Fruit Pest News. Volume 5, No. 9 May 11, In This Issue:

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1 Fruit Pest News Volume 5, No. 9 May 11, 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. Small-Batch Preparation of Pesticides 3. Peach Pest Management - Diseases 4. Apples: Phyto Reminder for Quadris/Abound 5. Apples: Trauma Blight Fire Blight 6. Grapes: Time for Botrytis Spray 7. Blackberries: Watch for Orange Rust 8. Tree Fruit: Pheromone Trap Catches 1. Current Conditions The weather has turned unseasonably hot. This could mean trouble for strawberry growers who receive showers. If the anthracnose fungus is present in a field, hot, rainy weather is a recipe for disaster. Let's hope the disease triangle (plant, pathogen, environment) is not completed on your farm. Thunderstorm activity is supposed to continue for the next week. First reports for the year during the past week: black rot of grape -- May 8, Williamson County; fruit anthracnose of strawberry -- May 3, Lawrence County. (SB) 2. Small-Batch Preparation of Pesticides When preparing small quantities of a spray mix (e.g. 1 gal.), it is often convenient to use a tablespoon to measure the product. That's fine if the product is a liquid. Any liquid pesticide mixed at 1 pint per 100 gallons of water is always going to be 1 teaspoon per gallon, because both measures are volumes. The problem comes with dry products (wettable powders, dry flowables, water-dispersable granules). Dry products have different densities, so it is not accurate to convert a weight measure into a volume measure (e.g. tablespoon), unless you know how much that volume weighs. The table below illustrates the range of densities of some common fruit fungicides. You can see the error that would ensue if you (1 of 9)12/6/2012 3:34:20 AM

2 assumed, say, that 2 tablespoons per gallon of any dry product was equal to 3 pounds per 100 gallons. Densities of common fruit fungicides. Product Grams per level tablespoon Approximate no. tablespoons/oz. basic copper sulfate Flint 50DF Cabrio 20WDG Captan 50WP /3 Carbamate 76WDG /3 Dithane DF /3 Kocide DF /3 Kocide 101 WP Manzate 200DF Nova 40W Pristine 38WDG /3 Switch 62.5WDG /3 Once you have weighed a level tablespoon of a dry product, you can use that tablespoon to measure the product, because it is then a unit of weight. (SB) (2 of 9)12/6/2012 3:34:20 AM

3 3. Peach Pest Management - Diseases Watch for certain indicators that can signal upcoming problems. You may need to adjust your control program, such as shortening the spray interval or changing to another control product. You're practicing IPM and may not even know it! Bacterial spot. Most diseases are favored by rainy weather, but some react more explosively to it than others. Bacterial spot can become epidemic quickly because of the ability of the bacteria to reproduce rapidly and because of their ability to exist epiphytically on the various surfaces of the tree. The number of overwintered shoot "blacktip cankers" is not necessarily a good indicator of the disease potential, because the epiphytic population represents an invisible source of infection. The level of bacterial spot in previous years is probably the best indicator of the disease potential in a block. On susceptible cultivars, successful control of bacterial spot requires a program involving dormant pruning of cankers and use of copper sprays, early-season sprays of copper or Mycoshield, and some help from Mother Nature (dry weather). When using Mycoshield, consider that it does not weather well. Because of its short residual activity, Mycoshield is most effective when applied shortly before rain, before it has a chance to inactivate. Try to apply within 24 hours before a wetting event, but allow time for the spray to dry. Copper sprays can be used at this time of year, but leaf damage can occur. If you choose to use copper now, use low rates of liquid coppers such as Tenn-Cop 5E (4-6 fl oz/acre) or Copper-Count-N (4-6 fl oz/acre) in at least 100 gal water per acre. Peach scab. As with most diseases, the risk of infection can be determined by the severity of the disease in previous years. With peach scab, disease potential can also be assessed by examining fruit-bearing shoots for the presence of lesions. Scab lesions on twigs are brown, circular to oval in shape, and best seen on the parts of the shoot that have not yet turned from green to brown. If scab potential is considered low, sulfur should be adequate for control. Remember that sulfur is not very rainfast. Scab control is not needed within 40 days of harvest, because that is the length of time needed for symptom development after infection. Green fruit rot. This is a good indicator for brown rot, as both diseases are caused by the same fungus. Clinging green fruit that has been damaged by frost and thinned fruit on the ground may be infected and serve as an indication of brown rot pressure. Insect- or wildlife-injured fruit is also susceptible to brown rot and serves as a good indicator. Adjust cover sprays or initiate pre-harvest brown rot sprays early when disease pressure is high. Use captan or Abound if infected green fruit is present. These materials will also control scab. (SB) 4. Phyto Reminder for Quadris/Abound (3 of 9)12/6/2012 3:34:20 AM

