Fruit Pest News
Volume 6, No. 10 May 24, 2005
A weekly, online newsletter whose goal is to update Extension agents and growers of commercial tree fruit and small fruit crops
on diseases and insects 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. Peach Pest Management - Diseases
2. Apples: Summer Rots Can Start Now
3. Apples: Sooty Blotch and Flyspeck Update
4. Cucurbits: Planning for Powdery Mildew Season
5. Apples: Leafrollers
6. Pheromone Trap Catches
1. Peach Pest Management - Diseases
Watch for certain indicators that can signal upcoming problems. You may need to adjust your control program, such as shortening the spray interval or changing to another control product. You're practicing IPM and may not even know it!
Bacterial spot. Most diseases are favored by rainy weather, but some react more explosively to it than others. Bacterial spot can become epidemic quickly because of the ability of the bacteria to reproduce rapidly and because of their ability to exist epiphytically on the various surfaces of the tree. The number of overwintered shoot "blacktip cankers" is not necessarily a good indicator of the disease potential, because the epiphytic population represents an invisible source of infection. The level of bacterial spot in previous years is probably the best indicator of the disease potential in a block. On susceptible cultivars, successful control of bacterial spot requires a program involving dormant pruning of cankers and use of copper sprays, early-season sprays of copper or Mycoshield, and some help from Mother Nature (dry weather).
When using Mycoshield, consider that it does not weather well. Because of its short residual activity, Mycoshield is most effective when applied shortly before rain, before it has a chance to inactivate. Try to apply within 24 hours before a wetting event, but allow time for the spray to dry. Copper sprays can be used at this time of year, but leaf damage can occur. If you choose to use copper now, use low rates of liquid coppers such as Tenn-Cop 5E (4-6 fl oz/acre) or Copper-Count-N (4-6 fl oz/acre) in at least 100 gal water per acre.
Peach scab. As with most diseases, the risk of infection can be determined by the severity of the disease in previous years. With peach scab, disease potential can also be assessed by examining fruit-bearing shoots for the presence of lesions. Scab lesions on twigs are brown, circular to oval in shape, and best seen on the parts of the shoot that have not yet turned from green to brown. If scab potential is considered low, sulfur should be adequate for control. Remember that sulfur is not very rainfast. Scab control is not needed within 40 days of harvest, because that is the length of time needed for symptom development after infection.
Green fruit rot. This is a good indicator for brown rot, as both diseases are caused by the same fungus. Clinging green fruit that has been damaged by frost and thinned fruit on the ground may be infected and serve as an indication of brown rot pressure. Insect- or wildlife-injured fruit is also susceptible to brown rot and serves as a good indicator. Adjust cover sprays or initiate pre-harvest brown rot sprays early when disease pressure is high. Use captan or Abound if infected green fruit is present. These materials will also control scab. (SB)
2. Apples: Summer Rots Can Start Now
The various summer rots are always a problem in the South. Some of these rots get started around this time of year, although the infections may not become apparent until mid- to late-summer. The recent deluges and humid weather can be expected to increase our problems with the summer rots if we don't keep our guard up.
White rot, in particular, is a fruit rot that can have a delayed effect. While lesions usually don't appear on the fruit until mid-summer or later, they can be the result of infections that occurred in May, and remained dormant until the sugar levels began to increase in the ripening fruit. The white rot fungus lives within the tree in dead wood. It can either invade already-dead wood such as fire blight strikes, or it can infect healthy wood through lenticels in the bark. In stressed trees, the latter type of infection can expand and produce cankers capable of killing branches. Spores of the fungus are spread to the fruit by rain.
Where problems with white rot are expected, captan plus Topsin M should be included in the cover sprays. The strobilurin fungicides Flint and Sovran also provide good control. (SB)
3. Apples: Sooty Blotch and Flyspeck Update (For Those Who Are Counting)
In last week's issue, we discussed the apple sooty blotch and flyspeck model that allows you to conserve your fungicide sprays aimed at preventing this complex. Actually, this forecast system spreads out the time between the first and second cover sprays. In this system, all fungicide applications are applied per the schedule up through the 1st cover spray. In the Kentucky model, the wetting hours are counted beginning at 1st cover and the spray is applied at 175 hours of accumulated wetting. In the Cornell model, the wetting hours are counted beginning at 21 days after 1st cover (use an EBDC at 1st cover), and the spray is applied at 100 hours of accumulated wetting.
