Fruit Pest News Volume 5, No. 5 April 13, 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. Strawberry Anthracnose Makes Its Appearance 3. Apple Disease Control During Bloom and At Petal Fall 4. Blackberry: Time to Watch for Rosette Disease 5. Apple: MaryBlyt Update 6. Tree Fruit: Pheromone Life Span 7. Grape Berry Moth 8. Tree Fruit: Pheromone Trap Catches and Biofixes 1. Current Conditions Cool weather has held everything back, and rainfall was fairly scarce until the soaker of April 11-13. There were several light frosts last week that killed some unprotected strawberry blossoms. Although there are no killing frosts in the forecast, there was some snow in West Tennessee on the morning of April 13. Crop development has been slow, but is still largely intact. (SB) 2. Strawberry Anthracnose Makes Its Appearance To refresh your memory, several strawberry growers received plants last fall that were infected with anthracnose. Most growers chose to use the plants and hope for the best, because there were no other plants available. Well, it appears that the dreaded time has come. Anthracnose was found on April 6 in some research plots at the Knoxville Experiment Station. Plants from Ghesquire Farms were used in these plots last fall. Symptoms. Click here for an image of the plants, taken on April 6. The disease is appearing as a crown rot and a rot of the petiole base. In the warm, humid environment of black plastic mulch, development of the disease is hastened, and the leaves may collapse due to a soft, wet rot of the petiole base. The petiole lesions appear dark and firm when they dry out. Infections of leaves appear as irregular lesions http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (1 of 6)12/6/2012 3:32:17 AM
associated with the leaf margins. What to do. If a small number of plants are affected, begin a spray program of Captan plus one of the strobilurins (Quadris, Cabrio, or Pristine). Repeat at weekly intervals, but do not apply Quadris, Cabrio, or Pristine more than twice consecutively, even if tank mixed with other fungicides. After the second application, use Switch fungicide, which has activity against both anthracnose and Botrytis. Pristine also has good Botrytis activity. During the bloom period, additional Botrytis protection may be needed when applying Captan + Quadris or Cabrio. Elevate can be used for this purpose. If a large percentage of the plants have crown rot, it is probably not worth the trouble and cost of trying to salvage a portion of the crop. When only the fruit rot phase of anthracnose is to be considered, there is always hope because the weather may cooperate. Crown rot infected plants are going to die regardless of the weather. If a limited number are infected, you can protect the healthy plants with sprays. Do not be mislead by the "systemic" name for many fungicides. They will not rescue infected plants. Any curative activity they may have is limited to recent, not-yet-visible infections, and for the strobilurins, this activity is very limited. (SB) 3. 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, 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) http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (2 of 6)12/6/2012 3:32:17 AM
4. Time for Blackberry Growers to Watch for Rosette Disease Blackberries will soon be blooming. Growers should look for evidence of rosette, also known as double blossom. This fungal disease can be very destructive, and indeed has been known to drive growers out of the blackberry business. The fungus can drastically reduce yields by causing sterility of the blossoms and through its debilitating effect on the plant. The key to managing rosette is to remove the infected blossom clusters before the blossoms open. That is because all of the spores that cause new infections come from infected blossoms. The infected blossom clusters should now be apparent. They are recognized as bunchy growths consisting of multiple shoots, rather than the normal single shoot. Such growths are known as rosettes or witch's brooms. The sepals (the green, leaf-like structures that enclose blossoms) are abnormally long and pointed. When the blossoms open, they will be pinkish and ruffled. Fungicide applications will help to control infections that result from spores that enter the planting from nearby wild blackberries. Benlate alternated with copper fungicides can be applied at 10-14 day intervals, beginning about 6 weeks before harvest. Do not expect the applications to control rosette in this year's crop. Fungicides