WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
April 3, 2006

Upcoming Events


Pheromone Trap Counts Plant Pathology



April 6, 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 presentations by various chemical company sponsors on use of their new products.  For more information contact the Frederick County Extension Office at 540-665-5699.

April 27, 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 early-season insect and disease management strategies.  For more information contact the Hampshire County Extension Office at 304-822-5013.


Pesticide update.  Dow AgroSciences has decided to initiate a voluntary phase out and global exit of the Kelthane (dicofol) miticide business.  This decision is based primarily on the fact that the U.S. and global market for Kelthane has been experiencing a steady decline for several years as many new miticide products and other technologies have been introduced.  In addition, Kelthane regulatory uncertainties and costs continue to escalate in key global geographies.  Dow AgroSciences will be ending Kelthane manufacturing in June of 2006 and will plan to sell out their entire inventory into channels of distribution during 2006.  Kelthane WSP and Kelthane MF can be distributed, sold, and applied legally until all supplies are exhausted.

Rosy apple aphid (RAA) is the major prebloom insect pest in most commercial apple orchards in West Virginia.  The importance of this insect pest is due to its potential to cause significant fruit injury (deformed and dwarfed fruit) in years when populations become abundant.  RAA is not typically problematic on an annual basis, however, in years of population abundance problems tend to occur in many orchards (i.e. 2003).  Prolonged cool, wet springs tend to result in higher populations because: 1) the foliage remains succulent and therefore more favorable for a longer period; 2) RAA development is delayed thus prolonging the time spent on apple trees before migration to the summer host, narrowleaf plantain; 3) these conditions are less favorable for predators which can provide some biological control; and 4) frequent rains can make it difficult to complete spray applications in a timely fashion and maintain spray coverage.

RAA overwinters as shiny jet black eggs, less than 1/16 inch long and oval in shape, on the bark of spurs and shoots.  These eggs cannot be distinquished from those of apple grain aphid, which are much more numerous on apple.  Eggs of apple grain aphid are the first to hatch, and young aphids (nymphs) of this species can often be found clustered on buds at silver tip.  Eggs of RAA begin to hatch about a week later (green tip), with hatch usually complete by the -inch green stage.  Young nymphs of both species tend to be dark green in color, but RAA can be distinguished by its longer antennae (half the length of the body) and cornicles ("tail-pipes").  Antennae of apple grain aphid are less than half the length of the body and cornicles  are very short, barely swollen discs.

Upon egg hatch, nymphs of both species move to the tips of buds to feed on emerging green tissue.  As the buds open, aphids move inside to continue feeding on leaf and fruit bud clusters.  Feeding of apple grain aphid is of no consequence.  However, RAA feeding causes leaf curling (also twig curling under high populations), and the translocation of toxic saliva from the leaves to fruit causes fruit distortion.  All nymphs hatching from overwintering eggs are female, which become adults (stem mothers) by the pink stage of bud development and initiate leaf curling, fruit injury and production of live young.
The best strategy to prevent fruit injury is to control RAA during the prebloom period, with specific timing dependent upon the management option selected.  Pyrethroids (Asana, Ambush, Battalion, Baythroid, Decis, Danitol, Pounce, Proaxis, Warrior) and organophosphates (Diazinon, Lorsban, Supracide) work best when good contact with RAA can be achieved, which occurs when aphids are clustered on the tips of buds (green tip to -inch green).  Aza-Direct, which is listed by the Organic Materials Review Institute (OMRI) as an option for organic production, and Esteem (Insect Growth Regulator) would also be effective options at this time period.  For most effective control with any of the above materials, a full (both sides of trees) or two alternate-row-middle applications should be completed by the -inch green stage of bud development.  One of the organophosphates or Esteem would be the preferred choice at this time if control of San Jose scale is also needed, especially if oil is not applied.

