Fruit Pest News
Volume 7, No. 5 April 12, 2006
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. Fruit Spray Guides: Update on Availability
2. Peach Disease Control
3. Apple: Disease Control During Bloom and at Petal Fall
4. Grape: Early-Season Disease Control
5. Blueberry: Twig Blight
6. Plum Curculio
7. Unknown Moths in Traps
8. Pheromone Trap Catches and Biofixes
1. Fruit Spray Guides: Updates on Availability
The March 15 issue of Fruit Pest News provided the availability of our fruit and vegetable spray guides. The online version of the regional apple guide was not available at the time, but now has become available. Updates to the list are provided in bold print below.
(SB)
2. Peach Disease Control
Many peach cultivars are now at the shuck split stage. Fungicide applications for control of peach scab should begin at the shuck split to shuck fall stage, about one week after petal fall. Do not wait until all the shucks have fallen to make this application. Scab pressure is greatest from shuck split through 2nd or 3rd cover because scab spore counts are high during this time and the cool, wet weather that occurs during this time favors infection. Continue on 10-day intervals until 40 days before harvest. Bravo cannot be used after the shuck fall stage. Captan, sulfur, Pristine, Flint, Scala, and Abound are other peach scab products. Pristine, Flint, and Abound are strobilurin materials and should be rotated with non-strobilurin products that have scab activity, such as captan or sulfur.
Shuck split is also the time to begin bacterial spot sprays on susceptible varieties. Mycoshield should be applied every 10 days until 3 weeks before harvest. (SB)
3. Apple: Disease Control During Bloom and at Petal Fall
The sterol inhibitors (SI's) are important fungicides for the control of apple scab, powdery mildew, and rust diseases. Examples of SI's are Nova, Rubigan, and Procure. Some areas of the country are beginning to experience loss of control of scab due to the development of strains resistant to the SI's. As far as I know, this has not happened in Tennessee. (If you think it is happening in your orchard, please let me know.) Let's try to prevent resistance from developing by always tank mixing our SI's with a protectant fungicide such as mancozeb, captan, ziram, etc., and using SI's only when necessary.
Bloom. If your bloom-time spray is applied only 6 or 7 days after the pink tip spray, it may not be necessary to use fungicides with lengthy kick-back activity (i.e. the SI's). A contact material such as mancozeb or ziram may be sufficient at that time, and these two materials would also provide rust control. However, these materials are not suitable for powdery mildew control. For mildew-susceptible varieties such as Jonathan, Ginger Gold, Rome Beauty, Stayman Winesap, Idared, Paulared, and Granny Smith, mildewcides such as the SI's, Topsin M, or sulfur should be used in each spray until terminal growth stops. Early season sprays (tight cluster to petal fall) are essential if mildew is to be managed successfully.
Petal fall. Petal fall through first cover is a peak risk period for powdery mildew, cedar-apple rust, and fruit infection by scab. Use an SI with a contact fungicide at each of these two growth stages. Note: I recommend that the strobilurin materials (Flint, Sovran) be reserved for use during the summer, when their characteristics are more fully utilized. (SB)
4. Early-Season Grape Disease Control
Grapes have begun growth and many are at the 1- to 2-inch shoot stage at which the first fungicide spray is recommended. Traditionally, it has been thought that successful black rot control required beginning the spray program at this early stage. Recent research conducted in New York and here in Tennessee has shown that this is not the case. The black rot fungus does not become active until later. The first spray is needed during the pre-bloom period, about 10 to 14 days before bloom. You could save yourself the cost of a fungicide spray at the 1-inch shoot stage if it weren't for the fact that other diseases such as Phomopsis cane and leaf spot, downy mildew, and powdery mildew can also begin activity at this stage of growth. However, this does mean that your fungicide selection at this time should be based on diseases other than black rot. Choose a fungicide(s) based on the history of disease problems in the vineyard, using an efficacy table such as the one in the regional spray guide. Sterol inhibitor fungicides can be used in the early sprays, but keep in mind that they do not provide control of Phomopsis or downy mildew. The multi-site inhibitors (e.g. captan, mancozeb, maneb, ziram) are better choices for control of theses diseases. The sterol inhibitors or sulfur should be used where powdery mildew is expected. Strobilurins have the broadest spectrum of activity, but are more expensive and are limited to 4 applications per year.
Considering the arsenal of fungicides available to the grape grower, it is a good idea to become familiar with the classification of the products. (SB)
5. Twig Blight of Blueberry
Blueberry growers should look for twig blight, caused by Phomopsis vaccinii, beginning in early spring, since the symptoms can begin to show shortly after budswell. Control measures can then be initiated.
Individual buds turn brown and die, followed by browning of the bark around the bud as the fungus moves from the blighted bud into the twig. The infection usually advances inside the twig until most or all of the flower buds on a twig are killed. Click here http://www.ces.ncsu.edu/depts/pp/notes/Fruit/fdin010/img_tret.htm to see images of these symptoms. Click the images to enlarge them. The dieback does not progress into the older wood, making twig blight easy to distinguish from stem blight, caused by Botryosphaeria dothidea. Frost injury can also resemble twig blight. Twig blight lesions usually continue to enlarge and may be centered around a bud.
It is helpful to prune out and destroy the infected twigs, but this should be done prior to the bloom period, for maximum benefit. Many spores are released from infected twigs beginning shortly after bud break. Those that land in opening buds germinate and invade the twig. However, all is not lost if you have not done this. Removing infected twigs between this time of year and August is helpful in that it reduces twig blight in next year's crop. That is because dead twigs continue to produce spores, which land on and infect buds that become next year's flowers.
