Fruit Pest News
Volume 9, No. 14 July 23, 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. Should I Fumigate My Strawberry Ground?
2. Cucurbit Downy Mildew Update
3. Cucurbit Powdery Mildew Reminder
4. Vegetables: Phytophthora Blight
5. Fruits and Vegetables: Movento 240SC Insecticide
5. Stone Fruit: Stone Fruit Pest Alert
6. Pheromone Trap Catches
1. Should I Fumigate My Strawberry Ground?
As supplies of methyl bromide dwindle under the Critical Use Exemption program, strawberry growers who have used or plan to use this fumigant should prepare for changes. New growers probably will not be able to get methyl bromide, and they will need to consider one of the alternatives. Existing growers may be able to get methyl bromide, but they should plan on using virtually impermeable film (VIF) and the lower rates of methyl bromide that this film allows while maintaining control. No one will be able to obtain methyl bromide in a few years, so we need to learn to do without it.
There are two questions you need to ask yourself:
1) Do I really need to fumigate? If you use a good crop rotation, or are moving onto new production land, then the need to fumigate is minimal. It might not even be needed at all. For many growers, though, rotations are not practical, and the same crop has been on the same fields for years, making fumigation the answer to reduce pathogens and weeds. Rob Welker, Methyl Bromide Alternative Project Coordinator at NC State, says that if you are unsure of your problems and have been fumigating simply because it is part of the plasticulture system, then try leaving some of your production unfumigated and see what the results are. You might be surprised. In an on-farm strawberry trial in the western piedmont of North Carolina, a nonfumigated treatment yielded statistically the same as the methyl bromide treatment. For most cases, however, he has seen approximately 20% reduction in yield when strawberries have not been fumigated.
2) If my crop benefits from methyl bromide fumigation, what is the fumigant doing that is beneficial? Is it controlling diseases? nematodes? annual weeds? perennial nutsedge? This knowledge helps you select the proper alternative to methyl bromide. Most of them are not as broad spectrum as MB. If you do not already know what pests are a problem on your farm, leaving an unfumigated area will provide the answer. If annual weeds are the only pest that methyl bromide has been controlling for you, that problem can be controlled with herbicides that have been labeled for plasticulture strawberries in recent years. However, don't assume that weeds are the only problem based on a visual observation of the treated and untreated areas of the field. There may be root diseases that are not obvious, as weeds are. You may need assistance from your university specialists in determining the cause of yield differences between the treated and untreated areas.
Remember that neither methyl bromide nor any other fumigant controls diseases other than those borne in the soil: Anthracnose, Botrytis, angular leaf spot -- none of these are controlled by fumigation. In assessing your farm's disease control needs by fumigation, only consider Phytophthora crown rot and the black root rot complex. When you consider that nematodes are not the problem in our fine-textured soils that they are in the coastal plains, the potential pest spectrum controllable by fumigation in Tennessee looks narrow! All the more need to leave an untreated area to determine the benefit of methyl bromide fumigation.
Please let us know if we can help you in your efforts. Contact your county Extension agent or Steve Bost (address at end). (SB)
2. Cucurbit Downy Mildew Update
Cucurbit downy mildew had been keeping its distance from Tennessee until a recent report from western North Carolina. A light infection was reported from a 6-acre cucumber field near Canton, with estimated first occurrence of July 18. Previously, there have been reports from the coastal regions of the Southeast and from the Great Lakes region. Tennessee growers should continue with the standard, preventive spray schedule of chlorothalonil, maneb, or mancozeb. Don't leave the cucurbit crop unprotected because you never know when a spore shower from a distant source may occur. Even if downy mildew never reaches you, the broad-spectrum fungicides mentioned above provide protection from other diseases. (SB)
3. Cucurbit Powdery Mildew Reminder
As powdery mildew season gets cranked up, remember that we no longer recommend the strobilurins (Quadris, Flint, Cabrio, Pristine) for control of this disease because of the prevalence of resistant strains and the resulting poor control. Use Nova, Procure, sulfur, or Quintec (melons only) in a tank mix with a basic fungicide such as mancozeb or chlorothalonil, preferably the latter during powdery mildew season. But watch for slippage with Nova and Procure, because this class of fungicides also is showing signs of resistance problems with powdery mildew. For further information on this topic, see the May 21 issue of Fruit Pest News, and for information on cucurbit spray programs, see the June 25 issue. (SB)
4. Vegetables: Phytophthora Blight
There has been a case of Phytophthora capsici blight in squash. It is worthwhile to reprint the following article at this time.
