While at the 42nd Tobacco Workers' Conference in Charleston, SC, I learned that Aliette WDG (Bayer CropScience) was recently labeled for control of blue mold on tobacco. Aliette can be used in the production of transplants (greenhouses, outdoor float beds, outdoor plant beds) and on transplanted tobacco in the field.
The use rate for transplant production is 0.5 lb of product per 50 gallons of water. Aliette WDG should be applied as a broadcast spray in a volume of water sufficient to provide good coverage of foliage and minimize contact with float-bed water or soil. According to the label, leaf burn can result if Aliette is allowed to wash into float water or the root zone of transplants. Bayer recommends 3 gallons of spray solution per 1000 square feet on small plants, increasing to 12 gallons/1000 square feet on large transplants. After application, wait 24 hours before applying any material over the top so that Aliette can be absorbed into the foliage and to avoid washing the fungicide into float water or soil. Applications of Aliette should begin before symptoms of blue mold appear, ideally, or when the first symptoms are observed. Two applications can be made 5-7 days apart.
For field use, apply 2.5-4 lb/A of Aliette in a minimum of 20 gal/A of water on newly transplanted tobacco. Increase the spray volume by 20 gal/A for each week of growth until 100 gal/A is reached. The first application of Aliette should be made immediately after transplanting and subsequent sprays can be made on a 7-to10-day schedule. Do not exceed 4 lb/A per treatment or 20 lb/A per season (5 applications); the pre-harvest interval for Aliette is 3 days.
Aliette should not be tank-mixed with copper compounds, surfactants or foliar fertilizers, and the pH of the spray solution should not be less than 6.0. Failure to observe these precautions could result in plant injury. Good spray coverage with Aliette and other fungicides is critical to good control of disease. Make sure that sprayers are properly calibrated and configured.
Our experience with Aliette in Kentucky is limited at this time. Reports from colleagues in the Burley Belt indicate that Aliette can be effective against blue mold if applied correctly and in a timely manner. We will test Aliette in field trials across Kentucky during the 2006 season so that better guidance on the efficacy of this fungicide can be provided to our growers in the future. A copy of the label will be made available on the KY Blue Mold Warning System site (www.uky.edu/Ag/kpn/kyblue/kyblue.htm) in the coming weeks.
For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System online.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm
For more information about tobacco pests, visit "Insect Management Recommendations".
Apple scab, caused by the fungus Venturia inaequalis, has the potential to be the most common and destructive disease of Kentucky apple orchards. Fortunately, most commercial growers have the tools and expertise to manage this disease well. Apple scab affects several different hosts including: apples and flowering crabapples (Malus spp.), hawthorn (Crataegus spp.), mountain ash (Sorbus spp.), firethorn (Pyracantha spp.), and loquat (Eriobotrya japonica). Pear (Pyrus spp.) is infected by a related fungus, Venturia pirina, which causes nearly identical symptoms.
Infections occur on leaves, fruits, blossoms, and leaf petioles and first appear as velvety brown to olive colored spore-filled lesions that turn black with age. Fruit scab lesions develop a corky appearance, and fruits infected early in their development may become cracked and deformed. When apple leaves become infected, they turn yellow and drop.
Overwintering apple leaves provide the spores that initiate primary infections on new growth in early spring. For newly emerging leaves to become infected, spores on the leaf surface must be bathed in a film of moisture for enough time as is necessary for the spores to germinate and penetrate the leaf. The length of time needed depends on the temperature. The temperature and leaf wetness relationship to infection levels is presented in the following table, sometimes referred to as Mills table.
| Approximate minimum number of hours of leaf wetting required for primary apple scab infection at various temperatures (Mills table, modified). | ||||
|---|---|---|---|---|
| Average temperature (F) | Light infection | Light infection | Heavy infection | Lesions visible (days) |
| 78 | 13 | 17 | 26 | - |
| 63-75 | 9 | 12 | 18 | 9 |
| 60 | 9.5 | 13 | 20 | 11 |
| 57 | 10 | 14 | 22 | 13 |
| 54 | 11.5 | 16 | 24 | 14 |
| 51 | 13 | 18 | 27 | 16 |
| 48 | 15 | 20 | 30 | 17 |
| 45 | 20 | 27 | 41 | 17 |
| 42 | 30 | 40 | 60 | 17 |
After primary infections occur in early spring scab lesions develop and conidia are produced in the lesions, providing secondary inoculum for continued infections of new leaves. Leaf wetness and temperature relationships for secondary scab infection are similar to the primary infection values presented in Mills table.
Apple scab management. Apple scab can be managed by doing the following:
Growers have several apple scab management tasks that need to be done now, before buds swell and new growth begins to emerge. Chop up fallen leaves in the orchard, prune trees to provide better air movement, purchase new trees, acquire needed fungicides, and calibrate the sprayer.
NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.
Lee Townsend
Extension Entomologist