Pest Control in Fall Rye

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 Weed control | Insect control | Diseases

Weed Control

Control of weeds in fall rye should be considered in the fall. Winter annuals can be controlled effectively with a 300 to 400 ml per acre application of 2,4-D amine 500 or an equivalent amount of the active ingredient of the esters. Leaving the winter annual weeds to the following spring allows them to become more tolerant and much more difficult to control.

Summer annual weeds, including wild oats, are not generally a problem in fall rye as it is a strong competitor. However, if stands are thinned through winterkill, herbicides can be applied as with spring cereals, but the time of application will be earlier in the spring and at the three-leaf to jointing stage. By early June, fall rye is generally in the shot-blade stage and is then susceptible to damage if treated with 2,4-D or related herbicides.

Fall rye should not be grazed in the fall or spring if maximum weed control and grain yield are desired.

For more detailed information on control of specific weeds, consult the latest edition of Crop Protection, Agdex 606-1 (the Blue Book).

Insect Control

Do not delay seeding because of grasshoppers. They are active when conditions favor plant growth, but become less active as cold hardening conditions set in. Grasshoppers usually feed on the margins of the field. Delaying seeding may prevent grasshopper damage on these margins, but the whole crop is now jeopardized by winterkill as a consequence of maximum cold hardening not being achieved. What is gained by reducing grasshopper damage is usually lost in reduced yield caused by lower cold tolerance.

Sevin, Cygon, ECO Bait, Lagon and Malathion are registered chemical insecticides for grasshopper control.

Aphids very rarely require control in fall rye because they are fairly advanced in their life cycle when the rye emerges. Malathion is registered for aphid control in rye.

Wheat stem sawfly can infest fall rye, but never damages it significantly because the rye is almost mature by the time the insect population reaches harmful levels.

Since wireworms move deep in the soil in late August, they do little damage to the emerging crop. In the spring, fall rye growth is sufficiently advanced by the time wireworms become active so that the plants generally experience far less damage than occurs in later emerging spring wheat. Therefore, treating fall rye seed with an insecticide is of doubtful value. It is better to reduce the wireworm population by cropping an infested field with treated spring wheat or barley. However, when sowing land either known to be infested with wireworms or freshly broken, it is good insurance to treat the seed.

When seeding into fallow in years of high cutworm risk, consider delaying seeding until mid-September. The main cutworm egg laying period is from about early August until mid-September. Maintaining a crust over the land during this period will greatly reduce egg laying.

Cutworms may be controlled by spraying with Pounce insecticide on the rare occasion when spring cutworm damage is significant.


Ergot is a common and important disease of rye. Rye is particularly susceptible to ergot because it is mainly cross-pollinated, whereas wheat, barley and oats are mainly self-pollinated. Ergot is caused by a fungus (Claviceps purpurea) and can be identified by large, dark purple or black bodies called sclerotia (ergots), which develop in place of the rye kernels.

The loss in yield from ergot infection results from the replacement of normal kernels by ergot bodies and the fungal blighting of normal flowers, which fail to form seeds. Economic losses are caused by lower yield and grade received for the grain and the poisonous effect of the grain if fed to livestock.

Ergotism, the disease caused by the presence of alkaloids in the ergot bodies found in feed, can cause abortion. It is marked in the early stages by feed refusal, non-descript infections that resemble shipping fever or BVD. High levels of contamination cause irritation and pain in the extrementies (tail, ears, feet), the loss of hair from the ears and tail, and later, a dry gangrene sets in.

Alkaloids present in ergot have been detected in flour and cereals intended for human as well as animal feed. The old method of using a kernel count (any grain containing more than 0.1 per cent ergot or 1 ergot in 1,000 kernels) is not accurate to determine if the grain is dangerous to feed.

The Prairie Diagnostic Laboratory in Saskatoon is able to test for seven different alkaloids that can be present in ergot. Total ergot alkaloids above 200 parts per billion (ppb) can cause a reduction in animal performance (blood flow reduced in the milk vein of dairy cows, which reduces milk production). When total ergot alkaloid levels are known, it is a matter of reducing the amount of infected grain in the ration to keep alkaloid levels below the 200 ppb level.

The varieties of Prima and AC Remington have good resistance to ergot; other varieties are less resistant. Seed treatment does not prevent ergot.

