Integrated Blueberry Disease anagement Successful management of blueberry diseases requires an integrated approach to disease management. Choosing appropriate varieties and a well-suited planting site and good soil preparation before planting are all important for preventing disease problems in blueberries. Well-drained soil is especially important for preventing Phytophthora root rot, one of the most significant blueberry diseases. For protection from both frost and disease problems, it also may be beneficial to choose a site from which air can easily drain (e.g., not low sites). Select varieties appropriate for your region. For variety recommendations as well as information on how to choose a suitable site and prepare soil before planting, see the LSU AgCenter publication Commercial Blueberry Production (Pub. 26) or Home Blueberry Production in Louisiana (Pub. 198), or the ississippi State University Extension Service publication Establishment and aintenance of Blueberries (Pub. 158). Start with clean plants. Use plants that have been propagated from clean (disease-free) planting material, and check plants for disease symptoms before planting. Use good cultural practices. Pruning is recommended to remove dead, damaged, or diseased limbs so that sunlight and pesticides can penetrate the plant canopy. Pruning recommendations are provided in the LSU AgCenter publication Commercial Blueberry Production (Pub. 26). Apply one inch of mulch under plants each year to minimize the effects of mummy berry disease. Avoid using equipment that has been in orchards infected with mummy berry. Use crop protectants. Prior to using chemicals, have the disease confirmed by a crop specialist. Once the disease has been confirmed, select a labeled product that has been shown to be effective in reducing disease, and apply the product at the correct stage of plant development (Table 1). Chemicals with proven efficacy against a pathogen will not reduce disease if applied at the wrong time. Always rotate between products with different modes of action (in different FRAC groups; see Table 2) to prevent the development of fungicide resistance in the pathogen (disease-causing agent). If a pathogen becomes resistant to a product, the product will no longer be effective.
Table 1. Seasonal fungicide spray schedule for blueberries Season Fungicide Application Timing Disease Early spring Pre-bloom Bloom Petal fall Summer At planting or, for established plants, while dormant, plus once while conditions favorable (see Table 2) Green tip or when 1-5% of blooms are open (whichever comes first), for mummy berry, followed by a second application -14 days later, for both mummy berry and twig blight 1-2 % bloom, followed by a second application at full bloom Immediately following bloom, followed by applications at -14 day intervals Pre-harvest Post-harvest Phytophthora Root Rot ummy Berry Twig Blight ummy Berry Twig Blight Botrytis Blight Fruit Rots Fruit Rots Fruit Rots Leaf Spots Fall Post-harvest Leaf Spots
Product Choices 1 and Product ode of Action Group 2 Efficacy Rate 4 PHI 5 aximum Use 6 Phytophthora Root Rot (Phytophthora cinnamomi) Symptoms: Initially, leaves become yellow and plant growth ceases. Rootlets are killed, and infected roots and crowns are discolored. Bushes may defoliate and die. Source of Inoculum: The pathogen survives as chlamydospores in the soil. Disease development is favored by wet soil conditions and temperatures between 68 and 9 F. anagement: Plant disease-free plants in well-drained soil or raised beds. efenoxam can be applied to soil while plants are dormant. or phosphite products can be applied to foliage during the entire growing season. If plants are severely infected, chemicals are not likely