WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
April 16, 2007

Upcoming Events Horticulture

Entomology

Pheromone Trap Counts Plant Pathology

 

UPCOMING EVENTS

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. 

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.

HORTICULTURE

Natural Chemicals Protecting Plants- Dehydrins.  Plants have had to adapt to a wide range of water availability throughout the year because in the growing season, rainfall may be inadequate or in excess and in winter water is unavailable to plants because it is often present as ice. These conditions may all result in plant drying (dehydration). Plants have structural features that help them limit water loss – for example the presence of wax on leafy surfaces and bark on a tree’s branches and trunk as well as small openings in leaves called stomata, which have the ability to close or open depending upon how well the plant is supplied with water. There are also special plant-produced natural chemical compounds (proteins) that enable the plant to deal with water shortages (stress) including a class of functional proteins called dehydrins. Originally coined from “dehydration induced” protein, dehydrins are found in every plant examined to date, and in most tissues, including seeds. Dehydrin production is stimulated by environmentally unfavorable conditions that results in cellular dehydration such as salinity, drought, freezing, etc.

Drs. Michael Wisniewski, Carole Bassett, and Tim Artlip are studying the presence of dehydrins in peach and apple trees and their role in making trees more resistant to a variety of unfavorable environmental conditions, especially freezes, frosts and water deficit. They identified several specific dehydrins in apple and peach trees and found that their natural content fluctuate with the seasons, reaching a maximum accumulation in winter through early spring. This higher level of dehydrin is coincidental with an improved plant hardiness during this time. Their study also showed that the plant hormone abscisic acid (ABA) has the ability to stimulate dehydrin production in plants. Ongoing genetic research is expected to further characterize how dehydrin genes respond to a variety of environmental conditions. Such knowledge will provide growers with potentially new tools to manipulate dehydrin content in plants and help them better cope with unfavorable environmental conditions such as freezing temperatures and drought. Additionally, AFRS scientists are over expressing dehydrin genes specifically in apple flowers in order to improve their hardiness to late spring frosts. For further information contact Dr. Wisniewski or Dr. Bassett at 304-725-3451or by email at Michael.Wisniewski@ars.usda.gov or Carole.Bassett@ars.usda.gov. (Reproduced with permission from AFRS Fruit Update, April 2007; edited by Joseph Uknalis).

ENTOMOLOGY

Acramite 50WS miticide, from Chemtura Corporation, was recently granted a federal (Section 3) registration for use on tart and sweet cherries for the control of various mite species, including two-spotted spider mites and European red mites. This new registration includes bearing cherry trees, which is in addition to the previously labeled use on non-bearing cherry trees. Acramite should be applied at 12-16 oz per acre, only once per year, in a minimum of 50 gallons of water per acre. It provides quick knockdown through contact activity and long residual control. Acramite is a reduced-risk chemical, with no special personal protective equipment requirements. It has a 12 hour restricted-entry interval (REI) and a 3 day pre-harvest interval (PHI) on cherries.

Tarnished plant bug adult

Tarnished plant bug apple injury

Tarnished plant bug and stink bug adults overwinter under bark and leaves in woodlots, fence rows and rock breaks, and around alfalfa, other legumes or weeds that are seeded late in the summer or early fall.  They become active and begin feeding on warm spring days. Tarnished plant bugs typically begin feeding on apple buds near the tight cluster stage. Injury to apple buds before bloom usually results in early bud abscission and is rarely a problem, whereas feeding from bloom to shortly after fruit set results in a deeply sunken dimple in the side or calyx end of the fruit. Tarnished plant bug is usually the first to begin feeding on peach and nectarine buds when they enter the pink stage of development, with brown and dusky stink bugs beginning to cause injury in the early postbloom period.  Feeding injury from pink through petal fall causes bud, flower or fruit drop, and is usually of no consequence except in years of light crops due to winter freeze or spring frosts.  Feeding injury from shuck split 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.

These pests are difficult to control because they are not  full-time residents on fruit trees, but move frequently between broadleaf weed hosts and fruit trees to cause injury.  On apple, control is best achieved with an application of pyrethroid (Ambush, Asana, Battalion, Baythroid, Danitol, Decis, Pounce, Proaxis, Warrior) or neonicotinoid (Actara, Assail, Calypso) insecticide at the pre-pink to pink stage of bud development. On peach,  maintaining thorough and frequent spray coverage from shuck split until a few weeks after shuck fall is critical to minimizing fruit injury.  Pyrethroids (Ambush, Asana, Baythroid, Pounce, Proaxis, Warrior) are considered the most effective chemical class for control, but application after petal fall is more likely to result in mite outbreaks, and therefore they should be used with caution.  Other options include Imidan and Actara (higher rate).  Maintaining good broadleaf weed control will also reduce fruit injury from this pest complex.

