July 26. 2004

ENTOMOLOGY

Tufted apple bud moth adults (second flight) have been emerging since the middle of July, which is about 2 weeks ahead of last year.  Based on degree day accumulations since biofix of spring brood moths (2074 DD through July 25), hatch of second generation egg masses is expected to begin the end of this week and continue for the next 4-6 weeks.  Larvae of this generation typically cause greater fruit injury than those of the first generation because: 1) the egg hatching period is usually more prolonged for this generation than the preceding one; 2) it is more difficult to obtain thorough coverage at this time of the season because the tree canopy is more dense and the larger size of clustered fruit provides better protection of larvae from spray contact; 3) some orchards are not sprayed after mid-August, when a substantial portion of egg masses have yet to hatch; and 4) the use of equipment and labor for peach harvest may prevent the proper timing of spray application in apple orchards. Control is best achieved by using degree days (DD) to time spray applications to coincide with egg hatch, so that larvae are killed before they cause fruit injury.  Intrepid and SpinTor are considered to be the most effective materials.  It is recommended that these products be used as two complete applications at 2355-2435 DD (20-30% egg hatch) and 2665-2740 DD (60-70% egg hatch) where pest pressure is high.   If alternate-row-middle applications are planned, a total of four sprays are recommended at 7-day intervals, beginning at 2280 DD (10% egg hatch).  A single complete application, or two alternate-row-middle applications would be sufficient in lower pressure situations.  Other control options, considered to be less effective, include Avaunt, BT, or an organophosphate [azinphos-methyl (Guthion), Imidan] in combination with Lannate.  When using these products, make two complete applications at 2280-2355 DD (10-20% egg hatch) and 2665-2740 DD (60-70% egg hatch), or four alternate-row-middle applications at  7-day intervals, beginning at 2210-2245 DD (1-5% egg hatch).  Pyrethroid insecticides (Asana, Danitol, Warrior) are also an effective option.  Because they can result in an increase in the motile stages and/or overwintering eggs of European red mite, pyrethroids should be limited to the last application of the season.  This strategy may not prevent the detrimental consequence of pyrethroid use, but it could reduce the severity of the mite increase.  Be sure to check the preharvest intervals when selecting products for use.

Oriental fruit moth third generation egg hatch is estimated at 42% complete on peach through July 25, based on an accumulation of 2402 DD since biofix on April 16.  A second insecticide application may be warranted this week at 2450-2500 DD (50-56% egg hatch), depending upon pest density and proximity to harvest.  Control options [days to harvest] include azinphosmethyl (Guthion) [21], Imidan [14], Intrepid [7], Lannate [4 on peach, 1 on nectarine], and carbaryl (Sevin) [3].

On apple, initiate applications (above materials, or Avaunt, Assail or Calypso) about 7 days after exceeding a trap threshold of 10 moths/trap/week, and maintain spray intervals on a 2 week (complete) or 5-7 day (alternate-row-middle) schedule for as long as this condition continues.

Codling moth second generation egg hatch is estimated at 74% complete through July 25, based on an accumulation of 1738 DD since biofix on April 30.  A second insecticide application should have been applied at 1550-1600 DD (45-53% egg hatch) in those orchards where the pheromone trap capture has exceeded 5 moths/trap/week.  Options include azinphosmethyl (Guthion), Imidan, Intrepid, Avaunt, Assail or Calypso.

Green June beetles have been observed feeding on peaches and nectarines.  This large beetle is often found in association with Japanese beetles.  Although, like Japanese beetles, they prefer ripe fruit, injury may occur 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 the most effective material, with the XLR Plus formulation considered to be less disruptive to mite predators than other formulations.

San Jose scale second generation crawler emergence should be monitored over the next few weeks in those blocks in which greater than 1% of the fruit was injured at harvest last season.  Monitor crawler emergence by wrapping black electrician's tape (sticky side out) around tree limbs that are encrusted with dark scale coverings.  A thin film of petroleum jelly may be spread on the tape surface to enhance crawler capture.  An alternative approach is to cover the black electrician's tape (wrapped with sticky side against the branch) with double sided cellophane tape.  Inspect the tape traps twice weekly for the bright yellow crawlers, and apply Esteem, Diazinon or Provado when emergence is first detected and again in 10-14 days.

