Fruit Pest News

Volume 5, No. 3   March 30, 2004

An online newsletter whose goal is to update Extension agents and growers of commercial tree fruit and small fruit crops

on diseases and insects in Tennessee.

Text appearing in blue or red can be clicked to link to other web sites. Be aware that much of the linked information is produced in other states and may not be applicable to Tennessee.

In This Issue:

    1. Current Conditions

    2. Blackberries: Plant with Certified Plants

    3. Strawberry Spray Schedule

    4. Apple: Tips for Fire Blight Control During Bloom

    5. Apple: Early-Season Fungicide Sprays

    6. Strawberry: Phytophthora Disease Control

    7. Tree Fruit: Pheromone Trap Catches and Biofixes

1. Current Conditions

We just completed an unseasonably warm week, but milder temperatures should be in order for the next week. Rainfall has been below normal, but showers are abundant during the early part of the week. The cooler weather should help apple growers by reducing fire blight pressure going into the bloom period. Low temperatures slow bacterial multiplication and reduce the activity of the insects that carry the bacteria. Apples are at tight cluster to pink tip, peaches are generally in full bloom, matted row strawberries have begun to bloom, and blackberry shoots are one to two inches long. (SB)

2. Planting Blackberries? Consider Certified Plants

If you will be planting blackberries this spring, consider purchasing certified plants. Viruses such as raspberry bushy dwarf virus and tomato ringspot virus can be problems in blackberries, and it is possible to buy infected plants, which will not show symptoms at the time of purchase. Certified plants will also be free of other damaging diseases such as rosette disease. Certified plants have only recently become available. Only one certified nursery, Jones Farms, is licensed to propagate cultivars from the Arkansas breeding program, which produced the major cultivars grown in the South. The plants sold by Jones Farms are derived from tissue culture stock, but come to you after growing in insect-free greenhouses in 3-inch pots since last summer. The plants are inspected and certified by the North Carolina Department of Agriculture. (SB)

Jim and Barbara Jones

c/o Jones Farms

7094 Honeysuckle Lane

Bailey, NC 27807

Home phone: 252-235-3248

Home fax: 252-235-0155

Barbara cell: 252-399-9844

Jim cell: 252-230-2084

email: jonesfarmsnc@aol.com

3. Strawberry Spray Schedule

Note: The table below was produced for the March 10 issue of this newsletter, but printed out too wide and cut off some of the content. So, here it is again and, hopefully, the problem is fixed!

Below is a recommended spray schedule to follow for springtime disease control in strawberries. The exact design of a spray schedule can vary depending on disease control needs and products available. However, the principles illustrated below should serve as a good general guide for management of the two most common diseases, Botrytis and anthracnose.

(SB)

4. Apple: Tips for Fire Blight Control During Bloom

Many varieties are within days of the first open blooms. The bloom period is a key time for fire blight management in apple and pear. It is during bloom that many of the most damaging fire blight infections take place. It is also the time at which streptomycin sprays are most effective . . . in fact, we no longer recommend streptomycin after bloom (unless there is a hailstorm) because of its lack of effectiveness against the shoot blight phase. The following points should help you to use streptomycin efficiently.

• Streptomycin works best when applied alone (not tank mixed with fungicides), under slow-drying conditions. The addition of a surfactant may improve its effectiveness.
• Streptomycin only protects open blossoms. Those that are not yet open need to be sprayed when they open. It is for this reason that sprays must be applied every 3 to 5 days during bloom, unless you are using the MaryBlyt program to guide you.
• Only fire blight-susceptible varieties need to be sprayed with streptomycin. This differs from the strategy for the use of delayed dormant copper sprays. Copper should be sprayed on all blocks in the orchard, because the objective is to kill epiphytic (on plant surface) fire blight bacteria. These can occur and multiply on the surface of any tree, resistant or susceptible. For a bacterium to infect a blossom and cause disease, however, the variety must be susceptible. Streptomycin is used top protect blossoms from infection, not to kill epiphytic bacteria.
• Streptomycin is most effective when applied the day before, or the day of, an infection. However, if you miss an infection period, you can still obtain some benefit. Streptomycin applied up to 48 hours after infection is better than no treatment. (SB)

5. Early-Season Apple Fungicide Sprays

Many trees are now at tight cluster. For many orchards, this is the time for the first fungicide application. Scab control at this time is a must. If scab was abundant last year, the first application should be made at green tip. Scab should be treated early to prevent primary scab infections and thus break the disease cycle. Also, it is important to avoid early infections on sepals (calyx), as these are difficult to detect and can provide secondary inoculum throughout the early part of the growing season.

There are several different strategies for scheduling scab sprays. The selection of a spray program (what fungicide to use and how often) depends on factors such as other disease organisms present and the ability to obtain good coverage of the trees with the sprays. If cedar-apple rust or powdery mildew are a threat, it is probably best to control scab with a sterol-inhibiting fungicide (Nova, Procure, or Rubigan), because control of all three diseases would be obtained. Tank mixing with mancozeb or captan would improve the protectant ability and discourage the development of resistance to the sterol inhibitor (SI). Do not uses captan within 2 weeks of an oil spray.

