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 48
AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
c. Data on the effectiveness of PGRs, and the
d. There are many factors that influence the
normal mowing frequencies on military bases,
effectiveness of PGRs. Two of the more signifi-
indicate that using an effectiveness-rate of 50
cant are climatic conditions and the type of
percent is reasonable under most circumstances.
grass being controlled. These factors were con-
The corresponding effectiveness-periods of cur-
sidered in determining the effectiveness-periods
rently available PGRs are given in table 6-2.
in table 6-2.
Table 6-2. Effectiveness-Periods of PGRs on Grass.
EFFECTIVENESS-PERIOD (Weeks)
Type of
Grass
PGR
Spring
Summer
Fall
5
7
7
Cool-Season
Amidochlor
Flurprimidol
8
10
10
Grasses*
6
8
Maleic hydrazide
8
6
8
8
Mefluidide
8
10
Warm-Season
Flurprimidol
10
4-6
4-6
4-6
Grasses**
Maleic hydrazide
6
6
6
Mefluidide
*Cool-Season Grasses:
Annual and Kentucky bluegrasses, tall and red fescues, perennial ryegrass, timothy, and bromegrasses.
**Warm-Season Grasses:
Bahiagrass, bermudagrasses, zosiagrass, centipedegrass, St. Augustinegrass, kikuyugrass (not labeled for
maleic hydrazide), and carpetgrass.
Note: Orchardgrass, velvetgrass, and tall oatgrass are not affected by PGRs. Performance of the
commercially available PGRs in regions where these grasses do not enter a state of winter dormancy has
been erractic, and the use of PGRs is usually not recommended.
total cost of mowing the areas where PGRs
6-8. Calculating the Cost-Effectiveness of Using
would be applied.
PGRs:
(5) Line 5. The cost of all the mowing that
a. Document D (attachment 25) is used to
would normally be required during the
compare maintenance costs with and without
effectiveness-period is obtained by multiplying
using PGRs. The general information at the top
line 3 by line 4.
of the document should be recorded so that the
(6) Line 6. The savings recorded here is the
cost comparison can be retained for future
cost of the mowings that would be eliminated by
reference.
using PGRs.
(1) Line 1. The effectiveness-period is dis-
(7) Line 7. Like the cost on line 4, the cost
cussed in paragraph 6-7. Table 6-2 may be used
of a PGR application is taken from document C.
for the PGRs and conditions listed therein.
(8) Line 8. The net savings is the difference
(2) Line 2. The normal interval between
between the savings in mowing costs and the
mowings is based on local requirements.
cost of applying the PGR (and herbicide, if
(3) Line 3. The number of mowings that
needed).
would normally be required during the
(9) Line 9. The recommended use of the
effectiveness-period is obtained by dividing line
savings is recorded on line 9.
1 by line 2.
b. The completed document D for our exam-
ple at Air Base Somewhere is shown in figure
(4) Line 4. The cost of one mowing opera-
6-5.
tion is taken from line 5 of document C. Use the
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