Fruit Pest News. Volume 5, No. 21 September 7, 2004

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1 Fruit Pest News Volume 5, No. 21 September 7, 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. Vegetable Corner a. Hurricane Weather b. Disease Reports c. Cucurbit Powdery Mildew d. Tomato Insect Report e. Using Bacteriophages to Control Bacterial Spot and Speck of Tomato 2. Apple: Phytophthora Crown Rot and Collar Rot 3. Apple: Cosmetic Storage Diseases 4. Apple: Prevent Storage Decays 5. Tree Fruit: Late-Season Insects 6. Tree Fruit: Pheromone Trap Catches 1. Vegetable Corner Hurricane Weather -- Hurricane Frances is moving through the state this week and there may be more on the way. These low pressure systems make for difficult disease control prospects. The extended rainy periods remove much of the fungicide protection and create favorable environmental conditions for the pathogens. Remember to try to apply your fungicides before the rains begin. They are needed during the rainy period. That is when the pathogens are dispersed to new tissue and infection takes place. Use systemic fungicides if possible, so that the rains will not wash them off the plant. If systemic fungicides are not an option, use contact fungicides that are known to have good resistance to wash off, such as chlorothalonil. (SB) Disease Reports -- Reports from the last two weeks include some serious cases of late blight of tomato, powdery mildew of cucurbits, and microdochium blight of pumpkins. One farm reported scab disease of squash, and cucurbit downy mildew is beginning to appear in several areas. If you are using Flint for control of microdochium blight and powdery mildew, remember that it is weak against downy mildew. Cabrio or Pristine would be better strobilurin choices for downy mildew control. (SB) Cucurbit Powdery Mildew -- Some growers are reporting difficulty in controlling powdery mildew. I (1 of 10)12/6/2012 3:39:12 AM

2 am running some fungicide resistance tests on powdery mildew isolates to determine how much of this problem is occurring in the state. If you would like to know how your powdery mildew reacts to the various fungicides, please send me some infected leaves. I will include it in the survey. What to do if the sterol inhibitors (Nova, Procure) and strobilurins (Quadris, Cabrio, Flint) are not controlling powdery mildew: If resistance to these two groups of fungicides does occur, sulfur would be the product of choice. Many growers are inhibited from using sulfur because of the frequent warnings of burn that can be caused by sulfur on cucurbits during hot weather. These warnings are aimed at growers of cantaloupes and cucumbers. Squash and pumpkins are not as sensitive to sulfur as these cucurbits. I have used sulfur on squash in high-90's weather without harm. Sulfur is an effective powdery mildew material that is not subject to the development of resistance. However, it is not systemic and thorough coverage of the plant is required. Also, some sulfur products do not include cucurbit crops. (SB) Tomato Insect Report -- Beet armyworm and whitefly outbreaks have been reported in East Tennessee (Hamblen County). Beet armyworms overwinter further south and the moths fly into Tennessee in the summer. Populations tend to build in August-September. This pest then can become a problem in maturing late-summer crops like tomatoes and also in fall-planted crops. Fortunately in the past few years, several new insecticides have become available for increased efficacy against this pest. These insecticides are methoxyfenozide (Intrepid 2 F), emamectin benzoate (Proclaim 5 WDG) and indoxacarb (Avaunt 30 WDG). Whiteflies tend to prefer more vegetative weeds and crops, which can occur in wet years. Whitefly populations can build quickly when the conditions are favorable for their development. Imidacloprid (Admire 2F) and thiamethoxam (Platinum 2 SC) are both soil applied and are usually applied early, around transplanting time. They can be applied later via trickle irrigation, but not too late because there is a 21 day pre-harvest interval (PHI) for Admire and a 30 day PHI for Platinum. Provado 1.6 F is a foliar applied imidacloprid that can be applied even on the day of harvest. Another fairly new foliar insecticide is pyriproxifen (Knack 0.86EC). It has a 14 day PHI and can only be used twice per season and at least 14 days must be allowed between applications. (FH) Using Bacteriophages to Control Bacterial Spot and Speck of Tomato -- Several tomato growers are trying bacteriophage products to control bacterial spot and speck. Bacteriophages (phages) are viruses that attack bacteria. They are very specific, attacking only the bacteria that they match. Thus, phages are safe to use and environmentally friendly. Agriphage brand, by Omnilytics, Inc., is available under an experimental use permit. The advantages of phages include their human and environmental safety, and their moderate effectiveness against the targeted bacterial plant pathogens, including those that have become resistant to the primary control product, copper. Phage use relieves the selection pressure on the bacterial populations caused by excessive copper use. The disadvantages of phages are several, with low effectiveness being one. Two years ago, I conducted a bacterial spot control trial in which Agriphage provided only about 33% control, versus 96% control by a copper/mancozeb tank mix. The problem many growers are facing is copper-resistant bacterial (2 of 10)12/6/2012 3:39:12 AM