To reduce ergot infestations, take the following measures:

  • Use ergot-free seed if possible.
  • Rotate with crops resistant to ergot, such as flax, canola and legumes.
  • As the source of ergot infection is often the grass in headlands or ditches, mowing this grass before flowering or seed set will greatly reduce or eliminate the chances of ergot infection.
  • Ergots germinate at or near the soil surface to produce infectious spores that attack cereal flowers. To prevent them from germinating, work the field to a depth greater than two inches to bury the ergot bodies.
  • Seed at a uniform depth as shallow as possible for adequate moisture to obtain a uniform early emergence.
  • Separate the seed collected from the first few combine rounds to prevent contamination of the entire lot as most of the ergot infested grain will likely be concentrated in this region.
  • Often, infestations of ergot occur with cool, moist conditions during flowering.
Snow molds
Snow mold is caused by one of several fungi that attack the rye plant in the early spring starting about the time the snow begins to melt. The disease appears as a grey or pinkish web-like mold covering the leaves. Some of these fungi also produce small black bodies about the size of pinheads.

Infected areas normally appear as different sized patches scattered throughout the field. Often, only individual plants are attacked. This patchiness occurs because the disease organisms grow under very specific temperatures and moisture conditions; these occur for a long enough period only in individual parts of the field. If single plants are infected, yield losses should be light. If there are many dead patches, losses can be heavy. Yield losses are usually heaviest if there is deep snow that melts slowly, which occurs frequently in the parkland and in northern Alberta.

Snow mold fungi increase with frequent winter cereal cropping or perennial forage cropping. Never sow fall rye on a field that has just been taken out of a forage crop, because the risk of severe snow mold damage is great. Poor winter survival has often been blamed on the lack of cold temperature tolerance, when, in fact, the damage resulted from snow mold fungi. At present, no chemical control is recognized for snow mold in fall rye.

Ice encasement and drowning are two other common causes of patchy stands, sometimes falsely blamed on a lack of cold temperature tolerance. As result, fall rye should only be seeded on well drained fields that do not puddle or pond.

Stem smut
Certain varieties of fall rye are susceptible to stem smut; they are AC Remington, Dakota and Hazlet. AC Rifle, Musketeer and Prima are all rated as good for stem smut resistance. Stem smut can be controlled by treating the seed with a systemic seed dressing. At the present time, the only registered systemic seed dressing is carbathiin (Vitaflo 280).

Plants affected by stem smut can be detected as soon as the crop begins to head, but the disease does not become conspicuous until after the crop starts to ripen. As the name of the disease suggests, masses of black smut spores appear on the uppermost part of the stems. The disease extends into the heads, which also become blackened with smut spores and yield no grain. Heads of infected plants often fail to emerge from the boot and are usually bent or otherwise distorted. Infected stems are much shorter than healthy ones.

Seed decay and seeding blight

Rye is particularly susceptible to seed decay and seedling blight caused by various soil fungi.

Various seed treatments will provide protection from these pathogens and markedly increase seedling emergence and plant stands.

Rye is also susceptible to diseases common to other cereals such as common root rot, scald, fusarium blight, powdery mildew and leaf rust, but yield is usually much less affected. Rye severely infected with leaf rust may have higher nitrate levels, making feeding dangerous.

More Information

For additional information see the publication Fall Rye Production, Agdex 117/20-1.


The author wishes to express a sincere thank you to Walter Yarish, Tim Ferguson, Ieuan Evans, Mike Dolinski, Doug Penney, J. Thomas, Don Salmon, Bob Nelson, Grant McLeod, Keith Briggs, Dave McAndrew, Myron Bjorge, Bob Wroe, Russel Horvey, Alan Toly, Bob Wolfe, Blair Shaw, Bill Chapman, Wayne Jackson, Larry Welsh, Ellis Treffry, Gordon Hutton, Allan Macaulay, Mike Rudakewich and Lu Piening for their constructive criticism in reviewing and improving this manual.

A special thanks to Arvid Aasen who wrote, with the help of Ken Lopetinsky, Vern Baron, Ellis Treffry and Myron Bjorge, the pasture, the hay and silage section.

Prepared by:
Murray McLelland formerly with Alberta Agriculture and Rural Development

Revised by:
Harry Brook, Alberta Agriculture and Forestry

Source: Agdex 117/20-1. Revised June 2018.

Other Documents in the Series

  Fall Rye Production
Seeding Fall Rye
Fertilizing Fall Rye
Winter Plant Survival of Fall Rye
Pest Control in Fall Rye - Current Document
Harvesting and Storage of Fall Rye
Fall Rye for Pasture, Hay and Silage, Grazing and Feeding
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For more information about the content of this document, contact Harry Brook.
This document is maintained by Jennifer Rutter.
This information published to the web on November 1, 1999.
Last Reviewed/Revised on July 9, 2018.