Fruit Pest News
Volume 7, No. 14 June 14, 2006
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. Brown Rot of Peach and Other Stone Fruits
2. Apple: Summer Disease Control Program
3. Apple: Powdery Mildew
4. Apple Leaf Blotches: Necrotic, Alternaria, and Glomerella
5. Apple: European Red Mites and Twospotted Spider Mites
6. Pheromone Tap Catches and Biofixes
1. Brown Rot of Peach and Other Stone Fruits
The two-week period prior to harvest is a critical period in the life of a peach. This is the period in which it is most susceptible to brown rot, the most important disease of peaches in Tennessee. Fungicide sprays just before and during the harvest period are very important. Because of the threat of resistance development in this fungus, use fungicides from two classes: the sterol inhibitors (Indar, Elite, Orbit) and the strobilurins (Pristine, Abound). Minimize the use of these fungicides, making no more than two applications of either class. Make at least two applications of brown rot fungicides during the pre-harvest period, beginning no later than two weeks prior to the beginning of harvest (you need to know when to expect harvest to begin). Make an additional one to two applications during harvest. Adjust spray intervals as needed based on weather conditions, inoculum carryover, and the amount of physical injury to the fruit.
Injuries to fruit that can increase brown rot problems include hail, frost cracks, bird feeding, and insects such as Oriental fruit moths, Japanese beetles, green June beetles, hornets, and wasps. Breaks in the fruit skin make it easier for the fungus to enter and begin the rot process. Wet, warm weather aids dispersal and germination of the fungal spores. The spores come mainly from mummified fruit from the previous year, and the spores are carried to fruit by wind, rain, and certain insects.
Some brown rot is not apparent at harvest and develops in storage. Storing the fruit in a cooler after harvest slows the development of infections. Try to avoid injuries to the fruit during the harvesting operation, as post-harvest brown rot can begin at these sites. We have a good peach crop in many areas; let's try to keep it! (SB)
2. Apple: Summer Disease Control Program
Your summer disease control program is, no doubt, well underway. The so-called summer diseases take a greater toll on Tennessee apple production than the spring diseases. The summer diseases are fueled by a continuing source of overwintered inoculum, and there are fewer effective fungicides from which to choose. Furthermore, it is more difficult to obtain good spray coverage during the summer than during the spring because of more dense foliage, fruit clustering, and limbs drooping under heavy crop loads.
Your choice of fungicides will depend to some extent on what diseases have historically been a problem in your orchard. If bitter rot has been a problem, captan should be a major component of your summertime spray program. Flint also performs well against bitter rot. If white rot has been a problem, captan or Topsin M should be relied on heavily. For sooty blotch and flyspeck, be sure to include Topsin M or a strobilurin (Flint, Sovran, Pristine). Strobilurins are also a valuable component of a program if scab is still active. In Golden Delicious blocks, it is a good idea to include ziram or thiram to help protect against necrotic leaf blotch (see article below). Mancozeb provides good control of most summer diseases, but cannot be used within 77 days of harvest when used at the 3/4 lb per 100 gallon rate.
Captan has had a 4-day (96 hr) re-entry interval in the past. The re-entry interval has been changed for all formulations, allowing workers to enter the treated area in 24 hours, rather than 96.
Remember that management of diseases with fungicides is improved if cultural practices that reduce inoculum and enhance coverage are used. (SB)
3. Powdery Mildew of Apple
Powdery mildew will continue to spread as long as there are new leaves developing on apple trees. When terminal growth stops, the potential for spread of powdery mildew will decrease. On susceptible varieties, apply effective mildewcides such as the sterol inhibitors, the strobilurins, or sulfur every 10 to 14 days until terminal growth stops. (SB)
4. The Apple Leaf Blotches: Necrotic, Alternaria, and Glomerella
During the summer in Tennessee, three apple diseases can occur, all having similar names and symptoms. Let's compare these diseases and their controls.
Necrotic leaf blotch is actually not a disease, but a physiological disorder. It occurs on Golden Delicious and its sports. The affliction often occurs in waves during the summer. It tends to be more severe when hot, sunny weather follows several days of mild, cloudy weather. Large, irregular-shaped, necrotic (brown) spots appear suddenly on green leaves (click here to view an image). Most affected leaves soon turn yellow and fall from the tree. Defoliation can be significant. Although necrotic leaf blotch is not caused by a fungus, severity is decreased by a regular fungicide program (see below).
Alternaria leaf blotch, caused by the fungus Alternaria mali, affects Red Delicious and related varieties such as Empire. Alternaria leaf blotch is a problem in the higher elevation areas of Tennessee. Symptoms (click here) include small, circular necrotic spots on the leaves. The leaf spots may have a purplish margin and, thus, resemble frogeye leaf spot and captan injury. Alternaria leaf spot is aggravated by European red mites. Control consists of mite control, fungicide spray programs, and adequate tree spacing and other cultural practices that enhance drying conditions.
