June 14, 2004

PEST MANAGEMENT ISSUES

Input is requested from stakeholders (growers, consultants, industry representatives, etc.) on important pest management issues in West Virginia .  Pest management issues (pesticide use, registration, labeling, available alternatives, etc.) will be addressed by a West Virginia Advisory Committee.  Please mail, phone or e-mail your comments to:

Dr. John F. Baniecki
West Virginia University
414 Brooks Hall
PO Box 6058
Morgantown , WV 26506-6058
Phone:  304-293-3911
E-mail:  John.Baniecki@mail.wvu.edu

ENTOMOLOGY

Periodical cicada abundance and activity has declined significantly over the past week.  Even where cicadas were relatively numerous, it was recently observed that very few females were engaged in oviposition (egg-laying).  It's very likely that most of the oviposition is over and spent females are merely residing on trees until their death.  Therefore, at this point, the need for continued insecticide application for cicada control should be based on whether or not oviposition is occurring, not merely on cicada presence.  Cicadas that may be on fruit trees, but not ovipositing, do not pose a threat.

Tufted apple bud moth first generation egg hatch continues and is estimated at 79% complete through June 13, based on an accumulation of 902 degree days (DD) since biofix on May 6.  Refer to the June 1^st issue of this newsletter for insecticide options and recommended timings for control.

Oriental fruit moth second generation egg hatch also continues and is estimated at 24% complete through June 13, based on an accumulation of 1230 DD since biofix on April 16.  Where the pheromone trap catch exceeds 10 moths/trap/week, control should begin this week (1150-1200 DD after biofix) in peach with an application of azinphosmethyl (Guthion) or Imidan.  This should be followed by a second application at 1450-1500 DD after biofix (in about 10-14 days) in high pressure situations.  In apple, apply Intrepid, Assail or Calypso at 1350-1400 DD after biofix (on about June 17-19), or Avaunt, azinphosmethyl (Guthion) or Imidan at 1450-1500 DD after biofix (on about June 21-23).

Spotted tentiform leafminer adults (second flight) have been emerging since the last week of May, based on pheromone trap capture.  To determine if control of the second generation is needed, begin sampling sap-feeder mines.  Start at the orchard edge and, moving toward the center, sample every other tree until enough trees have been sampled.  Begin by selecting five mature terminal leaves from each of three trees, and count the sap-feeder mines on the underside of the leaves.  After 15 leaves have been examined, begin comparing the accumulated total number of mines found with the limits given in Table 1 below for that number of leaves.  If the number of mines falls between the two values given, sample five more leaves from another tree, continuing to add the number of mines found to the running total while checking Table 1 again.  Continue sampling in this fashion until the total number of mines falls below the lower limit or above the upper limit.  If the total is less than the lower limit, sampling is stopped and no treatment is required.  If the total is greater than the upper limit, sampling is stopped and an insecticide such as Provado, Actara, Assail, Calypso, SpinTor, Vydate, or Lannate should be applied.  If 10 trees (50 leaves) are sampled and the total number of mines is less than 98, no treatment is needed.

Table 1.  Limits to determine status of second generation spotted tentiform leafminer infestations. 

	Second Generation Sap-feeder Mines
No. of Leaves Sampled	Lower Limit	Upper Limit
15	12	46
20	22	55
25	31	65
30	41	75
35	51	85
40	61	95
45	70	105
50	98	98

 

Apple maggot (AM) poses a threat to commercial apple orchards in West Virginia that are adjacent to abandoned orchards or wild hosts.    Fly emergence, which typically begins after mid-June, should be monitored in all commercial apple orchards that are adjacent to these sites.  Yellow pre-baited panel traps or red sphere traps should be installed on the outside row closest to the wild hosts or abandoned orchard.  Position traps about 5-6 ft above the ground so they are surrounded, but not touched or obstructed from view, by fruit and leaves.  Traps should be inspected and AM flies counted weekly.  When using the yellow trap, an insecticide [azinphos-methyl (Guthion) or Imidan] should be applied within 7-10 days of catching a single fly.  With the red sphere trap baited with apple volatiles, apply one of these insecticides immediately if an average of 5 or more flies per trap are caught within a week.  If no apple volatiles are used with the red sphere trap, the threshold should be lowered to 1 fly per trap.  Capture of flies for 1-14 days following the insecticide application can be discounted.  Once 14 days have elapsed since the last application, retreat immediately if the threshold is reached again.

PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC

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.

PLANT PATHOLOGY

Infection periods. We have recorded 16 infection periods to date (Table 2), three occurring since the last Orchard Monitor was published on June 1, 2004. I've listed infection period #15 because it was accompanied by 2.3 inches of rain, which can result in significant degradation of fungicide protection. Because proper spray timing is a key to good summer disease control, make sure the next fungicide application occurs prior to the next wetting period.

Table 2. Dates and conditions for infection periods at the WVU - KTFREC, 2004.

Accumulated wetting hours. As of June 14, 2004, we have accumulated 181 and 224 wetting hours, for petal fall dates of May 8 and May 1, respectively. 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. For early varieties under high disease pressure, we have arrived at the threshold.

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

HORTICULTURE

Leaf Analysis of Tree Fruits

An Important Tool for Determining Nutrient Needs

Chemical analysis of plant foliage is an important tool for establishing and maintaining a proper fertilizer program in fruit plantings. Leaf analysis can be used to confirm or diagnose a problem associated with a nutrient shortage or excess, and more importantly to prevent the development of a nutrient disorder in an orchard. Usually, it reveals that certain fertilizers being used are not necessary and results in the most economical fertilizer program.

For diagnosing a problem, only a single analysis properly taken may be needed. In other instances, a series of analyses may be necessary to arrive at a proper explanation. Paired comparisons, one from normal and one from the abnormal condition, are frequently helpful.

Foliar analyses made over a period of years can indicate an approaching deficiency of a nutrient element before the plant shows any visible symptoms. It is possible then, through proper corrective fertilizer applications, to prevent the deficiency from ever occurring in the tree. By the same token, it is possible to learn when an element may be increasing in a tree toward a level that will reduce fruit quality or bring about some other undesirable effect. When this condition is known, steps can be taken to alter the fertilizer program and cultural practices that influence the uptake of the element from the soil.

Grower use of leaf analysis should be aimed at reaching optimum production within the limits of good nutrition. Other factors such as diseases, soil moisture, and insects become the limiting factors once desired nutritional levels are reached and maintained. Using leaf analyses only when nutritional problems are suspected will not yield the greatest grower returns.

Common Nutritional Problems in West Virginia Orchards

Nitrogen control is the most common and serious nutritional problem in West Virginia orchards. Excessive levels of nitrogen occur more frequently than deficient levels. Deficiencies of potassium, magnesium, calcium and boron have been found in some orchards in the state. Manganese toxicity (expressed as Internal Bark Necrosis on apple trees) is also found in some locations. Although not widespread, these nutrient imbalances do cause problems in isolated blocks of trees.

All of these disorders can be most readily identified by leaf analysis. In many cases, growers have found that money spent for leaf analysis has been returned many times over in reduced fertilizer costs and in better crops of higher quality fruit.

Further Information on Leaf Analysis

Contact the WVU Tree Fruit Research and Education Center, P.O. Box 609, Kearneysville, WV 25430 (phone 304-876-6353) to obtain kits to submit leaf samples to the Penn State University Agricultural Analytical Services Laboratory. The proper time to take apple and peach leaf samples is between mid-July and mid-August.

Source: WVU Extension Service Publication OM 1020

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.

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