Fruit Pest News

Volume 3, No. 13    June 3, 2002

A weekly, 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. Tree Fruit: ORCHARD*A*SYST Available from Michigan State University

    2. Pome Fruit: New Insecticide

    3. Pome Fruit: Fire Blight Update

    4. Apples: Protect Against Necrotic Leaf Blotch of Golden Delicious

    5. Strawberries: Matted-Row Disease Control After Harvest

    6. Tree Fruit: Pheromone Trap Catches

1. ORCHARD*A*SYST Available from Michigan State University Web Site

Pesticide and nutrient management is addressed at http://www.msue.msu.edu/ipm/orchard.htm
This web site publication treats orchard management as a three-part process of nutrient management, safe and effective pesticide use and integrated pest management. It consists of a short questionnaire in which you answer questions pertaining to practices etc. at your orchard. The three possible answers to each question are ranked low risk, moderate risk and high risk. After this process is finished you can review your answers and then work on an action plan to target activities that reduce risk. An example of a high risk practice would be if you chose the answer stating that "a thorough calibration is performed infrequently or not at all and equipment is serviced only after it breaks." An action plan which I borrowed from the low risk practices would be to "service and calibrate application equipment each season and thoroughly rinse and recalibrate between applications of different types of pesticides. Calibration is repeated at least once during the growing season." Take a few minutes and see how your practices stack up against the low risk practices listed. You just might find something that you can use to improve your orchard management. (FH)

2. New Insecticide for Pome Fruit

Aventis CropScience USA Company has been granted registration by the EPA for the acetamiprid insecticide Assail 70WP. This insecticide is in the same class as Provado and Actara, the neonicotinoids. This insecticide is not only effective against aphids, leafhoppers, pear psylla and spotted tentiform leafminer but it also has good activity against codling moth. It is both ovicidal and translaminar systemic. The label rates range from 1 to 3.4 oz per acre depending on the target pest. The restricted entry interval is 12 hours with a pre-harvest interval of 7 days. (Information borrowed from The Orchard Monitor, West Virginia University Extension Service, May 28, 2002 at wvu.edu/~agexten/orchardmon/om052802.htm). (FH)

3. Fire Blight Update

Fire blight is especially noticeable in many areas now. The severity of fire blight this year once again illustrates the role of temperature during the bloom period in determining fire blight. The week of hot weather in April occurred during peak bloom for many apple trees. For most of the state, the weather was dry that week. As you can see, wet weather is not needed. The key determining factor is temperature. Dews provide all the moisture needed for infection if the temperatures are in the right range. And the dews do not need to be heavy ones. A moderate dew is all that is required. Remember that, during the bloom period next year.

Fire blight spread will become less likely as the shoot growth slows down and hardens off. Until then, however, be mindful of the potential for "trauma blight" fire blight. This can occur when hail or high winds injure leaves or stems and allow the bacteria to enter. If such a storm occurs, apply streptomycin within 24 hours after the storm, even if the leaves are still wet. Generally, the potential for severe trauma blight is greatest in orchards showing fire blight symptoms. However, it is possible to experience new fire blight symptoms after a trauma event even if no symptoms were present before the event, due to the presence of epiphytic bacteria. (SB)

4. Golden Delicious Growers - Protect Against Necrotic Leaf Blotch

Necrotic leaf blotch can strike with great suddenness. A prevention program should be begun right away on Golden Delicious and its bud sports, because a remedy is not possible after the disorder appears. Although necrotic leaf blotch is not a disease, certain fungicides will help control it. In the past, we relied on the EBDC fungicides (Dithane, Manzate, Penncozeb, etc.) for control. However, with the current label restrictions (77-day PHI and 3 lb/acre maximum rate), the EBDC fungicides are no longer useful for managing necrotic leaf blotch. Dr. Turner Sutton of North Carolina State University recommends ziram or thiram, applied on a 10-14 day schedule from mid-June through early August. Tank mixing with captan will improve the control of certain other diseases. Foliar zinc sprays have also been tested for necrotic leaf blotch control. Dr. Sutton reports that Ele-Max Super Zinc, applied at 1 pint/acre with captan in 3 to 4 cover sprays has been effective, although other zinc oxide products may be just as effective.

Necrotic leaf blotch begins as broad necrotic areas on green leaves. The green turns to yellow and the leaves fall from the tree. The affliction can occur in several "waves" throughout the summer. It is usually most severe when a period of overcast, rainy weather is followed by sunny weather. (SB)

5. Matted-Row Strawberry Disease Control After Harvest

Harvest has wound down, and now it is time to take steps to produce a healthy bed of plants for next year's crop. Proper renovation is the most important step in producing a vigorous crop. When new growth emerges after renovation, fungicide applications may be necessary, especially in rainy weather. Anthracnose is the greatest threat, since this disease can prevent bed fill and can debilitate established plants. However, the runner phase of anthracnose, which affects stolons, petioles and crowns, is difficult to control. Efforts to control anthracnose on these vegetative parts of the plant, even with effective fungicides such as Quadris and Switch, may lead to disappointing results.

Nova fungicide is registered for use on strawberries. In my field trials, I have found Nova to be very effective against common leaf spot and Phomopsis leaf blight, but that it does not control anthracnose or Botrytis. Phomopsis can be a problem in hot weather, whereas common leaf spot is a problem on certain varieties in cool seasons. Below is a summary of the results I have obtained with field trials on the leaf spot diseases.

Please note the following:

• The Nova label states a rate of 2.5 to 5.0 oz/acre, applied at 14 to 21-day intervals. In a trial in which I used 4.0 oz/acre on a 7 to 10-day schedule, it caused the plants to become compact, with dark green leaves and reduced yields. The results in the table above were obtained with 2.0 oz/acre applied on a 7 to 10-day schedule. For leaf spot and leaf blight control, I would recommend the shorter end of the 14 to 21-day interval on the label.
• The Quadris label only lists anthracnose and powdery mildew control. However, when applied according to the label (6.2 to 15 fl oz/acre at 7 to 14-day intervals), it should provide control of leaf blight and leaf spot as shown in the table above. Do not make more than 2 consecutive applications of Quadris before alternating to another labeled fungicide for at least 1 application.
• The use of a surfactant would probably enhance the performance of any of the fungicides, especially against diseases of the stolons, which tend to be slick. (SB)

6. Pheromone Trap Catches and Biofixes

                                        Nashville (Davidson County) Pheromone Trap Catches for 2002

Biofix for RBLR in Davidson County estimated as occurring on March 14

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Bradley County Pheromone Trap Catches

Codling moth biofix was April 14

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Putnam County Pheromone Trap Catches

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Obion County Pheromone Trap Catches

(FH)

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, Associate 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