WVU Extension Service: The Orchard Monitor: Committed to the Integration of Orchard Management Practices
June 2, 2008

Upcoming Events

Entomology

Pheromone Trap Counts Plant Pathology

 

UPCOMING EVENTS

June 11, 6:30-8:30 p.m. – Joint MD, PA, WV Twilight Fruit Grower Meeting at Gardenour Orchards in Smithsburg, MD. From Jefferson County take WV-480 north through Shepherdstown, crossing the Potomac River onto MD-34. In Sharpsburg, turn left onto N. Church Street (becomes MD-65, Sharpsburg Pike). Follow MD-65 north until you intersect I-70 (~ 10 miles). Take I-70 east for 5 miles to exit 35 – Smithsburg/Boonsboro (MD-66). Follow MD-66 north (left) towards Smithsburg for 5 miles. At the intersection of MD-66 and Smithsburg Pike/Jefferson Blvd. (MD-64), turn right. Proceed on MD-64 for about 4 miles (around the town of Smithsburg, past the intersection with MD-77 and a turn off for MD-491) to a left onto Gardenour Road (look for a big apple shaped sign for Gardenour Orchards). Gardenour Orchards is about mile down Gardenour Road on the left just after you cross a small one lane bridge. From Berkeley County take I-81 north to I-70 east to exit 35 and follow directions above. The agenda will include a conservation innovation planting tour by host Bill Gardenour; and tree fruit and small fruit updates by Drs. Alan Biggs, Henry Hogmire, Henry Ngugi, Anne DeMarsay, Greg Krawczyk, Joe Fiola, and Rob Crassweller. Recertification credits for pesticide applicator’s license will be provided. 

June 26, 6:00 p.m. – Twilight Fruit Growers Dinner and Meeting at Spring Valley Farm and Orchard, Slanesville, W. Va.  To reach the meeting location from Slanesville, take Route 29 south for about 4 miles, turn left on Hickory Corner Road, and travel mile to the farm on the left.  From Route 50, take Route 29 north for about 3.5 miles, turn right on Hickory Corner Road, and travel mile to the farm on the left.  Dinner will be followed by seasonal updates by the Extension Specialists from the WVU KTFREC and a tour by Eli Cook.  For more information contact the Hampshire County Extension Office at 304-822-5013.

ENTOMOLOGY

Codling moth hatch of first generation eggs has begun and is estimated at 10% complete based on an accumulation of 306 DD since biofix on May 2 at the WVU-KTFREC. Refer to the May 19 issue of this newsletter for control options and timing.

Tufted apple bud moth adult female and male

Tufted apple bud moth fresh egg mass

Tufted apple bud moth adults have been emerging since May 4 (biofix), which is 7 days earlier than last year.  First generation egg hatch is predicted to begin at 480 DD after biofix, which should occur on June 5, based on an accumulation of 392 DD through June 1 and forecasted temperatures this week.

The objective in controlling this insect is to apply sprays during the period of egg hatch, which are best timed by using DD accumulations (45F lower and 91F upper threshold temperatures) after biofix.  Options for controlling the first generation include Intrepid, Delegate, Altacor, SpinTor (Entrust), Rimon, Proclaim, BT, or an organophosphate insecticide [Azinphos-methyl (Guthion), Imidan] with Lannate.  Intrepid, Delegate, Altacor, SpinTor (Entrust), Rimon and Proclaim are considered to be the most effective products for the control of this pest.  It is recommended that any of these products be applied as a complete spray at 585-640 DD (20-30% egg hatch, expected on June 8-10) or as two alternate-row-middle applications 7 days apart beginning at 530 DD (10% egg hatch, expected on June 6).  An additional application may be needed (in 14 days for complete, in 7 and 14 days for alternate-row-middle) in high pressure situations.  If using BT or an organophosphate in combination with Lannate, make complete applications at 530-585 DD (10-20% egg hatch) and 805-855 DD (60-70% egg hatch).  Alternate-row-middle applications of these materials should begin 50-75 DD earlier and be repeated every 7 days for a total of up to four applications, depending upon insect pressure.

