June 1, 2004
|Upcoming Events||Pheromone Trap Counts||Plant Pathology||Horticulture|
- Twilight Fruit Grower's Meeting at Knouse Foods Cooperative, Inc.,
- Tree Fruit Grower Twilight Dinner and Meeting at Levels Fire Hall,
|Periodical cicada females have been laying eggs in pencil-diameter branches for about a week, which should continue for about 2-3 more weeks. Wilting of peach branches from oviposition injury was observed the latter part of last week. Many peach orchards have a heavy crop load and should be thinned as soon as possible where cicada pressure is high, in order to minimize branch breakage. Pyrethroids are performing very well in killing and repelling adult cicadas and reducing oviposition injury. Good activity from Calypso has also been reported. Applications should be maintained on a 7-10 day interval, especially in high pressure situations, throughout the oviposition period.|
Tufted apple bud moth adults have been emerging since May 6 (biofix). Because of very warm temperatures in May, first egg hatch was estimated to have occurred on May 25 based on an accumulation of 489 degree days (DD) since biofix. Predicted egg hatch, based on DD, of 27% through May 31 is about 15 days ahead of last year at this date. However, actual egg hatch is believed to be somewhat behind predictions.The objective in controlling this insect is to apply sprays during the period of egg hatch, which are best timed by using DD accumulations (45ºF lower and 91ºF upper threshold temperatures) after biofix. Options for controlling the first generation include Intrepid, SpinTor, Avaunt, BT, or an organophosphate insecticide [azinphos-methyl (Guthion), Imidan] with Lannate. Intrepid and SpinTor will provide the best control in most
Spirea aphids are beginning to increase on the terminals of apple trees, and will continue to do so for the next 2-3 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 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. The likelihood of biological control success from these predators has increased in recent years because of changes in pest management programs for tufted apple bud moth. Substitution of Confirm or Intrepid for Lannate has permitted increased survival of these beneficial insects to reduce aphid populations.
An insecticide application is recommended for spirea 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, Calypso, Lannate, Dimethoate and Thionex. Pyrethroids used for cicada are considered fair to good for spirea aphid control.
|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.
Widespread use of pyrethroids, which do not control scale, in place
of organophosphates (Lorsban, Supracide) and decline in oil use have
contributed to increased survival of overwintering scale in some orchards.
Most newer chemistries used during June and August are not
effective against the crawler stage.
Crawler emergence has begun and should be monitored in those blocks that had at least 1% scale injury on fruit at harvest last year. Crawlers generally begin to emerge about 3-4 weeks, or at 300-350 DD (base 50°F), after the first male catch in a pheromone trap. In most years, crawler emergence begins in late May to early June. 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, Diazinon or Provado, preferably as a high volume spray, when crawlers are first detected and again in about 10 days. Diazinon may increase the russeting of some varieties such as Golden Delicious. San Jose scale may also infest peaches and can be controlled with Diazinon. Adequate coverage of the tops of trees is critical to control of this insect.
Oriental fruit moth hatch of first generation eggs is complete and the second flight of moths has begun. 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 and sprayable formulations available. A second strategy is to control larvae with insecticides in those orchards where the pheromone trap catch exceeds 10 moths/trap/week. On peach, apply azinphosmethyl (Guthion) or Imidan at 1150-1200 DD after biofix (15-20% egg hatch). A second application may be needed at 1450-1500 DD after biofix (65-72% egg hatch) in high pressure situations. On apple, apply Intrepid, Assail or Calypso at 1350-1400 DD after biofix (45-55% egg hatch), or Avaunt, azinphosmethyl (Guthion) or Imidan at 1450-1500 DD after biofix (65-72% egg hatch). Pyrethroids used for cicada are also effective in controlling oriental fruit moth. Although second generation egg hatch is estimated at 3% complete through May 31, based on DD accumulations, it is doubtful that actual egg hatch has begun as of yet.
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 the application of Lorsban after harvest.
PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC
|DATE - 2004||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM1|
|DATE - 2004||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM1|
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.
1In a commercial orchard adjacent to an abandoned orchard near Kearneysville.
Apple scab. We recorded five additional wetting periods in the two weeks since the last Orchard Monitor, bringing the season's total number of favorable wetting periods to thirteen. Scab lesions were observed on unprotected trees in the Winchester area on April 29. Severe scab on leaves and fruit on Red Delicious and other varieties has been observed. Fire blight also is well established at a few locations and is spreading because of hail injury.
