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 32
24 May 1989
AFM 91-19 / TM 5-629 / NAVFAC MO-314
grasses, but does not suppress seedheads. Flur-
(1) Inhibition of growth persists for 6 to 8
primidol is root-absorbed and should be
weeks for most PGRs. However, inhibition may
watered-in following application. It suppresses
last 10 weeks or longer in some environments.
foliar growth for longer periods of time than
(2) Reapplication will be needed to achieve
other PGRs, but it may cause tip-browning of
season-long growth inhibition.
leaves. Flurprimidol may enhance tillering and
(3) Reapplication, however, may cause se-
rooting with continuous use, and it appears to
vere discoloration and reduce stand density, and
have preemergence herbicidal activity against
is generally not recommended for cool-season
some weeds.
grasses in areas where heat and drought stress
(3) The chemistry, toxicology, fate in the
normally begin in late spring.
environment, suggested rates, and other perti-
(4) Some periodic mowing will be needed to
nent information about these products can be
maintain the uniformity and appearance of
obtained from the manufacturers after they have
treated turf, if its visual quality is a consider-
received full registration from the EPA.
ation.
(5) Mixed plant species, which would not be
uniformly suppressed, may preclude the success-
Section B -- Using PGRs
ful use of PGRs.
5-5. On-Site Evaluation. Using PGRs under
5-6. Complementary Practices. When PGRs are
local conditions for several years provides the
used, they should be part of an overall manage-
best indication of their effectiveness and limita-
ment program.
tions.
a. If the turf grass manager intends to use
a. On-site testing is the most reliable way to
PGRs annually, he or she must be prepared to
determine PGR usefulness and safety. Small test
fertilize properly, to monitor and control weed
pots should be established at three or more
encroachment, and to overseed areas where
locations containing vegetation that is represent-
stand density begins to deteriorate. It is possible
ative of the general locale. Individual plots
that some of the savings achieved in reduced
should be at least 200 ft2 in size. An untreated
mowings will have to be directed to such other
check plot should be adjacent to the treated area
management actions. It may be wise to skip
for comparison. The PGRs should be applied to
PGR applications every third or fourth year to
the same plots once or twice annually for a
allow damaged turf to recuperate, particularly
minimum of 2 years, following the directions on
where it is growing on poor soil.
the label, so that the effects of different weather
b. Because PGRs can injure turf, nitrogen
conditions on the response to the PGRs can be
fertilizers are important in enhancing the turf's
observed.
recuperative capacity. This is important on
b. Notes and photographs taken before and
droughty or low fertility soils. In low mainte-
after each application provide valuable infor-
nance situations, it may be feasible to apply
mation on the PGR performance and any
nitrogen only once annually. Nitrogen reduces
adverse effects. Notes should be taken weekly
the capacity of PGRs to inhibit growth. There-
until the growth regulator effects of the chemi-
fore, it should be applied only after the de-
cal have ended. Special attention should be
sired growth regulator effects of the chemical
given to the amount of discoloration and the
have been achieved. The best time to apply
length of time that it persists, the change in
nitrogen to Kentucky bluegrass, tall fescue, and
growth rate in comparison with the untreated
other cool-season grasses in a single application
turf, the length of time growth inhibition
is early autumn in temperate climates. For
lasts, the presence or absence of seedhead pro-
warm-season grasses, such as bermudagrass, ni-
duction, the frequency of mowing needed, any
trogen should be applied spring and early sum-
thinning of the stand, any shifts in species
mer.
present, weed encroachment, and any other
adverse or beneficial effects. Although this is
c. Weed encroachment into PGR-treated
time consuming, it is the only means of develop-
stands should be closely monitored and con-
ing a realistic program for using PGRs on large
trolled with herbicides to enhance the competi-
areas of land.
tive and recuperative capacity of the treated
c. Judgement is required of the manager, if
turfs. Weeds also greatly increase mowing fre-
the use of PGRs is to be satisfactory. The
quency in PGR-treated areas and dramatically
following must be considered:
reduce the utility and aesthetic quality of turf.
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