July 10, 2006
|Upcoming Events||Pheromone Trap Counts||Plant Pathology|
July 20, 5:00 p.m. - Fruit Grower Twilight Meeting at Alson H. Smith Jr. Agricultural Research and Extension Center, Winchester, Va. For more information contact Josh Marvel at 540-665-5699 or at firstname.lastname@example.org.
August 1, 6:00 p.m. - Tree Fruit Grower Twilight Dinner and Meeting at Twin Ridge Orchards, Inc., Shenandoah Junction, W. Va. To reach the orchard, travel approximately 3 miles from Kearneysville on Rt. 480 to Rt. 16 (Ridge Road) on the right. Travel Ridge Road for 3 miles to the barn on the right. Following dinner, seasonal updates will be provided by Extension Specialists from the WVU KTFREC, and a tour will be conducted by Mary Frances Hockman and Gordon Hockman. For more information contact the WVU KTFREC at 304-876-6353.
Codling moth second generation egg hatch has begun and is estimated at 3% complete through July 9 based on an accumulation of 1188 DD since biofix on April 26 at the WVU KTFREC. Last week would have been the ideal timing to initiate applications of either Rimon, Intrepid, Esteem, Assail, Calypso, or CM granulosis virus (Cyd-X, Carpovirusine). Applications of either Avaunt, Azinphos-methyl (Guthion) or Imidan should be initiated early this week in order to prevent fruit injury from early hatching larvae.
Oriental fruit moth hatch of second generation eggs should be about finished, with third generation egg hatch just beginning (estimated at 2% complete through July 9), based on degree day accumulations (1822 DD). In reality, it is likely that there is currently overlap in egg hatch between the second and third generations. The third generation poses a threat to peach and nectarine fruits near or during harvest. Larvae can enter anywhere on the fruit, resulting in the exudation of gum and frass (excrement) from the wound area. As the gum ages, a sooty mold may form on it, turning the entire wound area black. Larvae can also enter the fruit through the inside of the stem, and therefore leave no evidence of entry except for a small mark at the stem end of the picked fruit.
Control of the third generation is justified where the pheromone trap capture exceeds 10 moths/trap/week in both peach and apple. In peach and nectarine, apply either Intrepid at 2000-2100 DD (6-11% egg hatch); or azinphosmethyl (Guthion), Imidan, Lannate or Carbaryl (Sevin) at 2100-2200 DD (11-20% egg hatch). A second application may be needed in about 2 weeks (300-350 DD), depending upon pest pressure and proximity to harvest. Be sure to consider the following days to harvest limitations when selecting materials for application in peach and nectarine: Azinphos-methyl (Guthion) , Imidan , Intrepid , Lannate [4 on peach, 1 on nectarine], and carbaryl (Sevin) .
As a general guideline in apple, apply Rimon at 2300-2350 DD (30-35% egg hatch); or Assail, Calypso or Intrepid at 2350-2400 DD (35-42% egg hatch); or Avaunt, azinphosmethyl (Guthion) or Imidan at 2450-2500 DD (50-55% egg hatch). A second application may be needed in about 2 weeks (450-500 DD), depending upon pest pressure. Since actual egg hatch often falls behind DD based predictions in apple, it is best to treat within 7-10 days of exceeding the above trap threshold and to maintain spray intervals on a 2 week (complete) or 5-7 day (alternate-row-middle) schedule for as long as this condition continues. Sprayable pheromone (CheckMate OFM-F) is also an option that can be targeted against adults to provide mating disruption in apple, peach and nectarine. Pheromone traps should be used to monitor performance and schedule applications, which provide about 4 weeks of control.
Japanese beetles continue to emerge, with numbers quite abundant in some areas and relatively low in other areas. All stone fruits are highly susceptible to attack as they reach maturity. Beetles are often found in clusters on fruit that is within two weeks of harvest, and may be accompanied by Green June beetles. Although, like Japanese beetles, Green June beetles prefer ripe fruit, they also may cause injury on green fruit. Since feeding may be "clumped" or unevenly distributed, care should be taken in looking at a representative sample before making a spray decision. Control is recommended if fruit feeding injury exceeds one percent. Sevin is considered the most effective material available for control on all stone fruits. Other options include Lannate, Provado and Surround. Since beetles will continue to move into trees for another 2-3 weeks, multiple applications may be needed in higher pressure situations.
Western flower thrips (WFT) is a potential threat to peach and nectarine fruits near harvest, especially if weather conditions become dry. WFT adults are slender, about 1/16 inch long, yellowish, and hold their wings over their backs. Larvae are smaller and wingless, but otherwise resemble adults. Several generations occur per year as populations buildup in white clover and other weeds in and around orchards, as well as in field crops such as alfalfa. Flight activity of WFT peaks in July through September in stone fruit orchards. If conditions are dry near harvest, ground cover hosts will become less attractive and make it more likely that thrips will move to stone fruit trees.
