Corn-lookalike weed #137016 - Ask Extension

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Corn-lookalike weed #137016

Asked June 26, 2013, 2:33 PM EDT

Hello,

I am having a large problem with a weed that has invaded my yard. It looks slightly like corn, (when the corn is first growing) and grows very rapidly. After mowing the lawn, in 2 days or less, this weed has grown about 3 inches higher than the lawn, having the appearance of stubble. This weed grows in other places around my property, too, and reaches a height of about 4 feet tall, if allowed to grow.
I have tried killing the weed by repeatedly mowing close to the ground, and by using a leading lawn weed killer containing 2, 4-D, mecoprop-p, and dicamba, but these methods don't work. I think a glyphosate-based product probably would kill this weed, but I don't want to kill my lawn. Would sulfentrazone possibly work?
I live in an agricultural/estate area, and have seen this weed growing at the edge of corn fields, but have not seen the weed in generally more suburban areas. Also, I believe that the weed is a monocot, due to not being affected by the 2, 4-D, and possibly a perennial, as it grows back in the same places as in previous years, if that helps.

Jefferson County West Virginia

Expert Response

What you have is Johnsongrass. Johnsongrass is a coarse grass that can grow up to 6 feet tall. It is very vigorous plant and in addition to spreading by seeds, it produces stout rhizomes, appearing in dense clumps or nearly solid stands.This plant is considered a perennial weed in West Virginia. However, it could be shattercane. The following links will explain the differances and offer some treatments t rid your property of these weeds. http://www.caf.wvu.edu/~forage/johnsongrass/johnsongrass.htm
Typical lawn weed killers will be ineffective as this plant is a grass. If it is in fact Johnsongrass, some herbicide resistant stands have been noted in many locations.
One aditional thought, you can rent a piece of equiepment called a weed wiper from the Conservation District. This tool allows you to apply concentrated round up or a similar contact herbicide to agressivly growing weeds without killing the less prolific shorter and or cool season grasses. To throughly kill a stand if this particular weed, it may take more than one application. The application efficacy will be enhanced if you apply the chemicals or treat the stand when the plants are moving neutrients into the roots (summer and fall) as opposed to when the roots are sending neutrients the other direction (spring).

Michael Harman Replied June 26, 2013, 10:14 PM EDT

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