Local systemic--This chemical runs
down the stalk and is absorbed by the suckers.
Topping times and application methods for the 3 types of chemicals differ
and are discussed separately.
Chemical Sucker Control on Burley Tobacco
Systemic Chemicals
Suckers in burley tobacco can be chemically
controlled with relative ease and certainty. Burley tobacco is harvested
3 to 4 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 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 prevents 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
When a systemic sucker control chemical
is to be used, plants should be topped when 50% or fewer plants in the
field have at least one flower open (Fig. 1). Any suckers present should
be removed when the plants are topped. Sucker control effectiveness is
not reduced when untopped plants are sprayed with MH, then topped within
two days.
How to Apply
When applying MH, the required amount
of chemical (1.5 to 2 pt per 1,000 plants or 1.5 to 2 gal per acre) should
be added to water to achieve a total spray volume of 20 to 40 gal per acre.
It is not necessary to spray the entire plant when using a systemic chemical.
The solution should be sprayed as a fine mist onto the upper portion of
the plant (Fig. 2).
Warnings
•Growers should be careful not to exceed
the label recommendation of maleic hydrazide. Excessive residues on the
cured leaf have in the past discouraged foreign buyers of burley tobacco.
Experiment station field tests have shown that higher-than-suggested rates
of a systemic spray or spraying two or more times does not improve sucker
control or increase tobacco yields. However, if rain occurs within 12 hours
after spraying, sucker control may be reduced. Plants should be inspected
daily to determine if sucker growth is beginning. If suckers are green
and growing, re-spray using the same amount of chemical that was used the
first time.
•Tobacco plants that have been growing
under drought conditions absorb maleic hydrazide more slowly and, consequently,
sucker control maybe less effective than in a normal season.
•Poor sucker control may occur because
of poor plant coverage if improper nozzles or less than 20 gal of solution
per acre are used.
•Chance of chemical burn increases
if plants are sprayed on bright sunny days when the temperature is above
90"F. This type of injury can be prevented by spraying on a cloudy or hazy
day, or in morning if the weather is clear and hot.
Contact Chemicals
The contact-type sucker control chemicals
contain "fatty" alcohols (FA) as the active ingredient. The suggested topping
time when a contact chemical is to be used is when plants are in the button
to early flower stage.
When to Apply
A contact-type chemical can be applied
immediately before or after topping or within 2 days after topping. Suckers
longer, than one inch should be removed at topping. Contact chemicals work
quickly to kill suckers and if no rain occurs within an hour after spraying
sucker kill should be completed.
How to Apply
This type of chemical must be applied
as a coarse spray so that it runs down the stalk and contacts the young
sucker buds. Two and one half gallons of chemical in 50 gal of total spray
solution are sufficient for one acre of tobacco.
•When power equipment is used, a 3-nozzle
arrangement with TG3 and TG5 full cone tips or equivalent should be used
(Fig. 3); pressure should not exceed 20-25 psi. The center nozzle (TG5)
should be directed straight down and the side nozzles (TG3) should be 8
to 10 inches to each side and directed in toward the upper part of the
plant.
•If a backpack or knapsack type 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.
Warnings
(1)Poor sucker control often occurs
if plants are not in an upright position, because the chemical will not
come in contact with all the sucker buds on a leaning or crooked plant.
If possible, leaning plants should be straightened prior to spraying.
(2)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.
(3)Do not mix contact sprays with insecticides
for application.
(4)Use nozzles that will deliver a
coarse spray. If power equipment is used, a 3-nozzle arrangement over each
row is necessary to get good coverage.
In special situations the use of both
a contact and a systemic chemical may be justified. For example:
Irregular Flowering-If flowering times
of plants in a field seem likely to vary by a week or more, top the earliest
maturing plants when about 50% of the plants are in the button to early
flower stage and spray the entire field with FA. About 7 days later, top
all plants not previously topped and spray the entire field with MH.