Feeding on fruit near harvest results in silvering injury, a benign surface blemish that can be quite extensive if thrips populations are unchecked. Injury usually occurs in protected sites, such as in the stem end, the suture, under leaves and branches that contact the fruit, and between fruit. Inspect the earliest maturing varieties during final swell for silvering injury. Monitor thrips by counting adults on 10 fruit at 5 locations in the orchard. Sample fruit from the ends of branches in the lower third of the tree canopy. Five adult thrips per 50 fruits and the presence of silvering injury may justify control, depending upon the potential market, because extensive silvering can result in downgrading of the fruit. Control options [preharvest interval] include SpinTor and Entrust [14 days on peach, 1 day on nectarine], and Lannate [4 days on peach, 1 day on nectarine].
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: At WVU-KTFREC, we recorded six significant wetting periods since the last newsletter on June 26th (see the list below). Our total rainfall for the month of July as of Monday morning July 10 is 1.36 inches at WVU-KTFREC (add that to the 7.36 inches of rain we received for the month of June).
Table 1. Dates and conditions for recent infection periods at the WVU - KTFREC, 2006.
|No.||Date 2006||Hours/ degrees F|
|11.||June 23 - 24||15 hr/70° F|
|12.||June 25 - 26||22 hr/70° F|
|13.||June 26-27||8 hr/72° F|
|14.||June 27-28||22 hr/70° F|
|15.||June 28-29||18 hr/70° F|
|16.||July 4 - 5||16 hr/71° F|
|17.||July 5 - 6||16 hr/66° F|
|18.||July 9 - 10||13 hr/65° F|
Accumulated wetting hours: As of June 26, 2006, we had accumulated 255 wetting hours, for petal fall date of April 27. As of July 10, we have accumulated 357 wetting hours. 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.
Managing flyspeck on apples - how to interpret
the accumulated wetting hour threshold and how to get the best control with
currently available fungicides (adapted from an article by David
Rosenberger, Cornell University).
Here is an in-depth application of the AWH threshold applied to flyspeck management. First, some biology. The fungi that cause flyspeck overwinter on and infect a wide range of host plants, growing on the external waxy cuticle of those plants. What are "those plants"? For our discussion, we'll say that "those plants" include most shrubs, bushes, vines, and trees that grow in orchard perimeters. Initially, these hosts produce ascospores, and then later, conidia, that blow into orchards. After a spore from one of the flyspeck fungi lands on an apple, the apple must be exposed to approximately 270 hr of accumulated wetting (AWH) before the flyspeck colonies become visible on the fruit. Brown and Sutton in North Carolina were the first to identify the incubation period for flyspeck, and they found the best correlations when they ignored wetting periods of less than 3 hr duration.
Ascospores from the overwintering flyspeck fungi
are released at around petal fall stage of apple fruit development. Therefore,
flyspeck colonies initiated by ascospores may begin appearing on unsprayed fruit
at 270 AWH after petal fall. Because sprays for scab, mildew and rust usually
prevent infection of apple fruit by the flyspeck ascospores, ascospore
infections are not usually seen in commercial orchards. However, a lot of
activity is taking place on those wild hosts we mentioned earlier. Infections
initiated by ascospores on those wild hosts begin releasing conidia coincident
with their becoming visible (after 270 AWH). When those infections produce
conidia, orchards are exposed to a continuous supply of conidia blowing around
and around throughout the remainder of the summer and fall. If fungicide
residues on fruit drop below effective levels, then the conidia will initiate
flyspeck infections on fruit.
In experiments where trees are left unsprayed after 2nd cover (i.e., they are protected from flyspeck ascospores but not from conidia), flyspeck incidence and severity on fruit increases dramatically around 540 AWH. Thus, flyspeck requires 270 AWH to produce conidia on wild hosts and another 270 AWH to infect and produce visible colonies on apples.
In New York, the results of two recent trials suggest some limitations to our currently available fungicides:
1 - Two inches of heavy rain may be enough to
eliminate fungicide residues. Pristine has the best residual activity, but none
of the fungicides had adequate residue to completely protect against flyspeck
after about 2 inches rain.
2 - Fungicides applied after flyspeck infections have been initiated can arrest growth of the flyspeck fungus temporarily, but they do NOT eradicate the infections. Sovran is better than Pristine or Flint for suppressing infections but it is not better than Topsin-M + Captan. So, Pristine provides the best residual protection, but Sovran and Topsin M provide the best post-infection activity.
Based on the above, what we know about the biology and the activity of our fungicides can be summarized in statement form to help us formulate our management options:
Conclusions: Control failures with flyspeck usually occur either because of poor spray coverage during the latter part of the growing season or because trees were left unprotected through more than 270 hr of wetting during the preharvest interval. Fungicide protection on fruit is exhausted after 2 inches of rain, so fungicide sprays may be needed in September if heavy rains occur with more than 25 days remaining before fruit will be harvested.
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