Fruit Pest News
Volume 8, No. 7 April 24, 2007
A weekly, 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. Current Conditions
2. Tomato: Beware of Spotted Wilt this Year
3. Vegetable Fungicide Seed Treatment News
4. Blackberries: Watch for Orange Rust
5. Strawberry Pest Outlook
6. Pheromone Trap Catches
1. Current Conditions
We are receiving a few showers this week, bringing some relief to plants stressed by the freeze injury and dry weather. Grape vines are finally starting to show some signs of life. On apple, cedar-apple rust lesions were first observed on April 18. Cedar galls are still producing spores when wetted, so apple trees still need protection. Trees need their leaves for future productivity, even in the absence of a current crop. The retention of leaves after the freeze by most fruit crops bodes well for their health prospects in the coming growing season. (SB)
2. 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. Rainfall has been much below normal in Tennessee this spring.
Several tomato varieties have been released in recent years that have resistance to spotted wilt. Slicing type varieties with resistance include Amelia, Bella Rosa, BHN 601, BHN 602, BHN 640, Crista, Quincy, and Talladega. Roma types include BHN 685 and Muriel. Since they are fairly new, little is known about their horticultural characteristics other than the information provided by the companies. Bella Rosa and Crista have performed well in certain areas of the state. Resistant varieties benefit from the addition of other spotted wilt control measures, since their resistance level is not complete.
Other methods of spotted wilt protection include the use of reflective mulch and insecticides. Metalized or virtually impermeable film mulch reflects light and disorients the thrips and reduces the number of infections. Attempts to reduce spotted wilt with the use of insecticides such as Admire at planting have met with limited success.
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)
3. Vegetable Fungicide Seed Treatment News
Seed treatment recommendations are not provided in the Tennessee or the southeast regional vegetable pest control guides. Following is a discussion of some of the most common fungicide seed treatment products. Your choice of a product depends on what seedling disease organism your expect to incur. Rhizoctonia is always a good bet to occur, and Pythium usually is. Whether to seek protection against Fusarium and others depends on what crop you are growing and on how much you wish to spend. Most of the products mentioned below must be applied by the seed preparer.
4. Watch for Orange Rust in Blackberries
Orange rust can be very
destructive to blackberries and black raspberries. Most of the blackberry varieties
that we grow in Tennessee are moderately to highly resistant to orange rust. However,
some varieties, such as Navaho, are quite susceptible.
The fungus causes
plants to be so stunted and weakened that they produce little or no fruit. The fungus
is systemic in the plant, and is perennial inside the below-ground parts. Once a
plant is systemically infected by orange rust, it is infected for life. It is
for this reason that removal of infected plants is recommended, to prevent spread
of the fungus to other plants.
The
time to control orange rust is in the spring. Your queue to take action is the appearance
of weak, spindly new shoots with pale green to yellowish leaves. Such plants should
be removed before they begin to produce the orange-colored, blister-like pustules
on the lower leaf surface. The orange pustules contain spores that spread to other
plants and cause new infections that may not become apparent until the following
spring.
The fungicides Nova, Pristine, and Cabrio can be used for control of orange rust. These fungicides help prevent leaf infections. They will not cure a systemically-infected plant. Begin applications soon (the orange pustules should mature and release their spores sometime in the month of May) and continue every 10 to 14 days until mid-summer. For Nova, the maximum amount is 10 oz per acre per year, and the rate per application is 1.25 to 2.5 oz per acre. Cabrio is labeled at 11 - 14 oz per acre, Pristine at 18 - 23.5 oz per acre, and the sum of the number of applications for these two materials cannot exceed four. (SB)
5. Strawberry Pest Outlook
Insect and mite populations can increase rapidly when
conditions are right. Aphids are an example of an insect that can become particularly
abundant during the spring and they can transmit strawberry viruses. For this reason,
wild strawberries should be eliminated from surrounding fields and fence rows. Fortunately,
beneficial insects can often regulate these populations if given time. Lady beetles,
syrphid fly larvae and parasitoid wasps can all help control aphids naturally. Remember,
any time that a broad-spectrum insecticide is used, the beneficial insect populations
can be significantly reduced.
The tarnished plant bug can attack the flower
buds and developing fruit. Since it injects toxic substances when it feeds with
its piercing-sucking mouthparts, injured berries stay small and woody in texture.
These knobbed fruit have the seeds grouped apically and this condition is called
button berry. Control tarnished plant bugs with bifenthrin (Brigade WSB), fenpropathrin
(Danitol 2.4 EC) or malathion when nymphs are present in the first blossoms. Another
fruit pest, the strawberry clipper can be controlled with carbaryl (Sevin). The
repeated use of Sevin or pyrethroids can reduce beneficial insect and mite populations,
which can lead to twospotted spider mite outbreaks.