The 3- to 4-day curative activity of the SI fungicides makes them useful at tight cluster in case some scab infections occurred prior to that time. The SI/protectant combination allows you to space the applications 7 to 10 days apart.

Where cedar-apple rust is a problem, mancozeb or ziram should be used as the protectant, to be mixed with the SI. The strobilurin fungicides Flint and Sovran can be used in lieu of the SI's, but I recommend reserving these materials for use during the summer. They may only be applied 4 times per year, and they play a more valuable role during the summer than during the spring.

Overwintering of powdery mildew is highly dependent on winter weather. Since we did not have prolonged cold temperatures this winter, there should be abundant inoculum in orchards that had mildew last year. If weather conditions are favorable (cool, wet) for mildew, disease pressure could be high on susceptible varieties. Be sure to use an SI on such blocks (see previous paragraph regarding the use of strobilurins). (SB)

6. Strawberries: Phytophthora Disease Control

Some growers planted some Sweet Charlies with Phytophthora crown rot last fall. Those fields and other fields known to be infested should be treated with fungicides before symptoms appear. The products discussed below should help reduce losses not only to Phytophthora crown rot, but also to leather rot (a berry rot caused by the same fungus) and red stele (caused by a different, but related, fungus).

Ridomil Gold and Aliette are systemic fungicides that are used in control of Phytophthora, Pythium, and the downy mildews of labeled crops. Their methods of application differ.

Ridomil performs best when taken up by the roots and translocated upwardly by the plant. The preferred method of application in strawberries is through the drip system. Ridomil Gold EC is injected into the drip system at the rate of 1 pint per treated acre. An actual acre would only receive 0.6 pint if the beds are 3 feet wide on 5-foot centers, because only 60% (3/5) of the ground would be treated. If you apply Ridomil with a sprayer, use enough water to move the fungicide into the root zone. An additional application may be made during fruit set or harvest.

Aliette is labeled for use against red stele and leather rot. Recent research has indicated that it is also effective against Phytophthora crown rot. Aliette is applied at 2.5-5.0 pounds per acre at 30-60 day intervals for red stele control and at 7-14 day intervals for leather rot control. Aliette can be applied through the drip system or through some sprinkler irrigation systems. A foliar spray is the preferred method of application of Aliette because of its downward systemic activity. Like Ridomil, Aliette can be applied on the day of harvest. Follow label directions carefully. (SB)

7. Pheromone Trap Catches and Biofixes

Abnormally warm weather last week increased flight activity of redbanded leafroller (RBLR) and brought out the Oriental fruit moth (OFM). In Nashville, the RBLR trap catch continued to increase with 62 being found in the trap on March 29. The first OFM was caught on March 22. On March 29, a total of 25 moths were caught with the biofix estimated as occurring on Friday, March 26. The OFM moths are dark grayish brown and small (4-5 mm long). Also caught in the OFM trap were some much larger gray moths with a dark area on the front wings and gray underwings. Do not count these larger, unidentified tortricid moths when making your OFM trap counts. (FH)


Nashville (Davidson County) Pheromone Trap Catches for 2004

* The three RBLR caught in trap left over from last year. New RBLR trap put out 3-4-04. Biofix for RBLR in Davidson County estimated as occurring on February 29.
**Biofix for OFM estimated to have occurred on March 26.

Bradley County Pheromone Trap Catches

*Four RBLR moths caught in last years trap. Biofix for redbanded leafroller in Bradley County estimated as occurring on February 29.


Putnam County Pheromone Trap Catches

*Biofix for RBLR in Putnam County estimated as occurring on February 29.


Smith County Pheromone Trap Catches

* Biofix for RBLR estimated as occurring on February 29.

The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm

Contacts:

Steve Bost, Professor and Extension Plant Pathologist

scbost@utk.edu

Frank Hale, Professor and Extension Entomologist

fahale@ext1.ag.utk.edu

Both authors available at:

615-832-6802

fax 615-781-2568

Plant and Pest Diagnostic Center

5201 Marchant Drive

Nashville, TN 37211

 Pesticides recommended in this publication were registered for the prescribed uses when printed.  Pesticides registrations are continuously reviewed.  Should registration of a recommended pesticide be canceled, it would no longer  be recommended by the University of Tennessee.  Use of trade or brand names in this publication is for clarity and information; it does not imply approval of the product to the exclusion of others which may be of similar, suitable composition, nor does it guarantee or warrant the standard of the product.

The Agricultural Extension Service offers its programs to all eligible persons regardless of race, color, age, national origin, sex, disability,

religion or veteran status and is an Equal Opportunity Employer.

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Acts of May 8 and June 30, 1914. Agricultural Extension Service  Charles L Norman, Dean