A Local Systemic
The only local systemic sucker control
chemical currently available is Prime+®. This material is applied to
the top of the plant so that it runs down the stalk and into each leaf
axil where it systemically controls the suckers. The method of application
is similar to that used for contacts, and Prime+® has, therefore, been
used 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.
That's important because the number and size of suckers should be small.
Suckers more than one inch long must be removed at topping.
If flowering is uneven, early flowering
plants should be topped and treated with Prime+®. If suckers are present,
they should be removed before application.
How to Apply
For best results, this chemical must
be hand-applied to each individual plant. This can be accomplished by 3
different methods (dropline, backpack and jug). Prime+® can be applied
with power equipment, using a coarse spray nozzle arrangement similar to
that used for the contacts. However, sucker control maybe less than that
achieved by the hand methods.
Dropline- This involves equipping
the sprayer (trailer, tractor mounted, or hi-boy) with droplines for each
row (Fig. 4). About 6 to 10 ft of pressure hose, equipped with a cutoff
valve and a large volume nozzle, is attached to each sprayer outlet. One
person operates each dropline, following the sprayer down the row, treating
plants that have reached the elongation bud stage.
Backpack- This method is similar
to the dropline with regards to application methods. The backpack consists
of a spray tank and a wand attachment with a nozzle body that can be adjusted
or fitted with a coarse spray nozzle (Fig. 5). The wand attachment allows
the spray to be directed to the top of each plant. Small acreage growers
prefer this or the jug method of application.
Jug- This method involves adding
the chemical to a gallon jug and pouring on about 1/2 oz of the solution
per plant (Fig. 6).
Rate- One gal of Prime+®
should be mixed in 49 gal of water, regardless of the application method.
An equivalent amount for the jug method is 2.5 oz of Prime+® in one
gal of water. If a hand application method is used, no more than 30 gal
of spray solution per acre should be used. With power equipment, a volume
of 50 gal per acre is necessary.
Warnings
•Sucker escapes may occur when using
Prime+®. MH escapes tend to grow slowly from leaf axils low on the
plant, and remain concealed. Prime+® escapes, however, grow only from
axils that did not receive adequate treatment, and will grow unchecked
until removed. Correct application of Prime+® will result in only scattered
escapes that are highly visible. However, if the spray volume is inadequate
for contact of all buds or if plants are not in an upright position, the
number of escapes can 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.
•Prime+® should not be mixed with
fungicides or insecticides.
•Failure to apply Prime+® at the
recommended flower stage can 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 already begun to grow.
Chemical Sucker Control on Dark Tobacco
The dark tobaccos produced in Western
Kentucky are harvested 4 to 5 weeks after topping. Early topping, a long
interval between topping and harvesting, and wider plant spacing in the
field result in the growth of many large suckers that must be removed either
manually or by chemical treatment.
Good sucker control can be achieved
with MH in dark tobacco by using 3 pt per 1000 plants of the 1 1/2 lb/gal
formulation. Apply the indicated amounts of MH, in 20 to 40 gal of water
per acre, as a fine mist to cover the upper 1/3 to 1/2 of the plant.
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 effects of MH, many growers use a contact type chemical (FA)just
before or after topping and delay the MH treatment for about 7 days. Another
alternative is to use two applications of FA, 5 to 7 days apart, and use
no MH. Fatty alcohols should be mixed for dark tobacco the same as for
burley-2 gal of FA in 48 gal of water. However, because of lower plant
populations of dark tobacco, only 30 to 40 gallons per acre of the mixture
is needed. Spray applications can be made the same as for burley (see contact
type spray used for sucker control on burley tobacco). The same precautions
noted for burley tobacco should be taken when using FA for sucker control
on dark tobacco.
Prime+® can be applied in the same
manner described for burley tobacco. Prime+® does not cause premature
yellowing that may occur with MH use and will control suckers longer than
the fatty alcohols. An adjustment in spray volume should be made for the
shorter growth habits of dark tobacco. When using power equipment, the
volume of solution should not exceed 30 gal/acre. Follow the same precautions
noted for burley tobacco when applying Prime+® to dark tobacco.