Fruit Pest News
Volume 8, No. 15 June 19, 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. Tomato Spotted Wilt Virus in East Tennessee
2. Leaf Rolling of Tomato
3. A Spray Program for Disease Control in Cucurbit Crops
4. Spider Mites in Fruit and Vegetable Crops
5. Vegetable Insecticide Update
6. Pheromone Trap Catch Reports
1. Tomato Spotted Wilt Virus in East Tennessee
Our first report of tomato spotted wilt virus in the eastern part of the state occurred Friday, June 15. This case, in Cocke County, was also the first of the year on commercial tomatoes.
It would be prudent to keep weeds down, in and around tomato fields. The thrips vectors can build up in the weeds, and certain weeds can carry the virus. Try to control the weeds while they are small -- killing or clipping large weeds can cause the thrips to scatter onto the tomato plants. (SB)
2. Leaf Rolling of Tomato
A frequent inquiry lately has regarded rolling of tomato leaves. This is a physiological leaf roll and is related to moisture conservation by the plant during the extreme heat and drought. It is not harmful to the plant. The lower leaves roll upward and inward from the margins, and become thickened and leathery. Other factors such as viruses and herbicide injury can cause leaf rolling, but other symptoms usually accompany these conditions. Physiological leaf roll of tomato may also occur under weather conditions other than hot and dry, and often just indicates that the plant has a high carbohydrate content, which is a good thing. Leaf roll can occasionally indicate cultural stresses such as root damage during cultivation or severe pruning. Leaf roll can also be associated with excessive moisture, excessive nitrogen, and transplant shock. Although there are several possible causes of leaf roll, the most likely at this time is our weather conditions. (SB)
3. Cucurbit Crops: Spray Program for Disease Control
Your strategy for spraying your cucurbit crop (watermelons, pumpkins, etc.) for disease prevention depends on the stage of growth of the crop. Elaborate spray programs are seldom needed on young crops. Following is the spray program I recommend:
Early season:
Use a primary fungicide (chlorothalonil, mancozeb, or maneb) every 7 to 14 days (more frequently in wet weather, less frequently in dry weather). Begin the program at vine tip-over to early bloom (3 to 4 weeks after seeding). Inspect the field for disease symptoms beginning at seedling emergence so that the spray program can be started sooner than planned, if needed. Also, look for insects regularly. If microdochium blight appears in pumpkin or squash, Flint or Cabrio should be alternated with the primary fungicide. Otherwise, there is little need to rotate the primary fungicides with other fungicides in the early season. (Chlorothalonil, mancozeb, and maneb are not subject to the development of resistance, so continued use is not a problem).
Mid-Late Season:
Scout for powdery mildew when this disease becomes a threat, around mid-summer. When the first powdery mildew colonies (circular, white patches) are seen, add sulfur, Nova, or Procure to the tank with the primary fungicide (preferably chlorothalonil, when powdery mildew is present). It is no longer recommended that the strobilurin fungicides (Flint, Quadris, Cabrio, Pristine) be used for powdery mildew control, because of resistance problems. Various diseases can occur in mid-late season, and the choice of fungicides should be determined by what diseases appear in the current year, or have occurred in the field in previous years. For example, Acrobat or Ranman should be included if Phytophthora blight is in the picture. Add a fixed copper to the tank mix if angular leaf spot or bacterial leaf spot appear. The relative effectiveness of the labeled fungicides can be found in UT's Commercial Vegetable Disease, Insect and Weed Control publication. Air blast sprayers are needed when canopies become thick. Apply sprays every 7 to 14 days, depending on rainfall. (SB)
4. Spider mites
Hot, dry conditions are ideal for outbreaks of spider mites,
especially if Sevin or a pyrethroid insecticide has been used. Under these conditions,
field scouting for spider mites on a regular basis is prudent. Examine the underside
of the leaf for small amounts of webbing, mite eggs, caste skins, and active mites.
Look on the top of the leaf along both sides of the mid-vein for the first signs
of mite feeding which looks like tiny yellow or chlorotic stippling-like spots on
the leaf. In general, chemical control of hot season mites such as twospotted spider
mites should be made when active mites and when this first leaf stippling is found.
They can mature from egg to adult to eggs again in as little as 8 days in these high
80s to low 90s temperatures. In other words, you really can not give twospotted spider
mite populations a chance to get rolling. If populations get high, chemical control
might not be able to control the mites before the damage is done. Hard rains are
the best environmental factor to limit the build-up of twospotted spider mite populations.
That is something that we all could use.
We really have a good number of
miticides for use on most fruit and vegetable crops. One new insecticide/miticide
labeled for many types of vegetables and strawberry with a unique mode of action
(inhibitors of lipid biosynthesis, mode of action group 23) is spiromesifen (Oberon
2 SC). Oberon 2 SC is labeled for cucurbit vegetables, fruiting vegetables, leafy
green vegetables, brassica leafy vegetables, and tuberous and corm vegetables. This
insecticide/miticide is active against all developmental stages of mites, although
the juvenile stages are often more susceptible than the adults. It is labeled for
control of whiteflies and psyllids on some of these crops.
