Fruit Pest News

Volume 6, No. 16  July 12, 2005

An 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. Apple: Sooty Blotch and Flyspeck Appearance

    2. Apple: Bitter Rot

    3. Peach: Brown Rot

    4. Peach: Rhizopus Rot

    5. General: Japanese Beetles at Harvest

    6. Apple: Variegated Leaf Roller

    7. Apple: Codling Moth

    8. Tree Fruit: Oriental Fruit Moth 3rd Generation

    9. Grape Berry Moth 3rd Generation

    10.Pheromone Trap Catches

Apple: Sooty Blotch and Flyspeck Appearance

Sooty blotch and flyspeck appeared on July 1 in Williamson County.  Its onset this year was later than normal due to the dry weather we have had this summer. The predictive models that indicate when it will appear are based on moisture and not temperature. Where SBFS was found, 305 wetting hours had accumulated, which is close to the 275-300 wetting hours indicated by the North Carolina model. (SB)

4. Bitter Rot of Apple

Bitter rot is the most potentially explosive of the apple fruit rot diseases. We sometimes get reports of growers, especially homeowners, losing the majority of their fruit to this disease. The restrictions placed on the most effective group of fungicides, the EBDC's, have increased our problems with bitter rot. The disease can move so rapidly because infection can occur in as little as 5 hours of wetting at 79-82 F. At 80 F, lesions can develop and produce spores within 11 days of infection. Fruit remain susceptible right up until harvest.

Identification. Bitter rot is recognized by round, sunken lesions on the fruit. When very young fruit are infected, the lesions appear as tiny gray-brown flecks, which usually do not develop further until fruit begin to ripen. Fruit infections occurring a month after petal fall begin as small, round, slightly sunken areas that are light to dark brown in color. As the lesions enlarge, concentric rings of spores or their fruiting bodies form around the center. Decay lesions extend in a cone-shaped pattern toward the core, observed by cutting the apple in half through the decayed area. This V-shaped lesion distinguishes bitter rot from white rot, which has a cylindrical decayed area.

Cultural control. A feared disease, bitter rot is controllable if trees are well-pruned and air circulation is good in the orchard. The removal of excess growth improves drying conditions and penetration of sprays into the canopy. Try to prevent the buildup of inoculum by removing overwintered mummified fruit, if feasible, or even diseased fruit during the growing season. Leaving fire-blighted shoots on the trees can increase fruit rot problems, because the fungi can colonize them. Do not allow prunings to pile up near the orchard. Prunings can be left on the orchard floor if they are chopped with a rotary or flail mower, which removes the bark on which the fungus can reproduce.

Monitoring bitter rot. Orchards should be scouted regularly for this and other fruit rots. In orchards in which this disease has been a problem, or in highly susceptible varieties, inspect the trees each week, beginning in early June. Highly susceptible varieties include Golden Delicious, Fuji, Arkansas Black, Granny Smith, Empire, and Yellow Newton. Almost as susceptible are Gala, Stayman, Jonagold, Jonathan, Grimes Golden, Ginger Gold, and Braeburn. Among the least susceptible are Delicious, Rome Beauty, and Winesap, but no variety has a high level of resistance.

Inspect as many fruit as is practical (this exercise provides another case for keeping trees trained to a manageable height). If more than 3 infected fruit are observed on any tree, a change in the control program may be needed. The needed change may be in the tree training and other cultural practices mentioned above. Or it may be in the spray program. The spray interval may need to be shortened (especially if the weather is rainy), the fungicide choice may need to change (a bitter rot fungicide should be used in each cover spray), or the application method may need adjustments.

Chemical control. The need for fungicidal protection against bitter rot is greatest from midseason until harvest, although some fruit infection can occur as early as petal fall. Where bitter rot has been troublesome in the past, use an EBDC fungicide (Dithane, Manzate, Penncozeb, or Polyram) as long as the label allows (until 77 days before harvest). Tank mixing with captan after petal fall will improve control of white rot and black rot.

Ferbam is also very effective against bitter rot, and can be used until 7 days before harvest. You can use ferbam if you have some old product, but it is no longer being produced for used in apples or being marketed in this area. Ferbam also produces a gray residue that is unsightly on fruit. Other disadvantages of ferbam are increased cracking on Stayman, and russeting on certain varieties if ferbam is applied in the pink through first cover sprays. Russeting is not a problem when ferbam is used after the first cover spray. Like the EBDC's, ferbam applied alone may not provide adequate control of white rot or black rot.