to result in a return to healthy plant growth. (O-ethyl phosphonate; Aliette WDG) s.5 2 lb efenoxam (Ridomil Gold SL) (Ultra Flourish) 4 4.6 pt.2 pt.2 pt 14.4 pt Phosphites (Fosphite, Rampart) (Fungi-Phite) (Helena Prophyt) (Phostrol) see label (rate varies by production and application method) ummy Berry (onilinia vaccinii-corymbosi) Symptoms: This fungus attacks and kills leaves, twigs, flowers and fruit. Infected fruit turn cream to pink as they begin to mature and then shrivel and harden into mummies. Source of Inoculum: The fungus survives in the mummified fruit. Spores are wind-dispersed. anagement: Remove or bury mummified fruit. If mummy berry is an ongoing problem then a fungicide spray schedule should be followed. For mummy berry, the first recommended sprays of the season (see Table 1) are very important. 11 6.-15.5 fl oz 4 Azoxystrobin and propiconazole (Quilt Xcel) 11, 14-21 fl oz 82 fl oz 18.5-2 fl oz (5 WP) (8 WDG) (8.5% FL).12 2.- lb 4. 5 qt 5 qt
Product Choices 1 and Product ode of Action Group 2 Efficacy Rate 4 PHI 5 aximum Use 6 and fenhexamid (CaptEvate 68 WDG),1 4. lb 21 lbs Cyprodinil and fludioxonil (Switch 62.5 WG) Fenbuconazole (Indar 2F) 24 fl oz etconazole (Quash 8 ).5 oz Propiconazole (Bumper 41.8 EC, Bumper ES, Propiax EC, Tilt) fl oz Ziram (6DF, Granuflo) lb -- 9 Stem Cankers and Blights (Phomopsis, Botryosphaeria) Symptoms: Phomopsis twig blight: Flower-bearing year-old stems die. Botryosphaeria canker: Lesions appear on new growth and turn into cankers on susceptible varieties. Botryosphaeria stem blight: Individual branches die. Source of Inoculum: The pathogens survive from year to year in infected stems. Spores are spread by wind or rain. Phomopsis infects stems through flowers. anagement: Avoid mechanical injury to stems. Remove canes infected with Botryosphaeria. For Phomopsis twig blight, follow the fungicide spray schedule. Fungicides are not likely to be very effective for management of Botryosphaeria. Fungicide efficacy ratings are for Phomopsis twig blight only. (O-ethyl phosphonate; Aliette WDG).5 2 lb 11 6.-15.5 fl oz 4 18.5-2 fl oz (5 WP) (8 WDG) (8.5% FL).12 2.- lb 4. 5 qt 5 qt Cyprodinil fludioxonil (Switch 62.5 WG) Fenbuconazole (Indar 2F) 24 fl oz etconazole (Quash 8 ).5 oz
Product Choices 1 and Product ode of Action Group 2 Efficacy Rate 4 PHI 5 aximum Use 6 Ziram (6DF, Granuflo) lb -- 9 Botrytis Blight (Botrytis cinerea) Symptoms: The fungus attacks tender young twigs, leaves, flowers and fruit, causing them to become brown to black. Infected fruit do not rot until after harvest. Source of Inoculum: The fungus survives as dormant mycelia or sclerotia. Spores are wind dispersed. anagement: Follow a fungicide spray schedule. 18.5-2 fl oz (5 WP) (8 WDG) (8.5% FL).12 2.- lb 4. 5 qt 5 qt and fenhexamid (CaptEvate 68 WDG),1.5-4. lb 21 lb Cyprodinil and fludioxonil (Switch 62.5 WG) Fenhexamid (Elevate 5WDG) 1 1. 6 lbs Ziram (6DF, Granuflo) lb -- 9 Fruit Rots (Alternaria, Colletotrichum, Phomopsis) (including Anthracnose Fruit Rot or Ripe Rot) Symptoms: A variety of rots develop on the fruit as they mature. Source of Inoculum: The fungi causing fruit rots survive from year to year on or in infected twigs and, for Alternaria, fallen debris. anagement: Harvest ripe fruit regularly, and cool it soon after harvest to minimize post-harvest disease development. Follow a fungicide spray schedule. Fungicide efficacy ratings are for Alternaria and Colletotrichum (ripe rot), unless noted. (O-ethyl phosphonate; Aliette WDG) (ripe rot only).5 2 lb 11 6.-15.5 fl oz 4 Azoxystrobin and propiconazole (Quilt Xcel) 11, 14-21 fl oz 82 fl oz 18.5-2 fl oz (5 WP) (8 WDG).12 lb 4.8 lb
