Fruit Pest News
Volume 8, No. 3 March 27, 2007
A weekly, 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. Apple: Tips for Fire Blight Control During Bloom
3. Early-Season Apple Fungicide Sprays
4. Water Quality and Fresh Produce
5. Apple: Insecticides for Tight Cluster to Pink Sprays
6. Pheromone Trap Catches
1. Current Conditions
The weather continues to be hot and dry, but some changes are in the forecast. Showers and thunderstorms may bring some relief from the drought.
Strawberries are in bloom, and the mid-80 degree weather we have been experiencing has approached the critical temperature level used by Dr. Barclay Poling for heat injury on Chandler blossoms. However, I think we escaped damage. The heat has been accompanied by considerable cloudiness, which has suppressed heat buildup near the plastic.
Apples are now in bloom, and the fire blight bacterial population has never been more ready. On trees that had fire blight last year, overwintering bacteria have enjoyed uninterrupted population growth after continuous warm day and night temperatures. Hopefully, you treated these trees with copper prior to green tip. If showers or dews occur at your location during bloom, frequent streptomycin sprays may be needed to protect the open blossoms. Daytime temperatures over the next week are expected to remain in the 70's and 80's. Refer to the following article for tips on using streptomycin.
Unless your apple location has had a shower lately, there have not been any cedar-apple rust or scab infections. As a result, no "kick-back" activity is needed from a fungicide now, and a protectant material such as mancozeb applied before the next shower should provide adequate control of rust and scab for the next week. (SB)
2. 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.
3. Early-Season Apple Fungicide Sprays
Although this has not been a spring for diseases, we shouldn't let our guard down on scab control. Scab needs to be treated early to prevent primary scab infections and thus break the disease cycle. Also, it is important to avoid early infections on sepals (calyx), as these are difficult to detect and can provide secondary inoculum throughout the early part of the growing season.
There are several different strategies for scheduling scab sprays. The selection of a spray program (what fungicide to use and how often) depends on factors such as other disease organisms present and the ability to obtain good coverage of the trees with the sprays. If cedar-apple rust or powdery mildew are a threat, it is probably best to control scab with a sterol-inhibiting fungicide (Nova, Procure, or Rubigan), because control of all three diseases would be obtained. Tank mixing with mancozeb or captan would improve the protectant ability and discourage the development of resistance to the sterol inhibitor (SI). Do not use captan within 2 weeks of an oil spray.
The 3- to 4-day curative activity of the SI fungicides makes them useful at tight cluster in case some scab infections occurred prior to that time. The SI/protectant combination allows you to space the applications 7 to 10 days apart.
Where cedar-apple rust is a problem, mancozeb or ziram should be used as the protectant, to be mixed with the SI. The strobilurin fungicides Flint and Sovran can be used in lieu of the SI's, but I recommend reserving these materials for use during the summer. They may only be applied 4 times per year, and they play a more valuable role during the summer than during the spring.
Conditions have been unfavorable for powdery mildew thus far, but that could change. Apple powdery mildew is favored by cool, wet weather. (SB)
4. Water Quality and Fresh Produce
by Dr. Bill Morris, UT Extension Professor, Food Science and Technology
If you are a grower of fresh produce, you need to be concerned about the quality of the water being used through out your entire production cycle. This includes irrigation water, chemical spray water, frost protection water and any water that comes in contact with the produce during processing. Because of the various situations the fresh produce industry has faced over the last year in the contamination of produce, it is incumbent on us to make sure any water that contacts ready-to-eat produce is of good microbial quality. The guidance on Good Agricultural Practices from USDA and FDA is found at: http://www.cfsan.fda.gov/~dms/prodguid.html.
Any water applied directly to ready-to-eat produce, such as overhead irrigation, should be tested and treated, if needed. Check with your local water district or the health department for that service. While the standard water testing for presence of coliforms is certainly a helpful monitoring program, it does not guarantee the water to be free of human pathogens.
Location of your field is also a very important issue today. If you have livestock production facilities nearby or if your field is positioned where run-off from such facilities can potentially be problem, you should be looking at buffer zones and how to prevent the run-off to your fields.
Remember the lowest common denominator in the industry is a reflection of the entire industry, so do your part. In addition, water quality is just one issue of concern. Get familiar with and start implementing Good Agricultural Practices at your farm today.
5. Insecticides for Tight Cluster to Pink Sprays for Apple
The
following information is provided for orchards in which the trees are not yet
in bloom. I had a call from a grower concerning
endosulfan (Thionex 3 EC, note that Thiodan 3EC and Phaser 3EC are no longer available
in Tennessee) about its effectiveness and safety. While it is probably less expensive
than the other recommended insecticides for this phenological plant stage, most of
the other insecticides have a higher effectiveness rating. Actara 25 WDG, Assail
30 SG, and Calypso 4F have a 5 star rating for effectiveness for rosy apple aphid,
plant bugs, and spotted tentiform leafminer. Danitol 2.4 EC has a 4 star rating and
Thionex 3EC and Diazinon 50W only have a 3 star rating.
All labels must have
a signal word that tells us how dangerous the product is to humans. Caution is the
signal word for a product that is only slightly toxic. Actara 25 WDG, Assail 30 SG,
and Diazinon 50W all have Caution on the label. Warning means moderately toxic and
Calypso 4F and Danitol 2.4 EC have Warning on their labels. Danger-Poison signals
that the product is highly toxic. The skull and cross bones can also be found on
these labels. Thionex 3EC has Danger-Poison flanked by the skull and cross bones
on the label.
Cost is not the only thing to consider when choosing a pesticide.
We just mentioned effectiveness and toxicity to humans. There is also toxicity to
beneficial insects and pesticide resistance. Using the same pesticide year after
year can sometimes lead to pesticide resistance problems. Rosy apple aphid has become
resistant to endosulfan, diazinon, dimethoate, and fenpropathrin (Danitol) in some
orchards in the southeast. (FH)
6. Pheromone Trap Catches
In Nashville,
plenty of redbanded leafrollers (RBLR) have been caught since February 22. Recently,
we have started to catch Oriental fruit moths (OFM) with the first one being caught
on March 21 in Nashville. There were 20 more OFM caught on March 26 [biofix].
Remember that the biofix is the date where you catch your first two or more moths
in the trap. This is the date which you use as a starting place for accumulating
degree-days (DD) that are used to predict future insect activity and help in the
timing of insecticide sprays. In Obion County, the first OFM (5) were caught on March
26 (biofix). In Putnam County, two OFM were caught on March 21 (biofix). In Putnam
County, only one OFM was caught on March 26 so the biofix has not yet been set.
There have been some unknown gray moths caught in the OFM trap. They are
twice the size of the actual OFM. Do not count these unknown tortricid moths. Also,
since March 16 in Nashville, there have been 54 unknown tortricid moths caught in
the codling moth trap (zero codling moth caught). These were also reported from
Bradley County traps. These moths are approximately the same size as codling moths
but are grey with a greenish tinge. They also have six or more raised bumps of scales
on the front wings. A dissecting scope or a good hand lens probably will be needed
to properly discern these unknown moths from codling moths. It is very important
that you correctly identify the first pest moths that you catch because these catches
will be used to set the biofix so that future moth flights can be predicted. (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 2007 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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