Tufted apple bud moth older egg mass
Tufted apple bud moth hatched egg mass
Oriental fruit moth injured peach shoot

Oriental fruit moth hatch of first generation eggs is complete and the second flight of moths is expected to begin in a week or so.  Orchards should be inspected for shoot injury at this time in order to evaluate the effectiveness of first generation control measures.

There are various options for controlling the second generation.  One strategy that could be targeted against adults is pheromone mating disruption, with various hand applied dispensers (Isomate-M100, Isomate CM/OFM TT, CheckMate OFM, CheckMate CM-OFM Duel, Disrupt OFM) and a sprayable pheromone (CheckMate OFM-F) available.  A second strategy is to control larvae with insecticides later this month in those orchards where the pheromone trap catch exceeds 10 moths/trap/week.

Oriental fruit moth injured apple shoot

Green aphids (spirea aphids) are  increasing on the terminals of apple trees,  and will continue to be abundant for the next 3-4 weeks.  In most situations, low to moderate populations of these aphids can be tolerated without detrimental effects.  High populations can stunt the growth of young trees, and indirect injury can result when aphids excrete large amounts of honeydew which supports the growth of a sooty mold that discolors the leaves and fruit.  The accumulation of honeydew is influenced by the amount of rainfall (less under wet conditions). 

Examine the foliage and fruit for buildup of honeydew, and monitor aphid abundance by sampling 10 actively growing shoots (not watersprouts) on each of 5-10 trees per block.  On each shoot, determine the number of leaves that have wingless aphids (winged aphids are black) and calculate the average number of aphid infested leaves per shoot across all trees sampled.  Also examine shoots and aphid colonies for the presence of aphid predators, such as ladybird beetle adults and larvae, and larvae of syrphid flies, aphid midges and green lacewings. 

An insecticide application is recommended for green aphid control if an average of four or more infested leaves per shoot are found, and less than 20% of the aphid colonies have predators.  Materials for control include Provado, Actara, Assail, Beleaf, Calypso, Clutch, Lannate and Thionex.

Spirea aphid colonyLadybird beetle larva, pupa and adultSyrphid fly larva feeding on a aphidAphid midge larva feeding on a aphidGreen lacewing egg, adult and larva

San Jose scale infestations continue to occur in some orchards.  Changes in pest management practices in recent years have increased the potential for this insect to become more of a threat.  Use of pyrethroids, which do not control scale, in place of organophosphates (Diazinon, Lorsban, Supracide) and decline in oil use have contributed to increased survival of overwintering scale in some orchards.  Most newer chemistries (Intrepid, SpinTor, Rimon, Proclaim, Delegate, Altacor) used during June and August are not effective against the crawler stage. 

Crawler emergence typically begins in late May to early June and should be monitored in those blocks that had at least 1% scale injury on fruit at harvest last year.  Crawler emergence can be detected by wrapping black electrician’s tape (sticky side out) around scale-infested branches.  A thin film of petroleum jelly may be spread on the tape surface to enhance crawler capture.  Inspect the tape traps twice weekly for the bright yellow crawlers.  On apple, apply Esteem, Centaur, Diazinon or Provado, preferably as a high volume spray, when crawlers are first detected and again in about 10 days.  San Jose scale may also infest peaches and can be controlled with Centaur, Diazinon or Provado.  Adequate coverage of the tops of trees is critical to control of this insect.

San Jose scale crawler
Tape trap for San Jose scale crawlers

Peachtree borer adult emergence monitoring with pheromone traps should begin at this time.  Control can be achieved with the installation of pheromone mating disruption dispensers at the beginning of moth flight or with an application to the base of trees of Thionex in late June to early July (21 day PHI) and/or chlorpyrifos (Lorsban, Nufos, Yuma) after harvest.

