By Sherri Roberts, AAg, Regional Crop Specialist Weyburn
Three things are needed in order for a disease to occur: a susceptible host, a disease-causing organism and favourable environmental conditions. Over the past few weeks, Mother Nature has provided us with rain and cool conditions, which have created the right environment for ergot infections to occur. These cool, wet conditions may also extend the flowering period in cereals, making them more susceptible to infection.
The ergot-causing fungal organism, Claviceps purpurea, has the ability to overwinter as sclerotia and remain viable for up to two years in or on the soil surface. Under favourable environmental conditions, the overwintering sclerotia will germinate in the spring just prior to flowering in cereals and grasses. The germinating sclerotia produce ascospores that are ejected into the air and are disseminated by air currents. If these floating ascospores land on a flowering cereal head, the ovary becomes infected and, instead of forming a seed head of grain, a sclerotia body will form (Photo 1). Secondary spread can occur via the honey dew stage (Photo 2). The honeydew contains the asexual spore stage of the fungus and can be transferred to uninfected plants by rain splash or insects.
Saskatchewan rye and triticale are more susceptible to ergot than other cereals because they are open-pollinated crops. However, self-pollinated grains such as barley and wheat, as well as numerous species of cultivated and wild grasses, are also susceptible. Broadleaf crops are not affected by ergot.
Ergot-infected wild grasses, particularly in fence rows, are often the primary inoculum in cereal and grass seed production fields. Mowing headlands to prevent spread of the disease into the field can be used as a management strategy to reduce this disease. Planting cereal varieties with short flowering periods, along with choosing resistant varieties, can also reduce ergot susceptibility. Lengthening crop rotations so any ergot bodies that may be present in the soil are robbed of a susceptible host can also prove to be effective.
While ergot can cause a yield reduction, the main concern should be the toxic alkaloids present in the ergot bodies. The Canadian Grain Commission has established limits for allowable ergot contamination. The toxic alkaloids remain active in flour and animal feed and are toxic to both humans and animals. The sensitivity of livestock to the alkaloids and the symptoms of ergot poisoning vary with species and animal age. Haying ergot-contaminated grasses does not lower the dangers. If in doubt, have your forage sampled.