Herbicide use in the greenhouse
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
A few products are available for postemergence weed control inside the greenhouse. Diquat (Reward), pelargonic acid (Scythe), glyphosate (Roundup and others), clethodim (Envoy), fluazifop (Fusilade II) and glufosinate (Finale) may be applied under labeled conditions. Roundup and most other glyphosate formulations may be applied in greenhouses, but no desirable plants may be present. However, application of glyphosate on plastic fabric or on surfaces that may come into contact with the plastic fabric can trap the herbicide in the fabric. Afterwards, glyphosate can move into the trays through root uptake and injure those plants.
Instead, I would recommend alternative herbicides such as Reward or Scythe for weedy areas near plastic fabric areas or underneath greenhouse benches. Scythe may be used before planting, before crop emergence, directed around desirable plants or applied to floors and walkways. Finale may be applied as a directed spray in greenhouses void of edible crops. Do not allow Reward, Scythe, Roundup or Finale to contact desirable foliage or severe crop injury may occur. Envoy and Fusilade II may be applied in greenhouses for control of grasses. These two herbicides may be applied over many broadleaf crops that appear on the label.
Some products are also available for control of “lower plants” in greenhouses such as moss, algae, liverwort etc. These products include Moegton, Terracyte and Zerotol.