4 With azoxystrobin (Quadris, Abound, Heritage) receiving registrations for so many commodities, its danger to certain apples bears repeating. Azoxystrobin is very phytotoxic to Macintosh and related apple varieties. When spraying strawberries or other crops with an azoxystrobin product, be careful not to allow any drift to nearby apples. Do not even use a sprayer for apples that has ever been used to apply azoxystrobin. Even trace amounts can burn the leaves. Before selling a sprayer that has been used to apply azoxystrobin, clean it out thoroughly, using a tank cleaner. The following varieties have been reported as sensitive to azoxystrobin: Akane, Bromley, Cortland, Cox/Cox's Orange Pippin, Discover, Gala, Grimes, McCoun, Macintosh, Molly's Delicious, Kent, Spartan, Summer Treat, and Summared. Also related to Macintosh are Bancroft, Empire, and Janamac. Note: Azoxystrobin injury on Gala could be mistaken for Glomerella leaf blotch, to which Gala is also susceptible. (SB) 5. "Trauma Blight" Fire Blight Last week's storms remind us of the bad things that can happen to trees to cause"trauma blight." This is fire blight that results from infections associated with injuries due to late frosts, hail, or high winds. Expect trauma type fire blight to be most severe when the bacterial population is high. Free water is usually thought of as necessary for infection, but infections can occur in the absence of rain under high wind conditions that tatter the foliage. Free water usually accompanies frost or hail. Action to take: If a trauma event occurs, a streptomycin application should be made within 24 hours, if fire blight symptoms are present in the orchard. The application should be made even if the foliage is still wet. If you think the fire blight bacterial population is high (the block has a history of fire blight and the weather has been constantly warm), apply the streptomycin even though no symptoms are present. Note: It is only after a trauma event that we recommend the use of streptomycin after bloom. It is not recommended for routine control of shoot blight. This is because it is not effective for control of shoot blight, and repeated use of this valuable product can cause resistance to it to develop in the fire blight bacterium. (SB 6. Grapes: Critical Period for Disease Control Most grape cultivars are at the late pre-bloom stage. The pre-bloom to early bloom period is a critical time for controlling black rot and other diseases. Early bloom is the time for the first application of a Botrytis fungicide. Botrytis bunch rot can be a problem in tight-clustered French hybrid or Vinifera varieties. With recent fungicide registrations, we have several classes of chemistry available to us in our efforts to combat resistance in the Botrytis fungus. Vangard 75WG, Elevate 50WG, and Rovral 50WP are botryticides that should be applied to susceptible cultivars. Since they do not provide black rot control, an effective fungicide should be added to the tank. (4 of 9)12/6/2012 3:34:20 AM