applied this year control rosette in next year's crop by protecting the new primocanes. Any rosettes you see this year arose from infections that occurred on last year's primocanes. Fungicidal control also has a place if you do not currently have rosette, but are growing a susceptible variety. Shawnee is particularly susceptible. Cherokee, Comanche, Triple Crown, and Black Satin are also quite susceptible. Chester, Hull, Lock Ness, Arapaho, and Navaho have good tolerance. (SB) 5. MaryBlyt Update There have not been any fire blight infections here at the Plant and Pest Diagnostic Center orchard, according to the MaryBlyt model. The weather has been too cool. We had a couple of days last week with light rain and temperatures warm enough for infection. However, those days were preceded by temperatures too cool to allow the bacterial population to build up. Serious fire blight infection requires several consecutive days of warm weather, specifically 65F or higher. On days in which the temperature does not reach 65, bacterial colonization is reduced and bee activity is reduced, thus spread is reduced. Meanwhile, flowers will continue to mature at temperatures above 40F and become resistant as they enter petal fall. (SB) 6. Pheromone Life Span http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (3 of 6)12/6/2012 3:32:17 AM
The redbanded leafroller, obliquebanded leafroller, tufted apple budworm and grape berry moth pheromone needs to be changed each month. I changed the Nashville trap pheromone for these pests last week. The Oriental fruitworm pheromone that I use will last all season while the codling moth pheromone will last 8 weeks. (FH) 7. Grape Berry Moth I do not have much experience with this pest but it seems to be out a bit earlier than I expected. I contacted Dr. Donn Johnson at the University of Arkansas and he said that they usually catch them until April 15. He said that if calculating degree days, use a base developmental temperature of 50 F. Time the first insecticide spray for 500 degree days (DD) after the first catch (biofix). This is just before the grapes are big enough for GBM larvae to feed internally (late May). Some larvae emerge earlier (400-500 DD) but will be killed by spray applied at 500 DD because all larvae are still exposed outside of the fruit. There is some new (2001) research that uses 47.14 F as the base temperature. This model says that 407 DD after biofix equals egg hatch. (FH) 8. Pheromone Trap Catches and Biofixes Nashville (Davidson County) Pheromone Trap Catches for 2004 OFM RBLR OBLR CM GBM 3-4 (put out RBLR trap) 0 3* 0 0 0 3-5 (put out new traps) 0 15 0 0 0 3-8 0 29 0 0 0 3-10 0 4 0 0 0 3-15 0 10 0 0 0 3-17 0 11 0 0 0 3-19 0 13 0 0 0 3-22 1 25 0 0 0 3-24 0 14 0 0 0 3-29 25** 62 0 0 0 4-1 0 17 0 0 6*** 4-2 0 9 0 0 0 4-5 1 24 0 0 0 4-7 14 10 0 0 1 http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (4 of 6)12/6/2012 3:32:17 AM
4-8 1 5 0 0 2 4-12 12 15 0 0 2 * The three RBLR caught in trap left over from last year. New RBLR trap put out 3-4-04. Biofix for RBLR in Davidson County estimated as occurring on February 29. **Biofix for OFM estimated to have occurred on March 26. ***Biofix for grape berry moth (GBM) estimated as occurring on 3-30. Bradley County Pheromone Trap Catches 3-10 new traps put out OFM RBLR CM TABM 0 4* -- 0 3-13 0 59 (catch for now on from 2 -- 0 traps) 3-19 2** 43 -- 0 3-26 put out CM traps 2 28 -- 0 *Four RBLR moths caught in trap from last year. Biofix for redbanded leafroller in Bradley County estimated as occurring on February 29. **OFM biofix on March 19. Putnam County Pheromone Trap Catches OFM RBLR OBLR CM 3-8 0 31* 0 3-15 0 51 0 3-29 0 49 0 0 4-3 0 73 0 0 4-10 13** 37 0 0 *Biofix for RBLR in Putnam County estimated as occurring on February 29. **Biofix for OFM estimated as occurring on April 7. Smith County Pheromone Trap Catches (Two orchards, a set of traps at each site)) Traps put out 3-9 OFM RBLR OBLR CM http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (5 of 6)12/6/2012 3:32:17 AM
3-18 0 89* 0 0 3-24 0 63 0 0 4-1 0 140 0 0 4-7 0 90 0 2** * Biofix for RBLR estimated as occurring on February 29. **Possible biofix. Need to confirm codling moth specimens. 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, Associate Professor and Extension Entomologist fahale@ext1.ag.utk.edu Both authors available at: 615-832-6802 fax 615-781-2568 Plant and Pest Diagnostic Center 5201 Marchant Drive Nashville, TN 37211 http://eppserver.ag.utk.edu/extension/fpn/fpn041304.htm (6 of 6)12/6/2012 3:32:17 AM