Fruit Pest News
Volume 3, No. 8 April 29, 2002
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.Current Conditions
2. Blackberries: Watch for Orange Rust
3. Strawberries: Phytophthora Crown Rot
4. Apple: Fire Blight "Strikes"
5. Tree Fruit: Oriental Fruit Moth Alert
6. Tree Fruit: Pheromone Trap Catches and Biofixes
1. Current Conditions
Most areas of the state have a decent peach crop. Maybe we are in a new trend -- This makes the fourth consecutive year that spring frosts have allowed most Tennessee peach growers to produce a respectable crop. That used to be unheard of. Hail storms caused damage over a large area last Wednesday night, and some damage Sunday afternoon. The heat wave of April 15 - 21 has given way to mild temperatures. For many apple varieties, the bloom period that appeared headed for short duration is now somewhat extended. Those high temps hastened some biological processes, including disease development. Cedar-apple rust lesions appeared today on Golden Delicious at Nashville! I don't recall ever having seen them this early. Blackberries are in bloom, and a case of orange rust has been reported. This week's forecast is for continued mild weather. Perhaps this will help extend the strawberry harvest. (SB)
2. Watch for Orange Rust in Blackberries
Orange rust can be very
destructive to blackberries and black raspberries. Most of the blackberry varieties
that we grow in Tennessee are moderately to highly resistant to orange rust. However,
some varieties, such as Navaho, are quite susceptible.
The fungus causes
plants to be so stunted and weakened that they produce little or no fruit. The fungus
is systemic in the plant, and is perennial inside the below-ground parts. Once a
plant is systemically infected by orange rust, it is infected for life. It is
for this reason that removal of infected plants is recommended, to prevent spread
of the fungus to other plants.
The
time to control orange rust is in the spring. Your queue to take action is the appearance
of weak, spindly new shoots with pale green to yellowish leaves. Such plants should
be removed before they begin to produce the orange-colored, blister-like pustules
on the lower leaf surface. The orange pustules contain spores that spread to other
plants and cause new infections that may not become apparent until the following
spring.
The fungicide Nova 40W can now be used for control of orange rust. Nova helps prevent leaf infections. It will not cure a systemically-infected plant. Begin applications soon (the orange pustules should mature and release their spores sometime in the month of May) and continue every 10 to 14 days until mid-summer. The maximum amount is 10 oz per acre per year, and the rate per application is 1.25 to 2.5 oz per acre. (SB)
3. Phytophthora Crown Rot of Strawberries
Symptoms of Phytophthora crown rot (wilting plants) have been called in from a couple of locations. I will see these plants this week and report on them in next week's issue. If you are considering using Ridomil to protect against Phytophthora, keep the following points in mind:
Ridomil performs
best when taken up by the roots and translocated upwardly by the plant. The preferred
method of application in strawberries is through the drip system. Ridomil Gold EC
is injected into the drip system at the rate of 1 pint per treated acre. An actual
acre would only receive 0.6 pint if the beds are 3 feet wide on 5-foot centers, because
only 60% (3/5) of the ground would be treated. If you apply Ridomil with a sprayer,
use enough water to move the fungicide into the root zone. Ridomil should also
help reduce losses to leather rot (a berry rot caused by the same fungus) and red stele
(caused by a different, but related, fungus).
Aliette is labeled for use against
red stele and leather rot. I am not aware of data related to its effectiveness against
crown rot, but it should at least be helpful in suppression. Aliette is applied at
2.5-5.0 pounds per acre at 30-60 day intervals for red stele control and at 7-14
day intervals for leather rot control. Aliette can be applied through the drip system
or through some sprinkler irrigation systems. A foliar spray is the preferred method
of application of Aliette because of its downward systemic activity. Like Ridomil,
Aliette can be applied on the day of harvest. Follow label directions carefully.
(SB)
4. Fire Blight Strikes
Fire blight blossom blight appeared on Golden Delicious in Franklin on April 24 and in Nashville on April 28. The MaryBlyt program indicated that the infection that produced the Nashville strikes occurred on April 18. The program indicated some earlier infections that apparently did not occur, because the symptoms did not appear on the predicted date.
