AGR-75 Burley and Dark Tobaccos Sucker Control:
Removing the tops of tobacco plants also removes the dominant influence of the terminal shoot over lateral shoots, or "suckers." If left unchecked, suckers can severely reduce tobacco yield and quality. Manual control of suckers, however, is increasingly handled by less expensive and more efficient chemical control.
Chemical sprays for controlling sucker growth on tobacco plants include three types:
- Systemic. These chemicals are absorbed by plants and move inside the plant to active growth sites.
- Contact. These chemicals are not absorbed by plants and must contact the suckers directly.
- Local systemic. These chemicals run down the stalk and are absorbed by the suckers.
Topping times and application methods for the three types of chemicals differ and are reviewed separately.
Chemical Sucker Control on Burley Tobacco
Suckers in burley tobacco are chemically controlled with relative ease and certainty. Burley tobacco is harvested three to four weeks after topping and, therefore, requires a shorter control period than tobaccos that have a longer duration between topping and harvesting. However, individual burley varieties may respond differently to chemical sucker control, and the degree of control obtained may vary.
The systemic chemicals contain maleic hydrazide (MH) as the active ingredient. Maleic hydrazide used at the proper rate does not kill suckers but does prevent their additional growth. Normal growth of small upper leaves also may be retarded. Therefore, plants should be topped to a leaf that is no smaller than 6 inches long.
When To Use
Before a systemic sucker-control chemical is used, plants should be topped when 50% or fewer plants in the field have at least one flower open. Suckers should be removed in conjunction with the plants being topped. Sucker-control effectiveness is not reduced when untopped plants are sprayed with MH and then topped within two days.
How To Apply
When applying MH, the required amount of chemical (1 1/2 to 2 parts per 1,000 plants or 1 1/2 to 2 gallons per acre) should be added to water to achieve a total spray volume of 20 to 40 gallons per acre. It is not necessary to spray the entire plant when using a systemic chemical. Spray the solution as a fine mist onto the upper portion of the plant.
Do not exceed the amount of MH recommended on the label. Excessive residues on the cured leaf have in the past discouraged purchases of burley tobacco by foreign buyers. Experiment station field tests showed that higher-than-suggested rates of a systemic spray or spraying two or more times did not improve sucker control or increase tobacco yields. However, rainfall within 12 hours after spraying reduced sucker control. Inspect plants daily to determine if sucker growth is beginning. If suckers are green and growing, re-spray using the same amount of chemical used the first time.
Other factors also impact sucker control:
- Tobacco plants growing under drought conditions absorb MH more slowly, resulting in less-effective sucker control than in a normal season.
- Poor sucker control occurs from use of improper nozzles that reduce coverage to less than 20 gallons of solution per acre.
- Chemical burns occur on plants sprayed on bright sunny days when the temperature is above 90 degrees Fahrenheit. Spraying on a cloudy or hazy day, or in morning if the weather is clear and hot, prevents this injury.
Contact-type sucker-control chemicals contain "fatty" alcohols (FA) as the active ingredient. Spray these chemicals when plants are in the button-to-early-flower stage.
When To Apply
Apply contact-type chemicals immediately before or after topping, or within two days after topping. Remove suckers longer than 1 inch at topping. Contact chemicals work quickly to kill suckers. If no rain occurs within an hour after spraying, suckers should be killed.
How To Apply
Apply contact-type chemicals as a coarse spray that runs down the stalk to the young sucker buds. For 1 acre of tobacco, a mixture of 2 1/2 gallons of chemical per 50 gallons of total spray solution is sufficient. The application of contact-type chemicals also requires special attention to other factors:
- When power equipment is used, a three-nozzle arrangement with TG3 and TG5 full cone tips or equivalent should be used; pressure should not exceed 20–25 psi. The center nozzle (TG5) should be directed straight down. The side nozzles (TG3) should be 8–10 inches to each side and directed in toward the upper part of the plant.
- If a backpack or knapsack sprayer is used, direct a coarse spray toward the upper end of the stalk; it is not necessary to cut off the spray between plants.
To reduce leaf damage, keep the nozzles of either type of sprayer at least 12 inches above the upper leaves while spraying.
- Poor sucker control occurs if plants are not in an upright position because the chemical will not contact all the sucker buds on a leaning or crooked plant. If possible, straighten leaning plants prior to spraying.
- During prolonged periods of high temperature and humidity, contact chemicals can cause some loss of lower leaves because of stem rot. This problem may be worse if higher-than-suggested rates or improper concentrations are used.
