May 17, 2004
|Upcoming Events||Pheromone Trap Counts||Plant Pathology||Horticulture|
May 27, 6:00 p.m. - Tree Fruit Grower Twilight Dinner and Meeting at Gourmet Central (in Hampshire Industrial Park), Romney, W. Va. Following dinner, seasonal updates will be provided by Extension Specialists from the WVU Kearneysville Tree Fruit Research and Education Center. For more information contact the Hampshire County Extension Office at 304-822-5013.
May 31. - West Virginia University Holiday. The WVU KTFREC will be closed in observance of Memorial Day.
June 1, 6:00 p.m. - Tree Fruit Grower Twilight Dinner and Meeting at Mountain View Orchard, Berkeley Springs, W. Va. The orchard is located on Route 9, 12 miles from Hedgesville and 7 miles from Berkeley Springs. Dinner will be followed by seasonal updates from WVU Extension Specialists and an orchard tour by host Gary Lutman. For more information contact the WVU KTFREC at 304-876-6353.
|Codling moth hatch of first generation eggs has begun and is estimated at 5% complete through May 16, based on an accumulation of 267 DD since biofix on April 30. Because of the very warm temperatures that we've experienced this month, egg hatch is estimated to be about 13 days ahead of last year at this date, even though biofix was the same both years. If control has not already begun, spray applications should be initiated this week in those orchard blocks where the pheromone trap catch has exceeded 5 moths/trap/week. Recommended options include azinphosmethyl (Guthion), Imidan, Avaunt, Assail, Calypso and Intrepid. An initial spray should be followed by a second complete application in about 10-14 days, or three additional alternate-row-middle applications 5-7 days apart.|
Periodical cicada adult emergence of Brood X began last week in and around area orchards. Emergence will continue this week and the droning noise of males calling for females will begin. Following mating, females will seek out pencil-diameter woody branches in which to lay eggs beginning about the last week of May. Each female will deposit 500+ eggs, in groups of 10-25, into slits cut in branches with her needle-like ovipositor. Egg-laying will continue over about a 4 week period. Eggs will hatch in 6-10 weeks, and the ant-like nymphs will drop to the soil and tunnel to the roots to begin their 17 years of development underground.
Oviposition injury will result in branch breakage and the death of branch tips. Reducing the weight on branches by practicing good thinning will reduce breakage and provide time for wounds to heal. It is especially important to aggressively thin peach and nectarine this year since the fruit are produced on smaller diameter branches which would be more likely to break from cicada injury.
Although many cicada will emerge within orchards, the greatest threat will come from cicadas that fly in from adjacent woods. Orchards adjacent to or surrounded by woods typically experience the most severe oviposition injury. Insecticide application will reduce injury, but even the most effective chemicals will not prevent it, especially in high pressure situations.
In a 1987 study, effective knockdown of adult cicadas occurred following application of Asana, Lannate and Vydate, but only Asana provided a significant reduction in oviposition injury. Three applications of Asana on an 8-day interval were as effective as five applications on a 4-day interval. Other pyrethroids that are likely to be very effective include Danitol and Warrior. Pyrethroids are highly recommended on young trees in high pressure situations, because of the many favorable branch sizes for oviposition on these trees and the potential damage to scaffold limbs that can result. Because of their high toxicity to predators, this multiple use of pyrethroids will almost certainly result in a high incidence of European red mites, unless preventative measures have already been taken for mites in anticipation of cicada control. Where preventative measures for mites have not been implemented, acaricide application will likely be needed following pyrethroid use for cicada control. Although the pyrethroid Danitol has acaricidal activity and will reduce mites, mite populations will rebound to high levels after Danitol applications have ended. On older trees, where some cicada injury can be tolerated, sufficient control may be achieved with Lannate. The use of a pyrethroid, or Lannate in combination with an organophosphate or Intrepid would also provide effective control of codling moth and tufted apple bud moth over the next few weeks.
Young trees up to 2-3 years old may be
protected economically with tubular plastic netting. Net-All insect netting
is a 3/8-inch mesh x 3 ft. diameter sleeve that is slipped over the tree and
tied off at the top and around the trunk. The netting is cut to length
(based on tree height) from a 375 ft. ($50) or 500 ft. ($66.70) roll.
Net-All insect netting is available from: Tipper Tie-Net
|Lesser peachtree borer
adults have been emerging since the first week of May. Moths are active
during the day, with mating and egg-laying occurring soon after emergence.