When you start using
an insecticide, increased pest sampling is needed. Inspect the under side of the
strawberry leaves for signs of webbing and twospotted spider mites. Also, look at
the top of the leaf along the midvein for the first signs of spider mite feeding
(tiny chlorotic spots or stippling). Control of twospotted spider mites is usually
best achieved when control measures are taken before mite populations have a chance
to build. Twospotted spider mite populations can build quickly, especially during
hot, dry weather. Under these conditions, they can develop from an egg to an adult
mite laying more eggs in as little as 8 days. Conversely, cooler weather is not
conducive for mite outbreaks and heavy rains tend to reduce mite populations.
(FH)
6. Pheromone Trap Catches for
2007
Nashville (Davidson County)
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 | |
| 2-22 (caught one RBLR in last year's trap) put out new trap | -- | 1 | -- | -- | -- | -- | -- | -- | -- |
| 2-26 | -- | 0 | -- | -- | -- | -- | -- | -- | -- |
| 2-28 | -- | 1* | -- | -- | -- | 1 | -- | -- | -- |
| 3-2 | -- | 3 | -- | -- | -- | 0 | -- | -- | -- |
| 3-12 | -- | 50 | 0 | -- | -- | 0 | -- | -- | -- |
| 3-14 (Put out OFM, CM, OBLR, BCW) | -- | 26 | -- | -- | -- | 0 | -- | -- | -- |
| 3-20 | 0 | 33 | 0 | 0 | -- | 0 | 0 | -- | -- |
| 3-21 | 1 | 7 | 0 | -- | -- | 0 | 0 | -- | -- |
| 3-26 | 20** | 34 | 0 | -- | -- | 0 | 0 | -- | -- |
| 3-27 (put out AW trap) | 8 | 4 | 0 | 0 | -- | 0 | 0 | -- | -- |
| 3-30 | 12 | 16 | 0 | 0 | -- | 0 | 0 | -- | 0 |
| 4-2 | 18 | 18 | 0 | 0 | -- | 0 | 0 | -- | 1 |
| 4-3 (put out DBM, GBM) | 10 | 1 | 0 | 0 | -- | 0 | 0 | -- | 0 |
| 4-5 | 11 | 0 | 0 | 0 | 4*** | 0 | 0 | 0 | 0 |
| 4-10 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-17 | 2 | 1 | 0 | 0 | 2 | 0 | 0 | 0 | 0 |
| 4-23 | 28 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
* Biofix for RBLR in Davidson County was February 28.
**Biofix for OFM in Davidson
County was March 26.
***Biofix for GBM in Davidson County was April 10.
Bradley
County Pheromone Trap Catches for 2007
| OFM | CM | |
| 3-26 | 1 | 0 |
Putnam County Pheromone trap Catches for 2007
| OFM | RBLR | OBLR | CM | VLR | |
| 3-19 | 1 | 9* | 0 | 4*** | 0 |
| 3-21 | 1** | 3 | 0 | 2 | 0 |
| 3-23 | 2 | 6 | 0 | 1 | 0 |
| 3-26 | 2 | 15 | 0 | 2 | 0 |
| 3-28 | 4 | 7 | 0 | 1 | 0 |
| 3-30 | 2 | 14 | 0 | 0 | 1 |
| 4-2 | 6 | 32 | 0 | 0 | 0 |
| 4-6 | 2 | 28 | 1 | 1 | 0 |
| 4-13 | 0 | 2 | 1 | 0 | 0 |
| 4-20 | 0 | 7 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County estimated as March 2 (trap not out early enough).
**Biofix
for OFM in Putnam County March 21.
***Waiting to verify biofix for CM, many unknown
moths being caught in these traps that can easily be mistaken for CM..
Obion
County Pheromone Trap Catches for 2007
| OFM | RBLR | OBLR | CM | VLR | |
| 3-19 | 0 | 17* | 0 | 0 | 0 |
| 3-26 | 5** | 89 | 0 | 1 | 0 |
| 4-11 | 0 | 0 | 0 | 0 | 0 |
| 4-16 | 2 | 0 | 0 | 0 | 0 |
| 4-23 | 0 | 0 | 0 | 0 | 1 |
*Biofix for RBLR in Obion County estimated to be on March 2 (trap not out early
enough).
**Biofix for OFM in Obion County on March 26.
(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 2007 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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