Captan, ziram, and thiram are good bitter rot materials, and should be used at full rate where problems with bitter rot are expected. The addition of a 1/2 rate of Topsin M helps with control of sooty blotch and flyspeck, as well as white rot and black rot. The new strobilurin fungicides, Flint and Sovran, appear to be slightly less effective at the rates commonly used. Cover sprays should be applied at 10- to 14-day intervals, using 10-day intervals during wet, rainy periods. (SB)

6. Brown Rot of Peach

Remember that special attention to brown rot is needed in orchards in which bird or insect damage is severe, hail damage has occurred, and in which trees are planted closely or are surrounded by woods. Post-harvest losses to brown rot can be significant, especially if harvested fruit are not kept cool. Try to minimize post-harvest losses by using care in the picking and handling of fruit to avoid punctures. Any break in the skin of the fruit enables brown rot to more easily cause infection.

A good pre-harvest spray program also minimizes losses at harvest and after harvest. The registration of Pristine fungicide has alleviated a problem with resistance management for brown rot. Since resistance to the benzimidazoles developed in brown rot, Topsin M cannot effectively be used for control. Until Pristine was labeled, there were no fungicides as effective as the DMI's (sterol inhibitors) with which to rotate. After using a DMI (Orbit, Elite, Indar) for two applications, rotate to Pristine for one application before returning to a DMI. Pre-harvest fungicides should not be applied more often than every 7 to 10 days. Orbit, Indar, Elite, and Pristine have 0-day pre-harvest intervals. (SB)  

7. Rhizopus Rot of Peach

Rhizopus rot is a common post-harvest rot of peach that can spread rapidly in containers of non-cooled fruit. It is characterized by a fluffy, black fungal growth on a rotted area of the fruit. Before the mold is produced, Rhizopus rot can be detected by an easy slippage of the skin from the rotting flesh. Skin slippage does not readily occur over brown rot lesions.

Brown rot fungicides used during the pre-harvest period are not effective against Rhizopus rot. Botran 75W is somewhat effective, but should be tank mixed with a brown rot fungicide and cannot be used within 10 days of harvest. Scholar 50W provides good control of Rhizopus rot, but can only be used after harvest, as a dip or through spray nozzles in the packing line. As with brown rot control, avoid puncturing fruit skin, and store harvested fruit at less than 40 F. (SB)

Japanese Beetle Adults at Harvest
Japanese beetles feed on many types of fruit, vegetable and ornamental plants as adults. Treatment of adults at harvest time can be a problem because the re-entry intervals (REI) and preharvest intervals (PHI) listed on the pesticide label need to be followed. I was recently contacted concerning Japanese beetles feeding on blackberries at harvest time. Sevin has a 7 day PHI for brambles so it is not a viable choice during harvest. One product that might be helpful is Pyrellin E.C. It is produced by the Webb Wright Corporation (EPA Reg. No. 30573-2). It has a 12 hour REI and a 12 hour PHI. This product could be applied in the late afternoon or early evening and the crop could be harvested 12 hours later starting the next morning. I do not know what level of control this insecticide will provide, but it should aid in control while allowing the harvest to continue without interruption. (FH)

Apple: Variegated Leaf Roller
On July 12, the first vareigated leafroller moths were caught. Starting on June 10, we were catching some larger unknown tan moths in the trap that were not variegated leafrollers. This again demonstrates the need for good color pictures of the target moths in order to correctly identify them in the traps. A good hand lens is a must and a dissecting scope sure helps in tough identifications. (FH)

Apple: Codling Moth
The pheromone traps for codling moth in Nashville and in Putnam County have not caught any codling moths this year. I tend to assume that this is a failure of the pheromone lure used. It might be a good idea to trap with more than one brand of codling moth pheromone lure in the future. (FH)

Oriental Fruit Moth Third Generation
For peach, nectarine and plum, an insecticide application for the third generation Oriental fruit moth (OFM) is to be made at 2,300 DD after biofix if OFM pheromone trp catches exceed 5 moths/trap/week after 1,900 DD after biofix and the existence of fruit damage caused by the second generation. In Nashville, 2300 was exceeded on July 7 and as of July 7 there have been 2458 DD accumulated using a base temperature of 45. (FH)

Grape Berry Moth Third Generation
Grape berry moth have accumulated 2204 DD from the biofix on April 4 through July 11 in Nashville using a base temperature of 47.14. A spray application for the third generation should occur at 2187 DD which was exceeded on July 11. While the time to spray in Nashville is now, check your DD calculations based on the biofix for your location. (FH)

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)

* 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.
"Biofix for VLR in Davidson County on July 12

Bradley County

*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

*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

*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
Diamondback Moth (DBM), American Plum Borer (APB), Cabbage Looper (CL), Armyworm (AW), Sod Webworm (SWW)

* 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
*****Biofix of SWW in Davidson County on May 9

Knox County*
Tufted Apple Budmoth (TABM)

*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.

The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm

Contacts:

Steve Bost, Professor and Extension Plant Pathologist

scbost@utk.edu

Frank Hale, Professor and Extension Entomologist

fahale@utk.edu

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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