Preventive fungicide applications may be needed in plantings in which twig blight has been a problem in the past. Captan, ziram, Cabrio, and Pristine are the most effective fungicides for twig blight.
The highbush varieties Murphy and Harrison are highly susceptible to twig blight and will surely need a control program. Croatan is moderately susceptible, while Reveille, Cape Fear, Bluechip, and Wolcott are relatively resistant. Some rabbiteye varieties are susceptible, especially Delite. (SB)
6. Plum Curculio
With apples in full bloom and stone fruit already set, we can
expect plum curculio to start attacking the young developing fruit. If plum curculio
have been a problem in previous years, protect the developing fruit starting with
an insecticide application at petal fall. The next two sprays are also extremely
important because much of the feeding and oviposition damage occurs from petal fall
through these sprays early in the fruit development. (FH)
7. Unknown Moths
On
April 11, I caught two unknown gray and black tortricid moths in the codling moth
trap and no codling moths. In the obliquebanded leafroller (OBLR) trap, I caught
seven tiny tan moths with some red coloration. These moths were slightly smaller
than redbanded leafrollers but much smaller than OBLR moths, which I have not caught
yet. I also caught a tan moth in the grape berry moth trap which was larger than
the grape berry moths caught starting on April 6. Make sure that you examine the
moths caught in the traps, because unknown species, probably of no economic importance
can fool you. These first catches are used to set the biofix which is an important
date used to predict when to spray for these pests in the future. (FH)
8. Pheromone Trap Catches and Biofixes
Nashville (Davidson County) Pheromone Trap Catches
for 2006
Oriental fruit moth (OFM), redbanded leafroller (RBLR), obliquebanded
leafroller (OBLR), codling moth (CM), grape berry moth (GBM), variegated leafroller
(VLR), black cutworm (BCW), diamondback moth (DBM)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | DBM | |
| 3-1 (put out RBLR, OFM, VLR traps) | -- | 0 | -- | -- | -- | -- | -- | -- |
| 3-2 | -- | 3* | -- | -- | -- | -- | -- | -- |
| 3-9 | -- | 15 | -- | -- | -- | 0 | -- | -- |
| 3-13 | 0 | 50 | 0 | -- | -- | 0 | -- | -- |
| 3-21 | 0 | 71 | 0 | -- | -- | 0 | -- | -- |
| 3-28 | 0 | 15 | 0 | -- | -- | 0 | -- | -- |
| 3-29 (put out GBM, BCW, & DBM traps) | 0 | 5 | 0 | -- | -- | 0 | -- | -- |
| 3-30 | 0 | 4 | 0 | -- | 0 | 0 | 0 | 2** |
| 4-4 | 24*** | 34 | 0 | -- | 0 | 0 | 0 | 2 |
| 4-6 | 5 | 14 | 0 | 0 | 1 | 0 | 0 | 1 |
| 4-7 | 14 | 4 | 0 | 0 | 3**** | 0 | 0 | 0 |
| 4-11 | 12 | 10 | 0 | 0 | 1 | 0 | 0 | 1 |
* Biofix for RBLR in Davidson County was March 2.
**Biofix for DBM in Davidson
County was March 30.
***Biofix for OFM in Davidson County is estimated to be April
3.
****Biofix for GBM in Davidson County was April 7.
Bradley County
Phoromone Trap Catches for 2006
| OFM | CM | |
| 3-29 | 3* | 0 |
| 4-3 | 26 | 0 |
| 4-5 | 0 | 1 |
| 4-10 | 16 | 0 |
*Biofix for OFM in Bradley County on March 29.
Putnam County Pheromone
trap Catches for 2006
| OFM | RBLR | OBLR | CM | VLR | |
| 3-21 (put out RBLR & OFM) | -- | -- | -- | -- | -- |
| 3-24 | 0 | 0 | -- | -- | -- |
| 3-27 | 0 | 0 | 0 | 0 | 0 |
| 3-31 | 2** | 12* | 0 | 2*** | 0 |
| 4-2 | 1 | 3 | 0 | 0 | 0 |
| 4-7 | 6 | 23 | 1 | 1 | 0 |
*Biofix for RBLR in Putnam County estimated as March 3 (trap not out early enough).
**Biofix
for OFM in Putnam county March 31.
***Waiting to verify biofix for CM, catch probably
too early.
Obion County Pheromone Trap Catches for 2006
| OFM | RBLR | OBLR | CM | VLR | |
| 3-13 | 1 | 49* | 0 | -- | 2*** |
| 3-21 | 0 | 40 | 0 | 0 | 0 |
| 3-27 | 1 | 2 | 0 | 0 | 0 |
| 4-3 | 2** | 13 | 0 | 2**** | 0 |
*Biofix for RBLR in Obion County estimated to be on March 3 (trap not out early
enough).
**Biofix for OFM in Obion County on April 3.
***Waiting to verify
biofix for VLR in Obion County, catch probably too early.
****Waiting to verify
biofix for CM in Obion County, catch probably too early.
(FH)
The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm
Contacts:
Steve Bost, Professor and Extension Plant Pathologist
Frank Hale, Professor and Extension Entomologist
Both authors available at:
615-832-6802
fax 615-781-2568
Plant and Pest Diagnostic Center
5201 Marchant Drive
Nashville, TN 37211
Copyright 2006 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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