The neonicotinoid chemistries (Actara, Assail, Calypso) would be the preferred option later in the prebloom period when more foliage tissue is exposed because of their translaminar (locally systemic) activity.  These products give growers more flexibility and would be more effective in high pressure situations in controlling RAA, as well as some other early season pests from tight cluster through bloom.  Actara at 4.5 oz/acre would be most effective from tight cluster to early pink.  Since Actara is toxic to bees exposed to direct treatment or residues on blooming crops, it should not be applied from full pink through bloom, or within 5 days of placing beehives in the orchard.  Assail (1.1-1.7 oz/acre) and Calypso (2-4 fl oz/acre) would provide very effective control from tight cluster through bloom.  Although direct contact with these materials is toxic to bees, residues are not.  Delaying application of Assail and Calypso until pink to bloom would also provide control of tarnished plant bug, mullein bug, European apple sawfly and early egg hatch of Oriental fruit moth.  However, effective control of all of these additional pests would require higher rates of application for both Assail (2.5-3.4 oz/acre) and Calypso (4-8 oz/acre).  See page 48 of the 2006 Spray Bulletin.

Rosy apple aphid fruit injury

Rosy apple aphid twig injury (curling)

Rosy apple aphid nymphs


March 20 0
March 27 29 0 0
April 3 155 920 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.


Apple scab.  We recorded two wetting periods last week on March 28 - 29 and March 31 - April 1. The first was initiated by 0.02 inches of rain and lasted for 14 hours at 45 F and, therefore, was not of suitable duration to qualify as a scab infection period. The second was initiated by 0.07 inches of rain, lasted for 10 hours at 59 F, and occurred at night. Because ascospore release is reduced during darkness, this wetting period is probably insignificant in low inoculum orchards. This wetting period will be recorded as our first apple scab infection period for the 2006 growing season.

Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2006.

No. Date 2006 Hours/ degrees F
1. March 31 - April 1 10 hr/59 F

It is important to avoid early infections on sepals, as these are difficult to detect and can provide conidial inoculum throughout the early part of the growing season. Copper applied last week would have provided adequate protection during this infection period. Copper sprays, even at the low label rate, will provide scab protection similar to that provided by a mancozeb fungicide applied at 3 lb/acre. However, Cu does not provide back action against scab. The relatively new AP-type fungicides, Vangard 75WG and Scala 5SC will provide about 48 hours of back action. These products should be used in a tank mix with a protectant material, preferably one of the EBDC's or captan (3 ounces of Vangard or 5 fluid ounces of Scala, combined with the 3-lb. rate of mancozeb 75DF or Polyram 80DF).

Powdery mildew spores are first available at about the tight cluster stage of bud development. For best mildew control, fungicide applications should begin at tight cluster and continue until terminal growth stops in midsummer. The spray interval is generally 10 days from tight cluster through petal fall, when leaf tissue is developing rapidly, and is lengthened to 14 days after petal fall. Excellent powdery mildew control can be expected when Nova, Rubigan, or Procure are used on a 7 to 10-day interval for scab control. The strobilurin fungicides, Sovran and Flint, also provide good control of powdery mildew (deciding how to configure sprays of SI's and strobilurins should depend upon other disease concerns, particularly the rust diseases, and whether or not your orchard contains scab that is resistant to the SI's). Severity of powdery mildew is directly related to the amount of overwintering inoculum in shoot and blossom buds and the length of the spray interval. Check blocks of highly susceptible cultivars (Jonathan, Ginger Gold, Rome Beauty, Stayman Winesap, Idared, Paulared, Granny Smith) to determine the amount of overwintering inoculum. Where mildew is a problem, maintaining shorter spray intervals (not over 7 days) more effectively reduces mildew infection than increasing fungicide rates. On highly susceptible cultivars, special mildew sprays applied between the regular sprays from pink through the cover sprays is the most economical way to effectively manage the disease and prevent a repeated buildup of mildew for the following year. These extra spray applications will easily pay for themselves with increases in yield and quality. When the protectant fungicides mancozeb, Polyram, captan, and Ziram are being used for scab control, the addition of sulfur will usually provide good control of mildew. The SI fungicide triadimefon (formerly Bayleton) may also be a good choice if more aggressive mildew and rust activity is needed (triadimefon is not effective against scab).

Current Conditions.  Fruit producers with access to the World Wide Web can access a web page called "Current Conditions" that will provide daily (or "as-needed") updates on current disease and insect development issues.  The page should help to bridge the information gap between issues of The Orchard Monitor and provide the grower with the timely information that is needed for making good pest control decisions.

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.


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.

Helping you put knowledge to work

P. O. BOX 609
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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