Fruit Pest News
Volume 7, No. 8 May 3, 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. Strawberry Diseases
2. Fire Blight: Secondary Bloom
3. Blackberries: Fungicide Spray Schedule
4. Blackberry Anthracnose
5. Greenhouse Tomato Leaf Distortion
6. Oriental Fruit Moth
7. Pheromone Trap Catches and Biofixes
1. Strawberry Diseases
The first report of the bacterial disease, angular leaf spot, was confirmed on a sample submitted on May 1 from plasticulture Chandler. Angular leaf spot can be expected to spread within a field during the showers we are getting this week. Sprinkler irrigation should only be used for frost protection in strawberries, primarily because of this disease, which flourishes under wet conditions. Chemical control is extremely limited. Fixed copper sprays have slight suppressive effect on epidemic development, but the main determining factor in disease spread, or lack thereof, is rainfall.
Don't allow all the distractions encountered during the establishment of a plasticulture crop to cause you to forget the most basic, but most important, production step: soil testing. One field with major problems was just tested to have a soil pH of 4.9! Have your pH where you want it before you lay plastic. (SB)
2. Fire Blight: Secondary Blooms
Most apple varieties have finished blooming, with the exception of secondary (tag-on) blooms. We do not recommend the use of streptomycin after bloom because of its ineffectiveness against shoot blight infections, and because such use increases the risk of resistance developing. The time to prevent shoot blight is during bloom (with streptomycin applications) and during the dormant period (by pruning out cankers).
Beware, however, of tag-on blooms. Streptomycin sprays may be needed as long as they are present. Loosing a few late blossom clusters to fire blight may not seem important, but the bacteria produced by just a few infected blossoms can result in a significant shoot blight epidemic. In such warm weather, tag-on blooms can easily become infected and negate all your hard work in preventing infections during the bloom period! If only a few secondary blooms are present, it would be worth your while to remove them by hand, because they potentially represent the beginning of a fire blight epidemic! (SB)
3. Fungicide Spray Program for Blackberries
Our blackberry fungicide recommendations are provided in the regional spray guide. I am providing a simplified program, below, for those who may need some help in designing a program.
The rosette (double blossom) schedule is based on research conducted by Dr. Barbara Smith, USDA-ARS, who has found that Pristine and Switch are among the most effective labeled fungicides for rosette control. Primocanes need protection in rosette fields as long as infected blooms are open, which can last from the bloom period until after harvest ends. Remember that the benefits of a rosette spray program will not be seen until the following spring, when this year's primocanes come out of dormancy.
Rates can be obtained from PB1197 or the product labels. Always read and follow label directions.
|
Application number (Applied every 10-14 days) |
If rosette disease is expected |
If anthracnose is expected, but not rosette |
|
1 (early bloom) |
Pristine |
Captan |
|
2 |
Switch |
Pristine |
|
3 |
Pristine |
Captan |
|
4 |
Switch |
Pristine |
|
5 |
Pristine |
Captan |
|
6 (harvest begins) |
Switch |
Pristine |
|
7 |
Pristine |
Elevate or Switch |
|
8 |
Switch |
Pristine |
|
9+ (after harvest) |
* |
* |
|
* Pristine and Switch are limited to 4 applications per year -- If rosette blooms are still present after harvest, fixed copper or Bordeaux mixture can be used, but can cause plant damage in hot weather. For anthracnose control after harvest, Captan can be used (limitation of 5 applications per year). For cane and leaf rust control, Nova can be used. Abound or Cabrio can be substituted for Pristine, but are not as effective against Botrytis. Captan is not recommended for use during harvest because of a 3-day preharvest interval. (SB) |
4. Blackberry Anthracnose
Anthracnose is characterized by dull brown, scabby, flattened, cracked drupelets on blackberry fruit. On ripe berries, recently-infected drupelets show a light purple discoloration. Leaf lesions are small, purple spots with white to tan centers. Spores produced by these spots can splash to the berries and produce the scabby berry condition. The fungus overwinters on leaf and berry debris and on canes.
I have found in my research trials with Benlate that control of blackberry anthracnose was best when applications were made at early bloom and at two-week intervals for two additional applications. In plantings with a history of anthracnose, this protectant schedule is recommended, using captan and a strobilurin (Pristine, Abound, or Cabrio). More frequent applications may be needed in excessively rainy weather. Do not apply a strobilurin more than twice consecutively before switching to captan. After harvest, floricanes should be removed and destroyed, to reduce the amount of carryover inoculum. (SB)
5. Greenhouse Tomato Leaf Distortion
There have some cases this spring of leaf distortion in greenhouse tomatoes. It is difficult to diagnose these cases. The damage appears to be chemical in nature, but what type of chemical is anyone's guess. What is important to the grower is where the damage is coming from. The potting mix and the greenhouse environment are two obvious potential sources. If the symptoms are widespread in the greenhouse, the grower should do an experiment to try to get information on the source of the damage.
Plant healthy transplants in containers filled with mix from the same source as the damaged plants, if it is available. Place one half of these plants in the greenhouse in which the damage occurred and the other half at another location. If the damage appears in both sets of plants, the potting mix would be implicated; if it occurs only in your greenhouse, the source of the damage would be the greenhouse. You would then need to try to track down the actual source of the chemical drift. (SB)
6. Oriental Fruit Moth
In the Southeast, early season insecticides for plum curculio,
plant bugs and stink bugs usually provide excellent control of OFM. a pheromone
trap threshold of 10 moths/trap/week should be used after third cover. In peach,
first generation OFM larvae feed primarily on tender vegetative growth. subsequent
OFM generations feed inside the fruit.
Pheromone trap catches and degree-day
(DD) models can be used to decide if and when to spray. The biofix is determined
by trap catches when two or moths are first caught in the spring. The biofixes for
Bradley, Putnam, Obion, and Davidson Counties were March 29, March 31, April 3 and
April 4, respectively. Begin to accumulate daily DD (base temperature of 45 F) when
the male flight (biofix) occurs. In peach for low OFM-density orchards, a single
insecticide application can be applied against OFM at 600 DD after biofix. A low
density OFM orchard is one in which less than 0.5 percent of the fruit was damaged
by OFM the previous year and pheromone trap catches do not exceed 10 moths/trap/week
anytime before the accumulation of 500 DD after biofix. In moderate to high-density
OFM orchards, two insecticide applications are applied 14 days apart, the first at
500 DD after biofix.
In apple, first-generation egg laying is usually low
and only one insecticide application between 400 and 500 DD after biofix is necessary,
which usually coincides with petal fall. (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 |
* 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 Pheromone 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** |
*Biofix for SWW in Davidson County for 2006.
**Biofix for AW in Davidson County
for 2006.
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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