Darrell Blackwelder
March 1, 2001
There are basically two types of homeowners with lawns in
Rowan County-anything that is green is a lawn and those that
strive for a weed-free, golf course type turf. It's evident that
the droughts have left us with plenty of weak and bare areas
within our lawns providing weeds ample opportunity to become
established.
Chickweed, henbit, wild garlic (most think of as wild onion)
and annual bluegrass are just a few weeds that have popped up
almost overnight. Garden centers and other retail outlets are now
fully stocked displaying many different types of fertilizers and
weed control products. There are quite a few weed control
products which can be somewhat confusing. Adding to the confusion
is certain summer weeds and grasses need to be controlled now
with preemergence herbicides. Our focus today is with pre-
emergence herbicides.
Crabgrass is an aggressive weed in fescue lawns.
This weed
is a well adapted annual grass that can overtake a weak lawn
with thin areas in one summer. The overbearing plant grows best
in hot weather when fescue growth is dormant. Poor cultural
practices such as over fertilization and close mowing stimulate
crabgrass growth. Crabgrass is primary concern of home owners
during the summer, however other summer annuals can also be a
problem.
Preemergence herbicides must be applied in early
spring.
The general rule of thumb to add preemmergence well before
dogwoods and forsythia bloom to control crabgrass is not entirely
accurate. Research has shown that crabgrass germinates at a soil
temperature of 58 degrees. Areas with southern slopes or
sandy soils warm quicker allowing crabgrass to germinate earlier.
Preemergence herbicides form an inpenetratable barrier
inhibiting the germination of crabgrass and other weed seeds. Pre-
emergence herbicides are available in various formulations,
usually in a granular form or impregnated on turf fertilizers.
Barricade, pendimethalin, treflan, and surflan are just a few
preemergence herbicides. These herbicides are often impregnated
on popular brand name fertilizers as a convenience for spring
application. Preemergence herbicides with fertilizers are very
effective and a popular method of weed control with commercial
landscape maintenance contractors.
The key to crabgrass control is timing. These
products can
be a waste of time and money if applied after the weed has
germinated. Preemergence herbicides need to be applied soon
before the soil temperature reaches 58 degrees.
A single application of a preemergence herbicide
controls crabgrass and other weeds from germinating until mid
summer. A second application is often needed 8 weeks later if
full season control is desired. A feasible plan would be to apply
fertilizer with preemergence now and just the preemergence in
May. Never fertilize cool season lawns after April.
Lawns seeded in the fall and newly seeded turf can be
damaged with some preemergence herbicides. Read the label
carefully before applying these herbicides to determine if your
lawn would be damaged with a spring application.
This very important, so please note: Fescue and other
grass
seed cannot be over seeded when a preemergence herbicide has been
applied. So in reality, you need to be satisfied with the
condition of the lawn before considering this type of treatment.
Seeds will fail to germinate when most preemergence herbicides
are used. Only one preemergence herbicide, Tuppersan, can be
applied to control crabgrass at the time of seeding. Late August
or September would be the earliest fescue could be over seeded if
you plan to use a preemergence herbicide.
There are a few products found in garden shops that
kill
crabgrass after it germinates. These are recommended only as
spot treatments and should used very early in the season. Fescue
is sensitive to these type of herbicides and damage will occur
in hot summer weather. Always read the instructions before applying any
pesticide.
Call the Cooperative Extension Service at 6330571 if you have
any questions about herbicide applications.