Fruit Pest News
Volume 6, No. 4 April 12, 2005
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 and Pest Reports
2. Grape: Early-Season Disease Control
3. Blueberry: Twig Blight
4. Apple: MaryBlyt Update
5. Tree Fruit: European Red Mite and San Jose Scale
6. Tree Fruit: Pheromone Trap Catches and Biofixes
1. Current Conditions and Pest Reports
The weather has been seasonal lately and plant development remains behind normal. Apples have begun bloom, peaches are at petal fall, most strawberries and blueberries are blooming, and blackberries have two-inch shoots. We have been amazingly free of frost for the last several weeks. The weather for the next week is supposed to be seasonal, with highs in the 70's and lows in the 40's and 50's, with a chance for storms.
Rhododendron borer was found damaging a blueberry bush. Significant damage to an Arapaho blackberry field was caused by cane blight, Coniothyrium fuckelii. (SB)
2. Early-Season Grape Disease Control
Grapes have begun growth and many are at the 1-inch bud stage (and growing rapidly) at which the first black rot spray is recommended. Other diseases such as Phomopsis cane and leaf spot and powdery mildew can also begin activity at this stage of growth. Choose a fungicide(s) based on the history of disease problems in the vineyard, using an efficacy table such as the one on page 26 in the small fruit spray guide, PB1197. Sterol inhibitor fungicides can be used in the early sprays, but keep in mind that they do not provide control of Phomopsis or downy mildew. The multi-site inhibitors (e.g. captan, mancozeb, maneb, ziram) are better choices for control of Phomopsis and black rot. The sterol inhibitors can be tank mixed with the multi-site inhibitors to provide control of powdery mildew and systemic control of black rot. Strobilurins have the broadest spectrum of activity, but are more expensive and are limited to 4 applications per year.
Considering the arsenal of fungicides available to the grape grower, it is a good idea to become familiar with the classification of the products, as listed on page 50 of the spray guide. (SB)
3. Twig Blight of Blueberry
Blueberry growers should look for twig blight, caused by Phomopsis vaccinii, beginning in early spring, since the symptoms can begin to show shortly after budswell. Control measures can then be initiated.
Individual buds turn brown and die, followed by browning of the bark around the bud as the fungus moves from the blighted bud into the twig. The infection usually advances inside the twig until most or all of the flower buds on a twig are killed. Click here http://www.ces.ncsu.edu/depts/pp/notes/Fruit/fdin010/fdin010.htm to see images of these symptoms. Click the images to enlarge them. The dieback does not progress into the older wood, making twig blight easy to distinguish from stem blight, caused by Botryosphaeria dothidea. Frost injury can also resemble twig blight. Twig blight lesions usually continue to enlarge and may be centered around a bud.
It is helpful to prune out and destroy the infected twigs, but this should be done prior to the bloom period, for maximum benefit. Many spores are released from infected twigs beginning shortly after bud break. Those that land in opening buds germinate and invade the twig. However, all is not lost if you have not done this. Removing infected twigs between this time of year and August is helpful in that it reduces twig blight in next year's crop. That is because dead twigs continue to produce spores, which land on and infect buds that become next year's flowers.
Preventive fungicide applications may be needed in plantings in which twig blight has been a problem in the past. Captan, ziram, Cabrio, and Pristine are the most effective fungicides for twig blight.
The highbush varieties Murphy and Harrison are highly susceptible to twig blight and will surely need a control program. Croatan is moderately susceptible, while Reveille, Cape Fear, Bluechip, and Wolcott are relatively resistant. Some rabbiteye varieties are susceptible, especially Delite. (SB)
4. MaryBlyt Update
The MaryBlyt program for fire blight prediction indicates infection when 4 conditions occur: (i) any blooms are open; (ii) rain or dew occurs; (iii) the average temp for the day is 60 or above; and (iv) there have been enough accumulated heat units to allow colonization of the blossoms by the bacteria. The risk of infection is rated as "low," "medium," "high," or "infection." These ratings correspond to any one, two, three, or four of the previously-mentioned conditions, respectively. All the program needs from the operator is the high and low temperature for each day beginning at green tip, and rainfall or dew for each day beginning at first open bloom.