Glomerella leaf blotch was first found in Tennessee in 1998. The two orchards in which it was found were the first North American reports of this disease. It has since been found in Georgia and North Carolina, but its distribution is still very limited. Symptoms (click here) resemble necrotic leaf blotch of Golden Delicious. However, Glomerella leaf blotch has only been found on Gala and Ozark Gold. Also unlike necrotic leaf blotch, Glomerella can infect the fruit, causing a bitter rot type of infection. The fruiting bodies of the Glomerella fungus on the surface of the rot have a black color, whereas those of Colletotrichum acutatum bitter rot have a salmon color. Appropriate fungicides for control of Glomerella are provided below. As with Alternaria leaf blotch, Glomerella is most severe where tree spacing or branch spacing is inadequate, or other conditions exist that interfere with drying conditions. Note: Necrotic areas on leaves of Gala can also be caused by Abound injury.
| Disease or Disorder |
Cultivars Affected | Spray Program |
| Necrotic leaf blotch |
Golden Delicious & its sports | EBDC's in early cover sprays*. Then ziram, thiram, or zinc oxide in succeeding cover sprays. Sprays from mid-June through early August are most important. |
| Alternaria leaf blotch |
Red Delicious, Empire | Flint or Sovran applied up to 3 consecutive times at 10-day intervals, beginning in mid-June. Use in conjunction with mite management program. |
| Glomerella leaf blotch |
Gala, Ozark Gold | EBDC's in early cover sprays*. Then Flint, ziram, or captan in succeeding cover sprays. Sovran is not effective. |
*The EBDC fungicides have a 77-day preharvest interval.
As you can see, the 3 blotches have different cultivar spectra and the chemical control specifications are different in some cases. If you find any of these blotches, we would be interested in knowing about it, and would be glad to assist you in selecting control products. (SB)
5. European Red Mites and Twospotted Spider Mites on Apples
European red mites
(ERM) overwinter as eggs on the tree so dormant oil sprays are very useful in managing
these mites. Twospotted spider mites (TSSM) overwinter as adults amongst weeds and
grass so dormant oil sprays are not effective for these pests. TSSM move up into
the tree with warm temperatures in the spring and summer. The use of pyrethroid
insecticides or Sevin as a thinning agent can flare mite populations because they
tend to kill beneficial insects and mites.
There are more miticides available
now than anytime that I can remember. At apple petal fall or first cover, Apollo
SC or Savey 50WP are most effective. FujiMite 5EC, Zeal 72WDG, or Envidor 2SC are
a good choice to use between petal fall and third cover, or when mites reach one
adult per leaf. FujiMite will also control white apple leafhoppers. For second
cover and later sprays, do not reapply Apollo or Savey if they were used at petal
fall. Other miticides for use at this time include Acramite 50WS, Nexter 75WP, Zeal
72 WDG, Envidor 2SC, Kelthane 50WP, Vendex 50W, Danitol 2.4 EC, wettable sulfur or
summer oil. Applying summer oil when mite populations are beginning to increase
(first and second covers) will suppress ERM populations. Do not apply captan 2 weeks
before or after an oil spray. (FH)
6. Pheromone Trap Catches and Biofixes
Nashville
(Davidson County) Pheromone Trap Catches for 2006
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)
| OFM | RBLR | OBLR | CM | GBM | VLR | BCW | DBM | |
| 3-1 (put out RBLR, OFM, VLR traps) | -- | 0 | -- | -- | -- | -- | -- | -- |
| 3-2 | -- | 3* | -- | -- | -- | -- | -- | -- |
| 3-9 | -- | 15 | -- | -- | -- | 0 | -- | -- |
| 3-13 | 0 | 50 | 0 | -- | -- | 0 | -- | -- |
| 3-21 | 0 | 71 | 0 | -- | -- | 0 | -- | -- |
| 3-28 | 0 | 15 | 0 | -- | -- | 0 | -- | -- |
| 3-29 (put out GBM, BCW, & DBM traps) | 0 | 5 | 0 | -- | -- | 0 | -- | -- |
| 3-30 | 0 | 4 | 0 | -- | 0 | 0 | 0 | 2** |
| 4-4 | 24*** | 34 | 0 | -- | 0 | 0 | 0 | 2 |
| 4-6 | 5 | 14 | 0 | 0 | 1 | 0 | 0 | 1 |
| 4-7 | 14 | 4 | 0 | 0 | 3**** | 0 | 0 | 0 |
| 4-11 | 12 | 10 | 0 | 0 | 1 | 0 | 0 | 1 |
| 4-17 | 39 | 9 | 0 | 0 | 23 | 0 | 0 | 4 |
| 4-18 | 6 | 0 | 0 | 0 | 1 | 0 | 0 | 0 |
| 4-24 | 49 | 0 | 14^ | 0 | 2 | 0 | 0 | 3 |
| 4-27 | 9 | 0 | 15 | 0 | 0 | 0 | 0 | 4 |
| 5-3 | 13 | 0 | 25 | 0 | 0 | 0 | 0 | 1 |
| 5-9 | 10 | 1 | 22 | 0 | 0 | 0 | 0 | 0 |
| 5-19 | 5 | 10 | 27 | 0 | 0 | 0 | 0 | 0 |
| 5-31 | 25 | 12 | 5 | 0 | 0 | 0 | 0 | 6 |
| 6-5 | 9 | 0 | 4 | 0 | 0 | 0 | 0 | 2 |
| 6-13 | 26 | 2 | 6 | 0 | 0 | 0 | 0 | 2 |
* Biofix for RBLR in Davidson County was March 2.
