Fruit Pest News
Volume 9, No. 5 April 16, 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. Deer and Strawberries
3. Strawberry Plant Dip for Anthracnose Control
4. Early-Season Grape Disease Control
5. Presidio Note
6. Apples: Disease Control During Bloom and at Petal Fall
7. Tufted Apple Budmoth
8. Pheromone Trap Catches
1. Current Conditions
Heavy frost occurred in much of the state on tax day, with apples, blueberries, and strawberries in bloom. The amount of damage remains to be seen. The weather for the next week should be mild with shower activity, but not excessive rainfall. Apple growers should find fire blight to be manageable under those conditions. Aphids were first seen on apples on April 8. (SB)
2. Deer and Strawberries
Most strawberry growers know how much deer love strawberry leaves. Most growers are also reluctant to build an expensive fence to keep them out. Here's another option -- Thiram Granuflo. As a taste repellent for deer, you get a lot of bang for your buck with thiram, because it is also a fungicide, effective against Botrytis and anthracnose. Labeled for decades, research has shown that thiram is essentially as effective as captan against those two diseases. The downside is a 3-day preharvest interval, so thiram is not compatible with a harvest schedule. But prior to harvest, thiram use makes a lot of sense. Note: Thiram Granuflo is labeled only for use on strawberries and peaches. (SB)
3. Strawberry Plant Dip for Anthracnose Control
Strawberry anthracnose sometimes enters a field on infested plants. The causal fungus may be present on the crown, root, and stem surfaces, or it may be internal, as infections that are not yet visible. Research has shown that the incidence of anthracnose in the field can be greatly reduced if transplants are dipped in appropriate treatments before planting, to kill the surface spores. These treatments will not rid the plants of anthracnose infections, because they are internal and beyond the reach of the chemicals.
The azoxystrobin products, Quadris and Abound, are labeled for use as strawberry plant dips. Wash soil off roots before dipping. Mix 5-8 fl oz of Quadris or Abound per 100 gal of water. Dip plants by immersing completely for 2 to 5 minutes. Plant treated plants as quickly as possible. The hydrogen dioxide product, OxiDate, is also labeled for this use. Mix 1 gal per 100 gal of water, immerse, remove, and allow to drain. Do not rinse. Plant as soon as possible after treatment. Use personal protective equipment as specified by the labels when dipping. (SB)
4. Early-Season Grape Disease Control
Grapes have begun growth and many are at the 1- to 2-inch shoot stage at which the first fungicide spray is recommended. Traditionally, it has been thought that successful black rot control required beginning the spray program at this early stage. Recent research conducted in New York and here in Tennessee has shown that this is not the case. The black rot fungus does not become active until later. The first spray is needed during the pre-bloom period, about 10 to 14 days before bloom. You could save yourself the cost of a fungicide spray at the 1-inch shoot stage if it weren't for the fact that other diseases such as Phomopsis cane and leaf spot, downy mildew, and powdery mildew can also begin activity at this stage of growth. However, this does mean that your fungicide selection at this time should be based on diseases other than black rot.
Choose a fungicide(s) based on the history of disease problems in the vineyard, using an efficacy table such as the one in the regional spray guide. Sterol inhibitor fungicides can be used in the early sprays, but keep in mind that they do not provide control of Phomopsis or downy mildew. The broad-spectrum protectants (e.g. captan, mancozeb, maneb, ziram) are better choices for control of theses diseases. The sterol inhibitors or sulfur should be used where powdery mildew is expected.