At Nashville, we have accumulated 57 hours of wetness periods since the 1st cover which was May 10, excluding periods that did not last 4 hours. (SB)
4. 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).
Since resistance to the sterol inhibitors is also a threat, you should rotate occasionally to sulfur. Remember that sulfur is strictly a surface protectant and coverage of both sides of the leaves is needed for good control. The strobilurins provide control of other diseases such as microdochium blight and downy mildew and, because of this property, 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. (SB)
5. Leafrollers
The obliquebanded leafroller (OBLR) started emerging in Middle Tennessee on May 11. This leafroller is much larger than the redbanded leafroller (RBLR) which was first caught in traps in mid-March. Another generation of RBLR moths are just beginning to emerge. While less damaging than codling moths and Oriental fruit moths, leafrollers can do some direct fruit damage by attaching a leaf to a fruit with silk and feeding on the skin of the fruit. An apple with an attached leaf covering part of it will not allow the covered portion of the apple to color in the fall. The variegated leafroller has only been caught at the Obion County location. The biofix was May 3 with catches increasing since. (FH)
6. 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)
| Date | OFM | RBLR | OBLR | CM | GBM | VLR | BCW |
| 3-11 (put out RBLR trap) | -- | 0 | -- | -- | -- | -- | -- |
| 3-14 | -- | 16* | -- | -- | -- | -- | -- |
| 3-18 (put out OFM, OBLR,CM, VLR traps) | -- | 1 | -- | -- | -- | 0 | -- |
| 3-21 | 0 | 17 | 0 | 0 | -- | 0 | -- |
| 3-24 | 0 | 19 | 0 | 0 | -- | 0 | -- |
| 3-29 | 0 | 23 | 0 | 0 | -- | 0 | -- |
| 3-30 (put out GBM & BCW traps) | 0 | 10 | 0 | 0 | 0 | -- | |
| 4-4 | 1 | 34 | 0 | 0 | 4** | 0 | 0 |
| 4-7 | 1 | 12 | 0 | 0 | 2 | 0 | 0 |
| 4-12 | 5**** | 12 | 0 | 0 | 10 | 0 | 2*** |
| 4-14 | 2 | 1 | 0 | 0 | 5 | 0 | 0 |
| 4-18 | 11 | 5 | 0 | 0 | 5 | 0 | 0 |
| 4-20 | 9 | 1 | 0 | 0 | 2 | 0 | 0 |
| 4-22 | 4 | 0 | 0 | 0 | 4 | 0 | 0 |
| 4-25 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4-29 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
| 5-2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 5-6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 5-9 | 10 | 0 | 0 | 0 | 2 | 0 | 0 |
| 5-11 | 4 | 0 | 1 | 0 | 2 | 0 | 0 |
| 5-13 | 1 | 0 | 2***** | 0 | 0 | 0 | 0 |
| 5-17 | 6 | 0 | 14 | 0 | 2 | 0 | 1 |
| 5-23 | 4 | 10 | 19 | 0 | 4 | 0 | 0 |
* Biofix for RBLR in Davidson County estimated as occurring on March 12.
**Biofix
for GBM in Davidson County is April 4.
***Biofix of BCW in Davidson County on
April 12.
****Biofix for OFM in Davidson County on April 12.
*****Biofix for
OBLR in Davidson county on May 13.
Bradley County
| Date | OFM | RBLR | CM |
| 3-10 (put out two RBLR traps) | -- | -- | -- |
| 3-12 | -- | 2* | -- |
| 3-21 | -- | 45 | -- |
| 3-23 (put out four OFM traps) | -- | -- | -- |
| 3-25 | 28** | -- | 0 |
| 3-28 | 18 | 41 | 0 |
| 4-4 | 67 | 12 | 0 |
| 4-11 | 43 | 8 | 0 |
| 4-15 | -- | -- | 1 |
| 4-16 | -- | -- | 4*** |
| 4-18 | 21 | 2 | 2 |
*Biofix for RBLR in Bradley County on March 12.
**Biofix for OFM in Bradley
County on March 25.