**Biofix for DBM in Davidson
County was March 30.
***Biofix for OFM in Davidson County is estimated to be April
3.
****Biofix for GBM in Davidson County was April 7.
^Biofix for OBLR in Davidson
County was April 24.
Bradley County Pheromone Trap Catches for 2006
| OFM | CM | |
| 3-29 | 3* | 0 |
| 4-3 | 26 | 0 |
| 4-5 | 0 | 1 |
| 4-10 | 16 | 0 |
| 4-17 | 19 | 5** |
| 4-24 | 17 | 17 |
| 5-1 | 17 | 2 |
| 5-8 | 15 | 1 |
| 5-15 | 2 | 0 |
| 5-29 | 13 | 3 |
*Biofix for OFM in Bradley County on March 29.
**Biofix for CM in Bradley County
on April 13.
Putnam County Pheromone trap Catches for 2006
| OFM | RBLR | OBLR | CM | VLR | |
| 3-21 (put out RBLR & OFM) | -- | -- | -- | -- | -- |
| 3-24 | 0 | 0 | -- | -- | -- |
| 3-27 | 0 | 0 | 0 | 0 | 0 |
| 3-31 | 2** | 12* | 0 | 2*** | 0 |
| 4-2 | 1 | 3 | 0 | 0 | 0 |
| 4-7 | 6 | 23 | 1 | 1 | 0 |
| 4-10 | 1 | 16 | 0 | 0 | 0 |
| 4-15 | 9 | 60 | 6 | 0 | 1 |
| 4-17 | 0 | 13 | 1 | 0 | 1 |
| 4-21 | 3 | 14 | 0 | 0 | 0 |
| 4-28 | 10 | 3 | 2 | 1 | 0 |
| 5-7 | 0 | 0 | 2 | 0 | 3 |
| 5-12 | 0 | 0 | 0 | 0 | 0 |
| 5-21 | 0 | 0 | 18 | 0 | 0 |
| 6-13 | 0 | 11 | 0 | 0 | 0 |
*Biofix for RBLR in Putnam County estimated as March 3 (trap not out early enough).
**Biofix
for OFM in Putnam county March 31.
***Waiting to verify biofix for CM, catch probably
too early.
Obion County Pheromone Trap Catches for 2006
| OFM | RBLR | OBLR | CM | VLR | |
| 3-13 | 1 | 49* | 0 | -- | 2*** |
| 3-21 | 0 | 40 | 0 | 0 | 0 |
| 3-27 | 1 | 2 | 0 | 0 | 0 |
| 4-3 | 2** | 13 | 0 | 2**** | 0 |
| 4-17 | 1 | 18 | 3^ | 1 | 5 |
| 4-25 | 7 | 0 | 0 | 0 | 4 |
| 5-1 | 4 | 0 | 3 | 0 | 4 |
| 5-15 | 0 | 0 | 1 | 0 | 0 |
| 5-22 | 0 | 1 | 0 | 0 | 0 |
| 5-29 | 0 | 1 | 1 | 0 | 1 |
| 6-13 | 0 | 1 | 0 | 0 | 0 |
*Biofix for RBLR in Obion County estimated to be on March 3 (trap not out early
enough).
**Biofix for OFM in Obion County on April 3.
***Waiting to verify
biofix for VLR in Obion County, catch probably too early.
****Waiting to verify
biofix for CM in Obion County, catch probably too early.
^Biofix for OBLR in Obion
County.
Additional Pheromone Trap Catches in Davidson County for 2006
Sod
Webworms (SWW), Armyworm (AW)
| SWW | AW | CL | |
| 4-18 | 3* | 0 | 0 |
| 4-24 | 15 | 4** | 0 |
| 4-27 | 15 | 1 | 0 |
| 5-3 | 16 | 0 | 0 |
| 5-9 | 52 | 3 | 0 |
| 5-19 | 41 | 0 | 0 |
| 5-31 | 22 | 0 | 0 |
| 6-5 | 7 | 0 | 0 |
| 6-13 | 47 | 0 | 1 |
*Biofix for SWW in Davidson County for 2006.
**Biofix for AW in Davidson County
for 2006.
Knox County Pheromone Trap Catches for 2006
Tufted Apple Budmoth
(TABM)
| OFM | RBLR | OBLR | CM | VLR | TABM | |
| 5-1 | 40 | 15 | 2 | 5 | 0 | 17 |
| 5-10 | 3 | 1 | 3 | 2 | 1 | 8 |
| 5-15 | 10 | 1 | 0 | 3 | 3 | 3 |
| 6-5 | 9 | 43 | 5 | 1 | 13 | 12 |
| 6-13 | 6 | 79 | 1 | 2 | 13 | 20 |
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 2006 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.
Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating. UT Extension provides equal opportunities in programs and employment.