Female moths are attracted to damaged and previously infested trees, and
deposit eggs in cracks or under bark scales of wounded sites. Eggs hatch in
7-10 days and larvae burrow, feed and develop in the inner bark and cambium
tissue for 40-60 days. An infestation of lesser peachtree borer is almost
always associated with previously damaged trees. The problem tends to be
more severe in older orchards that have a greater incidence of Cytospora
canker, winter injury, and pruning and other mechanical wounds. Infestation
occurs in these damaged bark areas from the ground to a height of about
eight feet. Although the majority of injury occurs in the upper trunk and
scaffold limbs, small diameter branches also may be infested. Larval
feeding enlarges the wounded area, which eventually results in complete
girdling of the trunk, scaffold limb, or branch. The primary and earliest
impact is a gradual decline in production on damaged limbs, which when
girdled will break under a fruit load. With time, tree loss will occur from
trunk girdling. Lesser peachtree borer feeding can also afford entry for
disease organisms, eventually resulting in limb and tree death.
In addition to monitoring adult emergence with a pheromone trap, inspect wounded areas on the upper trunk, scaffold limbs and branches when moth flight is increasing to determine the average number of empty pupal cases per tree protruding from the bark. Treatment is recommended if there are more than a total of two larvae or empty pupal cases per tree for each of two generations. Good control of adults can be achieved with an airblast sprayer application of a pyrethroid insecticide (Ambush, Asana, Pounce or Warrior) when moth flight is peaking, as determined with pheromone traps. This strategy is not recommended however if mites are already present in the orchard, since pyrethroid use will increase mite populations. An alternative, and more effective strategy, is to control the larval stage in early June (1st generation) with Asana (if no mites) or Thionex, and/or in August (2nd generation) with Lorsban 4EC or 75WG applied with a handgun to thoroughly wet all wounded areas. The preharvest interval for Asana is 14 days, and for Thionex is 21 days if spray contact is limited to wood and 30 days if fruit is contacted. Lorsban has a 14 day preharvest interval, but is best used after harvest since spray contact with fruit is prohibited. Blocks that receive a pyrethroid application should be monitored closely for mite outbreaks.
PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC
|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 one additional wetting period in the two weeks since the last Orchard Monitor, bringing the season's total number of favorable wetting periods to eight (Table 1). Two of the wetting periods were initiated at night (N) and may therefore be significant only in orchards with high inoculum levels or already established scab lesions. Scab lesions were observed on unprotected trees in the Winchester area on April 29. Severe scab on leaves and fruit was observed on Red Delicious and other varieties over the past weekend, probably initiated from the infection period on April 25 - 27.
The most recent wetting period resulted from intermittent showers during the period May 14 - 16. In the past, we have calculated wetting period duration from intermittent wetting periods by summing the numbers of hours in wet periods separated by less than 8 hours of sunny weather or 12 hours of cloudy weather. Recent research suggests that a better approach is to combine wet periods that are separated by less than 24 hours of dry weather, regardless of the weather conditions during the intervening dry period.
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 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.
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|
Fire blight. We've recorded seven fire blight infections this season (Table 2). High risk (according to Maryblyt) fire blight conditions occurred daily during the period April 18 - 25, 2004. Wetting during any of these days could have led to infection. We recorded wetting at WVU - KTFREC on April 20, 22, 23, and 24 during this period, with infection potential (EIP) well above the threshold level of 100 (Table 2). Infection also could have occurred May 1 - 2, and again on May 7. Any trees with blossoms remaining over the past weekend (May 14 - 16) also could have experienced infection, but this is unlikely in most locations. Fire blight blossom and shoot infections have been observed in some locations in Jefferson County.
Table 2. Dates and conditions for fire blight infection periods at the WVU - KTFREC, 2004.
Fire blight observed 5/17/04
Nectria twig blight. Advanced symptoms of Nectria twig blight are visible on Rome apples in several locations. Nectria twig blight is a minor disease that results in dieback of apple twigs and is mostly limited to the variety Rome. The fungus Nectria cinnabarina causes it. Symptoms of the disease are often confused with fire blight.
Usually in late May to early June, shoot growth on infected twigs begins to wilt and die. Small, sunken cankers are found at the bases of the wilted shoots. Leaves on infected shoots appear to die from the base, not from the tip, as with fire blight, and no signs of blighted blossom clusters remain on the twigs. Shoot death may be extensive. In mid‑ to late summer, bright orange or coral‑red structures (sporodochia) 1/8 to 1/6 inch in diameter appear on the surfaces of the cankers. Orange sporodochia also are often associated with pruning wounds and winter‑injured tissues on apple.
