Pest Control in Fall Rye

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 effective control is more difficult.

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 winter kill, 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

Grasshoppers
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 winter kill 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 and Guthion are registered chemical insecticides for grasshopper control.

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

Sawfly
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.

Wireworms
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.

Cutworms
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 Ambush insecticide on the rare occasion when spring cutworm damage is significant.

Diseases

Ergot
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. Further losses are caused by the lower grade received for the grain and the poisonous effect of the grain if fed to livestock.

Ergotism, the disease caused by the presence of ergot bodies in feed, can cause abortion. It is marked in the early stages by irritation and pain in the extremities (tail, ears, feet) 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. Any grain containing more than 0.1 per cent ergot is dangerous. This would be 300 to 600 ergot bodies per bushel, or one ergot body per 1,000 kernels of rye. If such feed must be used, the amount of ergot must be reduced through the use of grain cleaning equipment and mixing with ergot-free grain to reduce the ergot percentage below 0.1 per cent. There are no ergot resistant rye varieties. 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 in this region.

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