Strobilurins have the broadest spectrum of activity, but are more expensive and are limited to 4 applications per year. There have been some reports of resistance to the strobilurins in the grape powdery mildew and downy mildew fungi, similar to those for pathogens of other crops. Resistance should not be a serious problem if you follow the recommended guidelines for resistance management. The most recent reports are a reminder of the need to do so. (SB)
5. Presidio Note
As a reminder, the new vegetable fungicide Presidio is currently labeled only for use as a foliar spray, contrary to the information being given in press releases. Drip irrigation applications are expected on pending labels, not yet approved. (SB)
6. Apple: Disease Control During Bloom and at Petal Fall
The sterol inhibitors (SI's) are important fungicides for the control of apple scab, powdery mildew, and rust diseases. Examples of SI's are Nova, Rubigan, Indar, and Procure. Some areas of the country are beginning to experience loss of control of scab due to the development of strains resistant to the SI's. As far as I know, this has not happened in Tennessee. (If you think it is happening in your orchard, please let me know.) Let's try to prevent resistance from developing by always tank mixing our SI's with a protectant fungicide such as mancozeb, captan, ziram, etc., and using SI's only when necessary.
Bloom. If your bloom-time spray is applied only 6 or 7 days after the pink tip spray, it may not be necessary to use fungicides with lengthy kick-back activity (i.e. the SI's). A contact material such as mancozeb or ziram may be sufficient at that time, and these two materials would also provide rust control. However, these materials are not suitable for powdery mildew control. For mildew-susceptible varieties such as Jonathan, Ginger Gold, Rome Beauty, Stayman Winesap, Idared, Paulared, and Granny Smith, mildewcides such as the SI's, Topsin M, or sulfur should be used in each spray until terminal growth stops. Early season sprays (tight cluster to petal fall) are essential if mildew is to be managed successfully.
Petal fall. Petal fall through first cover is a peak risk period for powdery mildew, cedar-apple rust, and fruit infection by scab. Use an SI with a contact fungicide at each of these two growth stages. Note: I recommend that the strobilurin materials (Flint, Sovran) be reserved for use during the summer, when their characteristics are more fully utilized. (SB)
7. Tufted Apple Budmoth
In the mid-Atlantic region, tufted apple bud moth
resistance to organophosphate insecticides in the 90s made this pest one of the most
serious direct fruit pest of apples. Fortunately, the distribution of this pest
is not as wide-spread in Tennessee. Also, the advent of new chemistry has led to
better control of this pest. Currently recommended insecticides include the new
products Intrepid, Delegate WG, SpinTor 2 SC, Avaunt 30WDG, and Rimon 0.83EC. The
Bt insecticides Dipel 2X, CryMax, and XenTari plus the pyrethroid Danitol 2.4EC are
some older products that are also recommended. for best results, Bt products should
be applied at no less than 2X concentration. Also, be aware that Bts do not control
codling moths so it is important to monitor codling moths with pheromone traps to
determine when to use a recommended insecticide for this pest.
The tufted
apple bud moth has two generations per year. The larvae overwinter on the ground
sheltered in leaves or dried up fruit. In early spring, the larvae move to a variety
of host plants such as dandelion, wild strawberry, dock and apple tree root suckers
to feed and complete development.
Four tufted apple bud moths were caught
in pheromone trap in Bradley County on April 12 (biofix date) and two more were reported
for April 14. For first generation tufted apple bud moth, two insecticide applications
per generation are recommended when population densities are sufficiently high or
if a short residual insecticide is used. Make the first application at about 10
percent egg hatch, which occurs between 800 and 900 DD after biofix, and a second
application 14 days later. When populations are low or if using a long residual
insecticide, one application per generation should be used and this can occur anytime
between 10 and 30 percent egg hatch of the first generation, or from 800 to 1,200
DD after biofix. Control decisions for a second generation of this pest will need
to be made in early to mid-August or about 2,600 DD after biofix. More on that at
a later date.
One cultural control that can be done this spring is to thin
fruit to avoid excessive clustering because clustering of fruit is conducive to higher
levels of tufted apple bud moth injury.
8. Pheromone Trap Catches
The
biofix for redbanded leafroller was March 13 for Nashville (Davidson County) and
March 21 in Putnam County. This past week seven redbanded leafrollers were caught
April 9 in Putnam County while one redbanded leafroller was caught in the Nashville
trap on that same date. In Nashville, two Oriental fruit moths were caught by April
11 (biofix date). The biofix for tufted apple bud moth in Bradley County was April
12 (see prior article) (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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