Fruit Pest News

Volume 6, No. 12  June 7, 2005

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. Strawberries: Matted-row Disease Control after Harvest

    2. Apple: Sooty Blotch and Flyspeck Update

    3. Tomato Late Blight Found in South Carolina

    4. Tomato: Timber Rot

    5. Degree Day Predictions

        5.a. Oriental Fruit Moth

        5.b. Grape Berry Moth

    6. Tree Fruit: Pheromone Trap Catches

Guess What Time It Is? - Japanese beetles were first sighted on June 6 in Davidson County.

1. 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. Resistant varieties such as Delmarvel do not need control measures.

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)

2. Apple Sooty Blotch and Flyspeck Update

The change in the weather pattern this past week, with more shower activity, sped up the incubation of the sooty blotch and flyspeck infections. Fifty-three hours of wetness accumulated this week. The table below shows the wetting hours that have accumulated since the biofix for each of the two models discussed in previous issues. First cover was considered to be 10 days after petal fall. As you can see, the models will call for the second cover spray at about the same time. (SB)

AWH = accumulated wetting hours

3. Tomato Late Blight Found in South Carolina

Late blight was found in Beaufort County, near the South Carolina coast on Sunday, May 29.  With the increase in shower activity, we may experience some periods of extended cloud cover, which is required for late blight to proliferate.

Growers should keep a general protective fungicide cover on their tomato plants, preferably with chlorothalonil.  The second choice would be Cabrio, mancozeb or maneb.  Chlorothalonil provides excellent protection against late blight and has broad spectrum activity.  Where bacterial spot or speck is a concern, mancozeb or maneb may be preferable because of their synergistic activity with copper.  There are a number of fungicides rated highly for late blight control, but are more expensive and have severe label limitations in the frequency of use.  They should be reserved for higher-risk situations (late blight present in the field or in the vicinity). (SB)

4. Timber Rot of Tomatoes

Sclerotinia timber rot has appeared in a number of tomato fields. It is characterized by wilting and a light brown stem rot, either at the soil line or some distance above the ground. Under moist conditions, a white mold forms on the stem surface. A lengthwise slice up the stem shows internal hollowing, white mold, and black, elliptical sclerotia.

Timber rot is an early-summer disease and will run its course soon. In the meantime, you may wish to spray with a specialized fungicide, but the choice is limited. Endura is the best tomato fungicide for Sclerotinia control, but availability seems to be a problem. Quadris is the second choice, if Endura cannot be found. Endura is limited to two applications per season, and Quadris must be alternated with non-strobilurin fungicides. (SB)

5. Degree Day Predictions

5.a. Oriental Fruit Moth

Second generation Oriental fruit moths have been laying eggs and protective sprays can be made based on degree days accumulated since the biofix (April 12 in Nashville). In apple, a moderate-density OFM infested orchard should have two applications 14 days apart starting at 1100 DD. In Nashville, 1100 DD occurred on May 30 so the second spray should be on June 13. A low-density OFM infested orchard should have a single spray applied at 1400 in apple. We are currently (June 6) at 1268 DD, just 132 DD short of 1400 DD. Assuming continued hot weather and an average of 35 DD per day would mean that the orchard should be sprayed in 4 days.

In peach, low-density orchards may require one insecticide application for OFM at 1400 DD after biofix given no sign of damage by first generation larvae and pheromone trap catches are between 3 to 7 moths/trap/week between 800 and 1,500 DD after biofix. A moderate density OFM infested orchard will have fruit damage and/or higher pheromone trap catches requiring two insecticide sprays 14 days apart starting at 1400 DD after biofix. The accumulated 1400 DD should occur in approximately 4 days. (FH)

5.b. Grape Berry Moth

The time to spray for second generation grape berry moth based on accumulated degree days is soon approaching. Sprays for this generation should occur from 1297 to 1700 DD after biofix. We are currently (6-6-05) at 1080 DD after biofix in Nashville. We should reach 1297 DD in about one week. (FH)

6. Pheromone Trap Catches

Nashville (Davidson County)
Oriental Fruit Moth (OFM), Redbanded Leafroller (RBLR), Obliquebanded Leafroller (OBLR), Codling Moth (CM), Grape Berry Moth (GBM), Variegated Leafroller (VLR), Black Cutworm (BCW)

* Biofix for RBLR in Davidson County estimated as occurring on March 12.
**Biofix for GBM in Davidson County is April 4.
***Biofix of BCW in Davidson County on April 12.
****Biofix for OFM in Davidson County on April 12.
*****Biofix for OBLR in Davidson county on May 13.

Bradley County

*Biofix for RBLR in Bradley County on March 12.
**Biofix for OFM in Bradley County on March 25.
***Biofix for CM in Bradley County on April 16.


Putnam County

*Biofix for RBLR in Putnam County on March 21.
**Biofix for OFM in Putnam County on April 6.
***Biofix for OBLR in Putnam county on May 11.

Obion County

*Biofix for RBLR in Obion County estimated to be on March 12 (trap not out early enough).
**Biofix for OBLR in Obion County on April 4 (waiting for confirmation since this was much earlier than other locations).
***Biofix for CM in Obion County on April 4 (waiting for confirmation).
****Biofix for OFM in Obion County on April 11.
*****Biofix for VLR in Obion County on May 3 (waiting for confirmation).

Other Pheromone Trap Catches for Davidson County
Diamondback Moth (DBM), American Plum Borer (APB), Cabbage Looper (CL), Armyworm (AW), Sod Webworm (SWW)

* Biofix of DBM in Davidson County probably earlier than April 20
**Biofix of APB in Davidson County probably earlier than April 20
***Biofix of CL in Davidson County on April 29
****Biofix of AW in Davidson County on May 2
*****Biofix of SWW in Davidson County on May 9

Knox County*
Tufted Apple Budmoth (TABM)

*The Knox County traps were put out by a first time cooperator still learning to identify. the moths. Correspondingly, the trap counts for May 2 remain suspect. We do know that the traps were put out too late to accurately determine a biofix for Oriental fruit moth (OFM) and redbanded leafroller (RBLR). The obliquebanded leafroller (OBLR), codling moth (CM), variegated leafroller (VLR) and tufted apple budmoth (TABM) catches are possible biofixes or at least early in their moth flights.

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@utk.edu

Both authors available at:

615-832-6802

fax 615-781-2568

Plant and Pest Diagnostic Center

5201 Marchant Drive

Nashville, TN 37211

Copyright 2005 The University of Tennessee. All rights reserved. This document may be reproduced and distributed for nonprofit educational purposes provided that credit is given to University of Tennessee Extension.

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