Many varieties are at petal fall and, as a result, are no longer susceptible to blossom blight infections. However, streptomycin applications are needed on those varieties if any secondary blooms are present. Secondary blooms are quite susceptible to fire blight infection because of the warmer weather that usually accompanies them. Loosing a few late blossom clusters to fire blight may not seem important, but the bacteria produced by just a few infected blossoms can result in a significant shoot blight epidemic. If only a few blooms are present, it may worth your while to remove them by hand. The time to prevent shoot blight is during bloom (with streptomycin applications) and during the dormant period (by removing cankers). Attempting to control shoot blight by applying streptomycin after the bloom period is usually futile, and not recommended. (SB)
5. Oriental Fruit Moth Alert
In Nashville (Davidson County) the Oriental
fruit moth (OFM) biofix was March 28 for our moderate to high density OFM peach orchard
(more than 10 moths caught per trap per week anytime after biofix). Two insecticide
applications should be applied 14 days apart, the first at 500 DD after biofix. Since
we reached 505 DD on Saturday April 27, spraying should begin immediately.
On
apples, the spray recommendation for OFM is between 800 and 900 DD after biofix with
a second application 14 days later
Tufted Apple Budmoth
Tufted
apple budmoths have been caught in Putnam County traps since April 19. The distribution
of this relatively new pest in Tennessee is currently unclear.
6. Pheromone
Trap Catches and Biofixes
Nashville (Davidson County) Pheromone Trap Catches
for 2002
| 3-15 put out | OFM | RBLR | OBLR | CM |
| 3-21 | 0 | 34 | 0 | put out |
| 3-25 | 0 | 8 | 0 | 0 |
| 3-26 | 0 | 5 | 0 | 1 |
| 3-27 | 0 | 0 | 0 | 0 |
| 3-28 | 2 biofix | 0 | 0 | 1 |
| 4-1 | 2 | 13 | 0 | 1 |
| 4-2 | 5 | 12 | 0 | 0 |
| 4-3 | 1 | 5 | 0 | 0 |
| 4-5 | 0 | 0 | 0 | 0 |
| 4-8 | 0 | 5 | 0 | 1 |
| 4-9 | 1 | 5 | 0 | 0 |
| 4-11 | 4 | 5 | 0 | 0 |
| 4-12 | 5 | 0 | 0 | 0 |
| 4-15 | 22 | 7 | 0 | 0 |
| 4-18 | 39 | 3 | 0 | 0 |
| 4-19 | 24 | 0 | 0 | 0 |
| 4-22 | 29 | 0 | 0 | 0 |
| 4-25 | 5 | 1 | 0 | 0 |
| 4-29 |
Biofix for RBLR in Davidson County estimated as occurring on March 14
Bradley County Pheromone Trap Catches
| 3-14 put out traps | OFM | RBLR | CM |
| 3-15 | 6 biofix | 67 | 0 |
| 3-16 | 6 | 49 | 0 |
| 3-17 | 30 | 18 | 0 |
| 3-18 | 38 | 14 | 0 |
| 3-23 | 55 | 21 | 0 |
| 3-30 | 14 | 5 | 0 |
| 4-6 | 23 | 5 | 0 |
| 4-13 | 46 | 18 | 1 |
| 4-20 | 77 | 23 | 20 |
Codling moth biofix was April 14
Putnam County Pheromone Trap Catches
| OFM | RBLR | CM | TABM | |
| 4-2 | 0 | 11 | 2 biofix | 0 |
| 4-3 | 0 | 33 | 4 | 0 |
| 4-5 | 0 | 7 | 0 | 0 |
| 4-8 | 11 | 16 | 2 | 0 |
| 4-10 | 13 | 8 | 0 | 0 |
| 4-12 | 0 | 7 | 0 | 0 |
| 4-15 | 2 | 34 | 0 | 0 |
| 4-17 | 3 | 19 | 0 | 0 |
| 4-19 | 6 | 20 | 0 | 2 biofix |
| 4-22 | 3 | 11 | 0 | 5 |
| 4-23 | 0 | 0 | 0 | 13 |
| 4-26 | 0 | 0 | 0 | 2 |
Obion County Pheromone Trap Catches
| 4-10 put out | OFM | RBLR | CM |
| 4-12 | 2 | 3 | 0 |
| 4-19 | 21 | 9 | 0 |
| 4-26 | 8 | 4 | 0 |
(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, Associate 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