Peachtree borer adult female and male

PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC

DATE - 2008 RBLR STLM OFM CM TABM DWB LPTB PTB AM
March 17 0
March 24 6 0
March 31 31 17
April 7 98 376 2
April 14 74 2688 84
April 21 109 1152 376 0
April 28 33 392 329 3 0 0
May 5 12 114 210 19 3 0 1
May 12 1 114 138 14 16 0 12
May 19 1 37 51 30 31 1 38
May 27 0 17 78 31 36 7 36
June 2 0 448 20 24 46 4 16 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

Infection periods and general disease update.  We’ve recorded four additional infection periods since the last Orchard Monitor on May 19, 2008. Our disease pressure is still considerable, although it seems to be declining slightly as rainfall amounts are no longer removing all the fungicide residues. On May 20, we had leaf wetting for 15 hours at 48 F. On May 21 - 22, we had leaf wetting for 15 hours at 48 F. On May 26 - 27, we had leaf wetting for 13 hours at 69 F. On May 31, we had leaf wetting for 6 hours at 70 F. Total rainfall for May was 6.21 inches (normal for May is 3.8 inches), and I’ve heard reports from some meteorologists who say that this was the second wettest May on record. All of the above infection periods are considered to be secondary scab infections, as we recorded our first visible scab lesions on May 5th. Diseases showing up in area apple orchards include primary and secondary apple scab, cedar-apple rust, frogeye leaf spot (black rot), and primary and secondary powdery mildew. In peach orchards, leaf curl is visible and rusty spot lesions are beginning to show on developing fruits.

Got scab? What is the best approach for keeping apple scab off of fruit in orchards with a moderate level of scab on terminal leaves? There is no simple answer to this question, and several expensive options are available. The following option is relatively affordable and has a high probability of being effective unless the weather turns unseasonably cool and wet.

Make at least two applications of captan alone at the maximum label rate per acre. Applications at this time of year can be 10-14 days apart unless rainfall (>1.5 inches) removes captan residues before 10 days have elapsed. Captan is very effective for protecting fruit, especially when combined with high temperatures of 80-85F. However, if cool wet weather persists well into June, then continued applications (more than two sprays) using high rates of captan may be essential. If weather becomes more normal (hotter and drier), then the risk of fruit infection will subside until August/September when scab might become active again. An apple scab "fact sheet" is here: Apple scab.

Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2008.

No.

Date 2008

Hours / degrees F

11.

May 11-13

43 hr/46 F

12.

May 15-16

17 hr/56 F

13.

May 17-18

13 hr/57 F

14.

May 20

15 hr/48 F

15.

May 21-22

15 hr/48 F

16.

May 26-27

13 hr/69 F

17.

May 31

6 hr/70 F

Accumulated wetting hours.  As of June 2, 2008, we have accumulated 103 wetting hours for a petal fall date of May 3 (last year at this time AWH = 71). 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.

Powdery mildew.  I’m getting quite a few questions and comments about all the mildew on apples this year. What everybody is seeing are the overwintering primary infections in which every leaf becomes infected as the shoot emerges from the infected bud. It is important to remember that these buds were infected last year and are the result of last year’s weather and last year’s management practices. Indeed, the past two seasons have been extremely favorable for mildew. Secondary powdery mildew lesions are visible now as well, but are not as easily noticed as the primary infections (in fact, no one has ever said to me "gee whiz, look at all those secondary mildew infections"). Let’s review the mildew disease cycle and see where we can improve some of the problem situations. The bottom line is: in locations where mildew is a problem, susceptible varieties should be protected until shoot growth hardens off and terminal buds are set and suberized. Excellent mildew control can be achieved with the sterol-inhibiting fungicides (Nova, Rubigan, Indar, and Procure) and the strobilurin fungicides (Flint and Sovran). The recent registration of Indar means that this product has a good fit for late mildew management because, unlike the other sterol-inhibiting fungicides, Indar has activity against the summer diseases.

Powdery mildew occurs wherever apples are grown. In some areas of the country it is a major foliar disease. In other areas, it is only a minor problem. Economic loss from mildew varies with climatic conditions, cultivar susceptibility, and orchard or nursery management practices. Apple leaves, blossoms, and fruit can be infected.