Brown stink bug adultCatfacing injuryScarring injury

Green peach aphid typically overwinters in this area as wingless females in protected places on the tree and in ground debris.  Aphid feeding on flower parts or on the underside of leaves is usually first observed during the late bloom to petal fall stage of peach and nectarine.  Infestations are often first detected on leaf clusters attached to the trunk or scaffold limbs in the lower part of the tree.  Feeding on leaves causes them to curl, become yellow, and drop prematurely from the tree.  Feeding on fruit may result in distortion, cracking and drop, especially on nectarine.  Provado and Actara are the most effective treatments and are recommended for control if more than an average of one colony per tree is found. 

Pheromone traps should be installed for the monitoring of codling moth and tufted apple bud moth at the beginning and near the end of apple bloom, respectively.

Green peach aphid colony

PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC

DATE - 2007 RBLR STLM OFM CM TABM DWB LPTB PTB AM
March 19 0
March 26 2 0
April 2 121 3 0
April 9 54 28 1
April 16 23 93 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.

PLANT PATHOLOGY

Apple scab. We recorded one new infection period since the last Orchard Monitor newsletter on April 2. That one occurred during the Nor’easter weekend (April 14 – 15) and was accompanied by 1.75 inches of rain and some pretty fierce sustained winds. With rain beginning at around 7:00 p.m., leaves were wet for 24 hours at an average temperature of 44 F. Plant development has been slow because of the cool temperatures, so relying on fungicide redistribution to protect new leaves from infection should not be an issue. A rain event on April 11 – 12 was not an infection period in most orchards. This rain event was initiated at night and did not accumulate enough daylight hours to qualify as an infection period. However, in high inoculum orchards, this may have been an infection period, so I have included it in the table below. Our temperature data put into the Cornell ascospore maturity model suggests that our ascospore maturity might be around 25%.

The peak period of ascospore release usually occurs during the pink through petal fall stages of bud development, so this will be the time to be using the most effective scab materials. Growers who suspect decreased effectiveness of the sterol-inhibiting fungicides (Nova, Rubigan, Procure) may want to consider using the strobilurin class of materials (Flint, Sovran, Pristine) for two applications at this time. These materials provide excellent control of scab and mildew, but may need to be supplemented with an EBDC to boost activity against the rusts. For another choice in locations where mildew and the rusts are problems, you may want to use a sterol-inhibiting fungicide at the low end of the rate range to get excellent control of these diseases, combined with a full rate of protectant (3 lb. of EBDC + 3 lb. Ziram or captan 50W equivalent (avoid captan if oil is being used)) for scab.

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

2.

April 11-12

18 hr/47 F

3.

April 14-15

24 hr/44 F

Fire blight. At this time last year we were monitoring fire blight infection periods. Looking at the 15-day forecast and guessing when first bloom might be available, and then entering these guesses into our Maryblyt prediction program shows low risk of infection through April 30, 2007. 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.

Streptomycin reminders: For best blossom blight control, apply Streptomycin just before an anticipated infection, then re-apply it in 4 days if high risk conditions persist. High risk occurs with any combination of three out of the following four criteria: 1) blossoms open, 2) bacteria present on blossom surface, 3) average temperature for the day of 60 F, and 4) sufficient moisture in the form of rain or dew. Note that infection of susceptible cultivars is very likely to occur if all four of these criteria are satisfied. Streptomycin applied after infection can provide acceptable control, however the level of control that is achieved declines with time and declines more rapidly as temperature increases.

Avoid alternate-row-middle programs for fire blight control. If this method is used and if infection conditions occur after the first half spray, follow immediately with the second half spray of streptomycin. Do not exceed 3 - 4 antibiotic sprays per year in order to minimize the chance that the fire blight bacterium will develop resistance to streptomycin. Make blossom treatments strictly on whether an infection is expected or has occurred, not on how severe that event might be.

Peach scab and Rusty spot. The shuck split - shuck fall stage is the time to initiate fungicide applications for managing these diseases on peaches and nectarines. Follow instructions in the 2007 Spray Bulletin for the selection of spray materials for these diseases. For scab control, remember that Bravo is highly effective but is not labeled for applications after the shuck fall stage. Control of rusty spot will be facilitated by adequate control of powdery mildew in adjacent apple orchards.

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


WEST VIRGINIA UNIVERSITY
TREE FRUIT RESEARCH AND EDUCATION CENTER
P. O. BOX 609
KEARNEYSVILLE, WV 25430-0609
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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