Killing Perennial Weeds Using Light Blocking Tarps

Project Overview

Project Type: On-Farm Research
Funds awarded in 2023: $7,871.00
Projected End Date: 03/31/2025
Grant Recipient: Virginia Cooperative Extension
Region: Southern
State: Virginia
Principal Investigator:
Shawn Jadrnicek
Virginia Cooperative Extension


Not commodity specific


  • Pest Management: physical control, weed ecology

    Proposal abstract:

    This experiment will determine the amount of time required under light blocking covers to kill bermudagrass, johnsongrass, fescue and other annual and perennial weeds.  By determining the time required to kill various weeds, farmers will be able to maximize productivity by uncovering and returning land to production earlier.  Small market farmers report sales as high as $40,000/acre/year in intensively managed land (personal experience and communications).  Over a 24-week growing season this would amount to $1666/acre/week of production.  Therefore, returning land to production even a few weeks earlier could contribute significantly to farmer income.

    Project objectives from proposal:

    Cam Terry of Garden Variety Harvests uses occultation or covering land with light blocking tarps to eliminate annual and perennial weeds.  Local ANR agent Shawn Jadrnicek has been working closely with Cam Terry and Hunter Hartley in designing and developing Lick Run Farm site and co-teaching workshops at the farm.  An old field slated for conversion to perennial and annual crops is filled with a host of perennial and annual weeds including johnsongrass (Sorghum halepense) and bermudagrass (Cynodon dactylon).  The new field will be divided into 24 plots that are 6’ x 6’ in size and each plot will be marked and labeled with wire flags and analyzed between May 1 and May 15 to determine annual and perennial weed composition.  On May 15, the plots will be mown and covered in light blocking silage tarps 7’ x 7’ in diameter with 12” of overlap between adjoining plots.  Each plots tarp will be held down with 4 UV resistant weight bags weighing 15 pounds.  Plot numbers will be assigned to each plot and the plot numbers spray painted on the silage tarp. Three Plots with similar weed species will be uncovered every two weeks starting June 1 and ending September 15.  The plots uncovered will be irrigated with 20 gallons of water per plot after uncovering.  Two weeks after uncovering, perennial and annual weed growth will be assessed as species and percent cover and type of regrowth (rhizome, tuber or seed) and the plots will then be recovered until September 15th.  On September 15th all the plot covers will be removed and plots marked with wire flags.  All plots will be irrigated and two weeks after all covers are removed, weed species and percent weed cover and type of regrowth on each plot recorded.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.