Fruit Pest News
Volume 8, No. 11 May 22, 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 and Reports
2. Caterpillar Pests of Vegetables
3. Striped Cucumber Beetle
4. Grapes: Disease Control Needs During the Bloom Period
5. Stone Fruit: Leucostoma (Perennial) Canker
6. Planning for Cucurbit Powdery Mildew Season
7. Pheromone Trap Catches
1. Current Conditions and Reports
First report for the year in TN: Tomato spotted wilt virus on home garden tomato, Davidson County, May 21. No doubt, there will be many more to come.
Distinguishing freeze injury from fire blight on apple and pear can be difficult this year. The first round of fire blight blossom blight was just beginning to show when the freeze hit, causing some fire blight to be passed off as freeze injury. That said, most of what you are seeing is freeze injury, not fire blight. To make matters worse for diagnostic efforts, there are other diseases that can resemble fire blight, but they are not common.
Flocks of cedar waxwings have destroyed entire fields of strawberry fruit in the Overton County area. Extension agent Ron Johnson reports that the birds are so bad that all surfaces near the fields are covered with the birds' red droppings. Scare tactics have not worked in repelling the flocks. These birds have totally finished off the crop in that area. A very scary situation. (SB)
2. Caterpillar Vegetable Pests
While I have not detected black cutworms in
my traps, they have flown north from their southern overwintering sites. Monitor
sweet corn crops for this pest. Scout your fields and if 2% of the plants are cut,
then it will pay to use an insecticide for cutworms. Recommended insecticides include
Lorsban 4E, Asana XL, Warrior 1 CS, Ambush, Pounce, Sevin, Capture 2 EC, and Mustang
Max 0.88 EC. Armyworm moth activity has particularly increased over the past three
weeks. The resulting caterpillars feed on sweet corn and all types of other grassers.
Unlike the black cutworm that lays single eggs on the plant, armyworms lay masses
of eggs. When conditions are right, armyworm populations can seem to explode. In
the later caterpillar stages called instars, they do most of their feeding damage.
Sweet corn is most susceptible to armyworms prior to silking, before insecticide
sprays for corn earworm and European corn borer begin. (FH)
3. Striped cucumber
beetle
Striped cucumber beetles overwinter as adults and feed on the cucurbit
transplants or seedlings in the spring. They can do extensive feeding damage to
young plants but the primary concern is bacterial wilt. Since they can transmit bacterial
wilt to cucurbits (muskmelons and cucumbers are most susceptible), use an insecticide
to prevent bacterial wilt when cucumber beetles exceed 0.1 to 1 per plant. Admire
can be used at planting as a preventative insecticide. Otherwise, use a recommended
foliar applied insecticide. Organic growers can use a floating row cover until bloom
to exclude the cucumber beetles. (FH)
4. Grapes: Disease Control Needs During the Bloom Period
Botrytis bunch rot can be a problem in tight-clustered French hybrid or Vinifera varieties. The pre-bloom to early bloom period is a critical time for controlling black rot and other diseases. Early bloom is the time for the first application of a Botrytis fungicide. This very warm weather will move the grape vines through the bloom period rapidly, making it difficult to get two Botrytis sprays in. We have several classes of chemistry available to us in our efforts to combat resistance in the Botrytis fungus. Select more than one botryticide.
Scala 5SC, Vangard 75WG, Elevate 50WG, and Rovral 50WP are botryticides that do not provide black rot control, so another fungicide should be added to the tank. Sterol inhibitor (Nova, Elite, Bayleton, etc.) are preferred because of their locally systemic activity. Since the sterol inhibitors are not effective against Phomopsis or downy mildew, an effective product such as mancozeb or captan should also be applied. Pristine 38WDG is effective against all of these diseases, with only a slight sacrifice in Botrytis activity.
For Botrytis control, Vangard is used at 10 oz per acre at early bloom and at berry touch, veraison, or preharvest (20 oz per acre per year, 7-day PHI). See the label for precautions for use near aquatic areas. Elevate is used at 1 lb per acre at early bloom, bunch pre-close, and veraison, up to and including the day of harvest (up to 3 applications). Rovral 50WP may be applied at 1.5 to 2 lb per acre at early bloom, prior to bunch closing, veraison, and preharvest (7-day PHI). Although the Rovral label allows 4 applications, it is suggested that no more than 3 applications be made, in light of resistance problems that have occurred in other areas. Scala is used at 18 fl oz per acre when used alone and at 9 fl oz per acre in tank mixes (36 fl oz per acre, 7-day PHI). (SB)
5. Leucostoma Canker of Stone Fruit
Leucostoma canker, also called perennial canker, Cytospora canker, and Valsa canker, can be an important disease of stone fruit in the South. Affecting twigs, limbs, and trunks, the disease reduces fruiting surface and can shorten tree longevity. The causal fungus enters wood through wounds or infected twigs. Pruning wounds are the most common entry point, but winter injury, borer wounds, and southwest sunburn injury are other possibilities. Cankers are often elliptical in shape and may have a dry, blackened appearance.