3 strains, in which case the phage would outperform copper. Tank mixing the phage with copper might seem appropriate if you are not sure if your bacterial population is resistant to copper. However, Agriphage cannot be tank mixed with copper, because of reduced phage efficacy. How the program works: Omnilytics will provide you with a suspension of phage that genetically matches the bacterial population in your field. You need to send them a sample of your diseased plants so that they can develop the phage strain needed. About 10 days are required for this process, including shipping time. So that you can immediately begin spraying preventively with a phage, rather than waiting until the disease appears, Omnilytics will send you a generic mixture of phages that are matched against the common strains of your disease. When you receive the specific phage, you use it on a weekly schedule. If control does not appear to be satisfactory, you can re-sample and submit for production of a phage strain better matched to your predominant population. You will not be charged for strain testing; only for the product. The cost of the product is reasonable. Agriphage is well worth a try if you suspect problems with copper resistance in your bacterial populations. Information about Omnilytics can be obtained from their web site: (SB) 2. Phytophthora Crown Rot and Collar Rot of Apple Crown rot, collar rot, and root rot in apple trees are caused by Phytophthora species (root rots can also be caused by other types of fungi). These three diseases can occur on one tree and can be caused by a single infection, but are given different names to designate the part of the tree affected. Collar rot occurs in the scion part of the tree. This disease has decreased due to changing variety preferences and to the practice of raising graft unions above the soil line at planting. Crown rot is a disease of the rootstock portion of the tree. It has become more important because of the increased use of susceptible rootstocks such as MM106 and M26. Phytophthora root rot is a disease of the root system away from the crown region. It may occur along with crown rot or may occur by itself. In the spring, symptoms of Phytophthora include delayed bud break, leaf discoloration, and poor growth. Foliage is sparse, yellowish, and may develop an early purple discoloration in autumn. In dry weather, infected trees are the first to exhibit symptoms of water deficit. The most obvious symptom is a partial or complete girdling of the trunk with reddish-brown, watersoaked areas of dead tissue at the base of roots where they attach to the trunk. The entire underground portion of the trunk is usually water-soaked and brown with the dead area extending upward to the graft union. The fire blight bacterium can cause rootstock cankers on M26 and M9 that are almost indistinguishable from crown rot. Fire blight cankers form in July and August following early season blossom and/or shoot infections. Rapid decline of trees on these rootstocks in late summer may be caused by fire blight (3 of 10)12/6/2012 3:39:12 AM

4 cankers below the graft union. Avoid planting fruit trees in poorly drained locations, and do not allow depressions to form around the base of trees. Where drainage is questionable, use the less susceptible rootstocks such as seedling and M9. Moderately susceptible rootstocks are M7, M26, and MM111. Ridomil and Aliette fungicides are helpful in control, but should not be solely relied upon. They should be used in conjunction with cultural practices. Because Phytophthora diseases occur sporadically, it is usually not economical to treat entire orchards on a regular, preventative basis. Rather, use them in problem areas. Also note that these fungicides seldom are effective in reviving trees once the crown has become infected and moderate symptoms of decline have appeared. Ridomil can be used in the fall and spring only, applied as a soil spray. Dipping the roots of nursery-grown trees into a solution of Aliette prior to planting may reduce, but not eliminate, Phytophthora inoculum on roots. Aliette can be used as a foliar spray to nonbearing trees. (SB) 3. Cosmetic Apple Storage Diseases Apple scab, sooty blotch, and flyspeck can develop after harvest, in storage. Their appearance can reduce the marketability of the fruit. Although these diseases first appear or increase in storage, they are the result of infections that took place in the orchard before harvest. These diseases are favored by wet, mild weather. Storage scab is sometimes referred to as 'pinpoint' scab because of its small size, from barely visible up to 1/8 inch in diameter. The lesions are black and often shiny because of the intact cuticle. They are circular and differ from scab lesions that develop in the orchard by a darker color and a definite border. Late-season scab that becomes visible before harvest closely resembles storage scab. Late-season scab lesions often remain viable in storage and enlarge by forming a fringe of olive-green mycelia around the margin of the scab spot. At optimal temperatures for the scab, sooty blotch, and flyspeck fungi (roughly 62º to 76º F), about 8 to 10 days are required for symptom development after infection. Symptom development does not occur below 48º F. Control of these cosmetic storage diseases must take place before harvest; that is, infection must be prevented on the tree. In selecting fungicides, preharvest intervals for the fungicides in question are a primary consideration. Then consider what diseases to target. In orchards in which sooty blotch and flyspeck is active, Topsin M, Flint, or Sovran are good choices. Topsin M should be tank mixed with captan, not only for resistance management purposes, but also for bitter rot control. Where scab has remained or has become active, Dr. Turner Sutton, North Carolina State University, suggests using dodine (Syllit) at 1.5 to 2 lbs/acre plus captan at 5 lbs/acre. Flint or Sovran would also play a valuable role. (SB) (4 of 10)12/6/2012 3:39:12 AM