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 26 infection periods to date (Table 1), six occurring since the last Orchard Monitor was published on July 12, 2004. Proper spray timing is the key to good summer disease control.

Table 1. Dates and conditions for infection periods at the WVU - KTFREC, 2004.

This week (July 26 - 31). Favorable disease weather consists of daytime temperatures in the 80's, extended dew periods, and frequent rainfall. These temperatures and extended wet periods provide conditions that are ideal for fungal development and the initiation of disease. For optimum disease control under these conditions: 1) shorten intervals between fungicide applications; 2) when a rate range is provided for a fungicide, select the higher end of the range; and 3) select products that may be more effective than what you have been using. For the relative effectiveness of apple and peach fungicides, consult Tables 1 and 2 in the 2004 Spray Bulletin. Note that there is a good chance of wetting every day for the next 10 days.

Postharvest Handling of Peaches. Some general do's and don'ts for postharvest handling of peaches (including suggestions to reduce discoloration (also known as inking, ink spot, black spot, streak, or purple spot):

1) Avoid any operation that causes excessive vibration, rubbing or rolling; reduce operations that cause bouncing from the orchard to the packinghouse;

2) Keep field bins, held outside the packinghouse prior to hydrocooling, in a shaded area out of direct sunlight;

3) Remove "field heat" as soon as possible. Fruit temperatures in the field can range from 75 to 95 F. Remove field heat with a hydrocooler rather than trying to remove it with a ventilated cold room;

4) Keep hydrocoolers and dumptanks as clean as possible. Excessive iron in treatment water can cause discoloration. Failure to clean hydrocoolers and dumptanks properly can result in high levels of rust in the water, thus increasing the risk of discoloration. Drain and refill with fresh water on a regular basis;

5) Maintain the pH of water in hydrocoolers and dumptanks between 6.5 and 7.0. Water at pH's of 4.0 to 6.0 has caused problems with discoloration. Proper pH also reduces iron levels; and

6) Check any equipment that uses ammonia for refrigeration. Leaks can stimulate inking, and peaches can be affected by ammonia at levels less than 1 part per million -- below levels that emit an odor.

North Carolina State University has an excellent online reference on chlorination and postharvest disease control. The URL is (all on one line): http://www.bae.ncsu.edu/bae/programs/extension/publicat/postharv/ag-414-6/

Scholar postharvest fungicide for peaches and nectarines. Scholar 50W (fludioxonil) was recently registered for postharvest use on stone fruit. Scholar is a highly effective wound protectant fungicide and has very good activity against Rhizopus rot, brown rot, and other postharvest fungal infections that occur during and after harvest. The fungicide has been classified as a 'reduced risk pesticide' by the EPA and has an extremely low mammalian toxicity, thus accommodating packinghouse worker and consumer safety issues. In addition, its chemistry is based on a natural bacterial product that has been industrially synthesized. The labeled rate is 8 to 16 oz per 200,000 pounds of fruit. Scholar can be applied as a dip or through spray nozzles in the packing line. In the latter, the spray volume is 25 to 100 gallons, or if using low-volume systems, 7 to 25 gallons. For dips, fruit are dipped for 30 seconds and allowed to drain. For all three use patterns, the solution is replenished after treating 200,000 pounds of fruit. Do not expose the treatment solution or treated fruit to sun light because the fungicide breaks down and efficacy may be lost.

Handling practices are as important for preventing Rhizopus rot as for brown rot. Avoid puncturing fruit skin, and store harvested fruit at less than 40 F.

See our "Current Conditions" Web page for details that are updated as needed.

HORTICULTURE

Coloring and Ripening of Apple

Ethephon for Stimulation of Coloring and Ripening of Apple

Ethephon (Ethrel) provides several fruit modifying effects (Tables 19 and 20 on pages 123 and 124 of the 2004 Spray Bulletin). Used properly, it can spread out picking time for selected parts of orchards by permitting earlier harvesting of better colored fruit.

