Fruit Pest News
Volume 7, No. 6 April 19, 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. Apple: Scary Conditions for Fire Blight
2. Apple: Powdery Mildew
3. Peach Disease Control
4. Blackberry: Time to Watch for Rosette Disease
5. Tomato: Beware of Spotted Wilt this Year
6. Plum Curculio
7. Grape and Vegetables: Venon 70SG Insecticide
8. Pheromone Trap Catches and Biofixes
1. Apple: Scary Conditions for Fire Blight
Temperatures have been in the 80's for almost a week. Fire blight bacterial populations thrive under these warm conditions, building up on the surfaces of the wood. The bacteria are harmless until they are placed on an open flower and moisture occurs, allowing infection of the blossom. With the bacterial population that is present now, all that is needed for a serious outbreak of fire blight is rainfall. The forecast for Tuesday night and Wednesday is for a chance of thunderstorms and strong winds. If you have not applied streptomycin to your susceptible varieties within the last 4 days, do it now. If you receive rain or a dew, you will no doubt get infections. Streptomycin is most effective if applied the day before or the day of an infection. With the warm weather predicted for the next several days, a repeat application will probably be needed in 3 days, because the population will rebound. Spray intervals can be extended when cool weather occurs, and streptomycin applications should be discontinued when the petals fall. The upshot of this heat wave is that plant development has been rapid, resulting in a short bloom period. (SB)
2. Powdery Mildew of Apple
The mild winter followed by a dry spring may produce some powdery mildew conditions. A mild winter allows for good survival of the mildew-infected buds, and dry weather aids conidial germination and fungal growth of powdery mildew fungi. Watch for shoots that appear to be growing out entirely white, especially on inner, shaded sprouts. These shoots are developing from buds that were infected with powdery mildew the previous season. Fungicide protection is needed until terminal buds are set. The best mildewcides are the sterol inhibitors (Nova, Rubigan, Procure) and the strobilurins (Sovran, Flint, Pristine). (SB)
3. Peach Disease Control
Many peach cultivars are now at the shuck fall stage or past it. In this heat, plants are developing so fast that you really have to hustle to keep up with your spray program. Fungicide applications for control of peach scab should begin at the shuck split to shuck fall stage, about one week after petal fall. You shouldn't wait until all the shucks have fallen to make this application. However, the weather was clear from the time of the storms of April 7 until now, so there haven't been any scab infection periods since the fruit became susceptible.
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 usually occurs during this time favors infection. Apply fungicides on 10-day intervals until 40 days before harvest. Chlorothalonil cannot be used after the shuck fall stage. Captan, sulfur, Pristine, Flint, 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. If you are planning on using a strobilurin during the preharvest period, you should minimize strobilurin use as a scab material, to reduce selection pressure. The strobilurins were dropped from the scab sprays in this year's regional spray guide.
Shuck split is also the time to begin bacterial spot sprays on susceptible varieties. Mycoshield or FlameOut should be applied every 10 days until 3 weeks before harvest. (SB)
4. Time for Blackberry Growers to Watch for Rosette Disease
Early blackberry varieties have already started blooming. Growers should look for evidence of rosette, also known as double blossom. This fungal disease can be very destructive, and indeed has been known to drive growers out of the blackberry business. The fungus can drastically reduce yields by causing sterility of the blossoms and through its debilitating effect on the plant.The key to managing rosette is to remove the infected blossom clusters before the blossoms open. That is because all of the spores that cause new infections come from infected blossoms. The infected blossom clusters should now be apparent. They are recognized as bunchy growths consisting of multiple shoots, rather than the normal single shoot. Such growths are known as rosettes or witch's brooms. The sepals (the green, leaf-like structures that enclose blossoms) are abnormally long and pointed. When the blossoms open, they will be pinkish and ruffled.
Fungicide applications will help to control infections that result from spores that enter the planting from nearby wild blackberries. Pristine alternated with Switch can be applied at 10-14 day intervals, beginning at early bloom. Do not expect the applications to control rosette in this year's crop. Fungicides applied this year control rosette in next year's crop by protecting the new primocanes. Any rosettes you see this year arose from infections that occurred on last year's primocanes.Fungicidal control also has a place if you do not currently have rosette, but are growing a susceptible variety. Shawnee is particularly susceptible. Cherokee, Comanche, Triple Crown, and Black Satin are also quite susceptible. Chester, Hull, Lock Ness, Arapaho, and Navaho have good tolerance. (SB)
5. Tomato: Beware of Spotted Wilt this Year
Tomato growers need to pay attention to spring weather. It can have a bearing on an important summer disease, tomato spotted wilt. If you have the flexibility to choose tomato varieties at this time, it may be wise to order some spotted wilt resistant varieties, at least for part of your acreage. That's because the insect vector of this virus, called a thrips, proliferates during and after dry weather in the spring, and the disease follows suit. Early spring rainfall amounts have been used as an accurate predictor of spotted wilt severity in peanut crops in Georgia. Despite the recent tornadic weather in Tennessee, rainfall has been below normal since March 1.
Several tomato varieties have been released in recent years that have resistance to spotted wilt. Slicing type varieties with resistance include Amelia, BHN 640, Crista, Debut, and Quincy. Roma types include BHN 685 and Muriel. Since they are new, little is known about them other than the information provided by the companies. Amelia has performed well.
Spotted wilt has shown indications of becoming more problematic in tomato production in Tennessee. It may be prudent to evaluate the resistant varieties now, whether you get the disease or not, so that you will know which ones, if any, fit your system. (SB)
6. Plum Curculio
On April 12, I found a plum curculio adult that had accidentally
got stuck in the OFM trap located in a peach tree. As stated in last week's newsletter,
be sure to treat for these important pests. (FH)
7. Venon 70 SG Insecticide
Venon
is a Valent insecticide in which FIFRA Section 2(ee) recommendations have been made
and recently approved by the EPA. The first one is for additional pest control in
grapes. The pests listed are grape berry moth and multi-colored Asian lady beetles
at a rate of 1 to 3 oz/acre. While grape berry moth is commonly understood as a
pest of grapes, the multi-colored Asian lady beetle may not be. These beetles can
build up in huge numbers by late summer as they feed on aphids and other insects.
They are attracted to the mature grapes which are a carbohydrate source. During
harvest, these lady beetles can be brought in with the grape clusters. Unfortunately,
these beetles have an objectionable odor if disturbed or crushed. This can seriously
taint the favor of the grape juice and resulting wine. An application of Venom prior
to harvest (there is a one day pre-harvest interval) is meant to knock the beetles
off the clusters so they are not harvested with the grapes. This Section 2(ee) is
for use in the states of AL, CT, DE, GA, IL, IN, KY, MA, MD, ME, MI, MN, NH, NJ,
NC, OH, PA, RI, SC, TN, VA, VT, WV, and WI.
On cucurbits, fruiting vegetables,
head and stem brassica, and leafy vegetables, Venom has a Section 2(ee) for cucumber
beetle, grasshopper, harlequin bug, squash bug, and stink bug control. This Section
2(ee) is for use only within the states of AL, DE, FL, GA, MD, NJ, NC, SC, TN, and
VA. This is not for tomato varieties which produce fruit less than 2 inches in size
such as cherry or grape tomatoes. The pre-harvest interval is one day for cucurbits,
fruiting vegetables, and head and stem brassica. It is a 7 day PHI for leafy vegetables.
(FH)
8. 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 |
* 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.
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 |
*Biofix for OFM in Bradley County on March 29.
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 |
*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 |
*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.
^Waiting to verify biofix
for OBLR in Obion County.
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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