The powdery mildew fungus overwinters on apple as mycelium in dormant buds infected during the previous growing season. Conidia produced on overwintering mycelium initiate the primary infections in the disease cycle. Conidia infect young leaves, blossoms and fruit, which in turn provide inoculum for secondary cycles as new leaves, shoots and fruit develop. Leaves are susceptible for only a few days after they emerge. Conidia germinate readily over the range of 50 to 78 F (optimum 68 to 72 F) at relative humidity as low as 70%. Germination is slower at temperatures below 50 F, and no germination takes place in free water or at high temperatures (above 86 F). Conidia from overwintering mycelium can be found as early as the tight cluster stage and are released during early bloom. Infection that causes fruit russet occurs from about 3 weeks before to about 3 weeks after bloom. Infection of lateral and fruit buds occurs within a month after they are formed, apparently before the protective bud scales suberize. After bud infection, the mycelium is quiescent until budbreak the following spring. The percentage of terminal buds infected can be especially high when growth resumes in late summer following terminal bud set.

Secondary infections on leaves first appear as whitish, felt-like patches of fungal mycelium and spores, most commonly on the lower surface. These lesions may appear as yellowish spots on the upper surface or may spread to the upper surface and cover the entire leaf with a white, powdery mass of spores and mycelium. Infections along the leaf margin often result in leaf curling or crinkling. Severely infected terminals are stunted, have shortened internodes, and are covered with a silver-gray mat of mycelium that may persist through the dormant season.

Fruit infections are common on severely infected trees. Apple blossoms emerging from infected buds may give rise to small, russetted fruit. When apples are infected during bloom, their growth is stunted, and a fine network of russetted cells that may merge into a solid patch covers their surface, and is visible at harvest.

Management of powdery mildew depends upon cultivar susceptibility, the desired market quality of the fruit, and the importance of other diseases to be controlled. The main strategy is the timely application of effective fungicides. Excellent powdery mildew control can be expected when Nova, Rubigan, Indar, or Procure are used on a 7 to 10 day interval for scab control. Highly susceptible cultivars include Jonathan, Baldwin, Cortland, Ginger Gold, Idared, Rome Beauty, Stayman Winesap, and Granny Smith. Less susceptible cultivars include Delicious, Golden Delicious, Winesap, York Imperial, and Nittany. The practice of interplanting cultivars of different susceptibilities in an orchard often results in applications based on the need of the most susceptible cultivar, or more commonly, poor mildew control on the susceptible cultivar. Supplementary sprays may be required on highly susceptible cultivars to reduce inoculum for infection of less susceptible cultivars and other hosts (rusty spot on peach). Fungicide applications to control mildew should be made from the tight cluster stage until terminal growth ceases in midsummer. The interval between sprays is generally 7 days during the stages of rapid leaf development before petal fall, and 12 to 14 days during the postbloom period.

Orange Rust of Brambles  – Managing Orange rust disease.  Orange rust sporulation and infection is greatest during periods of cool, wet weather. There are two different periods when different types of infection occur. The first is in the spring, when the bright orange spores (called aeciospores) are produced. The spores released at this time cause localized infections on the leaves. In 21 to 40 days, another type of spore (called teliospores) forms on the underside of these newly infected leaves, and produces basidiospores that actually cause the systemic infections. These systemic infections usually take place when temperatures are cool in the late summer and fall. Therefore, there are 2 periods when a fungicide should be used. The first is starting in the spring when the bright orange spores are forming (early to mid May) on a 10-14 day schedule until the infected leaves die and dry up in early summer. The second period is starting when temperatures start to decline in late summer to early fall through the first killing frost. There is a good chance of resistance development, however, so Nova used when not necessary should obviously be avoided. Also, cultural controls, such as removing wild brambles from areas near the planting, and removing any infected plants from the planting early in the season should be used to the greatest degree possible. Improving air circulation by controlling weeds and using good pruning practices will decrease the duration of leaf wetness necessary for leaf infection.

The following materials are registered for orange rust management in West Virginia: Cabrio EG at 14 oz/A. Do not use more than 2 sequential applications or more than 4 applications per year. May be used at harvest. 24-hr REI.

Pristine at 18.5 to 23 oz/A. Do not use more than 2 consecutive applications or more than 4 times/year. Can be used day of harvest. 24-hr REI.

Nova 40 W at 2.5 oz/A. Applications may be made up to the day of harvest. Do not apply more than 10 oz/A/season. 24-hr REI. Nova, or the other materials mentioned above, can be applied on a 10 to 14 day schedule until leaves on infected plants dry up and stop producing the orange spores. This is usually around mid-July.

Herbicides can be used as a spot treatment to kill infected plants.

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