Table 1. Dates and conditions for apple scab infection periods at the WVU - KTFREC, 2004.
|No.||Date 2004||Hours/ degrees F|
|1.||March 31 - April 3||62 hr/44 F|
|2.||April 11 - 14||71 hr/43 F|
|3.||April 20 - 21 (N)||9 hr/57 F|
|4.||April 23 - 24||13 hr/62 F|
|5.||April 25 - 27||40 hr/55 F|
|First scab lesions observed 4/29/04|
|6.||May 1 - 2 (N)||7 hr/66 F|
|7.||May 2 - 3||9 hr/60 F|
|8.||May 14 - 16||37 hr/65 F|
|9.||May 18 - 20||38 hr/66 F|
|10.||May 21 - 22||13 hr/63 F|
|11.||May 25 - 26||16 hr/ 67 F|
|12.||May 27 - 28||16 hr/ 65 F|
|13.||May 31 - June 1||13 hr/62 F|
Accumulated wetting hours. As of June 1, 2004, we have accumulated 107 wetting hours (last year at this time we had 155). 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.
Summer fungicide programs. Excellent control of our summer disease complex can be achieved with well-timed fungicide sprays. Timing is one of the most important aspects of effective disease management. As always, read the labels for more detailed information about these materials.
1. EBDC fungicides (Dithane, Manzate, Penncozeb, Polyram): Will provide excellent control of summer diseases when combined with Captan, Ziram, or Topsin-M. EBDC's can be applied up to 77 days before harvest when using the extended application schedule at the 3 lb per acre rate. Early use of these materials provides the foundation for managing these diseases for the remainder of the season.
2. Topsin-M: Highly effective against sooty blotch, flyspeck, and the Botryosphaeria rots (black rot and white rot). In wet growing seasons, the spray interval should not be longer than 14 - 21 days, or 2 inches of rain. Adjust the rates of Topsin-M toward the high end of the rate range (10 oz per acre) when disease conditions are highly favorable. Use Topsin-M in mixtures with protectant fungicides to help prevent the emergence of fungal strains resistant to Topsin-M.
3. Protectant fungicides (Captan, Ziram, Sulfur): Captan and Ziram applied by themselves or in combination will provide adequate control of summer diseases if applied often enough at the proper rates (6 to 8 lb per acre total). Spray intervals should be 21 days under moderate disease pressure, and should be shortened to 10 - 14 days under prolonged, highly favorable conditions. The 8 lb per acre rate also is preferred under highly favorable conditions. Sulfur by itself is only fair, at best, in limiting these diseases. However, sulfur and copper are the only choices for organic spray programs. Under extreme disease pressure, the addition of Topsin-M at a "half rate" improves control of Botryosphaeria rots and sooty blotch and flyspeck. Where scab is well established, captan is the better choice to limit secondary infections.
4. Strobilurin fungicides (Sovran and Flint): These fungicides are very effective for controlling flyspeck (and sooty blotch) and could be used as substitutes for Topsin-M + protectant (captan or ziram) sprays during summer. The best timing for Sovran and Flint in summer sprays remains to be determined. If Sovran or Flint were used to control scab at tight cluster and pink, then they should not be used again prior to second cover. Sovran and Flint suppress sporulation of scab lesions, so their use at this time may be beneficial if your control of primary scab hasn't been completely effective. During early summer, good spray coverage is still possible whereas dense foliage, fruit clustering, and limbs drooping under heavy crop loads often compromise spray coverage in late summer. However, if Sovran or Flint is applied at petal fall and first cover, then additional summer applications would need to be delayed until July or August because of the requirement for intervening applications with some other class of fungicides.
Sovran has a 30-day preharvest interval and the label indicates that it should not be used as the last spray of the season. This prohibition was based on the assumption that growers might apply Sovran for scab control starting at green-tip, and using it both to end the season and begin the following season would compromise resistance management. Flint has a 14-day preharvest interval. Both Flint and Sovran have residual activity against flyspeck, although recent research suggests that the residual activity is not equivalent to that provided by Topsin-M.
