Fruit Pest News
Volume 7, No. 4 April 5, 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. Apple: Tips for Fire Blight Control During Bloom
3. Apple: Are there any Alternatives to Streptomycin?
4. Apple: Early-Season Fungicide Sprays
5. Strawberry Fungicide Reminder
6. Strawberry Plant Dip for Anthracnose Control
7. Pheromone Trap Catches and Biofixes
1. Current Conditions
Sunday night's tragic events in northwest Tennessee overshadow the weather picture. Numerous hail storms occurred across the state. Although fruit are not yet formed, blossoms may have been damaged by the hail. The rain events of Friday and Sunday caused the release of cedar-apple rust spores. However, the torrential rains that fell on Sunday are not as favorable for severe infection as light rains with extended cloudy periods. The frosts of mid- to late-March caused heavy losses on non-frost protected strawberries and peaches, but protected plantings probably came through with minimal losses. (SB)
2. Apple: Tips for Fire Blight Control During Bloom
The bloom period is a key time for fire blight management in apple and pear. It is during bloom that many of the most damaging fire blight infections take place. It is also the time at which streptomycin sprays are most effective . . . in fact, we no longer recommend streptomycin after bloom (unless there is a hailstorm) because of its lack of effectiveness against the shoot blight phase. The following points should help you to use streptomycin efficiently.
3. Apple: Are there any Alternatives to Streptomycin?
We must protect streptomycin from the development of resistance in the fire blight organism. Unfortunately, there aren't many suitable alternatives to streptomycin for fire blight control, which means there is a lot of selection pressure on the bacterium to adapt to streptomycin. We need to minimize usage of streptomycin to avoid as much of this pressure as we can. That is one of the goals of the MaryBlyt program. Another way to reduce usage of strep is to use alternative control products. You may have heard about a new biological control product. Full EPA registration for a product called Bloomtime Biological is anticipated by July 2006. If this occurs, it will be available for use by pome fruit growers during the spring bloom period in 2007. Another biological product, BlightBan A506, has been available for about 10 years and provides some control. The plant resistance activators such as Aliette generallly have not fared well in fire blight control tests. (SB)
4. Early-Season Apple Fungicide Sprays
Trees are tight cluster to bloom. Scab control at this time is a must. If scab was abundant last year, the first application should have been made at green tip. Scab should be treated early to prevent primary scab infections and thus break the disease cycle. Also, it is important to avoid early infections on sepals (calyx), as these are difficult to detect and can provide secondary inoculum throughout the early part of the growing season.
There are several different strategies for scheduling scab sprays. The selection of a spray program (what fungicide to use and how often) depends on factors such as other disease organisms present and the ability to obtain good coverage of the trees with the sprays. If cedar-apple rust or powdery mildew are a threat, it is probably best to control scab with a sterol-inhibiting fungicide (Nova, Procure, or Rubigan), because control of all three diseases would be obtained. Tank mixing with mancozeb or captan would improve the protectant ability and discourage the development of resistance to the sterol inhibitor (SI). Do not use captan within 2 weeks of an oil spray.
The 3- to 4-day curative activity of the SI fungicides makes them useful at tight cluster in case some scab infections occurred prior to that time. The SI/protectant combination allows you to space the applications 7 to 10 days apart.
Where cedar-apple rust is a problem, mancozeb or ziram should be used as the protectant, to be mixed with the SI. The strobilurin fungicides Flint and Sovran can be used in lieu of the SI's, but I recommend reserving these materials for use during the summer. They may only be applied 4 times per year, and they play a more valuable role during the summer than during the spring.
Overwintering of powdery mildew is highly dependent on winter weather. Since we did not have prolonged cold temperatures this winter, there should be abundant inoculum in orchards that had mildew last year. If weather conditions are favorable (cool, wet) for mildew, disease pressure could be high on susceptible varieties. Be sure to use an SI on such blocks (see previous paragraph regarding the use of strobilurins). (SB)
5. Strawberry Fungicide Reminder
In this strawberry bloom season, remember to pace yourself on the use of strobilurin fungicides (Quadris, Abound, Cabrio, Pristine). They are limited to 5 applications per crop, either individually or collectively. The most important role of this class of fungicides in strawberry production is control of anthracnose, and the critical time for anthracnose control is the harvest period. If your field has a history of anthracnose, you should reserve most of your allotment of strobilurins for the harvest period. Why? -- If you apply a strobilurin every 7 days during harvest, with a maximum of 2 consecutive applications before rotating, you could make 4 applications of strobilurins during a 5-week period. Granted, Switch is just as effective against anthracnose, but it, too, has a 5-application limit per crop, and is needed for Botrytis control during bloom.
If anthracnose is suspected of being present, I would minimize the use of strobilurins during bloom. Captan or thiram, tank-mixed with the Botrytis materials, should handle the light anthracnose activity that is likely to occur during bloom. (SB)
6. Strawberry Plant Dip for Anthracnose Control
Strawberry anthracnose sometimes enters a field on infested plants. The causal fungus may be present on the crown, root, and stem surfaces, or it may be internal, as infections that are not yet visible. Research has shown that the incidence of anthracnose in the field can be greatly reduced if transplants are dipped in appropriate treatments before planting, to kill the surface spores. These treatments will not rid the plants of anthracnose infections, because they are internal and beyond the reach of the chemicals.
The azoxystrobin products, Quadris and Abound, are labeled for use as strawberry plant dips. Wash soil off roots before dipping. Mix 5-8 fl oz of Quadris or Abound per 100 gal of water. Dip plants by immersing completely for 2 to 5 minutes. Plant treated plants as quickly as possible. The hydrogen dioxide product, OxiDate, is also labeled for this use. Mix 1 gal per 100 gal of water, immerse, remove, and allow to drain. Do not rinse. Plant as soon as possible after treatment. Use personal protective equipment as specified by the labels when dipping. (SB)
7. Pheromone Trap Catches and Biofixes
Nashville (Davidson County) Pheromone
Trap Catches for 2005
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 | -- | 2 | 0 | 0 | 2 |
* 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.
Bradley County Phoromone Trap Catches for 2005
| OFM | |
| 3-29 | 3* |
| 4-3 | 26 |
*Biofix for OFM in Bradley County on March 29.
Putnam County Pheromone
trap Catches for 2005
| 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 |
*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 2005
| 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.
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.