GARDEN COLUMN FOR THE SALISBURY POST

Darrell Blackwelder

March 6, 2002

 Last week's garden column dealt strictly with preemergence
weed control in home lawns. The column features information for
controlling weeds with postemergence herbicides.
 Postemergence herbicides control weeds after they have
emerged.  Broad leaf winter and summer weeds are usually the
weeds controlled with these type of herbicides.  There are a few
herbicides on the market that claim to controll crabgrass and
other grassey weeds after they have emerged, however, sucess with
these herbicides are somewhat limited.
     Broadleaf weeds are fierce competitors for space, sunlight,
water and nutrients. Homeowners can reduce weed competition by
employing sound cultural practices. A vigorous, healthy lawn
discourages winter weed growth.  Ironically, many weeds actually
thrive on poor soils and adverse growing conditions.
 One method of controlling weeds is to mow cool season
grasses to a height of three and a half to four inches.  Shade
from the turf discourages weed seed germination, especially
crabgrass and dandelion.
     Broadleaf winter weeds have emergeed in most lawns after the
brief period of warm weather. The fall drought and warm weather
in December triggered excessive growth of many winter weeds, most
notably chick weed. Winter annuals germinate in late September
when soil temperatures drop below 58 degrees and lay somewhat
dormant during the winter until early spring.  The cool weather
in October followed by record highs in February allowed many
weeds to grow prematurely. Chickweed seems to be the worst weed
so far, however, henbit, wild garlic(some refer to as wild
onions) and dandelion are  also becoming a serious problem.
     These weeds may be controlled with applications of a post­
emergence herbicide. Most broad leaf weed herbicides or "weed
killers" contain a mixture of various herbicides, such as 2,4­D
and dicamba. Post­emergence herbicides such as Trimec, Weed B-Gon,
Spectrum 33+ and various other formulations are applied to
existing weeds in turf. These broadleafed herbicides are
formulated not to injure cool season turf itself.
   Broadleaf herbicides are usually sold as liquid formulations
and are applied with compression sprayers or hose­on applicators.
Both systems work well for broadlead weed control.
     Some weeds may need more than one application for complete
control. Weed such as wild garlic have waxy coatings which repel
some water­based herbicides. Most commercial herbicides use a
wetting agent to help herbicides penetrate the waxy coatings
facilitating absorption. Spreader-stickers are additives that are
used in conjunction with herbicides to help these materials stick
to waxy leaf surfaces.
     Broadleaf winter annual weeds in bloom are difficult to
kill.  These plants generally do not absorb herbicidesat this
stage of growth.  Broadleaf weeds should sprayed at an early
growth stage; therefore the younger the weed, the easier to
control with herbicides. The problem facing now homeowners is
many of the winter weeds have achieved excessive growth and are
difficult to control.
     Broadleaf postemergence herbicides also are sold as granular
formulations or impregnated on fertilizers. Fertilizers with
herbicides are more convenient and easier to apply than liquid
herbicides.  Confront, an excellent broadleaf herbicide
impregnated on premium lawn fertililzers, controls a wide range
of broadleaf lawn weeds.