5 A sterol inhibitor (Nova, Elite, Bayleton, etc.) should be used because of their locally systemic activity. Since the sterol inhibitors are not effecitve against Phomopsis or downy mildew, an effective product such as mancozeb or captan should also be applied. The recently-labeled Pristine 38WDG is effective against all of these diseases, with only a slight sacrifice in Botrytis activity. For Botrytis control, Vangard is used at 10 oz per acre at early bloom and at berry touch, veraison, or preharvest (20 oz per acre per year, 7-day PHI). See the label for precautions for use near aquatic areas. Elevate is used at 1 lb per acre at early bloom, bunch pre-close, and veraison, up to and including the day of harvest (up to 3 applications). Rovral 50WP may be applied at 1.5 to 2 lb per acre at early bloom, prior to bunch closing, veraison, and preharvest (7-day PHI). Although the Rovral label allows 4 applications, it is suggested that no more than 3 applications be made, in light of resistance problems that have occurred in other areas. (SB) 7. Watch for Orange Rust in Blackberries Orange rust can be very destructive to blackberries and black raspberries. Most of the blackberry varieties that we grow in Tennessee are moderately to highly resistant to orange rust. However, some varieties, such as Navaho, are quite susceptible. The fungus causes plants to be so stunted and weakened that they produce little or no fruit. The fungus is systemic in the plant, and is perennial inside the below-ground parts. Once a plant is systemically infected by orange rust, it is infected for life. It is for this reason that removal of infected plants is recommended, to prevent spread of the fungus to other plants. The time to control orange rust is in the spring. Your queue to take action is the appearance of weak, spindly new shoots with pale green to yellowish leaves. Such plants should be removed before they begin to produce the orange-colored, blister-like pustules on the lower leaf surface. The orange pustules contain spores that spread to other plants and cause new infections that may not become apparent until the following spring. The fungicides Nova, Pristine, and Cabrio can be used for control of orange rust. These fungicides help prevent leaf infections. They will not cure a systemically-infected plant. Begin applications soon (the orange pustules should mature and release their spores sometime in the month of May) and continue every 10 to 14 days until mid-summer. For Nova, the maximum amount is 10 oz per acre per year, and the rate per application is 1.25 to 2.5 oz per acre. Cabrio is labeled at oz per acre, Pristine at oz per acre, and the sum of the number of applications for these two materials cannot exceed four. (SB) (5 of 9)12/6/2012 3:34:20 AM

6 8. Pheromone Trap Catches Oriental Fruit Moth In Nashville, the first OFM were caught and the biofix was set on March 26. On April 27, the cumulative Degree Days at a base temperature of 45 degrees F was DD. It exceeded 500 DD on May 3. In peach, nectarine and plum, for moderate to high density OFM orchards, two insecticide applications are applied 14 days apart, the first at 500 DD after biofix. In apples, first generation OFM egg laying is usually low on apple and only one insecticide application should have been applied between 400 and 500 DD after biofix. (FH) Obliquebanded Leafroller These moths are active now with the biofix being May 10 in Nashville. They are much larger than redbanded leafroller moths and codling moths. Redbanded leafroller moth catches are down after being active since early March. 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) ** *** (6 of 9)12/6/2012 3:34:20 AM

7 **** 0 2 * 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. Bradley County Pheromone Trap Catches 3-10 new traps put out OFM RBLR CM TABM 0 4* (catch for now on from traps) ** put out CM traps *** 2**** *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 (7 of 9)12/6/2012 3:34:20 AM

8 Putnam County Pheromone Trap Catches 3-8 set out OFM RBLR OBLR CM * ** *** **** *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 * ** *** **** * 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 confirmation) (8 of 9)12/6/2012 3:34:20 AM

9 The Fruit Pest News URL is: Contacts: Steve Bost, Professor and Extension Plant Pathologist Frank Hale, Professor and Extension Entomologist Both authors available at: fax Plant and Pest Diagnostic Center 5201 Marchant Drive Nashville, TN ÿÿ (9 of 9)12/6/2012 3:34:20 AM

Fruit Pest News. 1. Spray Program Strategies for Black Rot of Grape. Volume 4, No. 10 May 19, In This Issue:

Fruit Pest News. 1. Spray Program Strategies for Black Rot of Grape. Volume 4, No. 10 May 19, In This Issue: Fruit Pest News Volume 4, No. 10 May 19, 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