Little Ergot to be Irked About

Minor amounts of the disease showed up in some small grains last summer.

Seed treatment won’t help; crop rotation best bet in managing it

By Tracy Sayler

Ergot showed up in some fields of small grains in 2003, but at levels too low to cause yield and quality losses. 

North Dakota State University agronomist Joel Ransom says he became concerned after more ergot was showing up last summer than usual, including a rye field that he says “was loaded with it.” However, grain elevators he checked with indicated that the range in ergot levels was within acceptable limits, he says. 

Direct yield losses due to ergot are usually small, but if wheat contains more than 0.05% by weight of the ergot sclerotia (black fungal bodies), it is graded as ergoty and could be discounted or rejected for use in food related channels.

Marty Draper, South Dakota State University extension plant pathologist, says he saw scattered and isolated occurrence of ergot this year in South Dakota. “One rye field on the edge of an area that received repeated rainfall was the worst.  Generally, I think it is safe to say that the temps were too high to see widespread infection in wheat. Ergot seems to thrive in cool, wet years. We saw quite a bit of ergot in our scab fungicide plots a few years ago and took disease counts. Fungicides applied at flowering (for scab suppression) were ineffective at reducing ergot.”

(Photo: Marty Draper, SDSU)

NDSU extension plant pathologist Marcia McMullen says that ergot was detected in 2.7% of the post-flowering fields in NDSU’s 2003 wheat disease survey, all in northeast N.D. “In the northeast counties where it was picked up in our survey, they did have some isolated abundant rainfall in July, when the crop would have been flowering.  It was the same area that saw some scab, too, although not severe.”

Ergot appears as a dark purple or more often a black fungal mass that replaces kernels in the small grain head. Generally only a few kernels in a head are affected, but as the fungal body is usually larger than normal kernels and extends beyond the tip of the glumes of the kernels they replace, one can spot ergot when walking through a ripening field. In harvested grain, ergot bodies appear as black chalky kernels. These ergot bodies if returned to the soil will be a source of inoculum for future infection.

Ransom says there has been no recent screening of hard red spring wheat varieties for resistance to ergot in N.D.  During the summer, he visually evaluated varieties for presence of ergot in two variety trials that were planted in farmers’ fields in Ransom and Richland counties.  When considering the data from both locations, all varieties had some ergot; no variety was completely resistant. Granite was consistently the most affected. Hanna, Reeder and Parshall generally had less ergoty grains than the other varieties. 

He cautions, however, that these observations are from only two sites and for one year and should not be used to definitively characterize the level of resistance in HRSW varieties. They do, however, indicate that varietal difference may exist among varieties. He speculates that differences between the susceptibility of varieties to ergot may be related to the openness of the florets of the varieties (more open florets should enable greater infection) or to the timing of their flowering relative to the presence of inoculum.

McMullen says seed treatments don’t protect against ergot, as it is the overwintering ergot body that germinates next year if the soil is wet, and it releases spores that may infect the exposed flowers.  Crop rotation is the best way to manage ergot; plant a non-susceptible broadleaf crop in fields where ergot has been a problem.

More background on ergot (including it’s affect on livestock feed) can be found in the NDSU Extension online publication: www.ext.nodak. edu/extpubs/plantsci/crops/pp551w.htm.