In orchards in which Leucostoma canker is a problem, delay dormant pruning until a warm, dry period occurs in the spring. Host defenses will be active during such conditions and will resist infection or limit advancement of infections. Try to keep the tree actively growing with proper fertilization and, if needed, irrigation, but allow it to slow down in late summer. Follow recommended tree training practices to minimize narrow limb crotches and shaded, weak limbs that are susceptible to Leucostoma. To encourage rapid healing-over, cut branches just beyond the ridge of the thickened bark which connects them to larger limbs. Do not leave pruning stubs. Avoid large pruning cuts. It is helpful to surgically remove cankers from trunks or scaffold limbs. Remove in midsummer, then burn or bury cankers. Do not apply a wound dressing. (SB)
6. Planning for Cucurbit Powdery Mildew Season
Cucurbit powdery mildew typically does not begin until mid-summer, but it is not too early to plan your fungicide program and make sure the products you wish to use are available from the dealers. Don't forget about the occurrence of strobilurin-resistant powdery mildew. Resistant strains began appearing across the country in 2002, and now appear to cause a re-thinking of powdery mildew control plans. You will not know whether the powdery mildew you get in your field is resistant to the strobilurins (Quadris, Cabrio, Flint) until it is too late, when you fail to get good control. If that is too big a risk for you, use sulfur or a sterol inhibitor (Nova or Procure). The strobilurin fungicide Pristine has a second ingredient that offers some protection against powdery mildew. The zoxamide fungicide Quintec can be used on melons and hopefully will receive a registration for all cucurbits in the near future; it is highly effective against powdery mildew.
For the last two years, powdery mildew control by the sterol inhibitors has been significantly reduced in pumpkin fungicide trials at Springfield, although not as bad as that by the strobilurins. Loss of sensitivity to the SI's by the powdery mildew population resulted in only about 50% control. With the threat of resistance to the sterol inhibitors in mind, you should rotate occasionally to sulfur.
The strobilurins provide control of other diseases such as microdochium blight and downy mildew and, because of this, are usually applied alone. Sulfur and the sterol inhibitors are specific to powdery mildew and should be tank mixed with broad-spectrum fungicides such as chlorothalonil or mancozeb. Remember that sulfur is strictly a surface protectant and coverage of both sides of the leaves is needed for good control. (SB)
7. Pheromone Trap Catches
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), cabbage
looper (CL)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | DBM | AW | CL | |
| 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, CL) | 10 | 1 | 0 | 0 | -- | 0 | 0 | -- | 0 | -- |
| 4-5 | 11 | 0 | 0 | 0 | 4*** | 0 | 0 | 0 | 0 | 0 |
| 4-10 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-17 | 2 | 1 | 0 | 0 | 2 | 0 | 0 | 0 | 0 | 0 |
| 4-23 | 28 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-25 | 8 | 0 | 2**** | 0 | 0 | 0 | 0 | 4^ | 0 | 0 |
| 4-30 | 5 | 0 | 6 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
| 5-21 | 3 | 2 | 6 | 0 | 0 | 0 | 0 | 4 | 5 | 5 |
* 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.
**** Biofix for OBLR in Davidson County was April 25.
^ Biofix for DBM
in Davidson County was April 25.
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 |
| 4-23 | 0 | 1 | 1 | 2 | 1 |
| 4-25 | 0 | 0 | 1**** | 0 | 0 |
| 4-27 | 0 | 1 | 3 | 0 | 0 |
| 5-4 | 0 | 1 | 5 | 6 | 2 |
| 5-11 | 0 | 15 | 0 | 0 | 1 |
*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.
**** Biofix
for OBLR in Putnam County for OBLR was April 25.
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 |
| 4-30 | 7 | 0 | 10*** | 0 | 17**** |
| 5-7 | 10 | 0 | 3 | 0 | 2 |
| 5-17 | 11 | 3 | 7 | 1 | 14 |
| 5-21 | 0 | 7 | 1 | 0 | 5 |
* 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.
*** Biofix for OBLR
in Obion County on April 30.
**** Biofix for VLR in Obion County on April 30.
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.
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.