5 4. Prevent Apple Storage Decays The previous article discussed cosmetic apple storage diseases. Other storage diseases such as blue mold, caused by Penicillium expansum, and gray mold, caused by Botrytis cinerea, involve decays that actually reduce marketable yields. Unlike the cosmetic storage diseases, most of the decay disease infections occur in storage, mostly through wounds. Control tactics differ for the two types of storage diseases. However, certain late-season fungicide sprays in the orchard can help reduce both types. Applied at 14 days before harvest, a tank mix of Topsin M with either captan or ziram helps control storage decays and sooty blotch and flyspeck. Chemical control after harvest has become extremely limited. Sanitation practices are more important now than ever. If you have had problems in the past with storage decays, you are encouraged to visit cornell.edu/ent/scaffolds/2002/8.19.html#d1 for details on control. The article was written by David Rosenberger, Cornell University. (SB) 5. Late Season Tree Fruit Pests Late in the season, we tend to see less distinct pest generations so that some overlap in generations can occur. Predictions made earlier in the season with pheromone traps may not be as accurate this late in the growing season. Running pheromone traps now will give you a measure of any increase in pest activity. If an internal feeder such as Oriental fruit moth or codling moth shows activity, protect maturing fruit as needed. Be sure to always consider the preharvest interval as you near harvest. It is also a good idea to examine some fruit to look for signs of larval tunneling. (FH) 6. General: Pheromone Trap Catches Nashville (Davidson County) Pheromone Trap Catches for 2004 OFM RBLR OBLR CM GBM 3-4 (put out RBLR trap) 0 3* (put out new traps) (5 of 10)12/6/2012 3:39:12 AM

6 ** *** **** (6 of 10)12/6/2012 3:39:12 AM

7 * The three RBLR caught in trap left over from last year. New RBLR trap put out 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 ****Biofix for obliquebanded leafroller. Grape Berry Moth Pheromone Trap Catches,Williamson County 4-3 put out trap Bradley County Pheromone Trap Catches (7 of 10)12/6/2012 3:39:12 AM

8 3-10 new traps put out OFM RBLR CM TABM 0 4* (catch for now on -- 0 from 2 traps) ** put out CM traps *** 2**** *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. *** CM biofix on April 23. **** TABM biofix on April 23. Putnam County Pheromone Trap Catches 3-8 set out OFM RBLR OBLR CM * ** (8 of 10)12/6/2012 3:39:12 AM

9 *** **** *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). ****Biofix for CM. Smith County Pheromone Trap Catches (Two orchards, a set of traps at each site)) Traps put out 3-9 OFM RBLR OBLR CM * ** *** **** (9 of 10)12/6/2012 3:39:12 AM

10 * 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) The Fruit Pest News URL is: Contacts: Steve Bost, Professor and Extension Plant Pathologist scbost@utk.edu Frank Hale, Professor and Extension Entomologist fahale@utk.edu Both authors available at: fax Plant and Pest Diagnostic Center 5201 Marchant Drive Nashville, TN (10 of 10)12/6/2012 3:39:12 AM