Fruit Pest News
Volume 9, No. 9 May 21 2008
An 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. First Reports for the Year in TN
2. Update on Bacterial Spot in Garden Centers
3. Planning for Cucurbit Powdery Mildew Season
4. Keep on Lookout for Cutworms
5. Cucumber Beetles
6. Colorado Potato Beetles
7. Pheromone Trap Catches
1. First Reports for the Year in TN
Periodical cicada, Brood X IV, May 8, Cocke Co. (slow, sporadic emergence); bacterial leaf spot of leafy greens, May 8, Crockett Co.; cedar-apple rust, May 14, Williamson Co.; apple scab, May 16, Davidson County (later than usual).
2. Update on Bacterial Spot in Garden Centers
Despite efforts to clean up the bacterial spot outbreak on tomatoes and peppers on store shelves reported a couple of weeks ago, infected plants are still present at garden centers. Those little spots may look harmless enough, but wait until you get them in your garden.....it will be another story entirely. Do not buy tomato or pepper plants with spots. Locally-grown plants may be a safer bet until this issue is resolved. (SB)
3. 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. 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 future; it is highly effective against powdery mildew.
The sterol inhibitor fungicides have also experienced some loss in effectiveness at certain locations. With the threat of resistance to the sterol inhibitors in mind, you should rotate occasionally to sulfur when using one of these materials.
The strobilurins provide control of other diseases such as microdochium blight and downy mildew and, because of this, are usually applied alone. On the other hand, 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)
4. Keep on Lookout for Cutworms
Monitor sweet corn crops for cutworms when
plants are small. If 2% of the plants are cut, then it will pay to use an insecticide
for cutworms. Also, armyworms can feed on sweet corn and all types of other grasses.
Armyworms lay masses of eggs and if conditions are right, damaging populations of
armyworms can occur. Sweet corn is most susceptible to armyworms prior to silking.
(FH)
5. Cucumber Beetles
Control of cucumber beetles in cucurbits is
important because they can transmit bacterial wilt. Muskmelons and cucumbers are
the most susceptible to bacterial wilt. If Admire is not used at planting, scout
the field and make a foliar application of a labeled insecticide when cucumber beetles
exceed 0.1 to 1 per plant. A non-chemical option for organic production is the use
of floating row covers until bloom to exclude these pests. (FH)
6. Colorado
Potato Beetles
Colorado potato beetle adults overwintering several inches
deep in the soil. They emerge in the spring and are now feeding on susceptible crops
such as tomatoes, potatoes, peppers and eggplant. This pest has a history of developing
resistance to insecticides. The UMass Extension Vegetable Notes (Volume 19, Number
2) addresses some practices that can be done to better control this pest and slow
the advent of resistance. Since these beetles crawl to nearby fields to feed, try
to plant susceptible crops as far as possible from where Colorado potato beetles
were infesting crops the previous year. Barriers such as straw mulching or trenching
around the outer rows is used by some to slow movement of this pest into newly planted
fields.
The newsletter also suggest not using foliar insecticide applications
if damage is light. The amount of defoliation on potatoes that can be allowed before
an insecticide application is warranted is 20 to 30 percent prebloom, 5 to 10 percent
during flowering, and 30 percent when the tubers are growing.
While it has
been recommended in the past to rotate between classes of insecticides, we now know
that some insecticide classes are so similar in their mode of action that it is better
to rotate between insecticides with different modes of action. This approach has
been shown to be better at delaying pesticide resistance. (FH)
7. Pheromone
Trap Catches and Biofixes (FH)
Nashville (Davidson County) Pheromone Trap
Catches for 2008
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 | CL | |
| 3-10 (Put out RBLR trap) | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-13 | -- | 2* | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-19 | -- | 5 | -- | -- | -- | -- | -- | -- | -- | -- |
| 3-31 | -- | 7 | -- | -- | -- | -- | -- | -- | -- | -- |
| 4-1 (put out BCW, OFM, CM, VLR, OBLR traps) | ||||||||||
| 4-9 | 0 | 2 | 0 | 0 | -- | 0 | 0 | -- | -- | -- |
| 4-11 (put out AW trap) | 2** | 0 | 0 | 0 | -- | 0 | 0 | -- | -- | -- |
| 4-17 (put out GBM, DBM, CL traps) | 0 | 0 | 0 | 0 | -- | 0 | 0 | -- | 0 | -- |
| 4-18 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-24 | 2 | 0 | 0 | 0 | 3*** | 0 | 0 | 0 | 0 | 0 |
| 4-29 | 2 | 16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| 5-12 | 6 | 0 | 3^ | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
* Biofix for RBLR in Davidson County was March 13.
**Biofix for OFM in Davidson
County was April 11.
***Biofix for GBM in Davidson County was April 24.
^Biofix
for OBLR in Davidson County was May 12.
Bradley County Pheromone Trap Catches
for 2008
tufted apple bud moth (TABM)
| 3-18 (put out OFM trap) | OFM | CM | TABM |
| 4-6 (put out CM trap, TABM) | 0 | -- | -- |
| 4-12 | 0 | 1 | 4 |
| 4-14 | 0 | 0 | 2 |
| 4-19 | 0 | 1 | 0 |
| 4-21 | 0 | 0 | 23 |
| 4-29 | 1 | 5 | 14 |
| 5-5 | 0 | 2 | 5 |
| 5-11 | 0 | 2 | 13 |
| 5-19 | 0 | 1 | 23 |
Putnam County Pheromone Trap Catches for 2008
| 3-16 (put out RBLR, OBLR, VLR) | OFM | RBLR | OBLR | CM | VLR |
| 3-21 | -- | 12* | 0 | -- | 0 |
| 4-1 | -- | 5 | 0 | -- | 0 |
| 4-9 (put out OFM, CM) | -- | 7 | 0 | -- | 0 |
| 4-13 | 0 | 0 | 0 | 0 | 0 |
| 4-22 | 0 | 9 | 0 | 0 | 0 |
| 4-29 | 0 | 0 | 0 | 0 | 0 |
| 5-4 | 0 | 0 | 0 | 0 | 0 |
| 5-13 | 0 | 0 | 10** | 0 | 0 |
|
5-20 |
0 |
0 |
30 |
0 |
0 |
*Biofix for RBLR in Putnam County estimated as prior to March 21 (trap not out
early enough).
**Biofix for OBLR in Putnam County was May 7.
Obion County
Pheromone Trap Catches for 2008
| OFM | RBLR | OBLR | CM | VLR | |
| 5-19 | 0 | 0 | 3 | 1 | 0 |
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
Soil, Plant and Pest Center
5201 Marchant Drive
Nashville, TN 37211
Copyright 2008 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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