Fruit Pest News
Volume 7, No. 9 May 10, 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. Current Conditions
2. Small-Batch Preparation of Pesticides
3. Phyto Reminder for Quadris/Abound
4. Peach Pest Management - Diseases
5. Grapes: Botrytis and Other Diseases
6. Codling Moth
7. Pheromone Trap Catches and Biofixes
1. Current Conditions
A warm, dry April has given way to a cool, wet May. Temperatures remain below normal for the second week. Frequent showers may interfere with spray programs. First reports for the year: Strawberry anthracnose - May 4, Davidson County; blackberry rosette - May 8, Williamson County.
2. Small-Batch Preparation of Pesticides
When preparing small quantities of a spray mix (e.g. 1 gal.), it is often convenient to use a tablespoon to measure the product. That's fine if the product is a liquid. Any liquid pesticide mixed at 1 pint per 100 gallons of water is always going to be 1 teaspoon per gallon, because both measures are volumes. The problem comes with dry products (wettable powders, dry flowables, water-dispersable granules).
Dry products have different densities, so it is not accurate to convert a weight measure into a volume measure (e.g. tablespoon), unless you know how much that volume weighs. The table below illustrates the range of densities of some common fruit fungicides. You can see the error that would ensue if you assumed, say, that 2 tablespoons per gallon of any dry product was equal to 3 pounds per 100 gallons.
|
Densities of common fruit fungicides. |
||
|
Product |
Grams per level tablespoon |
Approximate no. tablespoons/oz. |
|
basic copper sulfate |
13.0 |
2 |
|
Flint 50DF |
7.1 |
4 |
|
Cabrio 20WDG |
7.0 |
4 |
|
Captan 50WP |
8.8 |
3 1/3 |
|
Carbamate 76WDG |
5.0 |
5 2/3 |
|
Dithane DF |
8.5 |
3 1/3 |
|
Kocide DF |
8.5 |
3 1/3 |
|
Kocide 101 WP |
4.6 |
6 |
|
Manzate 200DF |
10.2 |
3 |
|
Nova 40W |
3.1 |
9 |
|
Pristine 38WDG |
6.0 |
4 2/3 |
|
Switch 62.5WDG |
6.0 |
4 2/3 |
Once you have weighed a level tablespoon of a dry product, you can use that tablespoon to measure the product, because it is then a unit of weight. (SB)
3. Phyto Reminder for Quadris/Abound
With azoxystrobin (Quadris, Abound, Heritage) receiving registrations for so many commodities, its danger to certain apples bears repeating. Azoxystrobin is very phytotoxic to Macintosh and related apple varieties. When spraying strawberries or other crops with an azoxystrobin product, be careful not to allow any drift to nearby apples. Do not even use a sprayer for apples that has ever been used to apply azoxystrobin. Even trace amounts can burn the leaves. Before selling a sprayer that has been used to apply azoxystrobin, clean it out thoroughly, using a tank cleaner. The following varieties have been reported as sensitive to azoxystrobin: Akane, Bromley, Cortland, Cox/Cox's Orange Pippin, Discover, Gala, Grimes, McCoun, Macintosh, Molly's Delicious, Kent, Spartan, Summer Treat, and Summared. Also related to Macintosh are Bancroft, Empire, and Janamac. Note: Azoxystrobin injury on Gala could be mistaken for Glomerella leaf blotch, to which Gala is also susceptible. (SB)
4. Peach Pest Management - Diseases
Watch for certain indicators that can signal upcoming problems. You may need to adjust your control program, such as shortening the spray interval or changing to another control product. You're practicing IPM and may not even know it!
Bacterial spot. Most diseases are favored by rainy weather, but some react more explosively to it than others. Bacterial spot can become epidemic quickly because of the ability of the bacteria to reproduce rapidly and because of their ability to exist epiphytically on the various surfaces of the tree. The number of overwintered shoot "blacktip cankers" is not necessarily a good indicator of the disease potential, because the epiphytic population represents an invisible source of infection. The level of bacterial spot in previous years is probably the best indicator of the disease potential in a block. On susceptible cultivars, successful control of bacterial spot requires a program involving dormant pruning of cankers and use of copper sprays, early-season sprays of copper or Mycoshield, and some help from Mother Nature (dry weather).
When using Mycoshield, consider that it does not weather well. Because of its short residual activity, Mycoshield is most effective when applied shortly before rain, before it has a chance to inactivate. Try to apply within 24 hours before a wetting event, but allow time for the spray to dry. Copper sprays can be used at this time of year, but leaf damage can occur. If you choose to use copper now, use low rates of liquid coppers such as Tenn-Cop 5E (4-6 fl oz/acre) or Copper-Count-N (4-6 fl oz/acre) in at least 100 gal water per acre.
Peach scab. As with most diseases, the risk of infection can be determined by the severity of the disease in previous years. With peach scab, disease potential can also be assessed by examining fruit-bearing shoots for the presence of lesions. Scab lesions on twigs are brown, circular to oval in shape, and best seen on the parts of the shoot that have not yet turned from green to brown. If scab potential is considered low, sulfur should be adequate for control. Remember that sulfur is not very rainfast. Scab control is not needed within 40 days of harvest, because that is the length of time needed for symptom development after infection.
