Identifying Summer Annual Grasses in Field Crops

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Identifying grasses in the seedling stage takes some practice, but if you know what to look for, it is not as difficult. The key characteristics are the leaf blade (upper and lower surfaces); collar (region where leaf blade attaches to the stem); sheath (where leaf wraps around the stem); and ligule (feature in the collar region that is often hairs or membrane-like).

You may wonder “WHY WORRY ABOUT IT”, herbicides are equally effective on all grasses.

The table below is for comparisons only, but here are some things to consider:

• Texas panicum is quite sensitive to glyphosate, but it is one of the more difficult species to control with Impact or Assure II.
• Large crabgrass is controlled with most of the herbicides on the list, except Accent Q, which will not control it.
• If planning to use glyphosate for grass control, you have a wider window of opportunity to control giant foxtail or seedling johnsongrass. However, if fall panicum or goosegrass are in the field, it will need to be treated much sooner while these plants are small.

Abbreviations: +atrz= including atrazine; nl= not listed; PC= partially controlled

Seedling Grass Identification

A few keys to help identify common grass seedlings are listed in the table below. Also, refer to Virginia Tech Weed Id Website (https://weedid.cals.vt.edu/). Feeling comfortable knowing a few species will be useful when looking at an unknown grass and trying to identify it. Understanding the key features to look for will make seedling grass identification much easier. Refer to the diagram above for key features.

Common summer annual grasses in field crops and their characteristics. Those characteristics noted as bolded and underlined are helpful.