***Biofix for CM in Bradley County on April 16.
Putnam
County
| Date | OFM | RBLR | OBLR | CM | VLR |
| 3-21 | 0 | 52* | 0 | 0 | 0 |
| 3-23 | 0 | 10 | 0 | 0 | 0 |
| 3-25 | 0 | 12 | 0 | 0 | 0 |
| 3-28 | 0 | 20 | 0 | 0 | 0 |
| 3-30 | 0 | 0 | 0 | 0 | 0 |
| 4-1 | 0 | 5 | 0 | 0 | 0 |
| 4-4 | 0 | 5 | 0 | 0 | 0 |
| 4-6 | 3** | 7 | 0 | 0 | 0 |
| 4-8 | 0 | 1 | 0 | 0 | 0 |
| 4-18 | 6 | 7 | 0 | 0 | 0 |
| 4-22 | 2 | 3 | 0 | 0 | 0 |
| 4-25 | 0 | 4 | 0 | 0 | 0 |
| 4-27 | 2 | 0 | 0 | 0 | 0 |
| 4-29 | 0 | 0 | 0 | 0 | 0 |
| 5-2 | 0 | 0 | 0 | 0 | 0 |
| 5-9 | 0 | 3 | 0 | 0 | 0 |
| 5-11 | 0 | 0 | 2*** | 0 | 0 |
| 5-13 | 0 | 0 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County on March 21.
**Biofix for OFM in Putnam County
on April 6.
***Biofix for OBLR in Putnam county on May 11.
Obion County
| Date | OFM | RBLR | OBLR | CM | VLR |
| 3-25(put out traps) | -- | -- | -- | -- | -- |
| 3-28 | 0 | 0 | 0 | 0 | 0 |
| 4-4 | 1 | 9* | 3** | 8*** | 0 |
| 4-11 | 3**** | 0 | 0 | 0 | 0 |
| 4-18 | 0 | 0 | 7 | 0 | 0 |
| 4-25 | 2 | 0 | 0 | 0 | 1 |
| 5-3 | 1 | 0 | 0 | 0 | 6***** |
| 5-9 | 5 | 0 | 0 | 0 | 4 |
| 5-16 | 3 | 0 | 1 | 1 | 17 |
| 5-23 | 3 | 6 | 2 | 0 | 22 |
*Biofix for RBLR in Obion County estimated to be on March 12 (trap not out early
enough).
**Biofix for OBLR in Obion County on April 4 (waiting for confirmation
since this was much earlier than other locations).
***Biofix for CM in Obion County
on April 4 (waiting for confirmation).
****Biofix for OFM in Obion County on April
11.
*****Biofix for VLR in Obion County on May 3 (waiting for confirmation).
Other
Pheromone Trap Catches for Davidson County in 2005
Diamondback Moth (DBM), American
Plum Borer (APB), Cabbage Looper (CL), Armyworm (AW)
| Date | DBM | APB | CL | AW |
|
4-18 (put out traps) |
-- | -- | -- | -- |
| 4-20 | 5* | 3** | 0 | 0 |
| 4-22 | 3 | 3 | 0 | 0 |
| 4-29 | 6 | 0 | 3*** | 0 |
| 5-2 | 41 | 2 | 4 | 6**** |
| 5-4 | 23 | 0 | 0 | 0 |
| 5-6 | 27 | 0 | 0 | 0 |
| 5-9 | 106 | 1 | 0 | 0 |
| 5-11 | 6 | 1 | 0 | 0 |
| 5-13 | 10 | 0 | 0 | 0 |
| 5-17 | 7 | 2 | 1 | 0 |
| 5-23 | 7 | 0 | 0 | 0 |
* Biofix of DBM in Davidson County probably earlier than April 20
**Biofix
of APB in Davidson County probably earlier than April 20
***Biofix of CL in Davidson
County on April 29
****Biofix of AW in Davidson County on May 2
Knox County
*
Tufted Apple Budmoth (TABM)
| Date | OFM | RBLR | OBLR | CM | VLR | TABM |
| 5-2 (traps put out 4-18) | 20 | 0 | 3 | 3 | 2 | 17 |
*The Knox County traps were put out by a first time cooperator still learning to identify. the moths. Correspondingly, the trap counts for May 2 remain suspect. We do know that the traps were put out too late to accurately determine a biofix for Oriental fruit moth (OFM) and redbanded leafroller (RBLR). The obliquebanded leafroller (OBLR), codling moth (CM), variegated leafroller (VLR) and tufted apple budmoth (TABM) catches are possible biofixes or at least early in their moth flights.
(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 2005 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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