Fruit Pest News
Volume 10, No. 3 April 13, 2009
An online newsletter whose goal is to provide all interested persons with timely information on diseases and insects of commercial fruit and vegetable crops 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. Additions to Bravo Label and What this Means for Replacing Maneb
3. New Disease of Basil
4. Peach Disease Control
5. Apple Disease Control During Bloom and at Petal Fall
6. Early-Season Grape Disease Control
7. Pheromone Trap Catches and Biofixes
1. Current Conditions
The stormy weather is bringing lots of rain, but much of it is coming down too fast to soak in. There have been several frosts that have cost us some blooms. Peaches in Nashville are at shuck split, apples at petal fall, blueberries at late bloom, grapes at shoots up to 3-inches, and blackberries are at pre-bloom.
There was a report of blight in residential pear and apple caused by Pseudomonas syringae pv. syringae, in which there was an apparent interaction with frost, with the blight only occurring on limbs near the ground.
Apple growers: If you need a print copy of the regional apple production/spray guide, we have extra copies here at the Nashville office. Just let us know. (SB)
2. Additions to Bravo Label and What this Means for Replacing Maneb
The IR-4 program has succeeded in petitioning the EPA for additions to the Bravo WeatherStik label. These additions include peppers (bell, chili, and others), okra, eggplant, ginseng, rhubarb, and certain cucurbits and brassicas missing on the previous label. These changes have occurred since the printing of the 2009 Commercial Vegetable Disease Control Guide, thus are not included.
What does this mean for efforts to provide a replacement for maneb, following its discontinuation? This Bravo label fills a few of the gaps left by the loss of maneb, but not all. Bravo does not enhance the bacteria-controlling properties of copper as maneb or mancozeb do. We plan to have a Section 18 for mancozeb on pepper this year, to fill this need. Collards, kale, mustard, turnip greens, and lettuce are not on either the Bravo or mancozeb labels. However, the broad-spectrum activity of the strobilurins, which are labeled for these crops, makes them adequate replacements for maneb and would disqualify these crops as candidates for Section 18 labels for mancozeb. (SB)
3. New Disease of Basil
If you grow basil, be on the lookout for a new disease this year, basil downy mildew. It is easy to overlook, yet destructive because of the low tolerance level for leaf imperfections in basil at the marketplace. Basil downy mildew moved from Europe to south Florida in October, 2007, followed by reports from NC, PA, NJ, NY, MA, MO, and KS in 2008 and CA in 2009. It likely has occurred elsewhere, but has not been reported because of the subtlety of the symptoms. The disease is transmitted through infected seeds, aerial spread of spores, and marketplace movement of infected leaves. The article by Dr. M.T. McGrath, http://vegetablemdonline.ppath.cornell.edu/NewsArticles/BasilDowny.html will help you identify the disease. We will be including basil plants in our cucurbit downy mildew sentinel, or "lookout," plots this year. (SB)
4. 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. Oxytetracycline (Mycoshield, FlameOut, FireLine) or a fixed copper should be applied every 10 days until 3 weeks before harvest. (SB)
5. 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 Rally, Rubigan, Indar, Inspire Super MP, and Procure. They are also called demethylation inhibitors - DMI's. Should you tank mix your SI's with a protectant or apply them solo? If apple scab is present in your orchard, you should tank mix them, to discourage the development of resistance in the scab fungus.
NOTE: Nova fungicide is now being sold under the name Rally.
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, Pristine) be reserved for use during the summer, when their characteristics are more fully utilized. (SB)
6. Early-Season Grape Disease Control
Traditionally, it has been thought that successful black rot control required beginning the spray program shortly after growth began in the spring. 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, 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. (SB)
7. Pheromone Trap Catches and Biofixes (FH)
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), diamondback moth (DBM), armyworm
(AW), beet armyworm (BAW), squash vine borer (SVB), fall armyworm (FAW)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | DBM | AW | CL | BAW | SVB | FAW | |
|
3-13 (Put out RBLR trap) |
-- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-20 | -- | 29* | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-23 | -- | 14 | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
|
3-30 (put out BCW trap) |
-- | 9 | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
|
3-31 (put out OFM, CM, VLR, OBLR traps) |
-- | 10 | -- | -- | -- | -- | 0 | -- | -- | -- | -- | -- | -- |
| 4-2 | 4** | 2 | 0 | 0 | -- | 0 | 0 | -- | -- | -- | -- | -- | -- |
|
4-3 (put out AW trap) |
-- | -- | -- | -- | |||||||||
|
4-8 (put out GBM, DBM, BAW, FAW, SVB, CL traps) |
12 | 19 | 0 | 0 | -- | 0 | 2 | -- | 4 | -- | -- | -- | -- |
| 4-13 | 9 | 17 | 0 | 0 | 4*** | 0 | 0 | 0 | 7 | 0 | 0 | 0 | 0 |
* Biofix for RBLR in Davidson County estimated as prior to March 20 (trap not
out early enough).
**Biofix for OFM in Davidson County was April 2.
***Biofix
for GBM in Davidson County was April 13.
Putnam County
Tufted Apple Bud Moth (TABM)
| OFM | RBLR | OBLR | CM | VLR | TABM | |
| 3-16 | 0 | 10* | -- | 0 | 0 | -- |
| 3-18 | -- | 31 | -- | 0 | 0 | -- |
| 3-20 | -- | 2 | -- | 0 | 0 | -- |
| 3-23 | -- | 2 | -- | 0 | 0 | -- |
| 3-25 | -- | 0 | -- | 0 | 0 | -- |
| 3-27 | -- | 6 | -- | 0 | 0 | -- |
| 3-30 | -- | 11 | -- | 0 | 0 | -- |
|
4-1 (put out OBLR, TABM) |
||||||
| 4-3 | -- | 10 | 0 | 0 | 0 | 0 |
| 4-10 (put out OFM) | -- | 11 | 0 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County estimated as prior to March 16 (trap not out early enough).
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
Soil, Plant and Pest Center
5201 Marchant Drive
Nashville, TN 37211
Copyright 2009 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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