Summary. Control of early-season diseases with a program based on an SI fungicide plus an EBDC material, alternated with the strobilurin fungicides, provides a solid foundation for controlling summer diseases. The most flexible program for controlling sooty blotch and flyspeck is ziram or captan + Topsin-M, and optionally alternated with two applications of the strobilurin fungicides. This program may need to be modified if other summer diseases occur at moderate to high levels. For example, the combination of ziram + Topsin-M is rated as only "good" (rather than "excellent") against white rot and black rot, and is only "fair" against bitter rot. Alternating applications of ziram + Topsin-M or captan + Topsin-M with full rates of ziram or captan alone will improve your management of the summer rots. Remember that management of diseases with fungicides is improved if other cultural practices that reduce inoculum and improve coverage are employed.
Orange Rust of Brambles: Orange rust is the most important of several rust diseases that attack brambles. All varieties of black and purple raspberries, and most varieties of erect blackberries and trailing blackberries are very susceptible. Orange rust does not infect red raspberries.
Unlike all other fungi that infect brambles, the orange rust fungus grows systemically throughout the roots, crown and shoots of an infected plant, and is perennial inside the below ground plant parts. Once a plant is infected by orange rust, it is infected for life. Orange rust does not normally kill plants, but causes them to be so stunted and weakened that they produce little or no fruit.
Orange rust-infected plants can be easily identified shortly after new growth appears in the spring. Newly formed shoots are weak and spindly. The new leaves on such canes are stunted or misshapen and pale green to yellowish. This is important to remember when management is considered because infected plants can be easily identified and removed at this time. Within a few weeks, the lower surfaces of infected leaves are covered with blister-like pustules that are waxy at first but soon turn powdery and bright orange. This bright orange, rusty appearance is what gives the disease its name. Rusted leaves wither and drop in late spring or early summer. Later in the season, the tips or infected young canes appear to have outgrown the fungus and may appear normal. At this point, infected plants are often difficult to identify. In reality, the plants are systemically infected, and in the following years, infected canes will be bushy and spindly, and will bear little or no fruit.
Orange rust is caused by two fungi that are almost identical, except for a few differences in their life cycles. Arthuriomyces peckianus occurs primarily in the northeastern quarter of the United States and is the causal agent for the disease in Ohio. Gymnoconia nitens is a microcyclic (lacks certain spores) stage of A. peckianus. G. nitens is the more common orange rust pathogen on erect and trailing blackberries in the mid-Atlantic.
In late May to early June, the wind and perhaps rain-splash spreads the bright orange aeciospores from the pustules on infected leaves to healthy susceptible leaves where they infect only localized areas of individual mature leaves. When environmental conditions favorable for infection occur, the spores germinate and penetrate the leaf. About 21-40 days after infection, small, brownish black telia develop on the underside of infected leaflets. The teliospores borne in these telia germinate to produce a basidium, which in turn produces basidiospores. These basidiospores then infect buds on cane tips as they root. They also may infect buds or new shoots being formed at the crowns of healthy plants in the summer.
The fungus becomes systemic in these young plants, growing into the crown at the base of the infected shoot, and into newly formed roots. As a result, a few canes from the crown will show rust the following year. The fungus overwinters as systemic, perennial mycelium within the host. Orange rust is favored by low temperatures and high humidity. Temperatures ranging from 43 to 72 degrees F favor penetration and development of the fungus, but higher temperatures decrease the percentage of spore germination. At 77 degrees F, aeciospores germinate very slowly, and disease development is greatly retarded. Spore germination and plant penetration have not been observed at 86 degrees F. Aeciospores require long periods of leaf wetness before they germinate, penetrate, and infect plants.
Whenever possible, start with disease-free, certified nursery stock. When diseased plants first appear in early spring, dig them out (including roots) and destroy them before pustules form, break open, and discharge the orange masses of spores. If plants are not removed, these spores will spread the disease to healthy plants. Remove all wild brambles from within and around the planting site. Wild brambles serve as a reservoir for the disease. Maintain good air circulation in the planting by pruning out and destroying old fruited canes immediately after harvest, thinning out healthy canes within the row, and keeping the planting free of weeds. Fungicide sprays are generally not considered an effective control method for orange rust.
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 up to the 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. (Thanks to Dr. Mike Ellis, Ohio State University, for the information on orange rust and the link to the photographs).
See our "Current Conditions" Web page for details that are updated at least three times weekly.
PROVIDE FOR IMPROVING FRUIT FINISH
Fruit russetting is a common disorder that reduces the market value of Golden Delicious in most years. Provide is a combination of gibberellins and may reduce the severity of russet on Golden Delicious when applied during the first 50 days after bloom.