Green fruit rot. This is a good indicator for brown rot, as both diseases are caused by the same fungus. Clinging green fruit that has been damaged by frost and thinned fruit on the ground may be infected and serve as an indication of brown rot pressure. Insect- or wildlife-injured fruit is also susceptible to brown rot and serves as a good indicator. Adjust cover sprays or initiate pre-harvest brown rot sprays early when disease pressure is high. Use captan or Abound if infected green fruit is present. These materials will also control scab. (SB)
5. Grapes: Botrytis and Other Diseases
The unusually warm month of April moved the grape crop ahead of normal. Some cultivars, such as Concord, are already at the post-bloom stage. Some are still in bloom. With such rapid development, I hope you got your Botrytis sprays on in time. The bloom period is the key time for prevention of Botrytis bunch rot. Some cultivars are still blooming, and the persistent cool weather we are now experiencing is extending the bloom period on those. Following are the fungicides that can be used for Botrytis control on varieties that are in bloom.
Vangard 75WG, Elevate 50WG, and Rovral 50WP are botryticides that should be applied to susceptible cultivars. Since they do not provide black rot control, an effective black rot fungicide should be added to the tank. A sterol inhibitor (Nova, Elite, Bayleton, etc.) should be used because of their locally systemic activity. Since the sterol inhibitors are not effecitve against Phomopsis or downy mildew, an effective product such as mancozeb or captan should also be applied. The recently-labeled Pristine 38WDG is effective against all of these diseases, with only a slight sacrifice in Botrytis activity.
For Botrytis control, Vangard is used at 10 oz per acre at early bloom and at berry touch, veraison, or preharvest (20 oz per acre per year, 7-day PHI). See the label for precautions for use near aquatic areas. Elevate is used at 1 lb per acre at early bloom, bunch pre-close, and veraison, up to and including the day of harvest (up to 3 applications). Rovral 50WP may be applied at 1.5 to 2 lb per acre at early bloom, prior to bunch closing, veraison, and preharvest (7-day PHI). Although the Rovral label allows 4 applications, it is suggested that no more than 3 applications be made, in light of resistance problems that have occurred in other areas. (SB)
6. Codling Moth
Spring pheromone trap catches for codling moth allow the grower
to determine the biofix. After that, the grower only needs to check the traps once
per week and keep temperature records. In apples for first generation codling moth,
a single insecticide application should be made at 350 DD after biofix for low-density
codling moth orchards. A low-density orchard is one with less than 0.5% of the fruit
damaged the previous year and pheromone trap catches that do not exceed 10 moths
per trap per week anytime before the accumulation of 200 DD after biofix. In moderate
to high-density orchards, apply two insecticide applications 14 days apart, the first
at 150 to 250 DD after biofix: 150 if using a product which depends primarily on
ovicidal activity for control (such as Confirm or Intrepid), and 250 if using an
insecticide that has contact activity against larvae (such as organophosphates and
pyrethroids). (FH)
7. 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 |
| 4-17 | 39 | 9 | 0 | 0 | 23 | 0 | 0 | 4 |
| 4-18 | 6 | 0 | 0 | 0 | 1 | 0 | 0 | 0 |
| 4-24 | 49 | 0 | 14^ | 0 | 2 | 0 | 0 | 3 |
| 4-27 | 9 | 0 | 15 | 0 | 0 | 0 | 0 | 4 |
| 5-3 | 13 | 0 | 25 | 0 | 0 | 0 | 0 | 1 |
| 5-9 | 10 | 1 | 22 | 0 | 0 | 0 | 0 | 0 |
* 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.
^Biofix for OBLR in Davidson
County was April 24.
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 |
| 4-17 | 19 | 5** |
| 4-24 | 17 | 17 |
| 5-1 | 17 | 2 |
*Biofix for OFM in Bradley County on March 29.
**Biofix for CM in Bradley County
on April 13.
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 |
| 4-10 | 1 | 16 | 0 | 0 | 0 |
| 4-15 | 9 | 60 | 6 | 0 | 1 |
| 4-17 | 0 | 13 | 1 | 0 | 1 |
| 4-21 | 3 | 14 | 0 | 0 | 0 |
| 4-28 | 10 | 3 | 2 | 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 |
| 4-17 | 1 | 18 | 3^ | 1 | 5 |
| 4-25 | 7 | 0 | 0 | 0 | 4 |
| 5-1 | 4 | 0 | 3 | 0 | 4 |
*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.
^Biofix for OBLR in Obion
County.
Additional Pheromone Trap Catches in Davidson County for 2006
Sod
Webworms (SWW), Armyworm (AW)
| SWW | AW | |
| 4-18 | 3* | 0 |
| 4-24 | 15 | 4** |
| 4-27 | 15 | 1 |
| 5-3 | 16 | 0 |
| 5-9 | 52 | 3 |
*Biofix for SWW in Davidson County for 2006.
**Biofix for AW in Davidson County
for 2006.
Knox County Pheromone Trap Catches for 2006
Tufted Apple Budmoth
(TABM)
| OFM | RBLR | OBLR | CM | VLR | TABM | |
| 5-1 | 40 | 15 | 2 | 5 | 0 | 17 |
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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