Fruit Pest News
Volume 9, No. 4 April 9, 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. Current Conditions
2. Peach Disease Control Reminders
3. Fungicides for Pears
4. Strawberry Disease Reminders
5. Tips for Fire Blight Control During Bloom
6. What Level of Insect Pressure to Expect in 2008?
7. Pheromone Trap Catches
1. Current Conditions
Weeks of benign weather and good rainfall are making for good fruit crop potential. Hopefully, there will be reduced disease pressure because of less inoculum buildup during last year's drought. See Dr. Hale's article below for silver linings to last April's freeze. Peaches at Nashville are at petal fall, Golden Delicious apples are at pink tip, Tifblue blueberries at early bloom, blackberries at 2-inch shoot growth, and grapes at budbreak. Canker diseases are going to be a problem for trees this year, following the drought stress of last year. Fungal cankers are more severe on drought-stressed trees and tend to show their effects in the year following the stress factor. There is a chance of frost at higher elevations on Sunday morning. (SB)
2. Peach Disease Control Reminders
Your trees are probably not yet at shuck split, and fungicide sprays applied at petal fall are of little to no value for scab control, but don't be late with your shuck split spray. Damage caused by peach scab infections that occur because of a lack of protection cannot be undone. Curative fungicides applied within 3-4 days of an apple scab infection are effective in arresting its development, but not so much with peach scab.
If you use copper, take steps to reduce phytotoxicity chances. At petal fall, the rate should be no more than 0.5 lb metallic copper equivalent (e.g., 1.25 lbs Kocide 2000). At shuck split, the rate falls to 0.10-0.25 lbs metallic copper. The copper rate is reduced further at each growth stage because each stage is more sensitive than the previous. Apply copper only under good drying conditions and adjust spray tank water pH to 6.5 or higher. (SB)
3. Fungicides for Pears
We don't have a pear industry in the Southeast sufficient to justify the production of a spray schedule. However, there are a few trees, and some growers have noticed that the captan label does not include pears. This registration was lost as a result of the special review for this product. Captan is a very valuable fruit fungicide considering its broad spectrum of control and its freedom from resistance concerns. What should you use in its place on pears?
Commercial growers have several options -- Ziram, Topsin M, and the strobilurin products Sovran, Flint, and Pristine are broad-spectrum fungicides that would be suitable for use on pears during the spring or summer. Ferbam is also labeled but is not sold in Tennessee. Scala, Vangard, Procure, Rubigan, and mancozeb can be used during the spring, when the primary target would be pear scab. Mancozeb and maneb are sold in small containers for homeowner use, but cannot be used on home fruit trees. For home pear trees, copper and sulfur would be the only fungicide choices. (SB)
4. Strawberry Disease Reminders
Strawberries in full bloom plus rainy weather = Botrytis problems. They may not show up until harvest, but you need protection now. Keep up your fungicide spray program as best as you can. Elevate, Switch, and Scala are the best botryticides and are in different FRAC groups. It is best to rotate 3 different classes for resistance management.
If anthracnose is expected, include an appropriate fungicide in the schedule. If you are one of the few who were affected by the C. gloeosporioides type of anthracnose, your strategy will not differ appreciably from that of C. acutatum control -- basically, captan and strobilurins. The effects of Switch on Cg are not known. See the March 19 issue for details. (SB)
5. Tips for Fire Blight Control During Bloom
The bloom period is a key time for fire blight management in apple and pear. It is during bloom that the most damaging of the fire blight infections take place. It is also the time at which streptomycin (Agri-mycin, Firewall, Streptrol) sprays are most effective . . . in fact, we no longer recommend streptomycin after bloom (unless there is a hailstorm) because of its lack of effectiveness against the shoot blight phase. The following points should help you to use streptomycin efficiently.
6 . What Level of Insect Pest Pressure to Expect in 2008?
The effect of the
Easter freeze of 2007, which devastated most fruit crops in Tennessee, may have a
silver lining in 2008. The drought was so severe that if trees had carried a crop
last year, they would have been even more stressed and many more trees might have
died. Also, direct fruit pests such as codling moth, plum curculio, and apple maggot
need fruit for the larvae to feed and develop. Without commercial fruit, backyard
fruit, or even wild host plants producing fruit last year, the levels of many of
these direct fruit pests should be greatly reduced in 2008. The Oriental fruit moth
is also a direct fruit pest but it can tunnel near the end of succulent cherry, pear,
and cherry in May, June and July. This ability to develop for several generations
without fruit will probably allow Oriental fruit moths to better survive the adverse
conditions. Thus, populations of Oriental fruit moths should still have the potential
to cause significant damage this year. We will know much more about current pest
populations as we record pheromone trap catches this spring and compare them to past
trap catches.
The potential for low pest pressure for several of the key
pests may make this a good year to try mating disruption of codling moth and Oriental
fruit moth, especially on apple where codling moth is usually considered the number
one direct fruit pest.
In apples, Oriental fruit moth is much easier to control
with mating disruption compared with codling moth. While moderate to high codling
moth populations require that both mating disruption and insecticides should be used,
low codling moth populations should not require the addition of an insecticide with
the mating disruption. Mating disruption will not control infestations resulting
from immigrating fertilized female moths; hence, mating disruption alone is not recommended
in blocks located adjacent to a likely source of immigrating moths such as abandoned
orchards or bin storage areas. Note that mating disruption is effective only in blocks
of 5 acres or more.
In apples, place codling moth pheromone (mating disruption)
dispensers in the orchard before adults begin to fly in the spring and should be
completed by no later than petal fall. Dispensers should be hung in the upper third
of the canopy, because this is where mating occurs.
Season-long Oriental
fruit moth mating disruption dispensers should be in the orchard around green tip
of 'Delicious' apple cultivars. If insecticides are used for other pests at petal
fall, this spray application should control first generation Oriental fruit moth.
Thus, mating disruption of Oriental fruit moth can be delayed until just before emergence
of the second or third generation adults (950 and 1850 DD after biofix, respectively).
In peaches, Oriental fruit moth mating disruption is effective only in blocks
in excess of 5 acres with low populations. A one-year transition from insecticide
only to a combination of insecticide and mating disruption may be required in situations
with moderate to high Oriental fruit moth pressure. Accurately time insecticide
sprays targeted at larval populations in April and May, Then, before moth flight
begins in mid to late May, place in the upper third of trees 100 of the Isomate-M100
per acre for Oriental fruit moth (gives 90 days of control). A second application
of Isomate M100 may be needed in early August. Monitor for fruit damage weekly,
especially at the edge of the orchard where migrating females may lay eggs. Apply
insecticides to areas or blocks with damage. (FH)
7. Pheromone Trap Catches
The
biofix for RBLR at the Nashville location was March 13. Black cutworm, Oriental fruit
moth, codling moth, obliquebanded leafroller, and variegated leafroller pheromone
traps were put out at the Ellington Agricultural Center in Nashville last week. No
moths have been caught yet. (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
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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