Ethephon response is greatest under good fruit-coloring conditions and cannot substitute for conditions associated with poor color development, such as hot weather and poorly-pruned trees. Hot, dry conditions may stimulate ripening, softening, and watercore with inadequate red color, particularly on fruit treated with ethephon. Ethephon is not advised under conditions of severe water stress and high temperature.

Ethephon applied alone can cause early and severe fruit drop. Combination of NAA with ethephon will provide adequate drop control. Two sprays of NAA at 20 ppm may be needed. NAA will only prevent fruit drop for 7-10 days. Therefore, 7 days after the initial ethephon-NAA application, an additional NAA application should be used if treated fruit will not be harvested by 8-9 days after initial application. Since only two NAA applications are permitted for fruit drop control, ALL treated fruit MUST be harvested by 8-10 days after the second NAA application.

For stimulating red color on fruit to be marketed early, use a dilute spray combination of ethephon at 3/4 to 1 pt per 100 gal plus 4 oz of a surfactant plus NAA as shown in Table 20.

Use ethephon 1 to 2 weeks before normal picking time. Do not spray ethephon earlier than 3 weeks before normal harvest date because response may be limited.

Check fruit development closely, and harvest when treated fruit are ready. Do not spray more fruit than can be harvested in a 2-3 day period. Watch fruit condition because ethephon reduces starch levels, increases soluble solids, and stimulates ripening and softening of apples on the tree and after harvest. It may be possible to begin harvest earlier in some seasons, or to pick more or most fruit with better color at normal picking time.

Ethephon absorption is decreased at low temperatures. Apply when air temperature is between 60 degrees and 85 degrees F. Reduced response may be expected if application is followed by rain or excessive heat.

Preharvest Drop Control of Apples

Naphthaleneacetic acid (NAA) provides preharvest drop control (Table 19, 20, and 21).

Proper timing and rate are important for effectiveness (Table 21). Anticipating the expected time of drop is affected by weather conditions; however, the period is usually around the normal harvest period for a given variety. Heavy, late season rains or wind, particularly following drought conditions, have been associated with heavy preharvest drop.

Fruit should be harvested as near to the optimum harvest date as possible, even with the use of NAA. NAA reduces the drop of fruit, but fruit ripening continues at normal or even faster rates, especially for Rome and Golden Delicious. If allowed to remain on the tree too long, NAA treated fruit will be of poor quality and have decreased storage life.

NAA may not be effective when applied at low-volume concentrations. Use dilute or not higher than 3x concentration, based on tree-row-volume calibration. Thorough coverage is necessary. Healthy leaves are necessary for maximum stop-drop spray effectiveness; severe mite injury on leaves can reduce response.

Recent research results indicate that NAA may be most effective when applied before fruit loosen on the tree. We suggest an application at least 2 weeks before the first fruits drop (about 3 to 4 weeks before optimum harvest, based on flesh firmness, not color). NAA becomes effective 2-3 days after application. It may be necessary to apply a second spray of NAA if fruit start to loosen. Do not make more than two applications because additional applications may not be effective. Do not use within two days of harvest.

Aminovinylglycine (AVG, ReTain) + a silicone surfactant provide preharvest drop control and delay fruit maturation. 

ReTain delays the loss of fruit firmness and starch after the optimum harvest date for most cultivars. The delay is less for 'Red Delicious' and 'York' than for 'Rome' or 'Golden Delicious'. The delay in maturity may allow a cultivar to be harvested several days after the optimum harvest date since fruit quality is maintained better than with NAA. A delay in harvest will allow for an increase in fruit diameter and yields that may amount to 0.5% to 1% per day.

ReTain must be applied 4 weeks prior to the anticipated harvest in sufficient gallonage to ensure thorough coverage. A silicone surfactant will improve ReTain effectiveness. Do not use within 28 days of harvest. Mixing Retain in a tank mix with pesticides is not recommended.  See Table 21 in the 2004 Spray Bulletin for rates of application.

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