Phytophthora blight is a devastating disease particularly of cucurbit crops and peppers, but also tomatoes, eggplant, snap beans, and lima beans. The destructive nature of the disease and the long life (many years) of an infestation can prevent successful production of susceptible crops for many years. Because of the difficulty of controlling this disease after it occurs, prevention should be emphasized. The action to take when Phytophthora blight is first found in a field depends on the severity of the case. If the blight is widespread throughout a field, attention should be directed to prevention of spread to non-infested fields.
Chemical control of Phytophthora blight in such severe cases is not very effective and not generally recommended. Prevention of spread consists of cultural practices such as cleaning equipment after working in an infested field. Certain disease-control products have activity against P. capsici and may be helpful in light cases of Phytophthora blight. Pre-plant soil applications of mefenoxam can suppress root and crown rot phases of the disease, unless resistance to this fungicide develops. Other products are applied as foliar sprays to protect against airborne spores. The most difficult aspect of this disease to control is the fruit rot phase in crops in which the fruit lies on the ground, such as unsupported vine crops. The potential for disease-control products to be successful is highly dependent on the correction of soil drainage problems. Peppers and cucurbit crops are so susceptible to Phytophthora blight that it is risky to plant these crops in fields in which the disease has ever been known to occur. Some degree of control can be achieved with resistant pepper varieties and hard-rind pumpkin varieties, but cultural practices and chemicals would still be needed.
Be on the lookout for this disease, especially in irrigated fields. Dying plants and rotting fruit are the main symptoms. Be wary of borrowing or lending cultivation equipment, as this organism can be introduced into your field on anything that carries soil particles. (SB)
5. Fruits and Vegetables: Movento 240 SC, A New Two-Way Systemic Foliar Insecticide
Spirotetramat
(Movento) is a Group 23 insecticide from Bayer CropScience, with a new mode of action in the tetramic acid
class of chemistry. It is a lipid biosynthesis inhibitor that works by inhibiting
the insect's ability to produce lipids, which is fatal. The most exciting aspect
of this insecticide is its ability to move through the entire plant (two-way systemic).
Thus, a foliar application can move to new growth and even the inner leaves of vegetables
such as lettuce and cabbage. It can also move to the bark of fruit trees and even
the roots. It is effective against a wide range of sucking insects such as aphids,
thrips, psyllids, mealybugs, whiteflies and scales. It is labeled for use on grape
(not table grapes) and small fruit vine climbing (except kiwifruit), pome fruit,
stone fruit, tree nuts, hops, cucurbit vegetables, fruiting vegetables, leafy vegetables
(non-Brassica), leafy vegetables (Brassica [cole]), and tuberous and corm vegetables.
(FH)
6. Stone Fruit Pest Alert
Maturing fruit needs to be protected from
third brood Oriental fruit moth larvae. Attacked fruit will exude masses of gum
and insect excrement on which sooty mold will often grow. Be on the lookout for
catfacing insects such as tarnished plant bugs and stink bugs. These insects can
increase in number on fruit trees as weed host senescence occurs in the summer.
Thrips are another pest that tends to move to more succulent plants as weeds dry out.
Thrips can be a problem especially on highly colored peaches. (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 |
| 5-20 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 5-27 | 1 | 6 | 17 | 0 | 0 | 0 | 0 | 2 | 0 |
0 |
| 6-2 | 2 | 6 | 8 | 0 | 0 | 0 | 0 | 1 | 0 | 2^^ |
| 6-10 | 3 | 3 | 13 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 6-16 | 0 | 0 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| 6-24 | 1 | 2 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
| 7-23 | 1 | 2 | 9 | 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.
^^Biofix for CL in Davidson County was
June 2.
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 |
| 5-26 | 0 | 0 | 8 |
| 6-2 | 0 | 0 | 3 |
| 6-9 | 0 | 0 | 5 |
| 6-16 | 0 | 0 | 0 |
| 6-23 | 0 | 0 | 0 |
| 6-30 | 0 | 0 | 0 |
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
*Biofix for RBLR in Obion County was March 28
**Biofix
for OFM in Obion County was April 21
***Biofix for OBLR for Obion County was
May 19
| OFM | RBLR | OBLR | CM | VLR | |
| 3-22 (RBLR trap put out) | -- | -- | -- | -- | -- |
| 3-28 | -- | 10* | -- | -- | -- |
| 4-7 (other traps put out) | -- | 0 | -- | -- | -- |
| 4-14 | 0 | 0 | 0 | 0 | 0 |
| 4-21 | 2** | 0 | 0 | 0 | 0 |
| 4-28 | 0 | 0 | 0 | 0 | 0 |
| 5-5 | 1 | 0 | 0 | 0 | 0 |
| 5-12 | 2 | 1 | 0 | 0 | 0 |
| 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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