Apply Provide in 2-4 consecutive sprays, beginning at late bloom to petal fall, and continuing at 7-10 day intervals for remaining sprays. Apply 10-13 oz of Provide in 100 gallons of spray solution per acre. Do not apply more than 40 oz in a single season. Do not use spreader stickers or other spray adjuvants in combination with Provide because they may aggravate russet development. Provide can be used to suppress russet of varieties other than Golden Delicious.
PROVIDE FOR REDUCING STAYMAN CRACKING
Provide is a mixture of gibberellins that can reduce 'Stayman' cracking if applied before cracking begins. Apply Provide 3 or 6 times at 14- to 21-day intervals, starting 2 to 3 weeks before cracking begins (mid-June to early July). Apply Provide at the rate of one to two pints per acre per application and enough water should be used to wet the fruit (100 to 200 gallons per acre). Do not apply more than 12 pints in a single season. If Provide is used to suppress russet on Stayman, it cannot be used to suppress cracking. See page 123 of the 2004 Spray Bulletin for more information.
Small Fruit Notes-Pruning Brambles
Fruiting canes of all brambles die after fruiting is completed. Prior recommendations have stressed that spent fruiting canes should be removed immediately after fruiting to allow air to circulate through the canopy, and to remove possible sources of disease inoculate from the canopy. Research has shown, however, that on the cold-tender cultivar "Titan", winter injury was more severe when spent fruiting canes were removed in the summer than during the subsequent fall or winter. For this reason, we now recommend not removing the spent fruiting canes until dormant pruning. If cane diseases are a particular problem, and/or a more hardy cultivar is being produced (e.g., "Latham") spent fruiting canes can still be removed during the summer.
June-bearing red raspberries grow naturally in a hedgerow system. The suckers, originating from the root system, fill in the entire length of the row. No summer pruning (except for spent floricane removal) is necessary, although suckers growing outside the 12-inch hedgerow may be removed any time. March is the best time to prune, because any dieback from cold will be apparent. However, raspberries can be dormant pruned anytime canes are fully dormant. In the dormant season, remove canes outside the 12-inch width of the row, thin canes to 4-6 inches between canes (leaving four to five canes per linear foot), and top remaining canes to 48-60 inches in height, removing about one-fourth of the cane. Be sure to keep canes that have the largest diameter.
Black and purple raspberries require summer topping throughout the summer in addition to floricane removal. When possible, topping should be done three days before expected rain to lessen the chances for rain-splashed disease inocula to enter through the new wound. Black and purple raspberries should be topped at 36-48 inches, at a time during the season when only 3-4 inches of new growth needs to be removed to reach the desired height. Topping plants later than this can result in a greater incidence of cane blight, since the wound that results from removing larger-diameter wood takes longer to heal. Topping encourages lateral (fruiting) branches to develop and increases cane strength. (Note: Black raspberries tend to have a very prostrate growth habit in the first year. If canes are pruned as described above, they will attain a more erect habit in subsequent years).
For dormant pruning, remove all dead, damaged, and weak canes. Thin remaining canes to 5-10 inches (for blacks) or 6-10 inches (for purples). More vigorous plants can support longer lateral branches. Canes should all be topped to 36-48 inches if they were not topped earlier. If a trellis system is in use, even a nominal one such as a supported hedgerow trellis, canes can be topped higher (up to 60 inches) as long as they are supported by the trellis.
Everbearing red raspberries should be mowed to a height of 1-2 inches in the dormant season. Home gardeners or small producers may opt to fruit the canes again in spring. Fruit is borne on the overwintered canes at the leaf axils below where fruiting occurred the previous fall. While this is a viable option, only about 10-25 percent of the total "Heritage" yield is borne during the summer when fruited this way. Thus, most commercial growers prefer to plant a summer-cropping cultivar for this purpose.
Erect blackberries (thorny or thornless) do not require trellising. They have, as the name suggests, very strong upright canes. Prune similarly to black and purple raspberries; specifically, head back to 36-48 inches in the summer; cut back laterals to 12-18 inches and thin canes to 10 inches apart in the hedgerow during the dormant pruning.
Trailing blackberries should be summer tipped at about 6 inches above the highest trellis wire and tied to it during the summer months. For dormant pruning, select five to eight of the strongest canes; remove all laterals originating on the lower 3 feet of the canes, and tip back remaining laterals to 12-18 inches.
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.
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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