Fruit Pest News

Volume 5, No. 8  May 4, 2004

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: Fungicide Spray Program

    3. Apple: Fire Blight Secondary Blooms

    4. New System of Grouping Pesticides

    5. Periodical Cicadas

    6. Pheromone Trap Catches

1. Current Conditions

Some areas, particularly the higher elevations of Tennessee, received some frost this morning. The weather was unusually cool the past couple of days, but we have been spared major frost/freeze problems this spring. Apple scab lesions began to appear at Nashville on May 1. I have not seen grape black rot yet, but lesions should appear soon resulting from the infections of April 21 and 22, according to the Spotts model. I have not heard from the strawberry growers, so there must not be major problems yet, during the early part of the harvest season. (SB)

2. Fungicide Spray Program for Blackberries

The blackberry section of PB1197, Commercial Small Fruit Spray Schedules, is an index style guide in which pests are listed alphabetically. It is left up to the grower to taylor his/her own spray schedule, using the listed pesticides, because no single spray schedule fits all blackberry plantings. The spray schedule below is provided for those who may need some help in designing a program.

The rosette (double blossom) schedule is based on research conducted by Dr. Barbara Smith, USDA-ARS, who has found that Pristine and Switch are among the most effective labeled fungicides for rosette control. Primocanes need protection in rosette fields as long as infected blooms are open, which can last from the bloom period until after harvest ends. Remember that the benefits of a rosette spray program will not be seen until the following spring, when this year's primocanes come out of dormancy.

Rates can be obtained from PB1197 or the product labels. Always read and follow label directions.

3. Fire Blight: Secondary Blooms

Most apple varieties have finished blooming, with the exception of secondary (tag-on) blooms. The MaryBlyt program ceases to predict fire blight infection periods and the need for streptomycin sprays after all blooms are gone. We do not recommend the use of streptomycin after bloom because of its ineffectiveness against shoot blight infections, and because such use increases the risk of resistance developing. The time to prevent shoot blight is during bloom (with streptomycin applications) and during the dormant period (by pruning out cankers).

Beware, however, of tag-on blooms. Streptomycin sprays may be needed as long as they are present. 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. In such warm weather, tag-on blooms can easily become infected and negate all your hard work in preventing infections during the bloom period! If only a few secondary blooms are present, it would be worth your while to remove them by hand, because they potentially represent the beginning of a fire blight epidemic! (SB)

4. New System of Grouping Pesticides: Resistance Management

The EPA has rearranged the groups of pesticides so that the groups are more meaningful for pest resistance management purposes. The new classification is based on mode of action, which is the important factor in resistance management. When pests develop resistance, they are resistant to all compounds with the same mode of action (site of activity in the pest). The old classification system is by chemical class. The new system results in fewer groups, because several chemical classes can have the same mode of action, as shown in the table below.

Pesticide labels (and university publications) often say "Rotate with a non-related fungicide." Growers often ask "What fungicides are not related to this one?" The new system should clear this up. The list below provides the fungicide groups pertinent to fruit and vegetable crops. This is a voluntary classification system as far as inclusion on the label, but some manufacturers have already begun printing the group number on the label.

A complete list of all of the groups of all pests can be found at http://www.epa.gov/PR_Notices/pr2001-5.pdf (SB)

5. Periodical Cicadas

Brood X of the 17-year periodical cicada is due to emerge in May. They will probably emerge by May 12 or so. In 1998, brood XIX of a 13-year brood emerged in Nashville in mass on May 12 when the soil temperature was approximately 67 degrees F. I measured the temperature four inches deep today and it was only 59 degrees F after the cool rain. The soil temperature has some warming up to do before their emergence.

If you are not sure if you had brood X in 1987, one way to find out is to look for hundreds of holes beneath the trees. The cicadas are mature and are making exit tunnels to the surface even though they may mot come out for 10 days or more from now. If you do not see these half inch diameter holes, chances are that you will not be having an emergence to worry about. Another way to tell is to dig down 6 inches or so beneath your mature shade trees in the yard. comb through the soil for the cicada nymphs. The mature brood X nymphs are nearly 17 years old and 1 inch long. If you only find much smaller 3/8 inch nymphs, these are probably the 6 year old nymphs from the 13-year periodical cicada (brood XIX) that last emerged in 1998. They have 7 more years before they will be full grown and ready to emerge in 2011. There is another 17-year brood XIV slated for emergence in 2008. This on last came out in 1991 so these nymphs will be somewhat larger than 3/8 inch but not nearly fully mature and 1 inch long.

It is important to keep track of which broods that you have at you orchard. Plan your tree planting so that do not plant trees in the winter prior to a cicada emergence. Young trees have the greatest chance of suffering significant damage from cicada egg laying. (FH)

6. Pheromone Trap Catches

Bradley County Pheromone Trap Catches

*Four RBLR moths caught in trap from lat year. Biofix for redbanded leafroller in Bradley County estimated as occurring on February 29.
**OFM biofix on March 19.
*** CM biofix on April 23.
**** TABM biofix on April 23.

Putnam County Pheromone Trap Catches

*Biofix for RBLR in Putnam County estimated as occurring on February 29.
**Biofix for OFM estimated as occurring on April 7.
*** Biofix for OBLR on April 16 (waiting for confirmation).

Smith County Pheromone Trap Catches (Two orchards, a set of traps at each site))

* Biofix for RBLR estimated as occurring on February 29.
** Biofix for OFM estimated as occurring on April 9.
*** Biofix for CM on April 21(waiting for confirmation)
**** Biofix for OBLR on April 28 (waiting for conformation)

The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm

Contacts:

Steve Bost, Professor and Extension Plant Pathologist

scbost@utk.edu

Frank Hale, Professor and Extension Entomologist

fahale@utk.edu

Both authors available at:

615-832-6802

fax 615-781-2568

Plant and Pest Diagnostic Center

5201 Marchant Drive

Nashville, TN 37211