Topping tobacco removing the terminal bud results in growth of suckers from leaf axils. If suckers are not controlled both yield and quality will be severely reduced. Research has shown that tobacco topped at bud-elongation stage will yield 300 or more pounds per acre compared to tobacco that is topped at full bloom. Hand suckering has been replaced with more efficient and effective chemical control programs.
Local systemic chemicals must run down the stalk and contact each leaf axil for control. These products are "systemic" within the axillary area and will control all sucker buds within each leaf axil contacted. At present Prime+® is the only local systemic labelled for use.
Systemic chemicals are absorbed by the plant through the foliage and translocated to the actively growing areas (suckers). Maleic hydrazide (MH) is the active ingredient in systemic sucker control products.
Do not assume that uneven growth is weather related. If unevenness is a consistent problem check for other causes, such as disease, nutrition, or soil-related causes. Plants should fully mature and ripen before harvest. Variety, weather conditions, soil type, and nitrogen fertilization will affect ripening. As a general rule, dark tobacco should stand in the field a minimum of 4 weeks after topping. Improvement in yield and quality may continue for 6 to 8 weeks after topping.
Contact chemicals. A 4 to 5% solution is applied as a coarse spray in 50 to 60 gallons of water per acre. Use three hollow-cone nozzles per row directed to the bud area. Pressure must not exceed 25 psi. High rates applied on hot days or under high pressure may cause leaf injury. Rain within one hour of application can reduce control.
Local systemic chemicals. Use 30 to 50 gal/acre of a 2% solution, applied as described for contacts. Adjust finished spray volume to avoid puddling at the base of the plant, which could stunt or kill the cover crop.
Systemics. Apply 1 to 1.5 gal/acre (1.5 to 2.25 lb/acre active ingredient) in a finished spray volume of 20 to 30 gal/acre. Apply as a fine mist to the upper portion of the plant. Maleic hydrazide should not be applied to leaves smaller than 8 to 10 inches long. High rates of MH can cause yellowing.
Applications made when plants are weather stressed may result in poor performance. Do not apply in the heat of the day; morning applications are usually more effective. Sucker control can be reduced if rain occurs within 8 hours of application.
These application methods can greatly enhance the effectiveness of contact and local systemic materials. Increase in efficacy and yield may offset the additional expense of a manual sucker control application method.
Apply either at rates listed for "Power Spray Equipment" or as a coarse spray to the top of the stalk. Little pressure is needed. Take time to "calibrate" your application technique to ensure that finished spray is not puddling.
1. Apply a contact (1 gal in 20 to 25 gal of water) at bud stage and top plants that are ready. Repeat application at 5 to 7 day intervals two to three more times. Try to complete topping after the second application.
2. Make a first contact application and top as described in (1). Make the second (final) topping in 5 to 7 days and treat the entire field with either Prime+ or maleic hydrazide. The longer the MH application can be delayed the less likelihood there will be of yellowing or yield reduction.
3. If using dropline, jug, or hand sprayers plants can be topped at the bud elongation stage and sprayed with Prime+. Plants topped at the second (and third) topping are treated with Prime+ when topped. Do not repeat Prime+ application to plants already treated.
at the base of the stalk. Generally one-half to three-fourths ounces per stalk will be enough to contact all leaf axils.