June 26, 2006
|Upcoming Events||Pheromone Trap Counts||Plant Pathology|
July 4. - West Virginia University Holiday. The WVU Kearneysville Tree Fruit Research and Education Center will be closed in observance of Independence Day.
July 6. - 2006 Summer Tour sponsored by the Maryland State Horticultural Society and Maryland Cooperative Extension. The tour will depart from Catoctin Mountain Orchards (Thurmont, Md) and include stops at Coastal Sunbelt Produce in Savage, Md; Homestead Gardens in Davidsonville, Md; and Boyer Farms in Severn, Md. The cost of $30 per person (includes tour bus, beverages on bus and materials) must be mailed by June 30. Lunch is provided by Homestead Gardens. For more information or to request a registration form, contact Cindy Mason at 301-432-2767 x301.
Codling moth first generation egg hatch is almost complete (estimated at 98%) based on an accumulation of 871 degree days (DD) after biofix (April 26) through June 25 at the WVU KTFREC. Apple orchards should be inspected at this time for first generation larval injury to fruit in order to evaluate the effectiveness of management programs. Fruit injury is more likely to occur in the upper parts of apple trees since more moth mating and egg-laying occurs in this area, and spray coverage is likely to be weakest in this portion of the tree. Larvae may enter fruit from either the side or calyx end, resulting in the presence of frass (excrement, see photo) on the surface where tunneling has been successful. First generation larvae usually have greater success entering the calyx end because the side of the apple is harder early in the season. Injury also may be expressed as "stings", which consist of small shallow holes resulting from the death of young larvae that have been poisoned after puncturing the apple skin. The absence or size of larvae (1/2-5/8 inch long when mature in 3-4 weeks) found in injured fruit can indicate when the control failure occurred during the egg hatching period. The absence of a larva and the presence of an exit hole in apples with frass indicates that the larva has already matured and left the apple, having entered the apple early in the egg-hatching period (latter part of May). The presence of larger larvae in fruit indicates a control weakness during the first half of the egg-hatching period (early June), whereas smaller larvae indicate inadequate control during the second half of the egg-hatching period (mid June and later). Knowledge of larval size in injured fruit, when coupled with pesticide record information can increase understanding of management failures and lead to improved control against future generations.
The second moth flight is expected to begin within a week. In order to prevent fruit injury, control of the second generation should be implemented in those orchards where the pheromone trap capture exceeds 5 moths per trap per week. In order to delay the development of resistance, materials selected for control of the second generation should be from a different chemical class (different mode of action) than was used against the first generation (see page 33 of the 2006 Spray Bulletin for a listing of chemicals by class). Recommended options include Rimon at 1050-1150 DD (0-2% egg hatch); Intrepid, Esteem, Assail, Calypso, or CM granulosis virus (Cyd-X, Carpovirusine) at 1150 DD (2% egg hatch); or Avaunt, Azinphos-methyl (Guthion) or Imidan at 1250 DD after biofix (6% egg hatch). An initial spray of any material should be followed by a second complete application in about 10-14 days (300 DD), or three additional alternate-row-middle applications 5-7 days apart. Based on DD accumulations since biofix, development on this date is about 3 days ahead of last year.
Japanese beetle adults are expected to begin emerging very soon following the rain event of this past weekend. The most important threat from this insect is to dwarf and non-bearing apple trees and to stone fruits near and during harvest. Feeding injury on apple leaves results in a "lace-like" appearance as beetles consume the leaf tissue between the veins. Injury to apple fruits is not common and usually only occurs on mature fruits that have already been damaged by some other factor. Sevin is considered the most effective control option, with the XLR Plus formulation considered to be less disruptive to mite predators than other formulations. Other options include Lannate, Assail and Surround. Surround is most effective if application begins before beetles begin feeding on trees.
Rose leafhopper nymphs (second generation) have been observed on the undersides of leaves in a few apple orchards. The first generation develops on multiflora rose and brambles, with adults flying to apple trees to lay eggs in early to mid-June. Nymphs are white to pale yellow and initially appear identical to white apple leafhopper. As nymphs mature, they may be distinguished by a series of small black spots on the back and wingpads, which are lacking in white apple leafhopper. Determine the average number of nymphs per leaf by examining the underside of 10 randomly selected older leaves per tree. Apply Provado, Actara, Assail, Calypso, Clutch, Vydate, Lannate, or Thionex for control if nymphs average 3 or more per leaf.
PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC
|DATE - 2006||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM|
|DATE - 2006||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.
Infection periods. With the recent low pressure system taking up residence in the mid-Atlantic region, and the resulting "training thunderstorms," we've been able to catch up on some much-needed rainfall. At WVU-KTFREC, we recorded two significant wetting periods since the last newsletter on June 12th (see the list below). Our total rainfall for the month of June as of Monday morning June 26 is 4.75 inches at WVU-KTFREC (we had reported 1.28 inches of rain on June 12). Infection period #12 was associated with 2.9 inches of rain.
Table 1. Dates and conditions for recent infection periods at the WVU - KTFREC, 2006.
|No.||Date 2006||Hours/ degrees F|
|8.||June 1 - 2||18 hr/69 F|
|9.||June 2 - 3||14 hr/66 F|
|10.||June 7 - 9||23 hr/64 F|
|11.||June 23 - 24||15 hr/70 F|
|12.||June 25 - 26||18 hr/70 F|
Accumulated wetting hours. As of June 26, 2006, we have accumulated 255 wetting hours since a petal fall date of April 27. 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.
Brown rot. Incidence of brown rot fruit infection is proportional to temperature and wetness duration. Optimum temperature range is 72-77 F for infection of peach fruit, and infection can occur following only 3 hr of wetness at high inoculum concentrations. Longer wet periods during infection result in shorter incubation periods. Insects (nitidulid beetles and honeybees) also can be important as vectors of the brown rot fungus during fruit ripening, carrying conidia to injury sites produced by oriental fruit moth, Japanese beetle, green June beetle, stink bugs, and other insects, or birds, that injure fruit. Wounded fruit are infected much more readily than nonwounded fruit. Hail damage near harvest can lead to a devastating brown rot problem. At harvest, apparently healthy fruit usually are contaminated with spores or latent infections that, under favorable conditions, may later produce decay during storage and marketing.
Effective control of brown rot depends on attention to orchard sanitation; proper pruning of trees to facilitate drying and penetration of spray materials; monitoring for disease every 3 to 5 days during the preharvest period; being aware of favorable weather and the potential for bird, insect and hail damage; and use of effective fungicides at 7 to 10 day intervals during the preharvest and harvest periods. See the 2006 Spray Bulletin for suggested chemicals and rates of application. The sterol-inhibiting fungicides, Orbit, Elite, and Indar, are the best fungicides for controlling the disease and show generally similar performance in preharvest assessments. Fruit treated with Indar right before harvest generally shows less rot in the postharvest environment. Recent data from studies in Virginia, New Jersey, and California show that the recently-registered reduced-risk fungicides Pristine and Elevate are very good to excellent for managing pre- and post-harvest brown rot. Reduced-risk fungicides have a low impact on the environment, high specificity to target organisms, low potential for groundwater contamination, and low potential for human health risks. Pristine is registered for use on all stone fruits, whereas Elevate is limited to use on peaches, nectarines and cherries.
Alternation of the sterol-inhibiting fungicides with Pristine or Elevate may help reduce the risk of the brown rot fungus becoming resistant to the SI's. If fruit are washed during the packing operation, the efficacy of Pristine and Elevate for preventing wound infections is likely to be reduced relative to the sterol-inhibiting fungicides. For this reason, in years when the risk of brown rot is high or if packing conditions are unsanitary, the use of an SI fungicide right before harvest is recommended.
Scholar (fludioxonil), another reduced-risk material, is available for postharvest use on all pome and stone fruits (excluding cherries). Data show that infections of wounds that occur in the field at harvest are effectively stopped by post-harvest treatments with Scholar, which is typically done on the same day that fruit are harvested. Including Scholar as a postharvest treatment may be useful in years when inoculum pressure is high, conditions at harvest are favorable for brown rot infection, or packinghouse conditions are unsanitary. Scholar is stable in 100 ppm chlorine.
See our "Current Conditions" Web page for details that are updated at least three times weekly.
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