Fenproximate is
a insecticide/miticide first labeled for ornamental crops (Akari 5 SC) that is now
available for pome fruit as FugiMite 5EC and Portal 5 SC. In pome fruit, it is labeled
for mites such as twospotted spider mite, European red mite and apple rust mite (suppression
only), in addition to leafhoppers, mealybugs and pear psylla (on pear). This product
has contact activity which causes the pests to stop feeding and laying eggs. It could
take mites 3 to 7 days to finally die. FugiMite and Portal both have a 14-day preharvest
interval (PHI).
Another miticide labeled for use on apples (14 day PHI),
grapes (14 day PHI), as well as peaches, nectarines and plums (7 day PHI) is spirodiclofen
(Endivor 2 SC). Endivor is toxic to European red mite and twospotted spider mite
eggs, nymphal stages and adult females on contact. It unique mode of action, lipid
biosynthesis (mode of action group 23) is in the same mode of action group as Oberon
2 SC mentioned previously for use on labeled vegetable crops and strawberry. (FH)
5. Vegetable
Insecticide Update
Be sure to get a copy of the 2007 Commercial Vegetable
Disease, Insect and Weed Control guide, PB 1282. Since this publication is updated
each year, there are often many new chemical recommendations. Several of these pesticides
are fairly new and some even have unique modes of action. In PB 1282 on page 91,
a number of these new products are recommended for whitefly control on tomatoes.
Acetamiprid (Assail 30 SG) and dinotefuran (Venom 70 SG) are both neonicotinoid
insecticides (mode of action group 4) recommended for whitefly control. You are
probably more familiar with the neonicotinoid class insecticides thiamethoxam (Platinum
2 SC) or imidacloprid (Admire 2 F, Admire Pro 4.6 F, Provado 1.6 F), that have been
in our recommendations for several years, although Admire Pro 4.6 F is a new addition.
The
neonicotinoid class of insecticides are generally very systemic and effective in
controlling many types of insects, especially sucking insects such as whiteflies
and aphids. Some of the neonicotinoids also are effective on sawflies, leaf feeding
beetles such as cucumber beetles and Colorado potato beetles, and other listed pests.
Many of these products can be applied to the soil usually around planting time.
Root uptake moves the product up into the new growth for long lasting protection
from many types of insects. Some of these products can be either applied to the
soil or used in a foliar application. It is generally recommended that you only
make one type of application, not both, in a given season for resistance management
purposes. Provado 1.6 F and Assail 30 SG are labeled only for foliar application.
The insecticide is rapidly absorbed by the plant tissue and quickly moves via systemic
translaminar activity to protect the entire leaf. Foliar applications of neonicotinoids
generally protect the foliage for a much shorter period of time than the soil applied
ones, so repeat foliar applications may be required in some instances.
Another
new product for whitefly control, Oberon 2 SC, is mentioned in the 'Spider Mite'
article as also being an effective miticide. Buprofezin (Courier 40 SC) is an insect
growth regulator (inhibits chitin biosynthesis in the immature insect) with a unique
mode of action (group 16). Another insect growth regulator (juvenile hormone mimic
which prevents molting from the immature to the adult stage, mode of action group
7) that has been available for several years is pyriproxyfen (Knack 0.86 EC).
All
this new chemistry should give the grower a wider assortment of pest control tools.
For resistance management purposes, rotate insecticides not just by class, but by
mode of action since some insecticide classes are in the same mode of action group.
(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), 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 |
| 5-29 | 6 | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 6-4 | 7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
| 6-11 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
| 6-19 | 2 | 0 | 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.
**** Biofix for OBLR in Davidson County was April 25.
^ Biofix for DBM
in Davidson County was April 25.
Bradley County
| OFM | CM | |
| 3-26 | 1 | 0 |
Putnam County
| 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 |
| 5-25 | 0 | 24 | 0 | 0 | 0 |
| 5-28 | 0 | 15 | 0 | 2 | 0 |
| 6-2 | 0 | 26 | 0 | 0 | 0 |
| 6-4 | 0 | 8 | 0 | 0 | 0 |
| 6-8 | 0 | 0 | 0 | 0 | 0 |
| 6-13 | 3 | 11 | 0 | 0 | 0 |
| 6-15 | 4 | 0 | 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.
**** Biofix
for OBLR in Putnam County for OBLR was April 25.
Obion County
| 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 |
| 5-29 | 0 | 5 | 0 | 0 | 0 |
| 6-4 | 2 | 7 | 1 | 0 | 2 |
| 6-11 | 10 | 2 | 0 | 0 | 0 |
* 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.
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