Fruit Pest News
Volume 9, No. 8 May 14 2008
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. First Reports for the Year in TN
2. Peach Pest Management - Diseases
3. Grapes - Botrytis and other Diseases
4. Small Batch Preparation of Pesticides
5. Phyto Reminder for Quadris/Abount
6. Obliquebanded Leafroller (OBLR) and other Pheromone Trap Activity
7. Pheromone Trap Catches and Biofixes
1. First Reports for the Year in TN
Black rot of grape, May 8, Williamson County; strawberry anthracnose, May 9, Sumner County; tomato spotted wilt virus on tomato, May 13, Madison County. Thank you for the reports.
Also, soybean rust has been confirmed on kudzu in several locations along the coast from East Texas to Florida. Two of the counties in Florida reported soybean rust from snap beans.
2. 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)
3. Grapes: Botrytis and Other Diseases
The mild temperatures we have had this spring have resulted in a grape crop slightly behind normal in development. That provides plenty of time to get your Botrytis sprays on. The bloom period is the key time for prevention of Botrytis bunch rot. Following are the preferred fungicides for Botrytis control.
Vangard 75WG, Elevate 50WG, Rovral 50WP, and Scala 5SC 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.) are preferred because of their locally systemic activity. Since the botryticides and sterol inhibitors are not effective against Phomopsis or downy mildew, an effective product such as mancozeb or captan should also be applied. 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). Scala is used up to 2 times at 18 fl oz per acre, with a 7-day PHI. Rovral 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. Resistance management is very important in dealing with Botrytis - plan on using at least 2 of these materials, applied in alternation. Rotation with a fungicide that does not have Botrytis activity does not count as a rotation. (SB)
4. 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)
5. 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 Handcraft, Empire, and Jonamac. Note: Azoxystrobin injury on Gala could be mistaken for Glomerella leaf blotch, to which Gala is also susceptible. (SB)
6. Obliquebanded Leafroller (OBLR) and other Pheromone Trap Activity
Three
OBLR moths were caught in the Nashville pheromone trap (May 12 biofix). These moths
are much larger than redbanded leafrollers, grape berry moths, codling moths, and
Oriental fruit moths. Note that the redbanded leafroller moths have not been caught
since April 29. Oriental fruit moth trap catches have been very low this spring
in the Nashville (Davidson County), Bradley County, and Putnam County locations.
Codling moth trap catches have been reported only at the Bradley County location.
In earlier newsletters, we discussed the lack of tree fruit in 2007 and the potential
effect on pest numbers this year. So far in our trap catch data, it looks like we
are seeing a reduction in Oriental fruit moths and in at least some locations, codling
moths. (FH)
7. Pheromone Trap Catches and Biofixes (FH)
Nashville
(Davidson County) Pheromone Trap Catches for 2008
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)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | DBM | AW | CL | |
| 3-10 (Put out RBLR trap) | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-13 | -- | 2* | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-19 | -- | 5 | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-31 | -- | 7 | -- | -- | -- | -- | -- | -- | -- | -- |
| 4-1 (put out BCW, OFM, CM, VLR, OBLR traps) | ||||||||||
| 4-9 | 0 | 2 | 0 | 0 | -- | 0 | 0 | -- | -- | -- |
| 4-11 (put out AW trap) | 2** | 0 | 0 | 0 | -- | 0 | 0 | -- | -- | -- |
| 4-17 (put out GBM, DBM, CL traps) | 0 | 0 | 0 | 0 | -- | 0 | 0 | -- | 0 | -- |
| 4-18 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-24 | 2 | 0 | 0 | 0 | 3*** | 0 | 0 | 0 | 0 | 0 |
| 4-29 | 2 | 16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| 5-12 | 6 | 0 | 3^ | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
* Biofix for RBLR in Davidson County was March 13.
**Biofix for OFM in Davidson
County was April 11.
***Biofix for GBM in Davidson County was April 24.
^Biofix
for OBLR in Davidson County was May 12.
Bradley County Pheromone Trap Catches
for 2008
tufted apple bud moth (TABM)
| 3-18 (put out OFM trap) | OFM | CM | TABM |
| 4-6 (put out CM trap, TABM) | 0 | -- | -- |
| 4-12 | 0 | 1 | 4 |
| 4-14 | 0 | 0 | 2 |
| 4-19 | 0 | 1 | 0 |
| 4-21 | 0 | 0 | 23 |
| 4-29 | 1 | 5 | 14 |
| 5-5 | 0 | 2 | 5 |
| 5-11 | 0 | 2 | 13 |
Putnam County Pheromone trap Catches for 2008
| 3-16 (put out RBLR, OBLR, VLR) | OFM | RBLR | OBLR | CM | VLR |
| 3-21 | -- | 12* | 0 | -- | 0 |
| 4-1 | -- | 5 | 0 | -- | 0 |
| 4-9 (put out OFM, CM) | -- | 7 | 0 | -- | 0 |
| 4-13 | 0 | 0 | 0 | 0 | 0 |
| 4-22 | 0 | 9 | 0 | 0 | 0 |
| 4-29 | 0 | 0 | 0 | 0 | 0 |
| 5-4 | 0 | 0 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County estimated as prior to March 21 (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 2008 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.
Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating. UT Extension provides equal opportunities in programs and employment.
