Fungicides are an important tool for managing diseases in tobacco float beds, and getting the best results from these inputs hinges on using each product at a time when it will have the most impact in preventing a particular problem. The following is a suggested schedule for timing the applications of products labeled for diseases in tobacco float beds. The emphasis is on preventive use, and the timings are based on an 8-week transplant cycle (seeding to useable plant).
Suggested Spray Schedule
2 to 4 Weeks after Seeding
When roots of plants emerge from trays and enter float water, apply Terramaster EC at 0.7 to 1 fl oz/100 gal of float water for control of Pythium root rot. Make a follow-up application of Terramaster at 1 fl oz/100 gal of float water no earlier than 3 weeks later (see below).
3 to 4 Weeks after Seeding
When plants have reached the size of a dime, apply Manzate Pro-Stick for suppression of Rhizoctonia damping-off and target spot. The rate is 0.5 lb/100 gal of water (equivalent to 1 tsp/gal). Use 3 gal of spray solution per 1000 sq. ft of bed (~400 trays); apply as a fine mist to ensure good foliar coverage.
5 to 6 Weeks after Seeding
The first time plants are clipped:
- If target spot is not present, continue with Manzate Pro-Stick; increase spray volume to 6 (or more if needed) gal/1,000 sq. ft. Don’t exceed 12 gallons of spray volume per 1,000 sq. feet (even on the largest plants).
- If target spot is active, substitute Quadris for Manzate at a rate of 0.14 fl oz/1000 sq. ft of bed. This is the equivalent of 4 cc (~1 tsp), and should be diluted in 4 to 5 gallons of water before dispersing as a fine spray.
- One application of Quadris is permitted on tobacco seedlings in float beds.
6 to 7 Weeks after Seeding
- Make follow-up application of Terramaster EC at 0.7 to 1 fl oz/100 gal of float water.
- If Quadris was not applied earlier, make one application of this fungicide at the second clipping.
7 Weeks after Seeding.
Continue with Manzate Pro-Stick, slightly increasing spray volume per 1,000 sq. ft as plant size increases, not to exceed 12 gallons of spray volume per 1,000 sq. feet (even on the largest plants).
8 Weeks after Seeding (and beyond)
Continue with Manzate Pro-Stick. A final application of Terramaster EC can be made at 0.7 to 1 fl oz/100 gal of float water if needed; do not apply more than 5 days before transplanting.
- The amount of float water in a bed (in gallons) is calculated by the following formula: (the number of trays in the bed) X (the water depth in inches) X 1.64.
- 5 cc = approximately one teaspoon (tsp).
- 1,000 sq. ft = 400 trays.
- For more information on float-bed fungicides, refer to the “2014 Fungicide Guide for Burley and Dark Tobacco” (UK Plant Pathology Fact Sheet No. PPFS-AG-T-08).
- Manzate Pro-Stick is the only mancozeb fungicide currently labeled for tobacco float-beds. Growers must have a copy of the 24(c) label for Manzate at the time of application.
- Banrot, Rovral, Iprodione 50W or Ridomil Gold are not approved fungicides for use in tobacco greenhouses.
by Clint Hardy, Daviess County ANR Agent and Kenny Seebold, Extension Plant Pathologist