Wounds from fruit harvest, which probably take a long time to heal late in the season, combined with prolonged periods of wet weather after harvest, appear to favor infection. The disease has been noted primarily on cultivars with a large cluster‑bud base, such as Rome Beauty, Ben Davis and Northern Spy.
The disease is not usually severe enough to require special control measures. As a result, chemical control procedures have not been developed. Removal of infected twigs helps reduce the carryover of inoculum.
See our "Current
Conditions" Web page for details that are updated at least three times
Orchard Nutrition - Calcium and Boron
To obtain high quality fruit with good market acceptance, growers must maintain adequate calcium levels in their fruit. Low fruit calcium is associated with two major problems - cork spot and bitter pit.
Cork spot shows up as a shallow depression in the fruit surface, which when peeled has brown, firm corky tissue that is harder than the flesh. This corky area will usually extend into the flesh. Cork spot can also be internal in Yorks. The problem is associated with early-season water stress, irregular cropping, excessive tree vigor and poor nutrition. The disorder is initiated by midseason and does not develop after harvest.
Bitter pit is characterized by numerous small sunken pits of collapsed tissue softer than the apple flesh. Most pits are just beneath the skin, mostly on the blossom end of the fruit. The problem is associated with late-season moisture stress conditions, and fruit harvested too early is more prone. Bitter pit does not usually develop until after harvest.
The maintenance of adequate levels of calcium in the fruit to minimize losses from cork spot and bitter pit requires the use of a season-long management program. This program should include soil pH levels at 6.5 or higher, the encouragement of even, annual cropping by thinning, and the avoidance of excessive pruning and fertilization that stimulate too much growth. Most importantly, calcium should be included in each cover spray throughout the season.
Cork spot may have been misdiagnosed in the past. Research from the USDA in West Virginia indicates that late summer and fall stink bug feeding injury can produce symptoms very similar to cork spot. Symptoms appear as circular discolored depressions on fruit skin with corky flesh immediately below the skin that develops within a day of feeding. Corking can extend up to 1/4 inch into the flesh. Feeding punctures may be only visible with magnification and may occur anywhere on fruit as single or multiple damage sites. If multiple damage sites, they are often clustered. Damage takes place from mid-July until harvest.
Rate: Calcium can be applied in cover sprays at the rate of 2 to 8 pounds of calcium chloride per acre (for a total of 15 to 50 pounds per acre per year). At 15-19 pounds per acre per year, some cork spot and bitter pit control will be achieved, but storage life will not be enhanced. The standard rate to apply in blocks where these disorders are chronic is 20-29 pounds per acre per year. The 30-39 pound rates will give fairly good control of corking and bitter pitting most years. The 40-50 pound rates may increase storage life in addition to providing good control of cork spot and bitter pit. The higher rates can cause foliage burn and should not be reapplied unless at least 1/2 inch of rain has fallen since the last application.
Timing: All cover sprays.
Gallons Per Acre: No restrictions. Applications of as little as 20 gal per acre have been effective.
Compatibility: At the rates recommended, calcium chloride and/or Solubor may be mixed with spray oil (Superior 70 sec), with WP formulations, or with EC formulations of the more common fruit pesticides. Do not premix calcium chloride with Solubor in a small volume of water before adding to the tank, when both materials are to be applied together. ALWAYS DISSOLVE CALCIUM CHLORIDE IN A PAIL OF WATER and add this last, when the spray tank is nearly full, to insure that the calcium chloride is completely dissolved before spraying begins.
Additives: Surfactants are not needed when calcium chloride is applied with regular cover sprays.
Temperature: Spray on days when the temperature will not exceed 90 degrees F.
Leaf Injury: Some leaf injury may occur from calcium sprays made after wet, cool springs or during hot, dry summers. When injury is noticed, reduce calcium chloride to one-half rate in the next spray.
Corrosion: Calcium chloride can corrode equipment (by keeping it wet). Be sure all parts of the sprayer and the tractor are rinsed thoroughly with water following each use.
Boron is frequently deficient in Virginia and West Virginia apple orchards. The first symptom of a boron deficiency is usually internal cork. Scattered areas of brown corky tissue appear in the flesh of the fruit, often in the core area. If the deficiency becomes severe, the fruit may be misshapen with sunken corky areas.
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