- Do not mix contact sprays with insecticides for application.
- Use nozzles that deliver a coarse spray. If power equipment is used, a three-nozzle arrangement over each row is necessary for good coverage.
In special situations, the use of a contact and a systemic chemical may be justified. For example, if the flowering times of plants vary by a week or more, top the earliest maturing plants when about 50% of them are in the button-to-early-flower stage, and then spray the entire field with FA. About seven days later, top the remaining plants and spray the field with MH.
A Local Systemic
The only local systemic sucker-control chemical currently available is Prime+. Apply Prime+ to the top of the plant so that it runs down the stalk into each leaf axil, where it systemically controls the suckers. The application method is also used for contact-type chemicals, which has resulted in Prime+ being applied more extensively in dark tobacco regions where contact use is common.
When To Apply
Prime+ should be applied when most tobacco plants are in the elongated-button-to-early-flowering stage because the number and size of suckers are small. Suckers more than1 inch long must be removed at topping.
If flowering is uneven, top and treat early-flowering plants with Prime+. Remove suckers before application.
How To Apply
For best results, hand-apply Prime+ to each plant. using the dropline, backpack, or jug method. Prime+ can also be applied with power equipment with the same coarse-spray nozzle arrangement that is used for contact-type chemicals. However, sucker control may be less effective than the results achieved by hand methods.
Follow proper Prime+ application methods and mixing rates before treating plants:
- Dropline. Equip the sprayer (trailer, tractor mounted, or Hi-Boy) with droplines for each row. Attach 6–10 feet of pressure hose, equipped with a cutoff valve and a large-volume nozzle, to each sprayer outlet. One person operates each dropline, following the sprayer down the row, treating plants in the elongated-bud stage.
- Backpack. This application method is similar to the dropline. The backpack consists of a spray tank and a wand attachment with a nozzle body that is either adjustable or fitted with a coarse-spray nozzle. The wand attachment allows the spray to be directed to the top of each plant. Small-acreage growers prefer this or the jug application method.
- Jug. This method involves adding Prime+ to a gallon jug and pouring a 1/2 ounce of the solution on each plant.
- Rate. Mix 1 gallon of Prime+ with 49 gallons of water, regardless of the application method. An equivalent amount for the jug method is 2 1/2 ounces of Prime+ in 1 gallon of water. If a hand-application method is used, no more than 30 gallons of spray solution per acre should be used. With power equipment, use 50 gallons per acre.
- Sucker escapes may occur when using Prime+. MH escapes may be concealed as they tend to grow slowly from the leaf axils low on the plant. Prime+ escapes, however, grow only from axils that did not receive adequate treatment, and will grow unchecked until removed. Correct application of Prime+ results in only highly visible, scattered escapes. However, if spray volume is inadequate for contact on all buds, or if plants are not in an upright position, the number of escapes may be excessive. Removing escapes two weeks after application is recommended.
- Exceeding spray volume recommendation may result in carryover injury to cover crops or other sensitive rotational crops. The spray volume should be enough to contact each leaf axil without the spray material reaching the ground in sufficient quantities to injure a subsequent crop.
- Do not mix Prime+ with fungicides or insecticides.
- Failure to apply Prime+ at the recommended flower stage may result in upper leaf distortion if applications are made too early. Poor sucker control may result if applications are made at full flower or later when suckers have begun to grow.
Chemical Sucker Control on Dark Tobacco
Dark tobaccos produced in western Kentucky are harvested four to five weeks after topping. Early topping (a long interval between topping and harvesting) and wide plant spacing can result in the growth of many large suckers that must be removed either manually or by chemical treatment.
Good dark tobacco sucker control can be achieved with MH by using 3 pints of the 1 1/2 pounds per gallon formulation, per 1,000 plants. Mix the indicated amount of MH into 20 to 40 gallons of water per acre, and then apply as a fine mist to cover the upper 1/3 to 1/2 of the plants.
Although MH does a good job of controlling suckers on dark tobacco, using it immediately after topping may reduce expansion of the upper leaves. Also, many growers object to the yellowing of upper leaves resulting from MH used at topping time. To minimize these undesirable MH effects, many growers use a contact-type chemical (FA) just before or after topping, and then apply the MH treatment after about seven days.
An alternative is to use two applications of FA, five to seven days apart. Dark tobacco uses the same mixture measurements for FA that are used for burley tobacco—2 gallons of FA per 48 gallons of water. However, because of lower dark tobacco plant populations, only 30 to 40 gallons of the mixture is applied per acre.