MaryBlyt guides your streptomycin spraying decision-making with this rule: You should spray if the risk of an infection is high and an infection is predicted for the next day. You use the weather forecast with the prediction function of MaryBlyt to determine whether an infection is predicted for the next day. (SB)
5. European Red Mites and San Jose Scale
Mites: Check branches with a hand lens or
a dissecting microscope. The reddish eggs can be easily seen. While inspecting
some peach branches today, I saw unhatched eggs and some active mites. Oil sprays
should reduce the number of mites that you start out with in the spring.
San
Jose Scale are also best controlled with dormant and delayed dormant sprays each
year. They can build up to damaging numbers, especially if a year of oil sprays
is missed. I found immature male scale and one adult male on a scale encrusted peach
branch. There were also some immature female scale. Wrap black electrical tape
around the branch and coat it with a thin layer of petroleum jelly. Observe each
week for the presence of yellow, newly emerged crawlers. Treat crawlers this spring
with Esteem if San Jose scale is a problem. (FH)
6. Pheromone Trap Catches and
Biofixes
In Nashville at the Ellington Center, two black cutworms were caught
in the pheromone trap on 4-12-05. Black cutworm moths migrate north with the prevailing
winds each spring. They are pests of turfgrass, vegetables, and some ornamental
plants (especially flowers).
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)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | |
| 3-11 (put out RBLR trap) | -- | 0 | -- | -- | -- | -- | -- |
| 3-14 | -- | 16* | -- | -- | -- | -- | -- |
| 3-18 (put out OFM, OBLR,CM, VLR traps) | -- | 1 | -- | -- | -- | 0 | -- |
| 3-21 | 0 | 17 | 0 | 0 | -- | 0 | -- |
| 3-24 | 0 | 19 | 0 | 0 | -- | 0 | -- |
| 3-29 | 0 | 23 | 0 | 0 | -- | 0 | -- |
| 3-30 (put out GBM & BCW traps) | 0 | 10 | 0 | 0 | 0 | -- | |
| 4-4 | 1 | 34 | 0 | 0 | 4** | 0 | 0 |
| 4-7 | 1 | 12 | 0 | 0 | 2 | 0 | 0 |
| 4-12 | 5 | 12 | 0 | 0 | 10 | 0 | 2*** |
* Biofix for RBLR in Davidson County estimated as occurring on March 12.
**Biofix
for GBM in Davidson County is April 4.
***First catch of BCW in Davidson County
on April 12.
Bradley County Phoromone Trap Catches for 2005
| OFM | RBLR | |
| 3-10 (put out two RBLR traps) | -- | -- |
| 3-12 | -- | 2* |
| 3-21 | -- | 45 |
| 3-23 (put out four OFM traps) | -- | -- |
| 3-25 | 28** | -- |
| 3-28 | 18 | 41 |
| 4-4 | 67 | 12 |
*Biofix for RBLR in Bradley County on March 12.
**Biofix for OFM in Bradley
County on March 25.
Putnam County Pheromone trap Catches for 2005
| OFM | RBLR | OBLR | CM | VLR | |
| 3-21 | 0 | 52* | 0 | 0 | 0 |
| 3-23 | 0 | 10 | 0 | 0 | 0 |
| 3-25 | 0 | 12 | 0 | 0 | 0 |
| 3-28 | 0 | 20 | 0 | 0 | 0 |
| 3-30 | 0 | 0 | 0 | 0 | 0 |
| 4-1 | 0 | 5 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County on March 21.
Obion County Pheromone
Trap Catches for 2005
| OFM | RBLR | OBLR | CM | VLR | |
| 3-25(put out traps) | -- | -- | -- | -- | -- |
| 3-28 | 0 | 0 | 0 | 0 | 0 |
| 4-4 | 1 | 9* | 3** | 8*** | 0 |
| 4-11 | 3**** | 0 | 0 | 0 | 0 |
*Biofix for RBLR in Obion County estimated to be on March 12 (trap not out early
enough).
**Biofix for OBLR in Obion County on April 4 (waiting for confirmation).
***Biofix
for CM in Obion County on April 4 (waiting for confirmation).
****Biofix for OFM
in Obion County on April 11.
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 2005 The Unversity 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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