Japanese Stiltgrass Spring 2020. Time to get started!

Woodland edge inundated with Japanese stiltgrass in 2014.  This was my starting point

Japanese Stiltgrass, Microstegium vimineum, is an invasive annual grass that has taken over many natural woodland areas as well as suburban lawns.  Infestations are particularly bad in the Eastern US from Connecticut, south to Florida and Texas.  I have been posting blogs on my progress battling this grass a couple of times a year for the last 7 years.  Now that spring is rolling around it’s time to get into action.  Here a link to my initial post.

Stiltgrass germinates around the time of annual crabgrass and several pre-emergent herbicides used for crabgrass are effective at controlling stiltgrass.  I have been using a product containing Dimension™ (dithiopyr) on my lawn for 3 years now and it has significantly reduced the amount of stiltgrass present.

This is a comparison of treated and untreated areas in 2019 when the
pre-emergent was applied late.  The stiltgrass seedlings are about
an inch tall at this time.

Last year I tested this product in a mowed meadow area, but the application was at the end of the recommended application time (about 2 weeks late).  I saw a slight reduction in stiltgrass.  I was also concerned that the treatment would affect other plants growing in the meadow, but most of them are perennial species and not as strongly affected as annuals.  On casual inspection last year I didn’t see much difference in the types of plants growing in the treated and untreated areas.  This year I expanded the coverage treating both the lawn and the meadow at the same time at the beginning of the recommended treatment window.  (The meadow was mowed several days before treatment so that the treatment could have direct contact with the soil.)

Here's the mowed meadow after the pre-emergent was applied.  Lots of bare soil now. 
Various grass and sedges are starting to grow.  The wingstem, Verbesina alternfolia,
which dominates this area, has not started growing yet.

I use a website called GDD Tracker 4.0 to tell me when to apply the treatment.  It tracks the days that the average temperature is above 32F.  250 degree-days is the trigger for crabgrass pre-emergent treatment.  Here at my home we hit that on March 10 and I applied the treatment March 12.  (Optimum application time is projected to last through at least 3/21 in my zip code.  Watch out, time is running out!)

Wild Bergamot, Monarda fistulosa, that I planted last year is starting
 to sprout in the meadow with its purple-tinged leaves.