Spray application methods are also the same for dark tobacco and burley tobacco (refer to this document’s directions for using contact-type spray for sucker control on burley tobacco). Take the same precautions noted for burley tobacco when using FA for sucker control on dark tobacco.
Apply Prime+ to dark tobacco in the same manner described for burley tobacco. Prime+ does not cause the premature yellowing that may occur with MH use. It also controls suckers longer than fatty alcohols. Prime+ does, however, require an adjustment to the spray volume to account for the shorter growth habits of dark tobacco. When using power equipment, the volume of solution should not exceed 30 gallons per acre. Follow the same precautions noted for burley tobacco when applying Prime+ to dark tobacco.
AGR-154 Dark Tobacco Sucker Control:
Topping tobacco—removing the terminal bud—results in sucker growth from leaf axils. If suckers are not controlled, yield and quality are 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. Chemical control programs are more efficient and effective than hand suckering.
Types of Sucker-Control Chemicals
Fatty alcohols (contact chemicals) have no systemic activity. These products kill suckers which are less than 1 inch long within an hour of application. The chemical must run down the stalk and contact the sucker for control. Even current one-sucker varieties can have three to four buds per leaf axil, so multiple applications (two to three) of a contact chemical or a sequential application of a local systemic or systemic product is necessary.
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 labeled 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.
Topping Dark Tobacco
Dark tobacco is topped, leaving 12 to 16 leaves on the plant, depending on variety and growing conditions. Maximum yields are obtained when plants are topped in the bud elongation stage before flowers open. A single topping is desirable from a management standpoint, but uneven growth often necessitates two to three toppings.
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 problems. Allow plants to fully mature and ripen before harvest. Variety, weather conditions, soil type, and nitrogen fertilization affect ripening. As a general rule, dark tobacco should stand in the field a minimum of four weeks after topping. Improvement in yield and quality may continue for six to eight weeks after topping.
Methods of Application: Power Spray Equipment
Contact chemicals. Apply a coarse spray of 50 to 60 gallons of water containing a 4%–5% contact chemical solution 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. Follow label instructions for contacts to apply 30 to 50 gallons of water of a 2% local systemic chemical solution. Adjust the finished spray volume to avoid puddling at the base of the plant, which could stunt or kill the cover crop.
Systemics. Mix 1 1/2 to 2 1/4 pounds of active systemic ingredient per acre into 1 to 1 1/2 gallons of water per acre. Add this mixture to water until you reach a final volume of 20 to 30 gallons of water per acre. Spray as a fine mist onto the upper portion of the plant. MH 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 eight hours of application.
Backpack and Garden Sprayers, Jugs, and Droplines
These application methods greatly enhance the effectiveness of contact and local systemic materials. The increase in efficacy and yield may offset the additional expense incurred by using 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 the finished spray is not puddling.
Suggested Sucker-Control Programs
- Apply a contact (1 gallon in 20 to 25 gallons of water) to plants when they’ve reached the bud stage and top the plants that are ready. Repeat application at five- to seven-day intervals two to three more times. Complete topping after the second application.
- Make a first contact application and top plants as described previously. Make the second (final) topping in five to seven days and treat the entire field with either Prime+ or MH. The longer the MH application can be delayed, the less likelihood of yellowing or reduced yield.
- If using a dropline, jug, or hand sprayer, plants can be topped at the bud-elongation stage and then sprayed with Prime+. Plants receiving a 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, 1/2 to 3/4 ounce per stalk will be enough to contact all leaf axils.
Remember the basics when developing a sucker-control program that works for your conditions:
- Absence of excessive pesticide (including sucker control) residue is an important quality element to tobacco buyers. Always read and follow label directions. It is a violation of state and federal laws to use a product if it is not labeled for the crop, or to apply it at rates exceeding the pesticide label. Furthermore, such applications may result in illegal pesticide residues in the tobacco crop.
- No sucker-control material will control suckers over 2 inches long. Suckers approaching 2 inches may escape under some weather-related stress conditions.
- Remove suckers longer than 1 inch by hand at topping to avoid future work in the field.
- Use a sucker-control system that does not inhibit upper leaf expansion or cause off-color leaves, or that damages leaves.
Original authors (7/72) and reviewers (11/86): Gary K. Palmer; Jones H. Smiley; Jimmie R. Calvert; and Bill Maksymowicz, Professors Emeritus, University of Kentucky.