hatch).  Through April 29, 118 DD (4% egg hatch) have accumulated since biofix at the WVU KTFREC.

Oriental fruit moth adult
Plum curculio adult

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, which will occur this week.  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 in peach include pyrethroids (Ambush, Asana, Baythroid, Pounce, Proaxis, Warrior), Imidan, Actara and Surround. In apple,  recommended options include azinphosmethyl (Guthion), Imidan, Avaunt, Assail, Calypso, Actara, and Surround.

Plum curculio fresh egg-laying injury
EAS larval injury on young fruitEAS larval injury on older fruit

European apple sawfly has become more prevalent in area orchards during the past few years. Adults begin emerging from the soil at pink and females deposit eggs in the calyx end of young apple fruit from bloom through petal fall. Tunneling by the hatching larva creates a large circular russeted scar that originates from the calyx.  The larva will typically leave the first fruit and tunnel to the core of a second fruit, consuming most of the flesh.  Frass (excrement) will protrude from these injured fruits which will later fall from the tree.  Where white visual traps have been used for adult monitoring, petal fall control is justified if the accumulated  prebloom and bloom capture reaches 3 or more per trap.  Where traps have not been used, control is recommended if fruit injury was observed last year.  Early petal fall timing usually provides effective control, with options including Avaunt, Assail, Calypso, azinphosmethyl (Guthion), Imidan, Sevin, or Actara.

EAS larval tunneling in second fruit

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.   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, Calypso, or Clutch at petal fall if an average of one or more infested fruit clusters per tree are found.

Codling moth adult emergence is expected to begin this week, which is the optimum time to install pheromone mating disruption dispensers (Isomate CM/OFM TT, Isomate C+, Isomate CTT, Disrupt CM-Xtra, or CheckMate CM-OFM Duel) for the control of this pest. The use of pheromone mating disruption dispensers should especially be considered as a  supplement to traditional chemical application in those problem orchards where pesticides alone have failed to provide adequate control.

Rosy apple aphid fruit injury

What insects do I need to manage in orchards damaged by cold temperatures is a question that has been posed by a few West Virginia fruit growers. To begin with, one must determine the crop that remains to be protected on a block by block basis. Where absolutely no fruit remain, the primary focus will be on preventing damage to the woody parts of trees from peachtree borer and lesser peachtree borer on stone fruits, and dogwood borer on apple. These pests should be managed with a handgun application of chlorpyrifos (Lorsban, Nufos) in orchards where it is determined by monitoring that they pose a threat. In apple orchards where fruit injury from San Jose scale was detected at harvest last season, the woody parts of trees should be protected from further infestation. If a dormant to delayed dormant application of oil, Esteem, Diazinon, chlorpyrifos (Lorsban, Nufos), or Supracide was applied, control should be adequate for this year. If not, then Diazinon, Centaur, or Esteem should be applied in June for control of the crawler stage. Where injury to peach fruits from oriental fruit moth was evident at harvest last season, injury to shoots from the first generation this year should be controlled during May in orchards where the pheromone trap threshold is exceeded.

Where the crop is too light to justify an insect management program, it is strongly recommended that the trees be defruited either chemically or manually. This will prevent the build-up of internal worm (codling moth, oriental fruit moth) populations, which have been especially difficult to manage in recent years. For growers with crop insurance, be sure to check with your claims adjuster, who may need to make an inspection, before you defruit trees.

Where the crop is light, but still sufficient to justify an insect management program, higher populations of foliage pests can generally be tolerated since the stress on trees will be less from the reduced fruit load. On the other hand, increased foliar growth can be expected because of the reduced fruit load, so greater attention to spray coverage will be needed, especially later in the season to maintain protection of fruit. Keep in mind, that because of greater fruit loss in more southern states, fruit (especially peaches) in our area should be more valuable this year which could justify management costs of a reduced crop.

Pheromone traps should be installed at this time for monitoring emergence of lesser peachtree borer in peach orchards.


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 0 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.


Apple scab. We recorded one new infection period since the last Orchard Monitor on April 16. That one occurred on April 26 – 27 and was accompanied by 0.46 inches of rain. With rain beginning at around 8:00 p.m., leaves were wet for 18 hours at an average temperature of 52 F. Plant development has progressed rapidly because of warmer temperatures. Our temperature data put into the Cornell ascospore maturity model suggests that our cumulative ascospore maturity might be just about 75% (see the "waffle words" here - there is considerable leeway in the accuracy of the model). No visible lesions were observed on nonsprayed trees at WVU-KTFREC as of Monday, April 30. Visible lesions have been reported on nonsprayed trees in the Winchester area.

Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2007.


Date 2007

Hours/ degrees F


March 23-25

44 hr/50 F


April 11-12

18 hr/ 47 F


April 14-15

24 hr/44 F


April 26-27

18 hr/52 F

Fire blight. Warm temperatures during the period April 22 – 25 resulted in rapid progression of plant development into the bloom stage and high fire blight infection risk with the first open blossoms. We did not record any wetting during this period and, therefore, no fire blight infection was recorded. The forecast for the week of April 30 – May 4 shows a 30% chance of precipitation later in the day on May 1, and if this occurs, fire blight infection also could occur. Remember that once blooms are open, fire blight risk can increase rapidly with warm temperatures and wetting. See our "Current Conditions" Web page for details that are updated at least three times weekly during the bloom period.

Cedar-apple rust and quince rust. The wetting period recorded on April 26 – 27 was favorable for cedar-apple rust and quince infection.

Things to consider when managing a crop damaged by cold temperatures. Peaches and nectarines: As a result of the extensive damage to area orchards this season, a block by block evaluation will have to be conducted to determine crop status and justification for disease control for the remainder of the season. Unlike annual crops, the potential impact of diseases on next year's fruit crop must also be considered. In reality, a judgment of "total crop loss" generally means that some fruit is still present, although its value does not warrant the expense of a full spray program and normal harvesting procedures. Without a minimal fungicide program in place, peach and nectarine growers can count on having brown rot cankers develop from any fruit left hanging in the tree. These cankers can serve as sites for perennial canker to develop and will also increase the risk for blossom and fruit infections next year. For brown rot, it may be reasonable to send crews through the orchard in the early summer months to strip out all remaining fruits before they ripen and begin to rot. Build-up of peach scab on the twigs will occur in unsprayed blocks, and this should be avoided in order to reduce the chances for fruit infections next season. Growers will want to keep their expenses at a minimum while controlling these diseases at reasonable levels. Plan for two or three maintenance fungicides through the summer months to keep these pathogens from building to troublesome levels next year. Sulfur will control brown rot and peach scab and should provide growers with the least expensive alternative to their usual seasonal program.

Apples: Be sure of your crop situation before you decide to eliminate cover sprays entirely from an apple block. Apple fruit set can fool the eye sometimes, especially now that the foliage is growing so rapidly. One week may look like a total loss and the next week, the fruit will start to show up more readily. Also, if you have crop insurance, be sure to check with your insurance representative for the details that they may require of your pest management program so you are not disqualified in any way.

Return bloom for 2003: Next year will most likely have a tremendous return bloom. With little crop, the vegetative growth should be at a maximum this year - leading to extra pruning for the dormant season. A strong dormant pruning program will help regulate the 2008 crop. Apogee applications will help reduce terminal growth and could reduce pruning costs by as much as 30 percent. Apogee applications are expensive, and a grower should weigh the costs of the applications against the costs of dormant pruning. Apogee is best timed when the king bloom is starting to drop petals.

Apple scab: Hopefully you’ve been able to stay ahead of primary scab this year. If you have scab in blocks with little crop, it would be best to get the lesions under control before you reduce or eliminate fungicide applications from the block. If blocks have sheet scab in them, then these blocks could defoliate early and have reduced winter hardiness and a high potential inoculum level for 2008. At this time, many orchards have had a full primary apple scab program and scab should not be a problem for the 2007 season, even if you are seeing a few lesions. Once primary scab season is over, you can reduce further control measures if you had primary scab under control.

Powdery mildew: Just as with apple scab, powdery mildew left uncontrolled can lead to reduced vigor and winter hardiness. Again, as with apple scab, most commercial blocks have had some mildewcides in their programs already this year, so mildew might not be of concern in most blocks with no crop. If you have running mildew right now, it could reduce winter hardiness of buds and lead to a higher inoculum potential for the 2008 season.

Cedar-apple rust: Severe leaf rust infection can lead to premature defoliation and weakening of trees. Many materials applied to control primary scab will provide some control of leaf rust. Captan is weak against rust.

Fire blight: No bloom usually means no fire blight; although infections of shoots from overwintering cankers is still a possibility, especially in a trauma situation (i.e. a hail storm). Vigorous shoots are more likely to be susceptible to fire blight, so a shoot blight epidemic in a no-crop year is still a possibility. Application of Apogee may help reduce the vigor and therefore the susceptibility of lush shoot growth.


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
Boards of Education and County Commissions Cooperating.  Equal Opportunity / Affirmative Action Institution

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