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1998, No. 2
Spring, 1998
Herbicide Control of Cool Season Perennial Grassy Weeds
Spring is a great time to control creeping bentgrass, quackgrass, and tall fescue when these perennial grasses invade desirable turf.
These weeds are actively growing now and controllable using available postemergence herbicides.
For creeping bentgrass and quackgrass there are no selective herbicides available.
The nonselective herbicide glyphosate (Roundup, Roundup PRO) can be used to control these weeds, as well as tall fescue.
Roundup PRO is a newer form of glyphosate that reportedly works more rapidly than the older formulation.
Apply it when the weeds are green and actively growing.
Be aware that this nonselective herbicide will damage or kill other actively growing plants.
For creeping bentgrass and quackgrass be sure to spray an area large enough to include all creeping stems growing in the area; untreated stolons or rhizomes may continue to grow and develop into more unsightly weeds.
There is a selective herbicide available to control tall fescue.
Chlorsulfuron (TFC) is a postemergence herbicide that can be applied to control actively growing tall fescue that has invaded Kentucky bluegrass.
Chlorsulfuron often works slowly, causing the tall fescue to gradually decline, rather than quickly die.
It will kill or damage perennial ryegrass and may also cause yellowing or phytotoxicity to Kentucky bluegrass.
Always read, understand, and follow the directions on any pesticide label for the safest, most effective pest control.
Poa gone Crazy
This spring, it seems as though Poa annua populations are at an all-time high.
The mild, atypical winter and current wet spring conditions are great for Poa germination, survival, and flowering.
Also, these conditions may slow the growth of creeping bentgrass, thus allowing the Poa to have a greater presence.
There are morphological differences between the annual (Poa annua var. annua) and perennial (P. annua var. reptans) strains of annual bluegrass (Table 1).
Based on these descriptions, it appears that most of what is currently in heavy flower are the annual types.
Table 1. Differences between annual and perennial subspecies of annual bluegrass.
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| Annual types (P. annua var. annua) |
Perennial types (P. annua var. reptans) |
| upright growth habit |
creeping growth habit |
| no or few tillers per culm |
numerous secondary tillers per culm |
| prolific seed head production |
minimal seed head production |
| minimal rooting per culm |
several adventitious roots per culm |
| seed dormancy |
no seed dormancy |
| less than 6 nodes per culm |
more than six nodes per culm |
*
From Beard, J. B., P. E. Reike, A. J. Turgeon, and J. M. Vargas. 1978.
Annual bluegrass (Poa annua L.) description, adaptation, culture and control.
Michigan State University Research Report No. 352. East Lansing, MI.
Two types of chemical applications can reduce Poa seedheads in the spring.
First, an application of a preemergence herbicide such as bensulide in late summer can reduce the population of Poa the following spring.
Second, a spring application of a floral-inhibiting growth regulator, such as mefluidide, can reduce seedhead development.
Roots, Roots, Roots
Is this spring's weather starting to mimic the conditions of 1995? Most Illinois turf managers certainly hope not.
Spring, 1995, was cool and wet - not good turf root-growing conditions.
As you recall, the weather then became hot and dry in June and July.
The roof then caved during August when high temperatures, combined with increased humidity and precipitation, occurred.
To many turf managers, growing conditions in August, 1995, were the worst of their careers.
Many of that year's problems could be traced to the wet spring and poor growing conditions for turf roots.
Over the course of a typical growing season, the majority of root growth occurs during spring.
When spring conditions, such as cold, wet weather, keep turf plants from producing these roots, the plants are at a disadvantage going into the warmer weather.
Obviously, we don't know what type of weather conditions the remainder of this year will bring.
Regardless of the outcome we do think it important that you encourage as much root growth this spring as possible.
Avoid over fertilization with nitrogen and over irrigation.
When possible, use aerification to open compacted soils and encourage drainage and oxygen infiltration.
Withhold traffic as much as possible on wet soils to reduce soil compaction.
Raise mowing heights, even if only slightly, to develop maximum rooting.
Hopefully, 1998 will NOT follow the same track that 1995 took.
If it does, encouraging maximum root growth this spring should make a difference later this growing season.
Being proactive now may place 1998 in the annals as a tough growing season, but nowhere near as bad as 1995.
(Tom Voigt, Bruce Branham, Tom Fermanian, and Bruce Spangenberg)
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