Scouting for Ergot
This page was adapted from the article, "Check Small Grain Fields for Ergot," which appeared in Crop & Pest Report on August 25, 2022.
Ergot has been observed in both wheat and barley fields in North Dakota. In most reported observations, ergot was most noticeable on the edges of the field and the incidence lessened the further into the field. The pathogen infects through female flowers and mimics pollination in small grain crops. In other words, any disruption in pollination will increase the risk for ergot. Ergot can be easily identified in small grain fields that are at maturity. The hard black to purple ergot bodies protrude from florets and can be easily spotted in an amber colored small grain field (Figure 1). Ergot body size can vary and be smaller than a wheat kernel or four to five times bigger than a wheat kernel.
Ergot is a common disease in North Dakota and our state has over 50 reported grass hosts including wheat, barley, durum, rye, quackgrass, and smooth brome. One of the biggest carriers of ergot is smooth brome (Figure 2), which often lines road ditches and section lines in the state.
The observations of ergot on field edges is often the result of pathogen transfer from grassy weeds into the small grain field. For example, smooth brome tends to head-out earlier than a small grain field. If a smooth brome spikelet is infected, it will secrete “honey dew”, which is a mixture of sugar and spores. Insects will be attracted to the honey dew and then carry the honey dew into a nearby small grain crop as it is starting to head. If you are able to mow or swath grassy hosts on field edges before heading, this will significantly disrupt the disease cycle. In conversations with agronomists across the state, several field edges did not get mowed or swathed this year as an attempt to manage grasshopper movement into fields.
If you see heavier levels of ergot in your field, check to see how far the ergot extends into the field. A harvest strategy can be used for fields with heavier ergot levels on field edges. Harvesting and separating the grain collected from field edges will reduce the risk of contaminating high quality grain. Ergot thresholds are determined as the proportion of sclerotia weight per grain weight. The ergot threshold for wheat is 0.05% and 0.1% in barley. For reference, 0.05% in wheat can be as little as 10 ergot bodies in 2 pounds of wheat seed.