Fruit Pest News
Volume 4, No. 1 March 10, 2003
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.
Welcome! to the first issue of the fourth volume of Fruit Pest News. We hope the newsletter is helpful to you, so please let us know of any changes we can make to better meet your needs. One of our most important functions is to keep you apprised of pest occurrences in the state. So please let us know when you see a disease or insect for the first time for the year, or if you have an unusual outbreak. We won't use your name. Our contact numbers are at the end of each issue of the newsletter.
Fruit Pest News also brings you research reports, pesticide registration changes, and other pest-related news. The newsletter will be compiled each Monday and should be available for viewing on the Internet the following day. There will be a new issue each week through mid-July, then every two weeks through early October.
In This Issue:
1. Crop Development Stages
2. Blackberries: Prepare for Production Without Benlate
3. Blueberries: Cabrio Registered
4. Strawberries: Fungicide News
5. Strawberries: Field Sanitation for Gray Mold Management
6. Tree Fruit: Dormant Oil Sprays
7. Methyl Bromide Exemptions Applied For
1. Crop Development Stages
Old Man Winter was in rare form this year -- rare compared to the last several years! Hopefully, this is good news for fruit growers -- you should reap some benefits from this turn of events. Pest numbers should be reduced by the cold weather. And if we have frost damage this spring, at least it won't be because of premature bud development -- the cold weather has lasted long enough to delay bud development.
Buds are swelling now. Peach trees are at the green calyx stage of swollen bud and blackberries are at 1/4 inch green tip. At the Plant and Pest Diagnostic Center at Nashville, the earliest blueberry cultivar in the planting, O'Neal, has not yet begun to bloom, and is about two weeks behind normal. (SB)
2. Prepare for Blackberry Production Without Benlate
As you probably know, Benlate fungicide has been discontinued by the manufacturer. You can still use it if you can find it. Blackberry growers should make an attempt to locate some Benlate. For anthracnose control, there are no known effective alternative products registered for blackberries at this time. The new strobilurin fungicide, Cabrio, is labeled for brambles. However, its relative effectiveness for control of anthracnose is not known. As more research information becomes available, we will be in a better position to recommend Cabrio for anthracnose control in brambles.
What to do if you have anthracnose-susceptible cultivars and do not have any Benlate: Use liquid lime-sulfur at 1/4 to 1/2-inch green tip stage of growth (now). This will not provide an adequate level of control of anthracnose by itself, but it will reduce initial inoculum. If you use lime sulfur, it is important that this operation be done soon, as this material can burn leaves if applied later. Then, use a fixed copper at two-week intervals according to the label. Avoid mixing insecticides with copper, especially in hot weather, as phytotoxicity can occur.
Benlate is also used on blackberries for control of rosette disease. However, a suitable alternative is available in the form of copper. Extensive research conducted by Barbara Smith, USDA-ARS in Poplarville, MS, indicates that copper is as effective as Benlate for control of rosette. As always, don't try to rely entirely on chemicals for control of rosette disease. Timely removal of rosettes is key. (SB)
3. Cabrio Registered for Blueberries
Cabrio fungicide has received federal registration for use on blueberries. This material will be of particular use in plantings in which blueberry anthracnose (ripe rot) has been a problem. Cabrio also has activity against Phomopsis twig blight. Since Cabrio is limited to 4 applications per year, use it only during critical infection periods for these two diseases, i.e. beginning at full bloom. Repeat at 7- to 14-day intervals, but not for more than two consecutive applications before alternating to a non-strobilurin fungicide. Captan would be a good rotation fungicide for the strobilurins on blueberries, as captan provides good control of anthracnose, Phomopsis, and mummy berry. The two labeled strobilurin materials, Cabrio and Abound, offer particularly good control of blueberry anthracnose. (SB)
4. News on Strawberry Fungicides
The new strobilurin fungicide from BASF, called Cabrio, is registered for use on strawberries. As a strobilurin, Cabrio is related to Quadris, and should not be rotated with it, so as not to encourage fungal resistance. The disease-control profile for Cabrio on strawberries is not well defined. The label lists anthracnose, leaf spot, and powdery mildew, but little research data is available for these uses. North Carolina data indicates that Cabrio performs comparably with Quadris for anthracnose control, and Florida data indicates only moderate control of powdery mildew. Until more research data becomes available, I recommend proceeding cautiously with the use of Cabrio on strawberries.
Cabrio and Quadris were found to provide good control of leather rot in a trial I conducted last year at Nashville. This disease is not found on either label. Treatments were begun at full harvest and repeated at 7-day intervals. Remember that these materials should not be used in rotation with each other, and that you should rotate to captan or thiram after the second consecutive application.
Procure fungicide, from Crompton/Uniroyal, is a sterol inhibitor that is now labeled for use on strawberries. Only powdery mildew is on the label. Procure is known to provide excellent control of powdery mildew; what is not known is whether Procure will control leaf spot or leaf blight, as will the related fungicide Nova. (SB)
5. Strawberry Field Sanitation for Gray Mold Management
Many plasticulture strawberry producers remove senescent (dead and dying) leaves and stems from their plants before first bloom in the spring. This practice (leaf sanitation) eliminates a food base for the Botrytis fungus and, thus, reduces the amount of spores available for infecting the blossoms. This practice should be done before bloom, because leaf sanitation would damage the blooms. Recent research has cast some doubt on the usefulness of leaf sanitation, but is still practiced by many growers. (SB)
6. Dormant Oil Sprays
If anything, dormant oil sprays are more important now
than ever. Dormant oil sprays help prevent problems down the road. On peaches,
oil helps control San Jose scale and white peach scale as a dormant or delayed dormant
spray. At dormant, two applications at 10-14 day intervals works best. At delayed
dormant to 1-5% bud swell, Lorsban 4E can be added to strengthen performance against
scale crawlers and suppression of lesser peachtree borer on peaches. Do not use
oil after 5% bud swell.
European red mite eggs and San Jose scale are controlled
on apples at green tip to 1/2 inch green. The use of one of the recommended insecticides
with oil will help control scales and climbing cutworms. Esteem will control San
Jose scale if applied before 1/2 inch green. If you are having scale problems, avoid
using pyrethroid insecticides during the growing season, because they can kill scale
predators and parasitoids that normally would help manage scale populations. There
are new insecticides and miticides available for tree fruit, but if you can manage
a pest using the less expensive dormant oil, then it behooves you to get all you
can out of the oil sprays. (FH)
7. Methyl Bromide Exemptions Applied For
The soil fumigant methyl bromide is used in nearly all plasticulture strawberry production and much of our tomato acreage. The sale and use of this valuable material is due to be completely phased out by 2005 due to environmental concerns. Fifty-six requests for two-year exemptions for critical uses for methyl bromide beyond the 2005 deadline were filed with EPA. Tennessee was included in several of these requests. Many of these requests have been submitted to the Ozone Secretariat of the United Nations for the final decision. These two-year extensions would hopefully buy enough time for researchers to develop adequate alternatives to methyl bromide. (SB)
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