Rye: Seven Diseases and Treatment Recommendations

by Claus Nymand

KWS Product Manager, Hybrid Rye, USA and Canada

Plant breeding company KWS released a line of hybrid winter rye in the U.S. about three years ago, and Albert Lea Seed is proud to carry these hybrids for farmers looking for a grain crop or cover crop. The good news is that we haven’t observed any disease pressures so far in, but that doesn’t mean we shouldn’t remain diligent. Here are the seven most common rye diseases that farmers of which farmers should be aware.

Claviceps pupurea – Ergot

Ergot is a disease not limted to rye: it can affect all cereals and grasses. Sklerotier (black ergot) survives in the soil and emerges early summer at the same time as heading in most grasses and cereals. They can get up to about .3 inch high and ending with a round head. In the head many spores develop and are spread by wind. When the grasses flower, and if there is no pollen to pollinate them, the spores land on/in the flower and use the fruit as their grow media. The flower thinks it is pollinated and will close. The first sign of ergot is the honey dew (konidier) which is a sweet sticky secretion that insects feed on. When the crop flowers over a long time, the insects can spread the disease from early flowers to late flowers. As there are no fungicides which have an effect on the disease, it is very important that the crop flowers very evenly as pollen is the only protection against the disease. If a pollen and a spore land on the fruit at the same time the pollen will always win. This is why we encourage farmers not to drive in the crop after first elongation (without tramlines), because the plants they drive on will be delayed in flowering and therefore pose a greater risk for ergot infestation both from the emerging Sklerotier and from insects.

Pseudocercosporella herpotrichoides – Eyespot

Eyespot is seen only in very intense monoculture – meaning rye after rye over multiple seasons. The disease survives in old stubble and spreads in the autumn by spores transferred by rain splashes or wind from old stubble to the new plants. The disease can be seen from tiller stage by looking at the base of the plant where it turns brown and later in spring looks like an eye. When severe infestation the straw will break at basis and the whole crop will be lodging. Seed treatment and fungicides can help treat (or prevent) eyespot. Rye can be sprayed in late autumn or very early in the spring. Eyespot is more common in the U.S. on monoculture wheat farms. If planting rye after wheat, farmers may want to use a fungicide.

Erysiphe graminis f.sp. secalis – rye mildew

(Note: mildew pictured above is on wheat plants, but would appear the same on infected rye.)

This disease affects rye in autumn after early planting and if the foliage is very dense. Rye mildew requires moist and warm conditions in autumn. Also early spring mildew is often seen on the old leaves but the hybrid rye normally grows fast and seldom the disease follow up on the new leaves. KWS hybrids have a very good and efficient resistance to rye mildew, and typically it is seen in more maritime climates, like England and Nordic coastal regions. Many effective fungicides are available for rye mildew.

Rhynchosporium secalis – Leaf Blotch, Scald

Leaf blotch can affect all cereals. The disease develops very early in the spring even under low temperatures. To develop it needs very moist conditions, and it spreads quickly by water splash or by wind. It typically begins at the base of leaves and then spreads to the rest of the leaf. We have not yet seen the disease in U.S., but there are plenty of effective fungicides available for treatment. KWS hybrid ryes have a very good resistance to the disease.

P.recondita, f.sp. recondite – Brown rust/leaf rust

Different from wheat stripe rust (stripe rust only attaches to wheat and triticale), brown rust in rye does not affect wheat, and brown rust in wheat doesn’t affect rye. (They are two different races). Brown rust in rye appears in early summer as the temperature rises. Often it is seen just after flowering when rye is stressed from producing pollen. Although we do not recommend spraying rye during flowering (so as not to disturb pollination), farmers may consider a fungicide application at flag leaf or just after flowering. Effective fungicides that can protect against the disease, but fewer exist to knock down the disease once it has established. As few farmers in the U.S. make tramlines in their field, I would not recommend spraying at flag leaf as too many plants will be knocked down which creates a high risk for ergot infestation. Therefore, we recommend inspecting fields after flowering to determine if there’s a need for fungicide application. If no symptoms are visible 10-12 days after flowering, there will be no need for fungicides – these late infestations has no negative affect on the performance as the leaves are not the most important for the grain filling. Aerial spraying would be inadvisable as it doesn’t offer the level of precision needed in application.

Fusarium: Fusarium is relatively common, depending on the weather and specific crop rotations. Most years it is not a problem in rye, but it can flare up if it has been raining at flowering when spores are present. The most common source of spreading fusarium is corn stubble; therefore, we don’t recommend planting hybrid rye for grain purpose after corn (but for silage a corn-rye rotation is fine). There is no fungicide that is effective against fusarium in rye. 

Microdichium nivale – Snow mold

The disease appears in early spring during snow melt. Large areas of an infested field will reveal withered leaves so that plants look brown and “dead” – which they often are. Winter rye is the winter cereal which most affected by snow mold. The source of infection is stubble residues or infected seeds. The infection takes place mostly if the developed foliage is large at first snow fall, and if the soil is not yet frozen. It can severe damage the crop, so in regions where early snow is common before the soil is frozen, we recommend seed treatment against snow mold.