Product Choices 1 and Product ode of Action Efficacy Rate 4 PHI 5 aximum Group 2 Use 6 (8.5% FL) 2.- 5 qt 5 qt Cyprodinil fludioxonil (Switch 62.5 WG) Fluazinam (Omega 5F) 29 1.25 pt.5 pt etconazole (Quash 8 ).5 oz Ziram (6DF, Granuflo) lb -- 9 Leaf Spots (Septoria, rust) Symptoms: Septoria: Small, circular, light-colored lesions with a purple border are produced on leaves, and sunken lesions may be formed on stems. Rust: Spots develop on upper sides of leaves and change from yellow to red to brown. Orange spores are produced on the undersides of leaves. Source of Inoculum: Septoria: The fungus survives from year to year in infected leaf debris and stems. Spores are windborne. Rust: The fungus is believed to survive on evergreen plants in the blueberry genus (Vaccinium). anagement: Follow a fungicide spray schedule. Ratings with (S) next to them indicate they are for Septoria only. (O-ethyl phosphonate; Aliette WDG) (S).5 2 lb 11 (S) 6.-15.5 fl oz 4 Azoxystrobin and propiconazole (Quilt Xcel) 11, (S) 14-21 fl oz 82 fl oz 18.5-2 fl oz Chlorothalonil 1 (8.5% F) (54% F) (82.5% DF) (9% DF) 4.25-5.5 pt -4 pt 2.-.6 lb 2.5-.2 1 pt 12 pt 1.9 lb 1. lb Cyprodinil and fludioxonil (Switch 62.5 WG) (S) 5 Fenbuconazole (Indar 2F) 24 fl oz etconazole (Quash 8 ).5 oz
Product Choices 1 and Product ode of Action Efficacy Rate 4 PHI 5 aximum Group 2 Use 6 Phosphites (Fosphite, Rampart) (Fungi-Phite) (Helena Prophyt) (Phostrol) Propiconazole (Bumper 41.8 EC, Bumper ES, Propiax EC, Tilt) (S) (S) (S) (S) see label (rate varies by product and application method) fl oz Bacterial Leaf Scorch (Xylella fastidiosa) Symptoms: In susceptible Southern highbush varieties, the edges of leaves turn brown (marginal necrosis) and eventually drop off the plant, and young twigs and stems may turn yellow. Rabbiteye cultivars may show early fall color, and fruit production may decline over time. Source of Inoculum: Infected plants serve as reservoirs for this bacterium. Bacteria are transmitted through propagation or by sharpshooter insects. anagement: No chemicals are available for disease management. Plant disease-free plants, and choose resistant varieties if planting Southern highbush blueberries. See the Southeast Regional Blueberry Integrated anagement Guide (http://www.smallfruits.org/smallfruitsregguide/index.htm) for insecticide recommendations for leafhoppers. 1 Chemical name (trade name). Reference to commercial or trade names is made for the reader s convenience and with the understanding that no discrimination is intended nor endorsement of a particular product by LSU or the LSU AgCenter is implied. In some cases, other brands are available. 2 ode of action groups are determined by the Fungicide Resistance Action Committee (FRAC). Efficacy ratings are on a 1-5 scale where: 5 () is the most effective and 1 () is the least effective. uch of the information in this table, including efficacy ratings, is based on the 214 Southeast Regional Blueberry Integrated anagement Guide of the Southern Region Small Fruit Consortium (http://www.smallfruits.org/smallfruitsregguide/index.htm). 4 Rates are the amount of formulation (product) per acre unless otherwise indicated. Usually 1 gallons of water are required to give good coverage with boom sprayers. 5 Post-harvest interval (PHI) is the minimum number of days allowed between the last application and harvest. 6 aximum amount per acre per year or growing season. See labels for additional restrictions. If fenbuconazole (Indar 2F) is used during bloom, it should be mixed with captan to prevent a higher incidence of fruit rot. 8 Supplemental label (EPA Reg. No. 5969-14). Label expires Dec. 1, 216. 9 Do not apply later than three weeks after full bloom. 1 Do not apply until after harvest. any products are available. Revised by.h. Ferguson and Dr. C. Clark in December 214.