April 2, 2007
|Upcoming Events||Weed Science||Pheromone Trap Counts||Plant Pathology|
April 5, 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 Drs. Chris Bergh and Rongcai Yuan, and Dr. Keith Yoder will provide an in-depth look at tree fruit diseases. For more information contact the Frederick County Extension Office at 540-665-5699, or email Josh Marvel at firstname.lastname@example.org.
April 26, 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 new pest management tools, and early-season insect and disease management strategies. For more information contact the Hampshire County Extension Office at 304-822-5013.
Tree-of-heaven vs. Sumac. I realized that the slide I showed for tree-of-heaven at the Fruit Schools this year (2007) was that of sumac instead – please accept my apologies for the same. Tree-of-heaven (Ailanthus altissima), an invasive woody plant occasionally seen in orchards, can be mistaken for sumac (Rhus glabra). The difference between the two is that each leaflet of tree-of-heaven has one to three serrations at the base, while the leaflets of sumac are serrated throughout the entire margin. Also, tree-of-heaven has a characteristic odor that may resemble peanut butter when a leaf is crushed. Tree-of-heaven can spread very quickly if left uncontrolled. To control tree-of-heaven, mechanical removal, especially of saplings, or repeated cutting of older plants can be partially effective. In orchards, there are limited herbicide options. A 2% solution of glyphosate (4 lb AI/Gal) applied as a foliar spray during June – Sept has been noted to be effective. Repeat treatments may be necessary during the following season. Cut-stump applications with higher concentrations of glyphosate (1 part glyphosate with 3 parts water) may sometimes not provide uniform results. Next time you see a tree that looks like sumac, please take a closer look at it! (Prepared by Dr. Rakesh Chandran, WVU Weed Scientist).
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 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 ½-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, 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, 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 ½-inch green). Control of RAA with these materials works best when a complete spray is applied at half-inch green, or two alternate-row-middle sprays are applied at green tip and half-inch green. Control with these materials has been especially weak where the two alternate-row-middle sprays were applied at half-inch green and tight cluster to pink. 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.
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 30SG (2.5-4.0 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 30SG (5.5-8.0 oz/acre) and Calypso (4-8 oz/acre). See page 54 of the 2007 Spray Bulletin.
San Jose scale has been an isolated problem in some orchard blocks, but has the potential to increase in severity as use of oil is reduced or eliminated because of cost from the early season pest management program. If injury was detected on fruit (red spotting) at harvest last season, and oil is not planned for application this spring, other options need to be considered for control during the green tip to half-inch green stage. Lorsban, Supracide and Esteem are capable of providing very effective control of scale at this stage, especially if applied as a dilute spray. Thorough coverage of the tree tops is a critical component of an effective management program for this pest.
PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC
|DATE - 2007||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM|
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’ve recorded only one infection period so far; however, many of you may not have had green tissue showing at the time this occurred because it was very early. On March 23 – 25 we had 44 hours of wetting at 50° F with 0.40 inches of rain. Apple scab ascospores were caught in traps during this infection period at the Winchester Fruit Station. Over this past weekend, we had 0.03 inches of rain starting at around 2:00 am on April 2, 2007 and accompanied by an extended dew. This wetting period is insignificant in terms of scab infection. The wetting period of March 23 – 25 will be recorded as our first apple scab infection period for the 2007 growing season.
Why do we always make such a big fuss about early scab control? 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 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).
Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2007.
|No.||Date 2007||Hours/ degrees F|
|1.||March 23-25||44 hr/50° F|
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.
READ THE LABEL CAREFULLY AND USE THE CHEMICALS IN ACCORDANCE WITH LABEL CAUTIONS, WARNING AND DIRECTIONS. REQUEST A MATERIAL SAFETY DATA SHEET (MSDS) FROM THE MANUFACTURER FOR EACH PRODUCT YOU USE.
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
TREE FRUIT RESEARCH AND EDUCATION CENTER
P. O. BOX 609
KEARNEYSVILLE, WV 25430-0609
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